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Brewery wastewater treatment using aerobic sequencing batch reactors with mixed culture activated sludge Ling, Luqiong 1998

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Brewery Wastewater Treatment Using Aerobic Sequencing Batch Reactors with Mixed Culture Activated Sludge by Luqiong Ling M.Sc. (Environmental Biology), University of Liaoning, 1990 B.Sc. (Biology), University of Liaoning, 1985  A THESIS SUBMITTED IN PARTIAL F U L F I L L M E N T OF THE REQUIREMENTS FOR THE D E G R E E OF M A S T E R OF SCIENCE IN THE F A C U L T Y OF G R A D U A T E STUDIES (Department of Chemical & Bio-Resource Engineering) We accepptrus thesis as conforming to the required standard  THE UNIVERSITY OF BRITISH COLUMBIA October, 1998 ©Luqiong Ling, 1998  In presenting this thesis in partial fulfilment of the  requirements for an advanced  degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department  or by his  or  her  representatives.  It  is  understood  that  copying or  publication of this thesis for financial gain shall not be allowed without my written permission.  Department of  CJ-e^mi-zA^t  fc  The University of British Columbia Vancouver, Canada  Date  DE-6 (2/88)  Oct.  IV ,  t992  I3$p- /?e{t?ut~ce  Abstract  Laboratory-scale aerobic sequencing batch reactors, in both suspended-growth and attached-growth modes, were used to study the treatment of brewery wastewater. A Ringlaces material was selected and employed for the attached-growth reactors. Experiments were conducted employing a wide range of hydraulic retention times, from 0.56 to 6.06 days. The experimental results demonstrated that brewery wastewater could be successfully treated using both suspended-growth and attached-growth aerobic sequencing batch reactors. Treatment efficiencies in terms of the removals of total organic carbon (TOC), the five days biological demand (BOD ), chemical oxygen 5  demand (COD), and suspended solids (SS) were consistently maintained over 90%, with the suspended-growth reactors performing significantly better than the attached-growth reactors. As the results of these experiments demonstrated that the performance of suspended-growth SBRs was superior to that of attached-growth SBRs, only the suspended-growth SBR system was selected to study the optimal conditions of HRT and loading rate. The results showed that the maximum removal of TOC and SS could be reached at the optimal of HRT and  loading rate. The removal of T O C was more  sensitive to variations in the HRT than to variations in the loading rate; however, the effect of loading rate was dominant in the removal of SS compared to the effect of the HRT. The pH remained relatively constant during the aeration stage. The dissolved oxygen concentration changed as aeration proceeded. This may be related to T O C  ii  degradation and microbial activity. A lower sludge production rate was observed in the aerobic suspended-growth SBRs.  in  Table of Contents Contents  Page  Abstract  ii  Table of Contents  iv  List of Tables  vii  List of Figures  ix  List of Abbreviations  xi  Acknowledgement  xii  Introduction 1.1 General characteristics of brewery wastewater  1  1.2 Objectives  4  Literature Review 2.1 Previous researches on brewery wastewater treatments  5  2.1.1 Anaerobic process in brewery wastewater treatment  5  2.1.2 Aerobic treatment of brewery wastewater  7  2.1.3 Other systems  9  2.2 Sequencing batch reactor system 2.2.1 Operation of sequencing batch reactor  11 11  2.2.2 The applications of sequencing batch reactor system in wastewater treatment  12  2.2.3 Advantages of sequencing batch reactor  iv  15  Materials and Methods 3.1 Source of brewery wastewater and activated sludge  ;  17  3.2 Equipment  17  3.3 Experimental Design  21  3.3.1 The aerobic SBR start-up and operation scheme 3.3.2  Studies on comparison of treatment efficiencies under suspended-growth and attached-growth conditions  3.3.3  23  Determination of optimal conditions of hydraulic retention time and loading rate under suspended-growth condition  3.3.4  21  26  Track studies of pH, TOC, and dissolved oxygen vs aeration time in suspended-growth sequencing batch reactor  28  3.4 Sampling and analytical methods  28  3.5 Data analysis  29  Results and Discussion 4.1 Characteristics of brewery wastewater  31  4.2 The start-up of SBRs  32  4.3 Comparison of performance of suspended-growth and attached-growth aerobic SBR  34  4.3.1 Effects of HRT and loading rate under two growth type conditions.. .34 4.3.2 Effects of growth types on the performance of aerobic SBRs  43  4.3.3 The observation of microorganisms under the microscope  46  4.3.4 Correlation among TOC, B O D , and COD in brewery wastewater....50 5  4.4 Optimal conditions of HRT and loading rate in suspended growth SBR  51  4.4.1 Analysis of variance among the four reactors  51  4.4.2 Correlation between selected variables  53  4.4.3  Response surface analysis for the effects of HRT and loading rate on TOC removal  4.4.4  55  Response surface analysis for the effects of HRT and loading rate on SS removal  4.5  60  Track studies of pH, TOC, and dissolved oxygen vs aeration time in the suspended-growth aerobic SBR  65  4.5.1 The variation of reactors  65  4.5.2 The results of track studies  68  4.5.3 The relationship between TOC degradation and aeration time  69  4.5.4 Sludge production  75  Conclusions and recommendations 5.1  Conclusions  77  5.2  Recommendations  78  References  80  Appendix  85  vi  List of Tables Tables  Pages  1.1.  The general characteristics of brewery wastewater  3.1.  Apparatus required in the experiments  3.2.  Time courses of aerobic SBR under suspended-  3.3.  2 19  and attached-growth conditions  25  Factors in the factorial experiments  27  3.4. Experimental schedule of factorial experiments  27  3.5.  Sampling and analytical schedules for comparison of growth types  29  4.1.  Characteristics of brewery wastewater  31  4.2.  Correlation coefficients between studied variables in the experimental start-up....33  4.3.  Effects of HRT on the treatment efficiencies of aerobic SBR under suspended- and attached-growth conditions  4.4.  Summary of statistical analysis of HRT and loading rate effects on the performance of SBRs at two growth conditions  4.5.  38  41  Summary of the effects of growth types on B O D , COD, 5  and TOC removal  44  4.6.  Comparison of means from suspended- and attached-growth SBRs  44  4.7.  The ratios of B O D , COD, and TOC  50  4.8.  Correlation coefficient for the four reactors  52  4.9.  A N O V A for the four reactors in factorial experiments  52  5  4.10. Correlation coefficient and level of significance between variables in suspended-growth SBRs  54  vii  Tables  Pages  4.11. Summary of A N O V A in the factorial experiments  55  4.12. Response surface analysis of TOC for the effects of HRT and loading rate  56  4.13. The significance of TOC regression coefficient  58  4.14. Response surface analysis of SS removal for the effects of HRT and loading rate  61  4.15. The regression coefficient for the response surface of SS removalvs HRT vs loading rate  62  4.16. A N O V A the four reactors in the track study  67  4.17. The Tukey-test (LSD) of the four reactors in truck study  67  4.18. A N O V A for the effects of aeration time in the track study  72  4.19. The grouping of loading rate (based on the multiple-comparison)  72  4.20. Sludge production in the suspended-growth SBR  76  Vlll  List of Figures Figures  Pages  1.1.  Monthly monitoring of brewery wastewater  2.1.  The scheme of SBR operation  12  3.1.  Diagram of the reactors set-up  20  3.2.  The operation scheme of SBRs  22  3.3.  The photograph of a Ringlaces  24  4.1.  TOC removal vs loading rate  35  4.2.  TOC removal vs HRT  35  4.3.  B O D removal vs loading rate  37  4.4.  COD removal vs loading rate  37  4.5.  B O D removal vs HRT  39  4.6.  C O D removal vs HRT  39  4.7.  SS removal vs HRT  42  4.8.  SS removal vs the loading rate.  42  4.9.  Photograph of microbe taken from the suspended-growth SBR  47  5  5  4.10. Photograph of microbe taken from the attached-growth SBR  3  48  4.11. The response surface of TOC removal vs HRT vs loading rate in the suspended-growth SBR  59  4.12. The response surface of SS removal vs HRT vs loading rate in the suspended-growth SBR  63  4.13. Continuous monitoring of TOC vs aeration time in the four reactors  ix  66  Figures  Pages  4.14. The plots of TOC, DO, and pH vs aeration time in the suspended-growth SBR  70  4.15. TOC vs aeration time under different loading condition in reactor 2  71  4.16. The typical bacterial growth pattern in the pure culture  74  x  List of Abbreviations ANOVA:  Analysis of variance  BOD :  Biological oxygen demand in five days  COD:  Chemical oxygen demand  CORR:  Correlation analysis  DO:  Dissolved oxygen  LSD:  Least significant difference  MLSS:  Mixed liquor suspended solids  HRT:  Hydraulic retention time  SBR:  Sequencing batch reactor  SS:  Suspended solids  TKN:  Total kjeldahl nitrogen  TOC:  Total organic carbon  VSS:  Volatile suspended solids  VS:  Volatile solids  5  Acknowledgment  I would like to thank my committee members Dr. Richard Branion, Dr. Anthony Lau, and Dr. Victor Lo (my supervisor) for their support and guidance. I'd also like to give my thanks to Juergan Pehlke, Neil Jackson, and Dr. Ping Liao for helping me set-up the equipment, and to my fellow graduate students for their valuable advice. Mr. Tom Saunderes and Anh-long are also highly appreciated for their help to collect the wastewater. Many thanks must go to my husband Hong Qian and my parents (Xiehe Ling and Jiping Li) for their encouragement and support. Without their inspiration, I could not have completed this program.  xii  Introduction  1.1 General characteristics of brewery wastewater Brewery plants produce large quantities of highly polluting wastewater rich in organic substances. As the scale and production of the brewing industry increases, the amount of wastewater increases substantially, resulting in increasing pollution problems in the environment. Due to wide variations in its strength (in terms of COD, B O D , and 5  TOC), pH and the amount of wastewater discharged, brewery wastewater tends to be very difficult to treat. In view of this situation, there is a need to develop a technology which is capable of efficiently treating the increasing volumes and strength of wastewater from brewery plants. The wastewater discharged from breweries is generally a combined effluent comprising discharges from various sources within the plant. The fermented liquor is the final product in the brewing process. Wastes arise from the separation of grain residues, from spent-hops and yeast from the fermentation processes, from spillage, from possible spoilage of the beer, from fillers as well as from packaging and from washing wastewater. The wastewater production rates from the brewing and packaging sections vary independently of one another. While the packaging process produces a high flow, high pH, weak waste composed primarily of spilled beer and caustic bottle cleaning solutions, the brewing process produces a low flow, neutral pH, and high strength alcohol-carbohydrate-protein waste. A continuous monthly monitoring of the effluent from a brewery plant showed considerable variation in general wastewater characteristics in terms of biological oxygen  1  demand (BOD ), chemical oxygen demand (COD), and solids concentration. As 5  described in Table 1.1, total C O D varied from 87 mg/l to 6550mg/l, and the concentration of suspended solids varied from 16mg/l to 1162mg/l. The ratio of soluble BOD  5  to total BOD5 was about 0.91, which implied that most of the biodegradable  materials were in soluble forms. One important characteristic of brewery waste is its fluctuation in flow and quality at night and weekends, compared with the average working day flow. The fluctuations in the quantities of wastewater discharged from a local brewery is depicted in Figurel.l.  Table 1.1 The general characteristics of brewery wastewater. Total BOD5 Soluble BOD5 Total COD Soluble COD Total Suspended Solids Volatile Suspended Solids PH  41-4260 mg/l 34-3890 mg/l 87-6550 mg/l 37-4830 mg/l 16-1380 mg/l 11-1230 mg/l 6.1-9.1  The pH of the wastewater from various processes within the plant was neutralized in a pH tower within the plant. This ensured that the pH did not change significantly. Since brewery wastewater has a poor buffering capacity (Cronin, 1996; Cronin and Lo, 1998), hydrolysis and anaerobic activity usually reduce the pH. The pH tends to drop from 10 to 4 within a day at room temperature, and it will drop from 10 to 5 within 3-4 days in a walk-in cooler at temperature approximately 4 °C. Due to a preponderance of carbonaceous matter it tends to be relatively short of nitrogen-nutrients. Slight seasonal temperature variations in the wastewater ranged between 19 °C in the winter and 31.4 °C in the summer.  2  9000  9000 8000 ^  _J  7000 -I  O) 6000 e Q 5000 4000 JS 3000 O  H  2000 1000 0  10  15  20  25  Time (day)  Figure 1.1 Monthly monitoring of brewery wastewater  Data for the Figure 1.1 were obtained from a monthly continuous monitoring of brewery wastewater in a local brewery. Samples were collected randomly once a day. The sampling month was July, 1997.  3  1.2 Objectives The objectives of this study were: •  to start-up aerobic sequencing batch reactors for brewery wastewater treatment by using mixed culture activated sludge;  •  to compare treatment efficiencies of suspended-growth and attached-growth in the aerobic SBRs;  •  to investigate the effects of variations in loading rate and HRT on suspendedgrowth aerobic SBRs; and  •  to distinguish the relationships of T O C degradation, the concentration of dissolved oxygen (DO), and the pH with aeration time in suspended-growth SBRs.  4  Literature Review  2.1 Previous research on brewery wastewater treatment D u e to its h i g h organic content and h i g h b i o d e g r a d a b i l i t y , b r e w e r y wastewater is ideally  suited to b i o l o g i c a l treatment. A l l treatment methods b a s i c a l l y i n v o l v e the  c o n v e r s i o n b y m i c r o o r g a n i s m s o f f a i r l y c o m p l e x stable/unstable o r g a n i c c o m p o u n d s to c a r b o n d i o x i d e a n d water. B i o l o g i c a l treatment results i n the r e m o v a l o f B O D , the 5  c o a g u l a t i o n o f nonsettleable c o l l o i d a l s o l i d s , a n d the s t a b i l i z a t i o n o f o r g a n i c matter. M o s t o f the p r e v i o u s research i n v o l v i n g brewery wastewater treatment used anaerobic treatment systems.  2.1.1 Anaerobic processes in brewery wastewater treatment It has been w i d e l y r e c o g n i z e d that anaerobic treatment o f h i g h strength i n d u s t r i a l wastewaters those  c a n be c o m p e t i t i v e w i t h c o n v e n t i o n a l aerobic treatment processes. A m o n g  anaerobic  treatment  processes,  anaerobic  digestion,  i n particular, has been  suggested as a suitable process i n b r e w e r y wastewater treatment (Sax, 1985; Ince, et a l . , 1986; H u a n g , et a l . , 1989; L o et a l . , 1989; W a r e , et a l . , 1989; A n d e r s o n , 1 9 9 1 ; S t r o h w a l d , et a l , 1992; T a n e m u r a e t a l . , 1992; L i a n g , et a l . , 1993; C h u n g , et a l . , 1993; C r o n i n , 1 9 9 6 ) . T h e treatment o f b r e w e r y effluent b y the anaerobic d i g e s t i o n - ultrafiltration ( A D U F ) process has been studied o n a laboratory scale ( S t r o h w a l d , 1992). T h e results s h o w e d that C O D reductions o f 9 6 % - 9 9 % were possible at a l o a d i n g rate o f 15 k g C O D m - 3 . d - l a n d a h y d r a u l i c residence time o f 0.5-0.8 days. T h e C O D values o f the U F  5  permeate (final effluent) were generally below 100 mg/l for an 80 day test period. Since the brewery effluent showed a nitrogen deficiency, the addition of urea was found to result in more stable and improved digester performance. Tanemura et al. (1992) investigated the operation conditions for anaerobic treatment of wastewater  from  breweries, and they compared the efficiency of single- and double-anaerobic fluidizedbed reactors ( A F B R ) . They found that the double-AFBR process was more advantageous in obtaining treated effluent which could be discharged into rivers. The anaerobic pretreatment of brewery wastewater on an industrial scale has been reported by Sax (1985). A Biothane wastewater treatment system employing upflow anaerobic sludge blanket ( U A S B ) technology has been used and has been in nearly continuous operation at a brewery since late 1981. Soluble C O D removal efficiencies of about 90% are routinely achieved at volumetric loading capacities of 5 to 10 kg C O D per cubic meter of digester volume per day and a hydraulic retention time within the digester vessel of about 6 hours. The methane purity of the generated biogas approaches 80%, and the methane yield is close to the theoretical stoichiometric quantity of 0.35 cubic meter per kg of C O D removed. The system has been shown to perform consistently despite fluctuations in day-to-day C O D loading by nearly a factor of three. Normal anaerobic biomass growth within the digester occurs, and sludge losses due to washout are trivial. However, several problems appeared in this system; for example, filamentous bacteria were growing luxuriantly, and some ancillary equipment for odor control and upstream solids removal needed to be improved. The growth of filamentous bacteria was resolved by upstream  acidification to insure consumption of dissolved oxygen within  wastewater.  6  the  The anaerobic process potentially has many advantages. It produces methane gas which may be burnt as fuel resulting in the production of carbon dioxide and water. In addition, anaerobic fermentation produces far less sludge, than aerobic processes. Its wide applications has hindered by the inconvenience and difficulty of sufficiently intensifying the anaerobic process at ambient temperatures and the inability to adequately control the fermentation leading to methane formation. In addition, the resultant methane gas can be nauseating if leaked to the atmosphere. Furthermore, anaerobic treatment is generally considered as a pretreatment and usually requires post-treatment to meet effluent standards. In the specific case of the anaerobic treatment of brewery wastewater, the pH fluctuation, sludge bulking, and longer reaction times are among the problems encountered.  2.1.2 Aerobic treatment of brewery wastewater When the organic strength of a wastewater is not too high, conventional aerobic biological treatments are often a cost-effective form of treatment. In the case of brewery wastes, aerobic treatment has in the past proven to be successful on an industrial scale, as demonstrated by the deep shaft treatment system at Molson Brewery in Barrie, Ontario (Le Clair, 1984). This deep shaft process was capable of producing an effluent having an average TBOD5 and TSS less than 50 mg/l. It was claimed that the potential of deep shaft process would reduce energy and space requirements, have lower capital costs and reduced sludge production compared to conventional technology. However, the operation suffered from several mechanical problems such as the failure of the main downcomer section. In the case of a poorly flocculating sludge, an increased rotifer concentration and  7  nearly zero protozoa levels were seen during periods when yeast levels in the waste were high. Both protozoa and rotifer concentration dropped to low levels when beer levels in the waste were high. The high rate aerobic treatment of brewery wastewater using the Jet Loop reactor has been reported by Bloor et al. (1995). The use of a jet aeration system for the biological treatment of wastewater is becoming more commonplace as a means of combining efficient oxygen transfer with high turbulent mixing. In their studies, a loading rate of 50kg C O D / m / d was achieved with 97% C O D removal for a period of 5 weeks. 3  Although the settleability was found to be acceptable,  non-flocculating motile bacteria  caused the effluent to be cloudy and to have a high suspended solids concentration in the order of 200-350 mg/l. A Two-stage unitank system has also been developed for the treatment of brewery wastewater (Eyben, 1985). After a series of preliminary treatments including screening, grit-removal, no primary settlement, and eventually buffering, the wastewater is treated in a high-loaded combined aeration sedimentation stage. The BOD -reduction is about 805  85%. The partial purified water then flows by gravity to a second low-loaded combined aeration sedimentation stage where the residual B O D  5  is removal to obtain the high-  quality effluent resulting in more than 98% BOD -reduction. This two-stage unitank 5  system had better process performance in terms of high-treatment efficiency and control of sludge bulking. In addition it is a simple and reliable process and is easily controlled by microprocessor. Its flexible operation allows for temporary operation at half capacity and quick restoration to full capacity. It also allows for temporary operation as two highloaded one-stage systems (during periods of peak production or heavy rainfall) thereby  8  conserving a treatment efficiency of 80-85% BOD -reduction. Lower capital and 5  operating costs are also an advantage of the two-stage unitank system. Eyben (1995) also studied the use of the unitank system in the biological removal of nitrogen and phosphorus  from brewery waste water. They reported biological N and P removal  efficiencies of 90-99 and 97%, respectively, using this system. Sequencing batch reactor systems are receiving increasing use in the treatment of municipal, industrial and agricultural wastewater (Irvine and Busch, 1979; Lo et al., 1986). However, reports on the application of the SBR process to brewery wastewater are scarce. The performances of an SBR operated in the conventional mode and an SBR using an alternative mode called the contact-stabilization mode were compared in the treatment of brewery wastewater by Y u et al. (1997). The results showed that this new contact-stabilization operational mode, based on the concept of rapid uptake of organic matter by biomass in a short retention time and subsequent regeneration of biomass after decant, had no negative influence on organic material removal efficiency and biomass settleability. A new operating scheme for a three-tank SBR system was proposed in their study. This alternative scheme was able to expand the three-tank SBR system's capability of withstanding inflow variations.  2.1.3. Other treatment methods of brewery wastewater  As an alternative to the biological treatment of brewery effluent arising during the fermentation process, a recovery process for yeast and ethyl alcohol was analyzed in terms of its economic implications (Wysocki, 1973). Such an effluent can contain up to 16% yeast and 2.3% ethyl alcohol results in a BOD5 of 200 g/1. In economic terms, such a  9  recovery process for yeast and alcohol seems to be the most reasonable solution to this particular effluent problem. A n aerobic spore-forming Bacillus sp., isolated from a hot spring, was found to produce hydrolytic extracellular enzymes when cultured on opaque brewery wastewater supplemented with defatted soy, spent yeast, and malt flour (Zvauya, 1996). Fe (1974) reported on the efficiency of the biofiltration of brewery waste water treatment. Advantages claimed included high efficiency, low construction costs, fast start-up, insensitivity to environmental conditions, low space and personnel requirements, and production of an easily flocculated protein-rich sludge suitable for sale as animal feed. The treatability of high strength brewery wastewater with stabilized refuse was studied by Fan (1990). A column with a surface area of 790 cm and effective height of 2  105 cm was used for the study. The column was filled with stabilized refuse compacted to an average density of 500 kg/m . High strength brewery wastewater with a COD of 3  6000 mg/l was homogeneously trickled over the top of the refuse at flow rates of 8, 16, 24, and 36 1/day. After six month intensive study, it was demonstrated that the stabilized refuse method was effective in the treatment of the brewery wastewater. The C O D was reduced to as low as 60 mg/l after the wastewater had trickled through the 90 cm refuse layer which was equivalent to a removal efficiency of 99%. The variations in major parameters such as pH, alkalinity, and volatile fatty acids gave a strong indication that acidogenesis occurred quickly in the first 15 cm. As the flow rate increased, acidogenesis occurred deeper in the column and its recovery slowed. The oxidation reduction potential  10  (ORP) dropped to as low as -290 mV in the refuse column, indicating the anaerobic condition of the system (Fan, 1990).  2.2 Sequencing batch reactor The mass of contaminants present in domestic and industrial wastewater, in leachates and groundwater, and in soils generally varies with time and space. These natural and sometimes severe variations are coupled with the uncertainties associated with direct exposure to the environment. However, despite such unsteady-state behavior, facilities used for the removal of contaminants are often designed with the potentially unrealistic expectation that they can be operated as steady-state systems (Irvine et al., 1997). The SBR technology may be regarded as one of a number of methods which can be operated periodically and as a controlled unsteady-state system.  2.2.1 Operation of SBR An SBR biological treatment unit operates periodically in a typical cycle of five phases:  FILL  (inflow  of wastewater), R E A C T  (aeration), SETTLE  (quiescent  sedimentation of biomass and solids), D R A W (outflow of treated effluent) and IDLE. Figure 2.1 illustrates the scheme of a typical SBR process cycle. The filled phase and drawn phase are operated within a defined period of time. After completion of filled phase, variations in the influent of the treatment plant no longer have any effect on the process taking place in the reactor just filled. Before filling, the reactor contains an active and sizable microorganisms population which will biodegrade the influent wastewater. At start-up, microorganisms  11  W  aste  ( w h e n  sludge n e e d e d )  IDLE  FILL  DRAW  j Air REACT  SETTLE  Figure 2.1 The scheme of S B R operation.  must be seeded into the reactor from a suitable source. Once operating, however, the biomass remains in the reactor from cycle to cycle. The cyclic nature of the SBR process allows control over the dilution of operating conditions including the air supply and mixing, and it is thus possible to design a series of specific states in order to achieve a particular set of biochemical reactions on given waste materials.  2.2.2 The applications of SBR in wastewater treatment In recent years, SBRs have emerged as an innovative technology in the wastewater treatment systems. It has been found to be an efficient and flexible method for treating various dilute wastewater (Alleman et al., 1985; Decreon et al., 1985; Tarn et al., 1986; Imura, et al., 1993). Since SBRs are time-oriented, not space-oriented, fill/reaction ratios, aeration periods, and mixing cycles may be altered to accommodate specific operating conditions and to yield desired results. SBRs are therefore uniquely suited to wastewater treatment applications which are characterized by low and/or  intermittent flow conditions. Furthermore, advances have occurred in sludge bulking control technologies using selectors mechanisms. Because SBRs have the flexibility to incorporate many of these selectors mechanisms in their operation, they are also suited to applications under high organic/low nitrogen concentration conditions (Sheker et al., 1993). It has been reported that an SBR system, operated in a fill-and-draw mode under sequential anoxic/aerobic conditions in a single tank, yielded a high combined removal rate of organic carbon and nitrogen compounds (Fernandes et al., 1991, 1994). A n anoxic fill sequence, rich in exogenous organic carbon, favored denitrification and as a result oxidized nitrogen levels dropped. In the aerated react phase the ammonia accumulated during fill was oxidized to NO2-NO3-N. The nitrifiers were not inhibited by the anoxic operation. Some studies have also described SBR processes consisting of two or more tanks. The tanks were operated in a fill-and draw mode, which is the same as uni-tank system. One tank accepts the incoming wastewater while the others are in reaction, settling, drawdown, or idle phases. When the first tank is full, the incoming wastewater stream is diverted to a second tank which has been drawn and is in a standby phase ready to accept wastewater (Irvine et al., 1988; Ketchum et al., 1979). Ketchum et al. (1979) observed that a highly variable oxygen demand was exerted on an SBR system. They stated that the required aeration rate increased from a level needed for endogenous respiration in the standby phase, when the substrate concentration and liquid volume were both low, to a peak at the end of the filling cycle. During the reaction phase the required aeration rate  13  was dropped to a level needed for endogenous respiration and then shut off completely to allow settling and draw down to the minimum level needed to contain the settled solids. Novel approaches have also been developed based on sequencing batch reactor concepts. One was the sequencing batch biofilm reactor (SBBR) technology. Hirl and Irvine (1997) used anaerobic SBBR to dechlorinate reductively PCE (perchloroethylene). The A S B B R was a periodically operated up-flow packed column reactor. It was operated on a cycle consisting of three periods: FILL, REACT, and D R A W , and was constructed from glass columns filled with acid washed pea gravel as a support matrix. The consortium of microbes which can decholorinate was enriched by this A S B B R , and the reductive decholorination always occurred in the presence of methanogenesis. The efficiency of an SBR operation is also affected by factors such as nutrient levels, temperature, and fill strategies. It has been proven that temperature influenced nitrification and denitrification in anaerobic SBR (Fernandes, 1994; Schmit et al., 1994). It has been also proven that higher temperature exert a positive influence on the overall performance of the SBR in the range of 5-21 °C, and the process performance seriously deteriorated at 5 °C (Fernandes, 1994). The effects of anoxic and oxic fill strategies on SBR performance under nitrogen ( N H 4 C I as the nitrogen source) deficiency and rich conditions were evaluated using glucose as the sole substrate (Sheker, 1993). The performance was evaluated on the basis of substrate removal, sludge settleability, supernatant suspended solids, and reactor biomass concentration. Substrate removal efficiencies were found to be independent of the fill strategies adopted under all conditions tested. The incorporation of anoxic selector environment failed to prevent the development of bulking sludge under conditions of nitrogen deficiency, thereby resulting  14  in a gradual depletion of reactor biomass. Under nitrogen rich conditions, the sludge settleability improved significantly when an anoxic fill  strategy was  adopted.  Furthermore, suspended solids readings taken at the end of the settling period were greater with anoxic fill than with oxic fill, indicating that the latter discourages the growth of dispersed bacteria.  2.2.3 Advantages of an SBR system as a wastewater treatment Compared with continuous systems, SBR systems are more dynamic and flexible in terms of operation and more advantageous kinetically (Irvine et al., 1979, 1989, 1997). The SBR process covers a range from feast to famine during the reaction cycle and the different aerobic/anoxic/anaerobic conditions imposed. Since SBRs impose a diverse array of operating conditions and selective pressures, they can be used as a versatile tool for the enrichment of specific consortia and the induction of desired metabolic pathways. By adding the system's own periodicity of forcing function, the potentially negative impact of those forcing function associated with variations in contaminant concentration, and other environmental uncertainties, can be migrated (Irvine etal., 1997). Research concerning sequencing batch operations indicated that the SBR concept is a viable and economically attractive alternative to the conventional continuous flow activated-sludge process in B O D , SS and nitrogen removal, as well as in the chemical 5  precipitation of phosphorus. The dynamic and flexible nature of SBR systems allows ample room for expansion and operational adjustments at minimal costs.  15  The advantages of an SBR wastewater treatment system are summarized below: •  Less react volume because both aeration and settling are in the same tank;  •  Batch discharge of only treated wastes meeting effluent limitations (this is possible by monitoring the wastes and providing additional treatment if its quality is poor);  •  High oxygen transfer efficiency;  •  Facilitated design of a series of specific operating states;  •  Anaerobic periods enhance denitrification and nitrogen removal, control for filamentous organisms and reduce power consumption; and  •  Cost effective  16  Materials and Methods 3.1 Sources of brewery wastewater and activated sludge Brewery wastewater was collected weekly from a local brewery and stored in a cold room at 4 °C. The wastewater was allowed to reach ambient room temperature (20 ± 2 °C ) before being fed into the SBRs. A n acclimation period was provided for the microorganisms to adjust to the new environment. The characteristics of brewery wastewater are depicted in Section 4.1. A mixed culture activated sludge, taken from the municipal wastewater treatment pilot-plant at the University of British Columbia campus, was used as seed for all the SBRs. Before seeding the reactors, the mixed culture activated sludge was settled, and only the condensed sludge was used. The range of B O D of the activated sludge used to 5  seed the reactors was from 6.66 to 15.6 g/1, and the average of suspended solids was about 4.93 g/1.  3.2 Equipment Four lab-scale reactors made of acrylic plastic pipe, with 62 cm in height and 19 cm in inside diameter were used in these experiments. The total volume of each reactor was 15 1, and the working volume of each reactor was 12 1. A computer system with L A B T E C H Control software (Laboratory Technology Co., 1994) was used to control the sequencing cycle as well as to monitor the pH and dissolved oxygen concentration in the reactors. A PC-711 board was installed in the computer and connected with a relay box, which was linked to the pumps and aerators.  17  Signals coming from computer switched the pumps and aerator on and off. Other instruments used in this research are listed in Table 3.1. Ringlaces was selected to set up immobilized growth aerobic SBR due to its ability in rapid entrapment of microbial biomass. This Ringlace is a synthetic fibrous rope product with loops approximately 1.5 cm long protruding from the center all along the length of Ringlace. It is manufactured from polyvinylidene chloride fiber 100 microns in diameter. It was reported that the material is water resistant and chemically very stable. The fibers are knitted and twisted into individual strands. The flexible fibrous loops are supposed to provide a large surface area for the attached growth and in combination with the swaying motion of the flexible rope tend to improve shedding action to prevent clogging in the process (Setter, 1995). Two peristaltic pumps (each with four pump heads) were used to feed influent and withdraw effluent from the four reactors. Therefore, the same flow rate of feeding and discharging were carried out for the four reactors. Aeration was controlled by adjusting the aerator setting so that the air supply was kept at the same amount for these four reactors. The set-up of a suspended-growth reactor, and a reactor with Ringlace (attached-growth) is shown in Figure 3.1.  18  Table 3.1. Apparatus used in the experiments. Apparatus  Quantity  Description  Reactor  4  Acrylic plastic colume, 19 cm x 62 cm. Working volume: 12 1  Computer  1  386 I B M  Input/Output control card  1  PCL-711  Peristaltic pump  1  Cole-Parmer, 6-600 rpm  Peristaltic pump  1  Masterflex, 1-100 rpm, Model #661063  Pump speed controller  2  Masterflex, Model #7553-71, 50/60 Hz, 3 amp  DO probe  2  Oxyguard, PT4 system Inc.  DO meter  1  PT4 oxygen meter, PT4 system Inc.  pH probe  2  V W R scientific (Ag/AgCl), Cat. #34105023  pH meter  1  Good-Digital , 201 A T C  Aerator  2  Maxima/Optima, Rolf C. Hagen Inc.  19  (a) . Effluent pump (b) . Influent pump (c) . Control system (d) . Air stone (e) . Aerator (f) . Ringlace (g) . Reactor  (2)  (1)  Figure 3.1. Diagram of the reactor set-up: (1) a suspended-growth reactor; (2) a attached-growth reactor (i.e. reactor with Ringlace).  20  3.3 Experimental Design  3.3.1 The aerobic SBR start-up and operation scheme Four reactors were seeded with equal volumes of condensed activated sludge (2.5 1), and anoxically fed with brewery wastewater. The activated sludge was allowed to acclimate after innoculation in brewery wastewater for 3 to 4 weeks. Sludge retention time (SRT) was fixed at 21-28 days through the experiments. An anoxic fill strategy was adopted in order to prevent the development of bulking sludge (Sheker et al., 1993). The reactors were operated following the basic SBR operation scheme as described in Figure 3.2. Sequencing time length of cycles was set according to the purposes of the experiments. During the fill period, 4 1 of feed (brewery wastewater) was introduced to each of the reactor and the total working volume was brought from 8 to 12 1. Aeration was discontinued during the settle period, and sludge was allowed to settle under relatively quiescent conditions. In discharge stage, 4 1 of the clarified effluent was withdrawn and the liquid volume was decreased to 8 1. The idle period was set as a time to prepare and maintain the reactor for the next cycle. To study parameters related to the aerobic SBR start-up, two reactors were employed with the suspended-growth mode. One of them had a mixer installed and the other reactor was run without a mixer. The hydraulic retention time (HRT) was maintained at 1.56 days (including 12 hours for aeration, 20, 4, 3, and 3 minutes for settling, discharging, idle, and feeding time, respectively) throughout the start-up stage.  21  Influent (4 1) Waste sludge (when needed)  IDLE (3 min)  FILL (3 min, anoxic)  REACT (4-48 hrs)  DRAW (4 min)  SETTLE (20 min)  Effluent (4 1) Working volume: 12 1 SRT: 21-27 days  Figure 3.2 The operation scheme of SBR.  22  3.3.2 Studies on comparison of treatment efficiencies under suspended-growth a n d attached-growth conditions  In this study, two of the four reactors were used for suspended-growth, and the other two reactors were used for attached-growth. To set-up the attached-growth reactors, precisely tensioned strands of Ringlace, 5 cm apart, were attached between two horizontal plastic support rods. The support rods were then affixed to rigid frames installed in the reactors. The support rods were also spaced 5 cm apart, center to center, thus creating a matrix of Ringlace strands. Figure 3.3 is a photograph showing the set-up of Ringlace media. The operations of these reactors were the same as those of the suspended growth reactors. From our literature review and preliminary experiments, we found that the performance of these aerobic SBRs may be limited by factors such as inadequate oxygen transfer, settling of biomass, stability under different loadings, and hydraulic retention time. In this study, the HRT and loading rates were varied over a wide range of wastewater concentrations. Experiments were carried out with HRTs over a range of 0.56, 0.81, 1.06, 1.56, 3.06, and 6.06 days (Table 3.2). During these experiments, the sequencing cycles were adjusted according to the changes of aeration time, but the time for FEED, SETTLE, DRAW, and IDLE, was fixed at 3, 20, 4, and 3 minutes, respectively. Therefore, the difference of HRT was mainly due to the aeration time, and the time courses of the other stages had no effects on HRT.  23  Figure 3.3 The photograph of a Ringlace.  24  Due to the characteristics of the raw wastewater, variations of the influent concentration under each HRT would result in changes of the loading rate. All other experimental parameters, such as anoxic feeding, mean cell residence time (MCRT), influent and effluent flow rates, were maintained the same way in both suspended-growth and attached-growth reactors. The operations of the SBR were the same as described in Section 3.3.1.  Table 3.2  Time courses of aerobic SBR under suspended growth and immobilized growth condition.  Run#  Aeration  Settling  Discharge  Idle time Fill time HRT  time (hrs)  time (min)  time (min)  (min)  (min)  (day)  #1  48  20  4  3  3  6.06  #2  24  20  4  3  3  3.06  #3  12  20  4  3  3  1.56  #4  8  20  4  3  3  1.06  #5  6  20  4  3  3  0.81  #6  4  20  4  3  3  0.56  Experiments progressed from the longest HRT to the shortest HRT, and each of the HRTs was continuously run at least 5 cycles (i.e. replication 5 times). When conducting shorter HRT runs (HRT at 0.56, 0.81, and 1.06 days), a time interval of 2-5 days was given between the change of each HRT. If the organic contents were not  25  completely degraded under a shorter HRT, the microorganisms would continue to utilize the remaining nutrients. The given time interval was to minimize the effects of interactions among HRTs. HRT was calculated by the following equation:  HRT = V/Q  (3.1)  where, V represents the working volume of reactor, which was 12 1 in this study; and Q is the influent flowrate, which was calculated by: Q = 24/cycle time a day. The loading rate was calculated by:  Loading rate = Concentration of wastewater x Q  (3.2)  Where, the concentration of wastewater could be any of the parameters analyzed (TOC, B O D , COD, and SS). 5  3.3.3 Determination of optimal conditions of HRT and loading rate under suspended-growth condition Factorial experiments were performed, with HRT and loading rate being two factors studied (Table 3.3). Three levels of HRT were used based on the previous experimental results (results from comparison of efficiencies of suspended growth and immobilized growth). Loading rates were mainly based on the different batches of wastewater  26  Table 3.3 Factors in the factorial experiments. Aeration time (hr) 4  8  16  Factors  HRT (day) 0.56 (00  1.06 (02)  '2.06 (0 )  G xC  0 xC  Concentration of  High (C )  6ixC  wastewater (TOC)  Low (CO  0i x C i  2  2  2  3  3  2  2  03 x C ,  0 xC, 2  Table 3.4 Experimental schedules of factorial experiments. Reactor Run  1  2  3  4  1  0i x C i  0 xCi  0ixC  2  0 xC  2  2  03 x Q  0, x C ,  0 xC  2  0ixC  2  3  0ixC  2  e xc  0i x C ,  03 x C ,  4  0 xC  2  2  03 xC,  0, x C ,  5  0 xCi  0 xCi  02 xC,  0 xCi  6  0 xC  0 xC  0 xC  0 xC  3  3  3  Gix C  2  2  3  2  2  2  2  2  2  •  0i =0.56 days ;0 = 1.06 days; 0 = 2.06 days;  •  C i = Low loading rate; C = High loading rate.  2  3  2  27  2  3  2  2  2  collected. As shown in Table 3.3, "Low" concentration (TOC) of wastewater was obtained by diluting raw brewery wastewater with tap water. "High" concentration of wastewater was the original brewery wastewater. Experimental schedules are given in Table 3.4. Start-up of the aerobic SBRs in this study was achieved by seeding the four reactors with equal volume of activated sludge acclimated by brewery wastewater. The operation of the SBR was the same as described in Section 3.3.1. A complete factorial experiment was replicated 4 times (4 replicates).  3.3.4 T r a c k studies of p H , T O C , a n d dissolved oxygen vs aeration time i n suspended-growth S B R s  In this study, four reactors acted as four replications for each run. Before starting sampling, the reactors were reseeded, and activated sludge was acclimated by growing in brewery wastewater for a week. The operation of SBR was primarily the same as in Section 3.3.1, except for oxic feeding. Sampling was started from the first minute of feeding, and the time interval was 30 minutes. The aeration setting was fixed, and it allowed a dissolved oxygen level of 2.5-3 mg/l. Dissolved oxygen concentration was read by directly put the DO probes into the reactors.  3.4 S a m p l i n g a n d analytical methods  Influent, effluent, and sludge samples were taken for each run, and analyzed for TOC, BOD5, COD, total solids, suspended solids, volatile solids (VS), suspended volatile solids (VSS) according to the Standard Methods (APHA, 1995). Total Kjeldahl  28  nitrogen(TKN),  ammonia  nitrogen  orthophosphorus  (orthol-P) were  (NH -N),  nitrate  3  determined  nitrogen  periodically  using  (NO3-N), a  and  autoanalyzer  (Technicon) (Appendix table A-10). To study microbial populations under suspended and attached-growth conditions, samples were taken periodically to examine the quantitative change of the microbial population under a microscope, in order to estimate the dominant and sub-dominant microbes.  Table 3.5 Sampling and analytical schedules for comparison of growth types. Growth type  TOC  COD  BOD5  SS  VSS  Suspended  2x4*  2x3  2x2  2x4  2x4  Attached  2x4  2x3  2x2  2x4  2x4  *: Analytical replication x sampling time  3.5 Data analysis Statistical analyses were conducted by using the SAS software package (Anon, 1988). Correlation analysis was used to determine significance of relationships between variables (using the Pearson product-moment correlation, SAS procedure CORR). Statistical comparison of the results from suspended-growth and attached growth was performed by analysis of variance (ANOVA) and r-test (TTEST) was applied to detect the significance of differences between compared means. The response surface regression (RSREG) procedure was employed. The R S R E G procedure fits the parameters of a complete quadratic response surface and then  29  determine critical values to optimize the response with respect to the factors in the model. Many experiments were conducted to discover which factor values optimized a response. If a factor variable is measured at three or more values, a quadratic response surface can be estimated by least-square regression. The predicted optimal value can be found from the estimated surface if the surface is shaped appropriately. As mentioned in Section 3.3.3, two factors were selected and each of them had three (for HRT) or more (for loading rate) levels. Unless stated otherwise, the level of significance used throughout these studies was set at p < 0.05, and the results of data analysis of means were reported as Mean ± SD.  30  Results and Discussion  4.1 Characteristics of brewery wastewater Characteristics of the wastewater used in the experiments are summarized in Table 4.1. The wastewater, which was collected from a local brewery, was continuously discharged from various sources within the plant. The composition of the wastewater was typical of brewery wastewater which contained spent-grain, dead (or small amounts of live) yeast, spilled beer from fillers and packaging, and washing wastewater. The amount of wastewater discharged changed both diurnally and seasonally (Figure 1.1). This indicated that there were wide variations in the strength of the wastewater discharged, as shown in Table 4.1. These variations would undoubtedly affect the performance of treatment systems.  Table 4.1 Characteristics of brewery wastewater. Parameter  Range of concentration  TOC  677-1720 ppm  BOD  5  671-4200 mg/l  COD  1038-4524 mg/l  TSS  450-1044 mg/l  TP  6.3-56 mg/l  Orthol-P  2-60 mg/l  TKN  28-343 mg/l  NH -N  0-4 mg/l  pH  6.1-9.5  3  Even though the inorganic nitrogen-nutrients were very low in the brewery wastewater (NH3-N being around 0-4 mg/l), the nitrogen-nutrient was not a limiting nutrient, because the average T K N of mixed wastewater was about 343 mg/l. This average of T K N was higher than that of the supernatant wastewater (after solids settlement), which was about 34 mg/l. This is due to the spent grain and dead (or small amount of alive) yeast from fermentation contained in the solids contents of the wastewater. This suggested that most of the nitrogen-nutrient was in organic forms. Orthol-phosphate and total phosphate were sufficient for microbial growth. It has been reported that a suitable ratio of BOD:N:P is 160:4:1 for aerobic brewery wastewater treatment (Smith, 1986). Obviously, this ratio was attained in our experiments, and it was not necessary to add nitrogen-nutrients or phosphorus-nutrients to the reactors.  4.2 The start-up of SBRs During the reactor start-up, the deterioration of biomass was observed. It was caused by fed with influent containing wastewater with low levels of organic content (BOD being about 864mg/l) from the washing process. When these conditions pertained, 5  sludge settling was poor and effluent suspended solids removal was lower than 75%. This suggests that the reactors would need to be re-seeded with fresh activated sludge in order to promote the recovery of biomass in the reactors. This would in turn affect the treatment efficiency of the SBR. The correlation coefficients for the variables, which includes the effect of mixer, mixed liquor suspended solids (MLSS), and activated sludge concentration, clearly  32  indicate the importance of MLSS and activated sludge concentration for the performance of the reactors. As shown in Table 4.2, the correlation coefficient of M L S S and activated sludge concentration to B O D  5  removal was 0.887 and 0.853, respectively. It is  understandable why the amount of MLSS and activated sludge were strongly correlated with BOD5 removal and with reactor performance. Since SBR start-up is the process of biomass acclimating and accumulating, low concentrations of activated sludge and M L S S would lead to the biomass being washed out. As a result of insufficient biomass inside the reactor, the decomposition of organic compounds would not be achieved efficiently and therefore reactor performance would be poor.  Table 4.2. Correlation coefficients between studied variables (the upper value is the correlation coefficient, and the lower symbol represents the level of significance). Variable  Mixing  MLSS  Act.sludge  BOD  5  Concen. MLSS  0.000 n.s.  Act.sludge  0.000 n.s. 0.125  BOD5  n.s. Removal  -0.053 n.s.  ***p  0.958 *** -0.774 ***  -0.834 ***  0.887 ***  0.853 ***  -0.768 ***  < 0.001, n.s. = not significant (p > 0.05).  The results from correlation analysis revealed no correlation between the function of the mixer and reactor performance; the correlation coefficient of the mixing effect and  33  B O D removal was -0.053. This suggests that the reactors could be run without using a 5  mixer. In order to verify this suggestion, an additional t-test was conducted to compare the mean values of B O D removal from a reactor with a mixer and from a reactor without 5  a mixer. As expected, results of the t-test demonstrated that the difference in performance between the reactor with mixer and the reactor without mixer was not significant (F = 1.17, p = 0.794). It seemed that sufficient mixing could be achieved inside the reactors by the force of aeration. A higher air flow rate (> 4 1/min) was set after the mixer was removed. This resulted in the disruption of sludge particles. A large amount of sludge in a fine particle form was suspended during the aeration and failed to settle in the serttling stage. Under these conditions, the effluent SS removal was about zero. The reactors were then reseeded with acclimated sludge and air flow rate was reduced to 2.5-3 1/min. This aeration rate was then retained throughout the subsequent experiments. After the sludge had built-up in the reactors, the operation of SBRs attained a quasi-steady state. This was distinguished by a consistent concentration of TOC in the effluent and the visual observation of healthy sludge conditions in the reactors.  4.3 Comparison of the performance of suspended-growth and attached-growth aerobic SBRs 4.3.1 The effects of HRT and loading rate under two types of growth conditions Figure 4.1 shows the percentage removal of TOC influent brewery wastewater for different loading rates and under conventional suspended-growth and attached-growth biofilm conditions.  34  ioo ^  —«•  96 92 88 H  4  84 80 H  Suspended-growth Attached-growth  76 72  8  0  12  16  20  Loading rate (g/l/day) Figure 4.1 TOC removal vs loading rate.  100 96  ^>—r  92 88  /  84 80 H  •  76  A  Suspended-growth Attached-growth  72 0  3  4  HRT (day) Figure 4.2 TOC removal vs HRT.  35  As shown in Figure 4.1, the TOC removal trends in suspended-growth conditions differed from that in attached-growth conditions. When the loading rate was about or below 10 g/l/day, the overall percentage of TOC removal attained was over 90% under both growth conditions. The TOC percentage removal decreased in the attached-growth reactors as the loading rate increased. However, little change was detected in suspendedgrowth reactors in term of TOC removal at different loading rates. The effects of HRT on the performance of the reactors under different growth conditions are shown in Figure 4.2. The TOC removal trends as a function of H R T in suspended-growth were also different from that in attached-growth reactors. The effects of HRT on TOC removal in suspended-growth conditions were not as significant as they were under attached-growth conditions. Under attached-growth conditions, the TOC percentage removal increased with increasing HRT until the latter reached a certain point (within 2-3 days of HRT as shown in Figure 4.2). After that point, TOC removal levelled out with increasing HRT. The experimental results of the effects of HRT on the treatment efficiencies are summarized in Table 4.3. Parallel to the TOC analysis, B O D and C O D analyses were conducted for these 5  same samplings. Similar trends were found for the effects of HRT and loading rate on B O D and COD percentage removals. s  Figure 4.3 displays BOD5 removal as a function of loading rate, and Figure 4.4 plots C O D removal vs loading rate. Comparison of these two figures with Figure 4.1 reveals a general similarity. TOC, B O D and COD removal decreased as the loading rate 5  36  1 >•  a—m-  •  f-r-  j1  i _  £  T  X  f  !  96 j \  • A  2  Suspended-growth Attached-growth  4  6  8  10  12  14  16  18  20  Loading rate (g/l/day) Figure 4.3 B O D 5 removal vs loading rate.  a O O  80 H 75  Suspended-growth Attached-growth  70 10  20  30  40  50  60  Loading rate (g/l/day)  Figure 4.4 COD removal vs loading rate.  37  70  Table 4.3 Effects of HRT on the treatment efficiencies of aerobic SBR under suspended-growth and attached-growth conditions. HRT  Factor Influent (mg/l)  (day)  Sampling No.  Effluent (mg/l) Suspended  Percentage removal  Attached  Suspended  Attached  0.56 TOC  896.8±14.13  16 23.1+4.6  164.1±14.5  0.97+0.00  0.82+0.01  COD  2837±317.85  12 61.53+17.81  551.4+55.01  0.98+0.01  0.81+0.01  929.5±88.39  8 10.92±1.41  98.43±8.84  0.99+0.00  0.89+0.02  585±183.85  16 10.78+3.55  140.28+21.66  0.98+0.01  0.74±0.09  852.3±120.00  16 27.57±6.17  108.61±18.60  0.97+0.00  0.87+0.01  2449.3±439.83  12 66.3+20.94  273.3±70.13  0.96+0.02  0.84±0.04  43.81±26.69  0.97+0.02  0.96+0.01  BOD  5  SS 0.81 TOC COD BOD  5  SS  1018.0+490.73  8 36.30+33.67  597.5±17.68  16 9.91+3.83  100.7±25.23  0.98+0.01  0.83+0.04  905±62.00  16 32.55+31.07  79.17+18.81  0.96+0.03  0.91+0.02  COD  2853.3+661.99  12 89.43+81.08  223.5±124.9  0.97+0.03  0.93+0.03  BOD5  1548.0+483.66  8 20.30+28.34  43.12±12.29  0.99+0.01  0.97+0.01  SS  706.3+249.04  16 25.03+37.95  128.3+58.83  0.97+0.04  0.80+0.11  904.3±122.83  16 37.12+28.77  63.46±13.58  0.96+0.03  0.920+.01  2962.3±1841.9  12 142.2+112.0  236.9±135.1  0.94+0.03  0.89+0.03  12.07+5.17  1.00+0.00  0.99+0.01  1.06 TOC  1.56 TOC COD BOD  5  SS 3.06 TOC COD BOD  5  1327.5+354.97  8 0.53±1.13  638.7±292.82  16 18.88±21.48  72.63±42.78  0.97+0.02  0.87+0.07  965.5±0.577  16 34.81+18.34  63.3±8.81  0.96+0.02  0.93±0.01  2493.7+64.66  12 44.47±60.21  128.21±61.16  0.98+0.02  0.95±0.03  1237.5±180.31  8 3.34±3.21  12.83+4.72  1.00+0.00  0.99+0.00  1044  16 41.44±38.36  54.25+39.8  0.96+0.04  0.95+0.05  966.5±20.23  16 27.23±7.90  58.09+3.14  0.970.0+1  0.94+0.00  COD  2359.3±222.86  12 21.18+25.91  104.3+51.16  0.99+0.01  0.95+0.03  BOD5  1489.0±154.15  8 10.33±7.67  10.27+7.88  0.99+0.01  0.99+0.00  SS  1044  16 30.81+12.08  33.69+14.48  0.97+0.01  0.97+0.01  SS 6.06 TOC  38  i  1  • ±  3  Suspended-growth Attached-growth  4  HRT (day) Figure  4.5 B O D 5  removal vs HRT.  100 H  75 4 0  1  1  1  1  2  3  , 4  , 5  HRT (day) Figure 4.6 COD removal vs HRT.  39  , 6  1 7  increased in the attached-growth reactors, while in the suspended-growth reactor, the changes of loading rate were not reflected in changes in TOC, B O D , and COD removal. 5  COD removal was more sensitive to the effects of loading rate in both types of growth conditions than were B O D and TOC removal. A linear decrease of COD removal was 5  seen in attached-growth SBRs as loading rate increased (Figure 4.4). Figure 4.5 and Figure 4.6 show B O D and COD removal as a function of HRT. 5  As HRT increased, the COD removal in the attached-growth SBRs increased. However, it could never reach the same level as that in the suspended-growth SBRs. On the other hand, it appears possible for B O D removal to be increased to the same levels for both 5  growth regimes if the HRT was longer than 3 days. Based on the above results, it was inferred that the effect of HRT was more pronounced than that of loading rate on the performance of an aerobic SBR. This could be attributed to the fact that loading rate is determined by either the wastewater concentration or the influent flow rate, and HRT is related to loading rate by the influent flow rate (see Equation 3.1 and Equation 3.2). This inference was proven by the following results of statistical analysis. Table 4.4 contains the statistical results of HRT and loading rate effects on T O C percentage removal. Both HRT and loading rate had significant effects (at 90% confidence level). The effect of HRT was more sensitive to the growth regime than was the effect of changes in the loading rate. The effects of both HRT and loading rate on suspended solids removal were generally similar to those of B O D , TOC, and COD. The percentage removal of 5  40  suspended solids decreased slightly as HRT increased in suspended-growth reactors (Figure 4.7). Increased HRT facilitated solid removal in the attached-growth reactors but longer HRT (particularly over 4 days) would not stimulate higher solid removal as shown in Figure 4.7. As would be expected, suspended solids removal decreased as loading rate increased in the attached-growth reactors, and it remained at nearly the same levels in the suspended-growth reactors (Figure 4.8).  Table 4.4. Summary of statistical analysis of HRT and loading rate effects on the performance of SBRs under different growth conditions. Variable Effects (TOC)  Suspended-growth  Attached-growth  F value  p value  F value  p value  HRT  1.89  0.10*  239.4  0.000***  Loading rate  3.21  0.000***  3.14  0.001***  Level of significance is 0.1. *p<0.1, ***/?<0.001.  It was known that the influent wastewater contained rather high levels of both organic carbon-nutrients and nitrogen-nutrients. Microbial activity degraded nutrients inside the reactors and available nutrients were exhausted as the HRT increased. The depletion of nutrients led to sludge bulking and poor sludge settling. Suspended solids removal therefore decreased, as shown in Figure 4.7. Experimental results also revealed that a portion of the suspended solids could be removed by attachment to the Ringlace in the attached-growth reactors.  41  100 -f  Jt  95 90 85  «3  > O  80 H  E o i—  75  CO CO  70 H  •  65  Suspended-growth Attached-growth  A  60 3  0  4  HRT (day) Figure 4.7 SS removal vs HRT.  100 -I 95 90 re > o •E <D  85 -  CO CO  75  4  80 -  i—  70  •  Susoended-growth Attached-growth  A  65 60  -i  2  r  -  4  6  8  10  12  14  Loading rate (g/l/day) Figure 4.8 SS removal vs the loading rate.  42  16  4.3.2 Effects of growth types on the performance of aerobic SBRs The results of these experimental studies have demonstrated that the aerobic SBR is able to achieve a high level reduction in the levels of polluting components in brewery wastewater. The removal of TOC, B O D , and COD was over 90% in both the suspended5  growth reactors and the attached-growth reactors (as shown in Table 4.5). Statistical analysis demonstrated that the effect of the two growth type regimes on the performance of SBR was significantly different. Comparison of the treatment efficiencies revealed that the performance of the suspended-growth SBRs was significantly higher than that of the attached-growth SBRs (Table 4.6). In general, the brewery wastewater used in this study contained soluble, colloidal, and settleable organic materials. These organic materials can be removed by direct assimilation, adsorption, flocculation and coagulation, and settling. Thus there was rapid removal of the organic materials and a sharp drop of concentrations of TOC, B O D and 5  COD from the wastewater within reactors. Low molecular weight soluble, organic compounds can be assimilated directly by microbial cells using active, facilitated, and passive transport mechanisms. Large colloidal particles are also susceptible to removal by surface phenomena. Particles removed by flocculation and coagulation are expected to include cells, cell fragments, viruses, lipid micelles and other organic debris. The rapid removal of soluble materials arose for several reasons. Higher rates of molecular diffusion and enzyme specificity at  43  Table 4.5. The summary of the effects of growth types on B O D , COD, and T O C 5  removal. Percentage removal  Influent  Effluent concentration  Susupended-  Attached-  concentration  Suspended-  Attached-  growth.  growth  growth  growth  0.97±0.02  0.90±0.05  677-984 ppm  30.4  89.46  0.99±0.01  0.97±0.04  671-1890 mg/l  13.62  36.75  COD  0.97±0.03  0.9±0.06  1038-4709 mg/l  70.85  252.94  SS  0.97±0.02  0.86±0.1  450-1044 mg/l  22.81  88.30  TOC BOD  5  Table 4.6. Comparisons for the means of TOC, BOD5, COD, and SS from suspended-growth and attached-growth reactors (f-test). df  F value  p value  TOC  (95, 95)  5.19  0.0000  BOD5  (47,47)  6.64  0.0000  COD  (71,71)  4.86  0.0000  Suspended Solids  (95,95)  17.81  0.0000  44  least partly resulted in the rapid removal. Molecules taken into the cells may then be channeled into both anabolic and catabolic pathways, producing new cellular materials while providing energy for synthesis and other microbial activity. Macromolecules too large to be directly assimilated are likely to be removed from solution prior to enzymatic attack and further metabolism by adsorption phenomena on the surface in the pore spaces of biological floes (Yu et al., 1997). The significant difference in the results between the two growth types may be related to the oxygen transfer efficiency and the configuration differences between the reactors. Y u et al. (1997), using SBRs to treat brewery wastewater, observed that the microorganism in SBRs utilized the accumulated substrates at a very high rate when air was added.  Under suspended-growth conditions, the oxygen was efficiently used  resulting in healthy microbial growth. Under attached-growth conditions, the metabolic efficiency would be lower because the microbes attached to the Ringlace (the diameter of attached sludge floe was about 1.5-3 cm), and the inner layer could not access sufficient oxygen. In suspended-growth SBRs, sludge particles had an equal chance to come into contact with the nutrients, and substrates could therefore be utilized at maximum efficiency given sufficient aeration and mixing. While the attached-growth systems involved solid supports media (Ringlace) on which biomass developed, a large specific surface area of Ringlace would increase the amount of attached biomass. The mixed liquor contacted the outermost surface of the biomass layer. The nutrients required for life inside that layer were obtained by diffusion into the surface from the mixing liquor  45  flowing past (Barnes et al., 1983). In addition, mixing conditions in the attached-growth reactors were not as good as in the suspended-growth reactors, due to obstruction by the biomass attached to the Ringlace in the attached-growth SBRs. The utilization of nutrients was therefore less efficient in the attached-growth reactors than in the suspended-growth reactors. The experimental results from this study show that only slight changes occurred in the suspended-growth SBRs with variations in HRT and loading rate. This is in accordance with the properties of SBRs. The SBR provides for a diverse array of operating conditions and selective pressures and can thus become a versatile tool for the enrichment of specific consortia and induction of a desired metabolic pathway. By adding the system's own periodicity or forcing function, the potentially negative impact of those forcing functions associated with variations in composition and concentration of wastewater, operation time, and other factors can be mitigated (Irvine et al., 1997).  4.3.3 Observation of microorganisms by microscope The observations of microbial populations by microscopy demonstrated that the populations consisted mainly of healthy floe-forming bacteria under suspended-growth conditions (Figure 4.9), while under attached-growth conditions, filamentous microbial forms were dominant in the reactors (figure 4.10). The luxuriant growth of filamentous organisms was associated with the notorious condition known as "bulking" in which the sludge is difficult to separate from the treatment effluent by settlement. These phenomena were also noted when the reactors were loaded with highly concentrated wastewater or  46  Figure 4.9 The photograph of microbe taken from suspended-growth reactor (100X).  47  Figure 4.10 The photograph of microbe taken from attached-growth reactor (100X).  48  run at a shorter HRT under attached-growth conditions. As seen in Table 4.3, the SS removal was about 74% at 0.56 days of HRT. Bacteria, algae, ciliated protozoa/rotifer, and worms that were commonly found in domestic wastewater treatment processes were observed in both growth regimes. A n effort was made to estimate the quantitative changes in the microbial species. Even though the results failed to be statistically convincing, these observations will be useful for further studies. The quantitative changes of certain microbial species were mainly determined by the environmental conditions such as nutrients, pH, temperature, light, and oxygen. It was noted that there were generally more worms growing in the attachedgrowth reactors than in the suspended-growth reactors. However, excessive amounts of roundworms were found in the suspended-growth reactors when they  were run at a  longer HRT and over aeration was used. It was suspected that the depletion of nutrients was one of the reasons for the growth of the worms. In addition, one experiment has found that fluctuations in dissolved oxygen levels appeared to affect worm growth; an increase in the dissolved oxygen concentration stimulated the propagation of worms (Setter, 1995). Red color roundworms were mostly located on the upper part of reactors where the oxygen concentration is higher than in the lower levels. Some species of rotifer grew in the suspended-growth reactors. Rotifers are very effective in consuming dispersed and bacteria in small floes. Their presence in the effluent may indicate a highly efficient aerobic biological purification process.  49  4.3.4 Correlation among TOC, BOD , and COD 5  Establishment of the constant relationship among the various measures of organic content depends primarily on the nature of the wastewater and its source. Table 4.7 listed the ratios of TOC, B O D , and COD. The ratios of influent were calculated based on the 5  average values of TOC, B O D , and COD from the measures of raw wastewater collected, 5  and the ratios of effluent were calculated based on the average values of TOC, B O D , and 5  COD from the treated effluent. BOD5/COD is a good indicator of biodegradability of wastewater. The average ratio of B O D / C O D in the influent was 0.58, which indicated 5  that 58% of materials the influent wastewater were biodegradable. After treated by aerobic SBRs, the average ratio of BOD5/COD in the effluent dropped to 0.15. This value indicated that there was little biodegradable matter left. The accumulation of microbial metabolic products and non-biodegradable materials decreased the B O D as well as the 5  BOD5/COD ratio. It should be noted that the ratios of effluent vary considerably with the degree of treatment that the wastewater has undergone, therefore, the ratios listed here were relative values, and should not be used else where.  Table 4.7 The ratios of TOC, B O D , and COD. 5  TOC/BOD5  TOC/COD  BOD /COD  Raw wastewater  0.78  0.44  0.58  Effluent  4.86  0.48  0.15  50  5  Since the measurements of TOC were simple and had a higher precision than the BOD  5  and C O D measurements, only the TOC of the samples was analyzed in the  following experiments, Estimation of B O D and COD were made based on the initially 5  determined ratios of T O C / B O D and TOC/COD. 5  4.4 Optimal conditions of HRT and loading rate in suspended-growth SBR  4.4.1 The analysis of variances among four reactors Four suspended-growth reactors were run under identical conditions for about 10 days before factorial experiments were started. It is supposed that the sludge conditions in these four reactors were the same. The pH fluctuated between 6-8 and was monitored periodically. The correlation coefficients of the four reactors are listed in Table 4.8. The purpose of this correlation analysis was to analyze the consistency of the measured values from the four different reactors for the same variables. The null hypothesis was that there is no difference between the four reactors (a = 0.05). The results showed that the highest correlation coefficient between reactors was 0.76911, which was between reactor 2 and reactor 4, with p = 0.0001. The lowest correlation coefficient was 0.30698, which was between reactor 3 and reactor 1, and its probability was 0.0338. Thus, it was concluded that there was no significant difference among the four reactors (Table 4.8).  51  Table 4.8 Pearson correlation coefficient of the four reactors (the upper value is the correlation coefficient, and the low symbol represents the level of significance). Reactor 1 Reactor 2  Reactor 2  Reactor 3  0.515 ***  Reactor 3  Reactor 4  0.307  0.677  *  ***  0.740  0.769  0.613  ***  ***  *p < 0.05, **p < 0.01, ***p < 0.001.  Table 4.9 The A N O V A for the four reactors Sources of variance  Reactors  Degree of freedom  3  Sum of Squares  0.01483996  Mean Square  0.00494665  F value  1.52  Pr>F  0.2105  52  Experiments were performed in these four reactors, and each of the pair-wise combination of two factors was assigned to one of the reactors as randomly as possible. The A N O V A was performed to analyze the variance of the reactors, and results are listed in Table 4.9. With F = 1.52, and the significance probability value associated with this F value 0.2105, the conclusion drawn above was confirmed. That is, the variances among the reactors were not statistically significant. Based on the above conclusion, the variations among the four reactors could be ignored. The results from the four reactors could be treated as replicates under their corresponding experimental conditions according to the following analysis.  4.4.2 Correlation between variables The effects of different variables on the values of TOC removal were tested, and the results were described in the following Table 4.10. A N O V A was used to determine the significance of these variables (Table 4.11). As shown in the results (Table 4.10 and 4.11), samplings were not correlated with TOC removal, nor was the variance in samplings significant (a = 0.05). Even though the Pearson correlation analysis showed that the correlation coefficient between replication and TOC removal was not significant, A N O V A indicated a slight significance in variances of replications at (p - 0.102). T O C removal had a positive correlation with HRT, but had a negative correlation with loading rate and the concentration of influent. Thus, particular attention was paid to the relative dominance of HRT and loading rate effects. The HRT and loading rate were strongly correlated (r = -0.811). The relationship between HRT and loading rate can be described by Equation 3.2.  53  Table 4.10 Correlation coefficient (upper row) and level of significance (lower row) between variables under suspended-growth conditions Variable  Replication  HRT  0.000  HRT  Loading  Concentration  Sample  n.s. Loading  Concen  Sample  Removal  -0.003  -0.811  n.s.  ***  0.0195  0.053  0.427  n.s.  n.s.  ***  0.000  0.000  0.000  0.000  n.s.  n.s.  n.s.  n.s.  0.0608  0.354  -0.578  -0.224  0.016  n.s.  ***  ***  **  n.s.  *p < 0.05, **p < 0.01, ***p < 0.001, and n.s. = not significant.  54  Table 4.11 Summary of A N O V A in the factorial experiments  Variable  DF  A N O V A SS  F value  Replication  3  0.0202  2.10'  HRT  3  0.3226  100.38""  Loading rate  23  0.437  16.9""  Concentration  13  0.2218  7.51"*  Sample  1  0.0001  0.05  ns  * p < 0.1, *** p < 0.001, n.s. = not significant.  4.4.3. Response surface analysis for the effects of H R T and loading rate on T O C removal  Table 4.12 shows the response surface analysis of TOC removal vs loading rate and HRT. The response variable (dependent variable) was TOC removal; H R T and loading rate were treated as controlled variables. The mean value of response was 0.91 (TOC removal), and R-square was about 0.52 as displayed in Table 4.12. The relatively low value of the coefficient of variation (CV = 4.38) indicated good precision and great reliability of the experiments carried out. An optimum point (maximum point as well) of TOC removal was obtained by this response surface analysis, which was around 97% of TOC removal under HRT = 1.44 days with 3122 ppm/day of TOC loading rate.  55  Table 4.12 Response surface analysis of TOC for the effects of HRT and loading rate. (a) Parameters of TOC removal response surface Variable  TOC percentage removal  Response mean  0.913812  Root M S E  0.040004  R-Square  0.5247  Coef. of Variation  4.3777  (b) Critical Value Factor  Coded  Uncoded  HRT (day)  0.170594  1.437945  LOADING  -1.101631  3121.550113  (ppm/day) Predicted value at stationary point*  0.979589  (c) Eigenvectors Eigenvalues  HRT  LOADING  -0.010578  -0.043942  0.999034  -0.077435  0.999034  0.043942  * Stationary point is a maximum  56  The application of response surface methodology yielded the following regression equation which is an empirical relationship between the dependent variable and the test variables in coded unit*:  Y=0.965+0.020 X , - 0 . 0 2 3 X - 0 . 0 7 7 X , - 0 . 0 0 6 X , X - 0 . 0 1 1 X 2  2  2  2  (4.1)  2  Where Y is the response, (i.e. the TOC removal), and X i and X are the coded values of 2  the test variable HRT and loading rate, respectively. TOC removal with different HRT and loading rates can be predicted by using this regression equation. The significance of each coefficient, which are listed in Table 4.13, was determined by ?-test. The larger the magnitude of r-value and smaller the p-value, the more significant is the corresponding coefficient. This implies that the quadratic main effect of HRT (p < 0.0002) on the TOC removal was more significant than its first order effect. Both first order and quadratic effects of HRT were highly significant (p < 0.05). The loading rate had less effects on the TOC removal than did HRT, and the interaction between HRT and loading rate did not have a significant influence on the TOC removal (p < 0.90). This result was consistent with that given by the eigenvectors** (Table 4.12). As shown in Table 4.12, the HRT has higher eigenvectors than does loading rate.  *Coded units/coded data: are standardized data. In this case, H R T d d ( H R T j j — 1.31)/0.75; T O C loading r a t e e d = ( T O C loading r a t e e d - 20719)/15974. **Eigenvalue/eivectors: are from the matrix of quadratic parameter estimates, which determine the curvature of the response surface. =  C O  cod  u n c o d  5 7  e  unco(  e(  A 3-dimensional graph was constructed to show the relationship between TOC removal vs HRT and loading rate. This graph was based on the regression data, with HRT on the abscissa, loading rate on the ordinate, and TOC removal perpendicular to the plane (Figure 4.11). This is a quadratically smoothed surface. The relatively flat response surface along the axis of ordinate, which represents the loading rate, indicates that a relatively wide variation can be tolerated without TOC removal being seriously affected. The very pointed surface seen along the axis of abscissa, which represents HRT, suggests that the TOC removal would be sensitive to changes of HRT.  Table 4.13 The significance of regression coefficient (TOC). Model term  Coefficient  Standard Error  r-value  p-value  (coded) Intercept  0.965  0.140  4.933  0.0000  XI  0.020  0.144  2.765  0.0063  X2  -0.023  0.000  0.127  0.8988  XI*  -0.077  0.036  -3.799  0.0002  X2  -0.011  0.000  -0.393  0.6950  -0.006  0.000  -0.130  0.8967  2  X1X2  58  Figure 4.11 Response surface of TOC removal vs HRT vs loading rate vs in suspended-growth reactors.  59  4.4.4 Response surface for the effects of HRT and loading rate on SS removal The HRT and loading rate effects on the suspended solids removal in aerobic SBRs was also analyzed using the response surface analysis. The results are shown in Table 4.14. In this analysis, SS removal was the response variable, which is a function of HRT and loading rate. The mean of SS removal on the response surface was 91.6%, and R-square was 0.389. With the coefficient of variation being about 5.16, the experiments were considered to be reliable. To achieve the maximum percentage removal of SS in this response regression, the predicted critical values of HRT and loading rate are 1.44 days and 13,838 mg/l/day SS, respectively. The regression equation of this response surface is generated as the following Equation 4.2 which is in coded units*:  Y=0.996+0.017 Xi+0.046 X -0.090 X, -0.092 X,X -0.142 X 2  2  2  (4.2)  2 2  Where Y is the response (i.e. the SS removal), and X i and X are the coded values of the 2  test variable HRT and loading rate, respectively. The SS removal with different HRTs and loading rates can be explained using this regression equation. The significance of each coefficient of variables to SS removal was determined by Mests, which are listed in Table 4.15. Both the first order main effect and the quadratic main effect of HRT are highly significant (p < 0.05). This is in good accordance with the  *Coded units/coded data: are standardized data. In this case, SS loading r a t e  code  d = (SS loading r a t e  lincode  d - 12559)78174.  60  HRT  C 0 (  i | e C  —  (HRT  u n c 0  ded  —  1.31)/0.75;  Table 4.14 Response surface results of SS removal for the effects of HRT and loading rate. (a) Parameters of SS removal response surface Variable  SS percentage removal  Response Mean  0.916292  Root M S E  0.047314  R-Square  0.3890  Coef. of Variation  5.1637  (b) Critical value Factor  Coded  Uncoded  HRT (day)  0.014917  1.321188  L O A D I N G (mg/l/day)  0.156940  13838  Predicted value at stationary point*  1.00000  (c) Eigenvectors Eigenvalues  HRT  LOADING  -0.063279  0.863852  -0.503746  -0.169217  0.503746  0.863852  Stationary point is a maximum.  61  results from section 4.3.2. However, the SS removal was significantly affected by the loading rate, and the influence of the interaction between HRT and loading rate was not statistically significant (a = 0.05). The eigenvalues shows that the loading rate had a slightly stronger effect on SS removal than did the HRT (Table 4.14).  Table 4.15 The regression coefficient of response surface of SS removal vs HRT and loading rate. Model term  Coefficient  Standard error  r-value  p-value  (coded) Intercept  0.996  0.248  0.136  0.8920  XI  0.017  0.165  3.840  0.0002  X2  0.046  0.000  2.863  0.0052  -0.090  0.035  -4.646  0.0000  X2  -0.092  0.000  -1.821  0.0719  X1X2  -0.142  0.000  -2.878  0.0050  XI  2  l  Figure 4.12 is a 3-dimensional graph of the response surface showing the relationships between  SS removal, HRT, and loading rate. Here, loading rate is the  abscissa, HRT is on the ordinate, and response variable ( SS removal is perpendicular to the plane (HRT and loading rate). This response surface is a rather pointed surface, especially in the direction of the loading rate, which suggests that the SS removal is very sensitive to variations in the loading rate.  62  Loading Rate (g/l/day)  Figure 4.12 Response surface of suspended solids vs HRT vs loading rate in suspended-growth reactor.  63  Differences in the effects of HRT and loading rate on TOC removal and SS removal may be explained by the differences in the characteristics of the wastewater. As mentioned in Section 4.1, brewery wastewater contains a large amount of solids waste. These solids contain "non-volatile" materials, including spent grain. While these solids ( except for yeast) contain no biomass, they do take up room in the reactor. Since only small molecules can be absorbed into microorganisms and afterwards digested, the large particles would be removed by surface phenomena, and the removal of solids by surface phenomena can be limited. As mentioned in Section 4.3.1, the effect of loading rate on the performance of suspended-growth SBR can be related to HRT, as well as to the concentration of the wastewater. Microbial growth would flourish with sufficient nutrients, although a higher loading rate could stop microbial growth due to the impact of shock and to a choking effect caused by the overloading of the solids. In our study, we observed that the increase in the concentration of influent (especially with higher solids concentrations) did result in a decrease in treatment efficiency. In general, a longer HRT gave more time for microbial action to degrade the organic content of the wastewater. Treatment efficiencies therefore increased with an increasing HRT. This did not, however, imply that the longer HRT, the higher the efficiency. As shown in the results of Section 4.3.2, an optimal HRT does exist. Since the SBR is run in batch mode, the nutrients are fed to the reactors at the beginning of the sequencing cycle. As the reaction stage goes on, the nutrients will be exhausted, and the concentration of any toxic compounds will increase in the reactor with a longer H R T  64  (Schmit et al., 1994). Thus, a too-long HRT can result in a decrease in treatment efficiency.  4.5 Track studies of TOC, DO, and pH vs aeration time in suspended-growth SBRs  4.5.1 Variations among the reactors The four reactors were run as replications for this continuous track study of TOC, dissolved oxygen, and pH. Figure 4.13 pictures the patterns of T O C degradation vs aeration time in the four reactors respectively. It was showed that reactors 1 and 4 were more similar than were the other two reactors. Reactor 2 may have had a higher degradation efficiency. It was demonstrated that the variation of the four reactors was statistically significant (Table 4.16). To minimize the variance from the four reactors, the four reactors were grouped based on the results from statistical multiple comparison (Fisher's Least Significant Difference — LSD). In Table 4.17, the means with the same letter are not significantly different, which suggests that they can be grouped together. The results of L S D shows that reactor 2 was certainly in a different group than reactor 1 and 4, while reactor 3 could be grouped with reactor 2 or with reactors 1 and 4 (Table 4.17). Based on this result, reactor 2 was excluded in the final data analysis when averaging TOC concentration, and the average of the data were calculated only from reactors 1, 3, and 4. The L S D results also indicated that reactor 2 had significantly higher performance in terms of T O C degradation, which statistically proved the observations made in Figure 4.13.  65  500  Aeration Time (hrs)  Figure 4.13 Continuous monitoring of TOC vs aeration time in four reactors.  66  Table 4.16.Summary of A N O V A for the four reactors in track study of T O C degradation, D O and pH. Sources of Variance  Reactors  df  3  C.V.  64.92  Root M S E  104.18  F value  2.99  p value  0.04  Dependent variable was concentration of T O C . a = 0.05  Table 4.17 Grouping of the four reactors in track study of T O C degradation, DO, and pH (Using fisher's Least Significant Difference methods)  REACTOR  Mean*  1  191.21 (A)  2  108.24 (B)  3  155.14 (AB)  4  187.35 (A)  *Means with the same letter are not significantly different.  67  4.5.2 The results of track study of pH, dissolved oxygen, and TOC in the suspendedgrowth aerobic SBRs Environmental conditions pertaining to pH, temperature,  dissolved oxygen  concentration, and nutrient content have an important effect on the survival and growth of microorganisms. In this research, temperature was fixed at room temperature, which was about 20 °C. As depicted in Figure 4.14, the pH within the four reactors fluctuated between 6.7 to 7.8, which is the optimal pH range for most microbial growth. The degradation of organic compounds by microorganisms inside the reactors produced large amounts of C 0 , which, together with other small carbohydrate molecules (such as acetic 2  acids) plays an important role in maintaining the pH of reactors. It was not necessary to add buffer to the aerobic SBRs even though  raw brewery wastewater has a poor  buffering capacity (Cronny, 1996). The dissolved oxygen concentration, however, changed as aeration time increased, as did the concentration of TOC. Figure 4.14 shows that the dissolved oxygen concentration dropped slightly at the beginning of the reaction period after feeding with fresh wastewater. It decreased quickly from 9.7 mg/l to nearly zero (0.3 mg/l) within 6 hours. The start point of dissolved oxygen concentration in this figure was recorded when oxic feeding concluded. The reactors were saturated with D O by aeration at this point. The level of dissolved oxygen increased greatly at an aeration time of 6 -7 hours, and reached a platform at DO -9.3 mg/l. Meanwhile, the concentration of TOC inside the reactors was reduced from 441.9 to 126.05 ppm in 11.5 hours, most of the organic carbon  68  c o m p o u n d s w e r e spent w i t h i n an aeration time 0-6 hours, a n d the r e m a i n i n g T O C c o n t i n u o u s l y decreased as aeration time increased.  4.5.3 Relationship between T O C degradation and aeration time An A N O V A  a n d L S D procedure were r u n to statistically a n a l y z e the aeration  t i m e effects o n T O C degradation. A s s h o w n i n T a b l e 4.18, aeration t i m e h a d s i g n i f i c a n t effect o n T O C degradation. T O C degradation rate was calculated b y E q u a t i o n 4 . 3 f o r each o f the groups (grouped based o n the T - g r o u p i n g ) :  T O C degradation rate (ppm/min) = A [ T O C ] / A T i m e  (4.3)  W h e r e , A [ T O C ] is an increase o f T O C w i t h a certain A T i m e . A s s h o w n i n T a b l e 4.19, the degradation rate o f T O C (3.37 p p m / m i n ) w a s m u c h greater i n the first h a l f an hour after f e e d i n g w i t h fresh wastewater. It v a r i e d between 0 . 4 0 - 0 . 8 2 p p m / m i n u n t i l aeration time reached 6.0 hours. T h e degradation rate o f T O C was r e d u c e d to about 0.19-0.27 ppm/1 as aeration proceeded past 6 hours. F i g u r e 4.15 shows the concentration o f T O C vs aeration t i m e at different influent concentrations o f T O C i n reactor 2. T h e trend f o r the t w o curves i s a l i k e , w i t h the o n l y difference b e i n g b e g i n n i n g point. A t a higher influent concentrations ( T O C = 1539.5 p p m ) , there w a s a sharp decrease o f T O C after the first h a l f an hour. T h i s steep d r o p d i d not o c c u r w i t h l o w e r influent T O C concentrations ( T O C = 1109 p p m ) .  69  0  2  4  6  8  10  12  14  Aeration Time (hrs)  Figure 4.14 The plot of TOC (average of reactors #1, #3, and #4), dissolved oxygen, and pH vs aeration time in track study.  70  500  Aeration Time (hrs)  Figure 4.15 T O C vs aeration time under different influent concentrations in reactor 2.  71  Table 4.18. A N O V A analysis of aeration time effect in track study. Sources of Variance  Aeration time  df  21  C.V.  26.28  Root M S E  42.19  F value  23.88  p value  0.0001  Dependent variable was concentration of TOC.  a=0.05 Table 4.19 The grouping of loading rate (based on the multi-comparison of the means). T Grouping  Mean  A C C E E G G G I I K K K N N N N N N  B B D D F F H H J J L L L L 0 0 O 0 O O  M M M M M  441.90 340.70 315.97 292.57 267.80 247.30 227.70 212.57 198.67 177.10 165.07 143.43 126.05 113.97 110.10 98.28 85.74 83.98 69.81 66.97 66.72 61.40  TIME 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 11.5 9.5 10  72  T O C degradation rate (ppm/min) 3.37(A) 0.82(B) 0.78(C) 0.82(D) 0.68(E) 0.65(F) 0.48(G) 0.72(H) 0.40(1) 0.72(J) 0.49(K) 0.27(L) 0.25(M) 0.21(N) 0.16(0)  The stabilization of organic matter was achieved by the metabolic activity of microorganisms. A s mentioned previously, nutrients and energy are used for microbial growth , and in the batch mode reactor, the changes in nutrient condition would therefore result in changes in microbial growth. A general bacterial growth pattern in pure culture is shown in Figure 4.16. A lag phase occurred in the beginning. It represents the time required for the organism to acclimate to their new environment. During this lag growth phase, there is always an excessive amount of food surrounding the microorganisms, and the metabolic rate and growth is only a function of the ability of the microorganisms to process the substrate. This lag-growth phase was followed by a exponential growth phase, in which cell mass and cell number density increase exponentially with time, and  nutrient  concentrations are large. The next growth phase is stationary phase (also called declining growth phase), in which the cells have exhausted the substrate or nutrients necessary for growth. Thus the growth rate of the biomass declined because of limitations in the food supply, and the growth of new cells is offset by the death of old cells. In the death phase, the bacterial death rate exceeds the production of new cells. Even though this growth model is the general bacterial growth pattern, it can be used to explain the growth of more complex microorganisms as well. The changes in T O C and dissolved oxygen concentrations may be explained by this growth model. A s aeration  time  increased,  the  T O C concentration  decreased because of the T O C  degradation by microbial action. A n increase of biomass and oxygen demanded by the oxidation activities of the vigorously growing microbes resulted in a decrease in the  73  S  SN  cu  +J *J  a  &,  O OJD  "a • PM  u  IN  <U  a 'S. cu  in  H VO cu  u 3  dissolved oxygen concentrations, since the air supply was fixed. At about 6 hours of aeration time, the oxygen consumption attained a maximum level, and the dissolved oxygen concentration reached its lowest point (0.3 mg/l), with the concentration of TOC about 126.05 ppm. The TOC degradation rate at this time was about 0.27 ppm/min (Table 4.19). This low degradation rate also indicated that the activity of microorganisms had slowed. The exhausted nutrients (in terms of TOC) and low dissolved oxygen concentration would impose an effect on the activities of microorganisms. After 6 hours' aeration, TOC and dissolved oxygen were consumed mainly for the purpose of the maintenance of cells. As continuous aeration proceeded, the DO increased dramatically due to a decrease in the oxygen requirement for the slower metabolic activities. By the end of aeration (at about 11.5 hours from the beginning), the residue of TOC detected was mostly composed of non-biodegradable organic compounds.  4.5.4 Sludge production Throughout this study, it was noticed that the increase of sludge was quite slow. SRT was set at 28 days for most of the time. Unfortunately, biomass analysis was not carried out parallel to the continuous monitoring of TOC and dissolved oxygen. However, MLSS data from 0 hours of aeration (the beginning) and 11.5 hours of aeration (the ending) were collected and were used to calculated the sludge production rate. Sludge production rate was calculated by the following equation:  Sludge production rate = AMLSS / ATOC  75  (4.4)  Where, AMLSS was the net increase of mixed liquor suspended solids, and ATOC represented the TOC removed. As listed in Table 4.20, the average of sludge production rate was 0.16. This sludge yield was much lower than for other activated sludge treatment systems. A similar result of low sludge production in an SBR has been reported. In Dubeski's (1993) study, it was proven that aerobic SBR for C T M P wastewater treatment produced as much as one quarter the sludge of a typical activated sludge system, both on a COD and B O D basis. This discovery indicated an important virtue of an aerobic SBR 5  compared to other activated sludge systems.  Table 4.20 Sludge production in the suspended-growth SBR. MLSS (mg/l)  TOC (ppm)  initial  4078.93  391.83  End of aeration  4130.31+236.46  64.49+50.70  Sludge production rate  0.16  As we know, SBR is conducted in a semi-batch mode. Since the nutrient is expected to be exhausted before next cycle, there may be a period of nutrient limitation or even depletion inside of the reactor. Under these conditions, the microorganisms would undergo a endogenous metabolism, and they are forced to metabolize their own protoplasm without replacement as the concentration of available food is at a minimum. This results in expansion of the biomass is expended, and results in relatively low sludge yields.  76  Conclusions and Recommendations  5.1 Conclusions This study demonstrated that it was feasible to use an aerobic sequencing batch reactor system to treat brewery wastewater without any need for supplemental nitrogennutrients or phosphorous-nutrients. The performance of the suspended-growth SBR was significantly higher than that of the attached-growth SBR. In the suspended-growth SBR, over 94% removal of TOC, BOD5, COD was attained. The effects of HRT and loading rate on the treatment efficiencies were significant under both growth conditions. Greater sensitivity to changes in HRT and loading rate were seen in the attached-growth SBR. In terms of the microbial population, it was observed that the floe-forming bacteria were dominant in suspended-growth reactors, while in attached-growth reactors, filamentous bacteria flourished. To further study the effects of HRT and loading rate on the performance of the suspended-growth SBR, factorial experiments and response surface analysis were carried out. An optimum (maximum) TOC removal (as dependent response variable) was predicted based on this response surface, with HRT and loading rate at 1.44 days and 3122 ppm/day, respectively. For the optimum (maximum) suspended solids removal, the predicted critical value of HRT and loading rate were 1.32 days and 13.84 g/l/day, respectively. It was noted when comparing the two eigenvectors of response surfaces (TOC removal and suspended solids removal), that TOC removal was more affected by  77  changes in HRT, while the loading rate was more important than HRT for suspended solids removal. It was found that the dissolved oxygen concentration changed as the aeration time increased, even though the aeration rate was fixed in the track study. It was inferred from this that TOC degradation and the changes in dissolved oxygen concentration in the suspended-growth SBR were related to the microbial metabolic activities. The pH was maintained at the optimal range for microbial growth, which was between 6.7 to 7.8. It was also noticed that the sludge production rate was low in the aerobic SBR systems, which was about 0.16.  5.2 Recommendations In this study, the Ringlace was used to set up the attached-growth SBRs. The strands of the Ringlace were 5 cm apart. The diameter of biomass floes attached on the Ringlace was 1.5 to 3.0 cm. Results indicated that the Ringlace with its attached sludge blocked adequate aeration,  and the efficiency of the oxygen transfer was thereby  decreased. It is therefore suggested that the distance of the Ringlaces should be larger than 5 cm. It was found that the concentration of MLSS was one of the most important factors affecting the performance of SBR systems.  It is therefore suggested that a  further study should be done on the behavior of MLSS. Since the microbial population plays a  dominant role in biological treatment systems, the amplification of certain  species would greatly enhance treatment efficiency.  78  Another important consideration which should be taken into account is the sludge production rate. Given that the sludge production rate was low (0.16) in this study, this likely is one of the advantages of an aerobic SBR system over other systems used in the treatment of brewery wastewater. 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"The effects of fill strategies on SBR performance under nitrogen defficiency and rich conditions". Water Science Technology, 28(10): 259-266.  Setter, K., 1995. "Attached growth nitrification using Ringlace media". Master Thesis, the university of British Columbia, Vancouver, B C , Canada.  Smith, L . J., 1986. "The treatment of waste waters from malting, brewing and distilling". Water Science Technology, 18: 127-135.  83  Strohwald, N . K . H . and Ross, W. R., 1992. "Application of the A D U F process to brewery effluent on a laboratory scale". Water Science Technology, 25(10): 95-105.  Tarn, P. C , Lo, K . V., and Bulley, N . R., 1986. "Treatment of milking center waste using sequencing batch reactors". Canadian. Agricultural Engineering, 28: 125-130.  Tanemuna, K . , Kida, K . , Iwasaki, K . , and Sonoda, Y . , 1992. "Operation conditions for anaerobic treatment of wastewater  from a beer brewery". J. Fermentation and  Bioengineering, 73(4): 332-335.  Ware, A . J. and Pescod, M . B., 1989. "Full-scale studies with an anaerobic/aerobic R B C unit treating brewery wastewater". Water Science Technology, 21: 197-208.  Wysocki, G., 1973. "Treatment of brewery fermentation effluents: economics of recovery process for yeast, alcohol and water". International Brewing and distilling, 3(2): 23-24.  Yu, H., Tay, J., and Wilson, F., 1997. "An alternative operation mode for the sequencing batch reactor process". J. Environ. Sci. Health, A32(8): 2169-2182.  Zvauya, R., Parawira, W., and Mawadza, C , 1994. "Aspects of aerobic thermophilic treatment of Zimbabwean traditional opaque-beer brewery wastewater". Bioresource technology, 48(3): 273-274.  84  APPENIX Contents  Tables A-l.  Pages TS and V S removal in the suspended-and attached-growth S B R s under a series of the H R T  A-2.  87  TS and V S removal in the suspended- and attached-growth S B R s under a series of the loading rate  A-3  89  The effects of the H R T and the loading rate on the TS removal in suspended-growth S B R s  92  A-4.  Response surface analysis of TS removal in suspended-growth S B R s  94  A-5  The effectos of the H R T and loading rate on V S removal in suspended-growth S B R s  A-6.  95  The effects of the H R T and the loading rate on V S S removal in the suspended-growth S B R s  A-7.  97  The effects of the H R T and the loading rate on the B O D 5 removal in suspended-growth S B R s  A-8.  100  Response surface analysis of C O D removal in suspended-growth S B R s  A-9.  102  The effects of the H R T and the loading rate on the C O D removal in suspended-growth S B R s  103  A - 1 0 . Analytical methods and instrumentation  85  106  Figures  pages  A-1.  The picture of the experiment set-up  A-2.  The picture of the organisms (yeast spores) in the raw brewery wastewater  107  108  86  Table A - l . TS and VS removal in suspended- and attached-growth SBRs under a series HRT  HRT  Solids 0.56 TS  VS  0.81 TS  VS  1.06 TS  VS  1.56 TS  Stat. N MEM MAX MEAN STD N MIN MAX MEAN STD N MIN MAX MEAN STD N MIN MAX MEAN STD N MIN MAX MEAN STD N MIN MAX MEAN STD N MIN MAX MEAN STD  Growth Type Suspended-growth Attached-growth Effluent(mg/1) Removal Effluent(mg/1) Removal 11 11 12 12 555.00 0.54 757.00 0.29 788.00 0.70 1065.00 0.58 650.64 0.61 887.75 0.47 82.88 0.06 97.81 0.10 12 12 12 12 328.00 0.04 370.00 0.00 520.00 0.34 523.00 0.25 404.58 0.18 435.00 0.10 64.04 0.10 47.36 0.14 8 8 8 8 545.00 0.54 735.00 0.47 712.00 0.71 965.00 0.60 624.13 0.63 802.50 0.52 62.47 0.06 70.39 0.05 8 8 8 8 328.00 0.00 388.00 0.00 462.00 0.28 493.00 0.23 395.88 0.13 425.75 0.08 37.77 0.12 33.94 0.10 8 8 8 8 465.00 0.58 550.00 0.47 580.00 0.70 748.00 0.68 545.00 0.65 647.50 0.58 41.69 0.05 77.98 0.07 8 8 8 8 133.00 0.00 277.00 0.00 347.00 0.53 375.00 0.32 273.00 0.24 312.00 0.13 89.47 34.94 0.17 0.14 4 4 4 4 587.00 0.63 670.00 0.58 0.64 612.00 693.00 0.59 597.00 0.63 681.50 0.58 12.25 0.01 11.68 0.01  87  (Table A - l )  HRT  Solids VS  3.06 TS  VS  6.06 TS  VS  Stat. N MIN MAX MEAN STD N MIN MAX MEAN STD N MIN MAX MEAN STD N MIN MAX MEAN STD N MIN MAX MEAN STD  Growth type Suspended-growth Attached-growth Effluent(mg/1) Removal Effluent( mg/l) Removal 4 4 4 4 395.00 0.00 387.00 0.00 457.00 0.06 438.00 0.08 427.25 0.03 413.75 0.03 33.33 0.03 0.04 21.27 12 12 12 12 433.00 0.66 450.00 0.62 745.00 0.80 830.00 0.79 0.74 575.25 658.00 0.70 0.04 96.91 105.18 0.05 12 12 12 12 212.00 0.56 210.00 0.60 365.00 0.75 333.00 0.75 297.00 0.65 295.67 0.65 42.24 0.05 33.11 0.04 10 10 10 10 502.00 0.66 485.00 0.65 750.00 0.77 772.00 0.78 627.60 0.71 647.60 0.70 90.21 0.04 81.34 0.04 10 10 10 10 253.00 0.55 160.00 0.58 377.00 0.70 352.00 0.81 323.70 0.61 308.60 0.63 40.94 0.05 55.15 0.07  Table A2. TS and VS removal in suspended- and attached-growth SBRs under a series loading rate  SOLIDS Loading rate Stat, (mg/l/day) TS 4321N MIN MAX MEAN STD 8555 N MIN MAX MEAN STD 12538N MIN MAX MEAN STD 15627N MIN MAX MEAN STD 19687N MIN MAX MEAN STD 22746 N MIN MAX MEAN STD 27306 N MIN MAX MEAN STD  Growth type Suspended-growth Attached-growth Effluent (mg/l) Removal Effluent (mg/l) Removal 10 502.00 750.00 627.60 90.21 12 433.00 745.00 575.25 96.91 4 587.00 612.00 597.00 12.25 4 465.00 580.00 533.75 56.48 4 525.00 575.00 556.25 23.00 4 547.00 712.00 638.50 69.64 4 545.00 692.00 609.75 60.86  89  10 0.66 0.77 0.71 0.04 12 0.66 0.80 0.74 0.04 4 0.63 0.64 0.63 0.01 4 0.58 0.66 0.61 0.04 4 0.67 0.70 0.68 0.01 4 0.54 0.64 0.59 0.05 4 0.63 0.71 0.67 0.03  10 485.00 772.00 647.60 81.34 12 450.00 830.00 658.00 105.18 4 670.00 693.00 681.50 11.68 4 550.00 735.00 640.50 90.72 4 563.00 748.00 654.50 76.33 4 763.00 810.00 785.75 19.21 4 735.00 965.00 819.25 102.20  10 0.65 0.78 0.70 0.04 12 0.62 0.79 0.70 0.05 4 0.58 0.59 0.58 0.01 4 0.47 0.60 0.54 0.07 4 0.57 0.68 0.62 0.04 4 0.47 0.51 0.49 0.01 4 0.48 0.60 0.56 0.06  (Table A-2) Growth type Suspended-growth S O L I D S Loading rate  Stat.  Attached-growth  Effluent (mg/l) Removal  Effluent (mg/l)  Removal  (mg/l/day) 32128N  4  4  4  4  MIN  575.00  MAX  665.00  0.56 0.62  890.00 1065.00  0.29 0.41  MEAN  612.25  0.59  977.00  0.35  37.87  0.02  71.64  0.05  4  4  4  4  STD 36181N MLN  680.00  0.54  757.00  0.43  MAX  788.00  0.60  975.00  0.55  MEAN  743.25  0.56  858.25  0.49  50.62  0.03  102.98  0.06  STD 39540 N  4  4  4  4  MLN  555.00  0.68  780.00  0.51  MAX  590.00  0.70  903.00  0.58  MEAN  578.33  0.69  828.00  0.55  20.21  0.01  52.93  0.03  STD VS  1658 N  10  10  10  10  MLN  253.00  0.55  160.00  0.58  MAX  377.00  0.70  352.00  0.81  MEAN  323.70  0.61  308.60  0.63  40.94  0.05  55.15  0.07  4  4  4  4  MLN  133.00  0.00  277.00  0.00  MAX  290.00  0.53  375.00  0.01  MEAN  202.75  0.28  304.75  0.00  74.17  0.25  46.95  0.00  4  4  4  4  MLN  395.00  0.00  387.00  0.00  MAX  457.00  0.06  438.00  0.08  MEAN  427.25  0.03  413.75  0.03  33.33  0.03  21.27  0.04  12  12  12  12  MLN  212.00  0.56  210.00  0.60  MAX  365.00  0.75  333.00  0.75  MEAN  297.00  0.65  295.67  0.65  42.24  0.05  33.11  0.04  STD 3152 N  STD 3226 N  STD 3283 N  STD  90  (Table A-2) Growth type Suspended-growth S O L I D S Loading rate  Stat.  Attached-growth  Effluent (mg/l) Removal  Effluent (mg/l)  Removal  (mg/l/day) 4855 N  4  4  4  4  MLN  338 00  0.19  347 00  0 19 0 22  292.00  MAX  347.00  0.32  MEAN  343 25  0 20  319.25  0.26  3 86  0 01  22.47  0.05  STD  4  4  4  4  MLN  328 00  0 00  388.00  0.00  MAX  418 00  0 11  427.00  0.00  MEAN  383 75  0 03  405.75  0.00  40 10  0 05  20.69  0.00  4  4  4  4  MLN  385 00  0 13  410.00  0.07  MAX  462 00  0 28  493.00  0.23  MEAN  408 00  0 23  445.75  0.16  36 45  0 07  34.53  0.06  5428 N  STD 7847 N  STD 10585N  4  4  4  4  MLN  328 00  0 24  370.00  0.10  MAX  377 00  0 34  448.00  0.25  MEAN  356 00  0 28  396.75  0.20  20 51  0 04  34.90  0.07  STD 11492.00 N  4  4  4  4  MLN  427 00  0 04  410.00  0.03  MAX  520 00  0 21  523.00  0.24  MEAN  479 75  0 11  451.00  0.16  39 68  0 07  62.55  0.12  STD  91  Table A-3. The effects of the HRT and the loading rate on TS removal in suspended-growth SBRs  HRT (day) 0.56  1.06  2.06  Loading rate (mg/l/day)  Stat.  TS (Effluent)  15493 N MIN MAX MEAN STD 23040 N MIN MAX MEAN STD 26133 N MLN MAX MEAN STD 31360N MLN MAX MEAN STD 16885 N MLN MAX MEAN STD 21106N MLN MAX MEAN STD 4225 N MLN MAX MEAN STD  TS removal 4 463.00 533.00 508.25 31.70 4 560.00 660.00 595.50 46.02 4 515.00 640.00 582.50 52.36 4 475.00 587.00 535.50 52.13 8 525.00 643.00 591.63 47.25 8 553.00 713.00 661.63 50.74 4 460.00 577.00 498.75 53.44  92  4 0.27 0.36 0.30 0.04 4 0.39 0.48 0.45 0.04 4 0.48 0.58 0.52 0.04 4 0.57 0.59 0.58 0.01 8 0.60 0.68 0.63 0.03 8 0.62 0.70 0.65 0.03 4 0.21 0.37 0.31 0.07  (Table A-3) H R T (day)  Loading rate  Stat.  TS(Effluent)  T S removal  (mg/l/day) N  4  4  MEM  547 00  0.32  MAX  735 00  0.49  MEAN  654 25 87 34  0.39 0.08  4  4  MEM  458 00  0.47  MAX  650 00  0.63  MEAN  570 00  0.53  80 87  0.07  •  4  4  MEM  532 00  0.51  MAX  718 00  0.64  MEAN  633 00  0.57  77 34  0.05  STD N  STD N  STD  93  Table A - 4 . Response surface analysis of T S removal in suspended-growth S B R s (a) Parameters of T S removal response surface Variable Response Mean Root M S R  T S percentage removal 0.518458 0.059270  Coef. of Variation  11.4319  2  0.8121  (b) Critical value Factor  Coded  Uncoded  HRT  3.011363  3.568522  LOADING  2.144313  46885  Predicted value at stationary point *  1.541512  (c) Eigenvectors Eigenvalues  HRT  LOADING  -0.055647  0.929299  0.369328  -0.146275  -0.369328  0.929299  Stationary point is a maximum.  94  Table A - 5 . The effects of the H R T and the loading rate on V S removal in suspended-growth SBRs  H R T (day)  Loading rate  Stat.  V S (Effluent)  V S removal  (mg/l/day) 0.56  3147 N  4  4  MLN  192.00  0.00  MAX  295.00  0.00  MEAN  258.50  0.00  45.57  0.00  STD 4987 N  4  4  MLN  250.00  0.00  MAX  325.00  0.00  MEAN  280.50  0.00  35.09  0.00  4  4  STD 6293 N MLN  190.00  0.00  MAX  333.00  0.36  MEAN  275.25  0.13  70.36  0.17  4  4  MLN  202.00  0.13  MAX  297.00  0.41  MEAN  252.25  0.26  47.33  0.14  8  8  MLN  287.00  0.00  MAX  383.00  0.00  MEAN  338.13  0.00  31.81  0.00  8  8  MLN  350.00  0.00  MAX  427.00  0.12  MEAN  386.75  0.04  26.00  0.05  4  4  MLN  265.00  0.00  MAX  313.00  0.00  MEAN  277.50  0.00  23.69  0.00  STD 7307 N  STD 1.06  3078 N  STD 4504 N  STD 2.06  858 N  STD  95  (Table A-5) H R T (day)  Loading rate (mg/l/day)  Stat.  V S (Effluent)  N  V S removal 4  4  MIN  272.00  0.00  MAX  357.00  0.00  MEAN  320.50  0.00  36.61  0.00  STD N  4  4  192.00  0.00  MAX  362.00  0.35  MEAN  280.25  0.12  72.10  0.16  MIN  STD N  4  4  230.00  0.08  MAX  315.00  0.33  MEAN  281.75  0.18  37.40  0.11  MIN  STD  96  Table A - 6 . The effects of H R T and the loading rate on V S S removal in suspended-growth SBRs  I H R T (day) 0.56  Loading rate (mg/l/day)  Stat.  V S S (Effluent)  N  V S S removal 8  8  MLN  0.00  0.00  MAX  4.00  1.00  MEAN  1.00  0.50  STD  1.41  0.53  N  8  8  MLN  0.00  0.00  MAX  4.00  1.00  MEAN  1.06  0.63  STD  1.37  0.40  N MLN MAX  8  8  1.00  0.00  10.00  0.89  MEAN  4.50  0.51  STD  3.17  0.33  8  8  MLN  1.00  0.76  MAX  3.50  0.93  MEAN  2.25  0.85  STD  0.89  0.06  8  8  MLN  3.50  0.75  MAX  16.00  0.94  MEAN  8.63  0.86  STD  5.10  0.08  8  8  MLN  3.50  0.87  MAX  8.50  0.95  MEAN  5.81  0.91  STD  1.75  0.03  N  N  N  N  8  8  MLN  12.00  0.76  MAX  20.00  0.86  MEAN  15.50  0.81  2.62  0.03  STD  97  (Table A-6) H R T (day)  Loading rate  Stat.  V S S (Effluent)  V S S removal  (mg/l/day) 1829 N MIN  1.06  8  4.00  0.90  MAX  8.50  0.95  MEAN  5.88  0.93  STD  1.60  0.02  16  16  MIN  0.00  0.60  MAX  29.50  1.00  MEAN  7.47  0.90  STD  7.98  0.11  16  16  MIN  0.00  0.88  MAX  12.00  1.00  836 N  1132N  MEAN  4.69  0.95  STD  4.00  0.04  1304 N  16  16  MIN  0.00  0.91  MAX  10.00  1.00  MEAN  4.44  0.96  STD  3.45  0.03  16  16  MIN  0.00  0.44  MAX  65.00  1.00  MEAN  13.75  0.88  STD  16.03  0.14  8  8  MIN  1.00  0.00  MAX  7.00  0.00  MEAN  5.13  0.00  STD  1.89  0.00  8  8  0.00  0.33  1313 N  2.06  8  1N  13 N MIN MAX  1.50  1.00  MEAN  0.44  0.81  STD  0.50  0.22  8  8  MIN  0.00  0.50  MAX  4.50  1.00  MEAN  1.56  0.83  STD  1.45  0.16  52 N  98  (Table A-6) HRT (day) Loading rate (mg/l/day)  Stat.  VSS (Effluent)  N MLN MAX MEAN STD N MIN. MAX MEAN STD N MLN MAX MEAN STD N MLN MAX MEAN STD N MLN MAX MEAN STD  VSS removal 8 2.00 12.00 6.38 3.58 8 0.00 4.50 1.76 1.82 8 1.70 4.00 2.99 0.80 8 2.00 6.00 3.83 1.32 8 1.00 4.50 2.73 1.26  99  8 0.19 0.86 0.57 0.24 8 0.93 1.00 0.97 0.03 8 0.94 0.97 0.95 0.01 8 0.93 0.98 0.95 0.02 8 0.95 0.99 0.97 0.01  Table A - 7 . The effects of the H R T and loaidng rate on the B O D removal 5  in suspended-growth SBRs  H R T (day)  Loading rate*  Stat.  B O D (effluent)** (mg/l)  0.56  25063 N  8  8 0.98  MAX  19.98  0.99  MEAN  14.58  0.99  4.20  0.00  8  8  STD 34147 N MIN  17.48  0.96  MAX  63.48  0.99  MEAN  45.27  0.97  STD  18.35  0.01  35283 N  8  8  MIN  7.96  0.98  MAX  35.04  1.00  MEAN  23.09  0.99  STD  10.41  0.01  47042 N  8  8  MIN  38.58  0.97  MAX  69.01  0.98  MEAN  57.07  0.97  STD  11.88  0.01  13549 N  8  8  MIN  2.89  0.99  MAX  11.56  1.00  MEAN  6.86  0.99  STD  3.04  0.00  8  8  MIN  3.62  0.99  MAX  14990N  2.06  5  8.67  MIN  1.06  B O D removal  5  (mg/l/day)  14.91  1.00  MEAN  7.77  0.99  STD  3.71  0.00  9313 N  8  8  9.25  0.97  MAX  42.40  0.99  MEAN  20.30  0.99  STD  13.84  0.01  MIN  100  (Table A-7) HRT (day)  Loading rate* _STAT_ (mg/l/day) 12829N MIN MAX MEAN STD  BOD (effluent)** (mg/l) 5  BOD removal 5  8 7.79 78.92 37.87 27.50  8 0.96 1.00 0.98 0.01  The loading rate of B O D was calculated by the ratio T O C / B O D = 0.78; * The concentration of B O D in the effluent was calculated by the ratio T O C / B O D = 4.86. 5  5  5  5  101  Table A - 8 . Response surface analysis of C O D removal in suspended-growth S B R s  (a) Parameters of C O D removal response surface Variable Response Mean Root M S E R  C O D percentage removal 0.921036 0.036663  Coef. of Variation  3.9806  0.5247  2  (b) Critical Value Factor HRT  Coded 0.170224  Uncoded  Loading rate  -1.086927  7628.141586  1.437668  Predicted value at stationary point  0.981236  (c) Eigenvectors Eigenvalues  HRT  LOADING  -0.009846  -0.044490  0.999010  -0.071003  0.999010  0.044490  * Stationary point is a maximum.  102  Table A - 9 . The effects of the H R T and loading rate on the C O D removal in suspended-growth SBRs  H R T (day)  Loading rate*  Stat.  C O D (effluent)**  (mg/l/day) 0.56  C O D removal  (mg/l) N  8  8  193.80  0.82  MAX  338.30  0.90  MEAN  274.34  0.85  52.73  0.03  8  8  MLN  STD N MLN  87.80  0.90  MAX  202.30  0.96  MEAN  147.66  0.93  42.49  0.02  STD N  8  8  MLN  184.70  0.81  MAX  480.10  0.93  MEAN  344.80  0.86  STD  103.83  0.04  N  8  8  176.90  0.77  MAX  642.70  0.94  MEAN  458.29  0.84  STD  185.74  0.07  MLN  N  8  8  80.60  0.88  MAX  354.80  0.97  MEAN  233.81  0.92  STD  105.36  0.04  8  8  429.00  0.82  MAX  528.00  0.86  MEAN  485.74  0.84  37.64  0.01  8  8  MLN  340.10  0.85  MAX  532.60  0.90  MEAN  440.75  0.87  60.24  0.02  MLN  N MLN  STD N  STD  103  (Table A-9) H R T (day)  Loading rate*  Stat.  C O D (effluent)**  (mg/l/day) 83393 N  1.06  C O D removal  (mg/l) 8  8  MIN  390.60  0.82  MAX  698.80  0.90  MEAN  577.83  0.85  STD  120.28  0.03  8  8  MIN  36.00  0.92  MAX  162.20  0.98  MEAN  116.00  0.94  52.50  0.03  22211 N  STD 24018N  8  8  MIN  29.30  0.95  MAX  117.00  0.99  MEAN  69.49  0.97  STD  30.80  0.01  8  8  24045 N MIN  37.10  0.97  MAX  70.30  0.98  MEAN  51.73  0.98  STD  14.55  0.01  8  8  MIN  50.40  0.97  MAX  77.70  0.98  MEAN  67.20  0.97  STD  11.34  0.00  8.00  8.00  MIN  36.70  0.94  MAX  150.90  0.98  MEAN  78.69  0.97  STD  37.53  0.02  8  8  25880N  26573 N  28441N MIN  80.80  0.94  MAX  143.10  0.97  MEAN  110.23  0.96  22.60  0.01  STD 32173N  8  8  MIN  60.00  0.96  MAX  127.90  0.98  MEAN  94.30  0.97  STD  26.39  0.01  104  (Table A-9) H R T (day)  Loading rate*  Stat.  C O D (effluent)**  (mg/l/day)  (mg/l) 39516N  8  8  MLN  115.50  0.92  MAX  266.30  0.97  MEAN  185.29  0.95  62.81  0.02  8  8  MLN  74.80  0.90  MAX  185.30  0.96  MEAN  140.68  0.92  40.31  0.02  STD 2.06  C O D removal  10784 N  STD  8  8  MLN  118.30  0.90  MAX  215.60  0.94  MEAN  161.95  0.92  36.64  0.02  12118N  STD 14652 N  8  8  69.30  0.92  MAX  203.10  0.97  MEAN  139.38  0.94  49.59  0.02  8  8  MLN  STD 16509N MLN  93.70  0.85  MAX  429.30  0.97  MEAN  205.55  0.93  STD  140.11  0.05  8  8  MLN  139.80  0.90  MAX  292.90  0.95  MEAN  227.79  0.92  65.08  0.02  8  8  17059 N  STD 17457 N MLN  57.80  0.89  MAX  324.50  0.98  MEAN  179.46  0.94  STD  108.44  0.04  105  (Table A-9) H R T (day)  Loading rate * (mg/l/day)  Stat.  C O D (effluent)** (mg/l)  N MIN  C O D removal 8  8  70.60  0.92  MAX  272.70  0.98  MEAN  132.74  0.96  83.79  0.02  8  8  STD N MIN  78.80  0.80  799.10  0.98  MEAN  383.43  0.90  STD  278.47  0.07  MAX  The loading rate of C O D was calculated by the ratio T O C / C O D = 0.44; The concentration of C O D in the effluent was calculated by the ratio TOC/COD=0.48.  Table A-10 Analytical methods and instrumentation Parameter  Methods  Instrument/Reference  TKN  Digested with H 2 S 0 4 and K 2 S 0 4  Technicon Autoanalyzerll  TP  Digested with H 2 S 0 4 and K 2 S 0 4  Technicon Autoanalyzer II  NH3-N  Automatic phenate methods  Technicon Autoanalyzer II  N03-N/N02-N  Calorimetric automated cadmium reduction methods  Technicon Autoanalyzer II  P04-P  Automated ascorbic acid reduction  Technicon Autoanalyzer II  methods  106  Figure A - l . The picture of the experimental set-up.  107  Figure A - 2 . The picture of organisms (yeast spores) in the raw brewery wastewater (40X).  108  


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