UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Upgrading aerated lagoons for the treatment of egg processing wastewater Olsson, Michael Paul 1995

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata


831-ubc_1995-0230.pdf [ 2.79MB ]
JSON: 831-1.0098936.json
JSON-LD: 831-1.0098936-ld.json
RDF/XML (Pretty): 831-1.0098936-rdf.xml
RDF/JSON: 831-1.0098936-rdf.json
Turtle: 831-1.0098936-turtle.txt
N-Triples: 831-1.0098936-rdf-ntriples.txt
Original Record: 831-1.0098936-source.json
Full Text

Full Text

U p g r a d i n g Aerated Lagoons for the Treatment of E g g Processing Wastewater by  M I C H A E L P A U L OLSSON B . S c , The University of British Columbia, 1990 A THESIS SUBMITTED IN PARTIAL F U L F I L L M E N T O F T H E REQUIREMENTS FOR T H E D E G R E E O F M A S T E R O F SCIENCE in T H E F A C U L T Y O F G R A D U A T E STUDIES (Department of Bio-Resource Engineering) We accept this thesis as^onforming to the r e q u i r ^ ^ n d a r d 7  T H E UNIVERSITY O F BRITISH C O L U M B I A APRIL, 1995 © Michael Paul Olsson  In  presenting  degree freely  at  the  available  copying  of  thesis  in  partial  fulfilment  University  of  British  Columbia,  for  this  department publication  this  or of  reference  thesis by  for  his  this  and  scholarly  or  thesis  study.  for  her  I  of I  further  gain  Department  of  £lQ -  ft£SouRc£  The University of British Columbia Vancouver, Canada  Date  DE-6  (2/88)  flPftlL.  3fc  ^  1 ^ 5 '  £ N &->^ £&(g11[ &  that  agree be  It  shall not  permission.  requirements  agree  purposes may  representatives.  financial  the  is be  that  the  for  Library  an  shall make  permission for  granted  by  understood allowed  the  advanced  extensive  head  that  without  it  of  copying my  my or  written  Abstract  The treatment of egg processing wastewater is typically accomplished in an aerated lagoon.  However, to meet current wastewater guidelines, processing facilities must  upgrade their systems.  Without changing the dimensions of the system and without  installing liquid-solid separation, upgrading to an sequencing batch reactor system is an attractive alternative.  For this reason, two parallel lab-scale SBR systems were  operated over an eight month period for the treatment of egg processing wastewater. The results showed very good removals of B O D , C O D , and TSS.  Aeration  requirements were found to be 1.5 L/min for a single 4 litre reactor and 1.5 L/min & 0.5 L/min for two 4 litre reactors in series.  K a values of 5.0 h r and 10.8 h r were 1  1  L  established for egg processing wastewater and clean water, respectively. Values for a and P were determined to be 0.46 and 0.97, respectively. The coefficients a', and b', for the determination of oxygen requirements, were established at 0.68 g 0 /g B O D 2  and 0.36 d , respectively. The kinetic growth coefficients were found to be: K. = 822 1  mg/L, k = 1.98 d , k = 0.07 d , and Y = 0.32. 1  1  d  The reductions in coliforms were  from 3500 MPN/100 mis in the influent to 80 MPN/100 mis in the effluent. Confirmed coliforms were identified as  Bacillus sp. and Micrococcus sp.. Salmonella  and fecal coliforms were absent in both the influent and effluent wastewater.  ii  Table of Contents Abstract  ii  Table of Contents  iii  List of Tables  v  List of Figures  vi  Acknowledgment  viii  Introduction  1  Literature Review  3  1. Aerated Lagoons  3  2. Pathogens Associated with Egg Products  7  3. Sequencing Batch Reactors  9  4. Microbial Kinetics  11  Materials and Methods  14  1. Basis of Design  14  2. Lab Scale SBR System  16  3. Analysis of Egg Processing Sanitary Chemicals  18  4. Analytical  19  5. Aeration Studies  20  6. Microbial Identification  22  Results and Discussion  25  1. Waste Characterization  25  2. Sanitary Chemicals and Treatment Efficiency  29  3. Aeration Requirements  33  4. Determination of Kinetic Coefficients  43  5. Mean Cell Residence Time  46  6. Pathogens  50 iii  Conclusions  52  Recommendations for Further Study  54  Bibliography  55  iv  List of Tables  1.  Common Microorganisms Found on Egg Shells  8  2.  Kinetic Coefficients for Various Wastewaters  13  3.  Sanitary Chemicals Used in Egg Processing Plants  4.  BOD and COD Reductions for Various Aeration Rates  37  5.  Results of SBR Aeration Study  40  6.  Characteristics of Egg Processing Lagoon System  42  7.  SBR Results for the Determination of Kinetic Coefficients  46  8.  Determination of Bacterial Isolates  50  v  ...  19  List of Figures  1.  Aerated Lagoon with Solids Recycle.  6  2.  The Sequencing Batch Reactor Process  10  3.  Flow Diagram of an Aerated Lagoon System for the Treatment of Egg Processing Wastewater...  15  4.  Process Flow for Experimental SBR System.  17  5.  B O D and C O D Reductions for Egg Processing Wastewater Treated by an Aerobic Lagoon System  6.  7.  26  Solids Reductions for Egg Processing Wastewater Treated by an Aerobic Lagoon System  26  Settling Velocities for Egg Processing Wastewater Treated by an Aerobic  27  Lagoon System 8.  T K N , Ammonia,  and Ortho-Phosphate Values for Egg Processing  Wastewater Treated by an Aerobic Lagoon System 9.  Dissolved Oxygen Levels of (A) Egg Processing Wastewater and of (B) Simulated Egg Processing Wastewater and Sanitary Chemicals Over Time  10.  30  The Effects of Sanitary Chemicals on the Dissolved Oxygen Levels of (A) Distilled Water and (B) Different Egg Fractions  11.  28  32  Dissolved Oxygen Levels of Egg Processing Wastewater at the Aeration Rates of (A) 0.2L/min for Reactors 1 & 2 and (B) 0.5 L/min for Reactors 1&2....  12.  34  Dissolved Oxygen Levels of Egg Processing Wastewater at the Aeration Rates of (A) 1.0 & 0.5 L/min for the First and Second Reactors, Respectively and (B) 1.5 & 0.5 L/min, for the First and Second Reactors, Respectively  35  vi  13.  K a Determination for Egg Processing Wastewater and Clean Water  38  14.  Determination of the Coefficients a' and b'  41  15.  Determination of the Coefficients K_ and k  44  16.  Determination of the Coefficients Y and k  45  17.  Dissolved Oxygen Levels of Egg Processing Wastewater for MCRTs of  L  d  (A) 5 days and (B) 10 days 18.  47  Dissolved Oxygen Levels of Egg Processing Wastewater for an M C R T of 20 days  48  vii  Acknowledgment  I would like to thank Andrea for her support and understanding during the course of this thesis.  I would also like to thank my supervisor, Dr. Victor Lo, for his  guidance and encouragement.  Thanks to my committee, Dr. Anthony Lau and Dr.  Richard Branion, for their valuable advice and time. A special thanks to the staff of Bio-Resource Engineering.  viii  Introduction  Aerated lagoons  are widely used for the treatment of food processing  wastewater for two main reasons: low capital expenditures and operating costs (Nemerow and Dasguptu, 1991).  For example, the cost of constructing an aerated  lagoon is low as the reaction vessel is merely an earthen basin rather than a fabricated reactor, common to other secondary waste treatment systems.  Operational costs are  also kept to a minimum as lagoons require very little operator attention and maintenance (Branion, 1992). For example, Nemerow and Dasguptu (1991) have determined that the costs to treat potato processing wastewaters using aerated lagoons is $495/MGal while the use of other biological treatments such as activated sludge costs $4425/MGal.  However, while lagoons provide an inexpensive form of wastewater  treatment, the construction of new or additional lagoons is not always possible due to the expense and/or lack of available land. For instance, processing facilities which experience an increase in loading rates may have to upgrade to a more efficient system with a lower hydraulic retention time (HRT) if land is not available for additional lagoons.  Another disadvantage of aerated lagoons is that they do not operate well at  temperatures below 14.4°C (Batsch and Randall, 1971) or with wastewaters high in biochemical oxygen demand (BOD).  As traditional aerated lagoons are operated as  processes without solids recycle and adequate clarification (Tchobanoglous and Franklin, 1991), their use is limited to a simple reduction in B O D . To achieve a reduction in total suspended solids (TSS) many aerobic lagoons now use solids recycle and employ a settling unit such as a clarifier (Metcalf and Eddy, 1991) to increase the mean cell residence time (MCRT) of the system.  For this reason, an aerated  lagoon is designed following many of the principles for activated sludge systems. However, the addition of a clarification unit and sludge recycle is expensive and may not be viable for many smaller food processing facilities.  1  A n inexpensive option is to  aerated lagoon as an SBR system, whereby the need for a clarifier and solids recycle is eliminated. The objective of this study was to determine if upgrading an aerated lagoon system for the treatment of egg processing wastewater to SBRs results in a more efficient system in terms of an effluent lower in BOD, TSS, and devoid of pathogens. The specific objectives of this study were to:  a) determine if the disinfecting chemicals used at egg processing facilities affect the dissolved oxygen (DO) levels of the wastewater, b) assess the aeration requirements for a lab scale SBR system including K a, L  a, and 13 values, c) determine the kinetic coefficients K , k, k , and Y for egg processing s  d  wastewater, d) compare the DO levels of the SBR system using different MCRTs, e) establish if the egg processing effluent is devoid of the pathogens which are normally associated with egg products.  2  Literature Review  1. Aerated Lagoons  Aerated lagoons are designed to be either completely mixed or incompetely mixed (Kouzell-Katsiri, 1987). For a lagoon to be properly aerated, the liquor must be well mixed which causes the solids to remain in suspension. If there is no clarification of the effluent, the B O D and TSS levels will be considerably higher.  Therefore,  lagoons without final clarification require HRTs of up to 4 weeks (Rich, 1985) for a sufficient reduction in B O D and TSS. Clarification units are often designed on the basis of interface settling velocities.  If settling data is not available, the design can be  based on surface overflow rates or solids loading rates (Tekippen and Bender, 1987). Typical design values use overflow rates of 16,000-32,000 L / m d or solids loading 2  rates of 1.64-2.46 kg/m h. As overflow rates are decreased, a higher quality effluent 2  is produced. It has also been found that effluent TSS are directly related, to a degree, to the overflow rate.  This correlation varies depending on the tank depth and the  flocculation ability of the influent.  Recommended depths range from a low of 3.7  meters to a high of 6.1 meters with the radius not exceeding five times the sidewater depth (Tchobanoglous and Franklin, 1991). The most common settling tanks are either circular or rectangular (Metcalf and Eddy, 1991).  Kormanik (1972) found that a  clarifier was not needed if the aerobic lagoon was followed by a facultative lagoon. A facultative lagoon has a mixing level low enough to allow much of the solids to settle. However, as the hydraulic retention times required to adequately treat the wastewater are much longer, larger lagoons or an equalization basin would be required. A study which  analyzed the  effluents  from  lagoons  showed  that many exceeded  the  recommended levels for BOD and TSS. Rich (1985) studied the effluents of six aerated lagoons constructed during the period from 1965 to 1975 and it was found that while  3  the B O D in the effluent met discharge requirements, high TSS levels (over 49 mg/L) were common. A correlation between effluent BOD and TSS was found to be  B O D = 13.0 + 0.31 TSS  (eq. 1)  5  As the systems employed polishing ponds, the high levels of TSS were determined to be a direct result of algal growth.  If the algal population was removed, the TSS on  average would not have exceeded 22 mg/L.  Therefore, it is beneficial to suppress  algae in order to achieve an adequate TSS removal. Algal growth can be inhibited by reducing the amount of solar radiation incident on the pond surface (Branion, 1992). This can be achieved by covering the pond surface, reducing the H R T , or by decreasing the pond surface area. Middlebrooks et al. (1982) found that algae are not a problem if the lagoon is completely mixed as turbulent conditions prevent light penetration.  If the depth must be increased to prevent algae growth, it must not be  increased too much as to create facultative and anaerobic zones. Lagoons under these conditions require higher retention times and often create obnoxious odours due to anaerobic metabolism. To maintain an aerobic environment, Eckenfelder (1972) recommends a lagoon depth of 8-16 feet (2.5 - 5m). Lagoons with depths closer to 16 feet are used in colder climates to reduce the chances of freezing.  For shallow lagoons, surface aerators are  sufficient to maintain a recommended dissolved oxygen (DO) level of 2.0 to 3.0 mg/L (Branion,  1992).  For lagoons  of greater depth or contaming a high strength  wastewater, the system usually requires submerged diffusers.  Mechanical surface  aerators can only supply a maximum aeration intensity of 125 g0 /m h while fine 3  2  bubble air diffusers can supply 200 g0 /m h. 3  2  Rich (1985) has determined that the  maximum oxygen demand in a completely suspended lagoon can be found using  4  Ro - 6.24 x 10" Q S  (eq. 2)  5  2  0  where: RQ, = maximum oxygen demand (kg/h) Q — wastewater flow rate (m /d) 3  S = influent B O D (mg/L) 0  5  Middlebrooks (1982) recommends that the maximum value (Ro ) should be multiplied 2  by 1.5 to allow for peak  flows.  After determining the oxygen requirements, the  aerators can be sized using the following method given by Middlebrooks et al. (1982).  N = a(C  sw  ^Q2 - C /C ) x (1.Q25T-20) L  S  (eq. 3)  where: N = equivalent oxygen transfer to tapwater (kg/hr) a = 0 transfer to waste/0 transfer to water 2  2  P = relative oxygen solubility C  s w  C  s s  = P(C )P SS  = oxygen saturation of tapwater at waste temperature, mg/L  P = barometric pressure at site/barometric pressure at sea level C = D O to be maintained in treatment, mg/L L  C = oxygen saturation at 20°C and 1 atmosphere pressure s  = 9.17 mg/1 T = lagoon temperature, °C  Surface aerators are estimated at 1.4 kg oxygen/hp-h and a 90% efficiency for gear reducers (Middlebrooks et al., 1982).  Balasha and Sperber (1974) report that the  power required to maintain complete mixing can vary from 3-4 W/m for larger 3  5  lagoons (above 10,000 m ) to 20 W/m for smaller lagoons (500m ). Galil et al. (1991) 3  3  3  determined that the best bioflocs were achieved using 4.9 watts/m in an activated 3  sludge process.  The placing of aerators is also important (Branion, 1992). Spacing  aerators on the center of the sides creates poor oxygen transfer efficiencies. aerators may be suspended (i.e. by cables) or floated.  Surface  Suspended aerators are  recommended in colder climates as floating aerators tend to tip over when the surface of the lagoon freezes.  If a higher oxygen transfer rate is required submerged aerators  can be placed on the bottom of the lagoon or attached to the sides.  Side attachments  also help in mixing by creating currents which cause a rolling action within the lagoon. Aeration devices, through mixing, also ensure that an adequate amount of substrate is available to the microorganisms. To maintain an active microbial population, the recycling of solids is an option. This involves the design of a solid-liquid separation device (i.e. clarifier) and return of a fraction of the sludge to the aeration lagoon (figure 1).  Influent  4  4 Aeration Basin Snlifk R e c y c l e  Ffflnent  Clarifier  ^ Waste SlnHge  y  Figure 1. Aerated Lagoon with Solids Recycle  By recycling the solids, the solid retention time (MCRT) can be increased to the recommended time of 3 to 15 days. good settling characteristics.  A M C R T in this range results in a sludge with  A M C R T less than 3 days results in a biomass which  does not form floes, leading to slower settling velocities.  6  A M C R T greater than 15  days results in a biomass which forms "pin floes" which act as colloids with poor settling characteristics. A longer M C R T also results in a microbial population that has a higher death than growth rate. Cell death (lysis) releases cell debris into suspension which is difficult to settle. Easily settleable sludges have zone settling velocities in the order of 1.52 to 7.62 m/h (Branion, 1992).  As lagoons are open to the atmosphere,  temperature is a major concern in terms of effluent quality.  A study by Bartsch and  Randall (1971) determined that effluent B O D levels in aerated lagoons increased sharply at temperatures below 14.4°C. lagoons  operating below  Schneiter et al. (1993) also reported that  19°C experience  greater levels of undigested  sludge  accumulation.  2. Pathogens Associated with Egg Products  Egg processing wastewater can experience microbial contamination through a number of sources (Frazier and Westhoff, 1988).  Potential sources include hen fecal  matter, washwater, human contact, or egg packaging material. In addition, processing, rough handling and washing of the eggs facilitate the penetration of microorganisms through the shell and the membrane. Total number of bacteria on a hen's egg ranges from 10 to 10 and include a diverse group as listed in table 1. 2  7  For egg processing  facilities, the World Health Organization (WHO) considers that the examination for  Salmonella is the most important test for the indication of the effectiveness of pasteurization for egg products.  Tests for coliforms and Enterobactericaceae where  also acknowledged as valuable. Safe levels for coliforms in egg products were set at lOVlOO ml or below and at zero for food processing effluents,  Salmonella and fecal coliforms. However, for  Helmer et al.  (1991) report that coliforms at any  concentration and fecal coliforms <_1000 faecal coliforms/100 ml of sample are not a concern to public health when applied to field crops. 7  A more stringent guideline of less than 200 fecal coliforms/100 mis is given for effluents that are applied to lawns where the public have direct contact.  Table 1. Common Microorganisms Found on Egg Shells  Percent of the flora No. of Farms  Type  Egg-breaking Plants*  Packing Stations*  8(5)  Streptococcus Staphylococcus  5  30  9(16)  Micrococcus  18  23(20)  37(94)  Sarcina  2  20 5(23)  Arthrobacter (18)  30  Bacillus  (2.5)  Pseudomonas  6  22.5(36.5)  Achromobacter  19  1.5(3)  Flavobacterium  3  Coli-aeorgenes  5  Aeromonas  10.5(11.5)  20(20)  1  20(50)  1  Proteus  19(12)  10(20)  Serratia 7  Molds  12(14)  Unclassified  *Numbers represent data from clean eggs; numbers in parentheses represent soiled or cracked eggs (from Frazier and Westhoff, 1988).  Studies indicate that effluents  with <_1000 faecal coliforms/100 ml contain few  pathogens and any pathogens present will eventually be inactivated by ultraviolet radiation, desiccation,  or biological predators.  While fecal coliforms are not  recognized as a direct concern, they are valuable as indicators of possible pathogens such as Salmonella. Without adequate sanitation, microorganisms such as Salmonella sp. may build up in the washwater after processing.  8  A study done by R . H . Shertzer  (1986) found that  Salmonella were effectively eliminated from wastewaters during  chlorination. For this reason, food processing facilities disinfect their equipment on a regular basis with chlorine based sanitizers.  However, if the sanitizing chemicals are  directed to the wastewater treatment system, the system's microbial population can be easily "upset".  Bulley et al. (1973) found that 1.3% of the total wastewater coming  from an egg processing plant was disinfecting water. This water contained 100 mg/L chlorine and arrived at the lagoon in a "slug load". Favero (1985) describes chlorine compounds (500-5000 mg free chlorine per litre) as having an intermediate level of microbial potency.  It is described as a disinfectant which inactivates virtually all  recognized pathogenic microorganisms but not all microbial forms.  Fernandez et al.  (1992) report that one of the main functions of a wastewater lagoon is for the elimination of potentially pathogenic  microorganisms.  Important factors which  influence the die-off of pathogens in lagoons are temperature, u.v. light penetration, dissolved oxygen levels, p H , and aggregation and sedimentation. microorganisms effectively  form a resistance  towards die-off.  By aggregating, the Aggregation or  clumping is a natural state for many water borne microbes (Sobsey, 1989).  3. Sequencing Batch Reactors  The SBR process is a batch system which operates on a fill and draw mode of operation utilizing one or more reactors. Figure 2 illustrates the fate of the wastewater through an SBR system.  The typical SBR system operates in five discrete stages: fill,  react, settle, draw, and idle. While react stage can vary from hours to days, the typical settling time is usually from 0.5 to 1.5 hours in length (Irvine, 1989). The idle stage is necessary in a multiple tank system when the other reactors are not completely full. To control the concentration of biomass within the reactor, sludge wasting is usually accomplished during the idle stage.  9  One of the main benefits of the SBR system is its flexibility. As the SBR process is time oriented, each stage can be adjusted to replace any conventional activated sludge system including extended aeration and contact stabilization.  For example, during the  fill stage, by restricting aeration and creating an anoxic environment, a condition is created which results in a reduction in filamentous organisms and an improved sludge settleability (Irvine et al., 1983).  In addition, as the sedimentation is accomplished  within the SBR, the need for separate final clarifiers and return sludge is eliminated (Arora et al,  1985). To achieve nitrogen removal, an additional anoxic stage can be  added between the aeration and draw stages (Siverstein and Schroeder, 1983). Irvine et al.  (1983) have  determined  that  nitrification and denitrification  occur  almost  simultaneously during the anoxic stage. In addition, Irvine et al. (1985) reported good phosphorus removal when approximately 40% of the fill stage was without aeration.  1. Fill  2. React  3. Settle  4. Draw  Figure 2. The Sequencing Batch Reactor Process  Past studies by Lo et al. (1985) and Irvine et al. (1979) have reported excellent removals of B O D and SS for milking parlour and municipal wastewater. Irvine et al. 5  were able to easily achieve effluents below 10 mg/L for B O D and SS while adequately 5  removing biological phosphorus.  In addition, tiie upgrading of an activated sludge  plant to a SBR process (Irvine, 1983) in Culver, Ind. resulted in an effluent of similar  10  quality. Okada et al. (1990) also reported good results for the removal of nitrogen and phosphorus using an SBR system for the treatment of soybean fermentation wastewater. Arora et al. (1985) evaluated the SBR systems at eight municipal treatment plants. The HRT of each system varied from 7.6 hours to 49 hours. Due to the difference in loading rates and wastewater quality objectives, each plant's H R T varied. Here, the ability to easily manipulate the HRT and M C R T of an SBR system is major advantage over conventional systems such as aerated lagoons and activated sludge.  Irvine also  determined that the power requirements for aeration ranged from 6.0 to 6.7 Watts/kg B O D oxidized. While SBR systems were not feasible in the past due to the need for 5  manual control at each stage, new process control devices have made the SBR an attractive alternative for todays' wastewater treatment needs.  4. Microbial Kinetics  The kinetic modelling of biological wastewater treatment systems was first explored by Monod (1959) and was based on the Michaelis-Menton equation for enzyme kinetics (US E P A , 1971).  At this time, a relationship between microbial  growth and substrate concentration was established as the following.  c  \i = ji  -k  max  K  +  . s  s  (eq. 4)  d  where: ji = specific growth rate, time p  max  1  = maximum specific growth rate, time  1  S = concentration of growth limiting substrate in solution, mass/unit volume K = half velocity constant, substrate concentration at s  1/2 the maximum growth rate, mass/unit volume  11  k = endogenous decay coefficient, time  1  d  While the kinetic modelling of SBR systems is not well established at this time (Orhon et al., 1986), a model has been developed which follows the design for other modes of biological treatment such as activated sludge. The mass balance equations for substrate removal and microbial growth for SBR systems are described as follows:  d  =  S  dt  d  ( S - S ) -  Q  V + Qt  X  -  "° V +Qt  dt  0  X + \i  ^ Y(K + S ) S  S  (eq.5)  X  - k X  X  K +X  (eq.6)  d  where: Q = influent flow rate, vol/time S = influent substrate concentration, mg/L BOD, 0  C O D , or T O C S = effluent substrate concentration, mg/L e  X = biomass concentration in reactor (MLVSS), mg/L Y = yield coefficient (mass biomass formed/mass substrate consumed)  To use the above model, the parameters Y , k, K , k must be established using a lab or s  d  pilot scale reactor (Metcalf and Eddy, 1991; Orhon et al,  1986), using equation 7. By  plotting X0/S -S versus 1/S , the coefficients K and k can be determined. By further o  plotting 1/9  C  e  s  e  versus S -S /X9, the coefficients Y and k can be determined. 0  e  To  determine these coefficients, a system is typically operated using several different mean cell residence times with mean values being set for Q, S , S , and X . 0  12  e  K  x e  S -S o  kS  +  1 T~  ( e q  -  7 )  e  where: 6 = hydraulic retention time, time X = M L V S S = biomass concentration, mg/L k = maximum rate substrate utilization per mass of microorganism = p  max  /Y, d  1  The kinetic coefficients for the aerobic treatment of a number of food processing wastewaters have been reported by Branion (1992) and are presented in table 2.  Table 2. Kinetic Coefficients for Various Wastewater  Kinetic Coefficient (BOD basis) Wastewater  K,(mg/L)  Y (mg/mg)  Poultry Processing  500  1.32  54.5  0.72  Shrimp Processing  85.5  0.50  37.0  1.60  Soybean  355  0.74  16.3  0.14  Skim Milk  100  0.48  11.6  0.05  Municipal  25-100  0.4-0.8  2-10  0.05-0.10  Reference: Branion (1992)  13  k  (d-0  kd (d ) 1  Materials and Methods  Basis of Design  At Vanderpol's Eggs Ltd., Abbotsford, British Columbia, egg processing wastewater is presently being treated in two aerated lagoons arranged in series (figure 3).  The volumes of the first and second lagoons are 246 m and 364 m respectively 3  with depths of approximately 2 m.  3  The retention times are 4.5 days and 6.7 days  respectively with an average influent flow rate of 55 m /d. 3  As the flow through the  system is continuous, the flow rate varies according to the water usage within the plant. The wastewater is aerated in three small equalization tanks prior to entering the first lagoon. Aeration in the first and second lagoons is supplied by 5 hp and 10 hp surface aerators,  respectively.  While these two aerators were  assumed adequate for  maintaining a D O between 2 and 3 mg/L, the D O of both lagoons was consistently below 0.5 mg/L in the first lagoon and 1.0 mg/L in the second lagoon.  After  treatment, there is no liquid-solid separation and the effluent, high in BOD and TSS, is simply used to irrigate adjacent fields.  Part way through the study, a storage lagoon  was constructed to store effluent when irrigating was impractical (e.g. rainy days, freezing conditions, or shutdowns).  As Vanderpols' plans on expanding to include an  egg grading facility, the treatment efficiency of the two lagoons must be improved in order to handle an increase in loading rates. The projected increase in the influent flow rate to a total of 73 m /d would decrease the hydraulic retention time to 3.4 days in the 3  first lagoon and 5 days in the second. The increase in the flow rate would also result in higher loading rates on the adjacent fields. As the company does not want to change the dimensions of the two lagoons, the hydraulic retention time (HRT) of the system cannot be altered unless the effluent flow rate is changed. Therefore, a lab scale SBR system was designed to determine if the efficiency of the lagoon could be improved by  14  INFLUENT  55  m /d 3  EQUALIZATION TANKS WITH AERATION  LAGOON 24 6 m  #1 3  t LAGOON #2 3 64 m 3  STORAGE  LAGOON  EFFLUENT  TO  FIELDS  <-  Figure 3. Flow Diagram of an Aerated Lagoon System f o r the Treatment of Egg Processing Wastewater  15  upgrading to an SBR system using the anticipated system HRT of 8 days. Before the present lagoon system could be deemed inefficient, an evaluation of the wastewater for any antimicrobial products was undertaken.  As the sanitary chemicals used during  production were emptied into the lagoons, lab scale batch tests were first completed using each of the chemicals.  2. Lab Scale SBR System.  Lab scale fermentations were completed in two parallel SBR systems consisting of four vessels constructed from acrylic plastic pipe (figure 4).  Two parallel systems  were constructed for the replication of experiments. The working volume for all four reactors was 4 litres.  The wastewater was obtained from an egg processing plant  (Vanderpols', Abbottsford, B.C.) at the.influent inlet pipe. A l l samples were taken on days when the plants' production was similar to ensure a uniform influent throughout the study.  The samples were stored at 4°C in 20 litre plastic pails. The wastewater  was fed to the SBR systems from a 20 litre pail immersed in a cooling water bath maintained at 4°C.  The wastewater was added and withdrawn using peristaltic pumps  and controlled using microprocessor timers. The system was automated with the use of solenoid valves and timers to deliver a predetermined volume at regular intervals. The system was run continuously for two months before testing was initiated. This period was necessary for a stable microbial population to be established.  The M C R T was  changed by withdrawing different ratios of effluent during the draw stage (figure 2) either with the air on or with the air off. For example, to achieve a 20 day M C R T for an SBR operating with a 4 day HRT, 200 mis and 800 mis was withdrawn with the air on and off, respectively.  As this method requires that the 800 mis be very low in  solids, a one hour settling time was used before withdrawing the effluent.  As the  system involved two SBRs in series, the sequence was to draw from the second SBR  16  Effluent Withdrawal Tubes  Fine Bubble Diffuser  CD  Mixer  Cooling Water  ^.  I n f l u e n t Feed  Tank (20  L)  SBR  (4 L)  CD  Figure 4„ Process Flow for Experimental SBR System  17  first.  All SBR cycles involved one fill and draw stage per 24 hour period.  Air was  supplied through a sparger placed on the bottom of each reactor and regulated with a flowmeter.  The dissolved oxygen in both reactors were monitored using D O meters  connected to an automatic digital data recorder.  The pH was monitored using a  benchtop pH meter.  3. Analysis of Egg Processing Sanitary Chemicals  To determine if the cleaning chemicals were responsible for the low D O levels in the first lagoon, a number of batch reactors were monitored for D O levels after chemical additions.  The aeration rate (Q ) was set at 1.0 L/min. air  Table 3 lists the chemicals  and concentrations, used on a daily basis at Vanderpols', reactors.  that were added to the  As the chemicals added at the plant go through a number of reactions (i.e.  oxidation) before reaching the lagoons, the concentrations used in the lab reactors represent the extreme case (i.e. high concentrations).  To determine which chemicals  were responsible for this sudden decrease in D O , separate batch digests were performed using different combinations of distilled water, a simulated wastewater (devoid of chemicals), and one of the eight chemicals listed in table 3. The simulated wastewater was made using either whole eggs, yolks, or whites and diluted with distilled water.  As the influent wastewater has a total solids (TS) level of 0.5%, the  simulated wastewater was diluted to this concentration.  Each batch digest was  monitored for dissolved oxygen and biomass activity. Biomass activity was determined by determining colony forming units (CFU) on plate count agar.  18  I  Table 3. Sanitary Chemicals used in Egg Processing Plants 1. Sodium Hypochlorite (10-20 %) at 0.15 ml/L 2. Bolt-569 caustic alkaline cleaner at 0.1 ml/L -active ingredients: -sodium hydroxide (10%) -sodium dodecylbenzene sulfonate (3 %) 3. D-Foam 477 silicone defoamer at 0.06 ml/L 4. Interest chlorinated cleaner at 0.01 ml/L -active ingredients: -potassium hydroxide (20-25 %) -alkaline phosphate (10-15%) -sodium silicate (5-10%) -available chlorine (3%) 5. Ova-Clean 589 alkali cleaner at 0.18 g/L -active ingredient: -sodium dichloroisocyanurate (2%) 6. Procid-573 acid cleaner at 0.04 ml/L -active ingredients: -phosphoric acid (35%) -nitric acid (15%) 7. Solo-578 or Ovaclean alkali cleaners at 0.18 g/L -active ingredients: -sodium dodecylbenzene sulfonate (5 %) -sodium dichloroisocyanurate (2%) 8. Sting caustic-alkali cleaner at 0.2 g/L -active ingredient: -sodium hydroxide (80%)  -  4. Analytical  Solids Analysis. Ceramic dishes and glass fibre filter paper were heated to 105°C overnight and then cooled to a constant weight.  The 20 ml samples were dried  overnight and recorded on a dry weight basis for TS and TSS.  For volatile solids, the  samples were placed in a muffle furnace for 15 min. at 550°C.  Solids were expressed  in terms of mg/L.  19  Chemical Oxygen Demand (COD). Samples were acid digested for 3 hours in a block heater set at 150°C. The C O D of the samples was then determined using a colorimeter.  Biochemical  Oxygen Demand. The B O D was carried out according to Standard  Methods (APHA, 1985). The dissolved oxygen of each sample was determined using a YSI dissolved oxygen meter.  Nitrogen and Phosphorus. Total Kjeldahl nitrogen (TKN), ammonia nitrogen (NH -N), 3  and ortho-phosphate levels were determined using a Technicon Auto Analyzer 2 as described by Schumann et al. (1973).  5. Aeration Studies.  All studies involving aeration were performed at temperatures ranging from 19°C to 21°C.  A l l tests utilized a 4 litre SBR with a submerged diffuser placed on the bottom  of the reactor.  D O was measured in situ using a membrane electrode.  A l l tests  involving aeration were started after the SBR was subjected to at least one week at the prescribed aeration rate.  Ka L  Determination.  K a was determined using the unsteady-state aeration method L  described by the A S C E (1984) and Campbell, Jr. (1986). A l l tests were performed using aeration rates of 1.0 L/min.  Non-steady state testing involved purging the  wastewater or clean water with N until a D O of 0 mg/L was reached. Once the D O 2  reach 0 mg/L, aeration was reintroduced to the reactor. monitor the increase in D O over time.  A D O probe was used to  Equation 8 was used to evaluate the data  obtained during the unsteady-state tests.  20  ( C - C ) = (C - Co) e x p - K a R  R  (eq. 8)  L  where: C  R  = D O concentration as time approaches infinity, mg/L  C = D O concentration in liquid phase, mg/L C  0  — D O concentration at time zero, mg/L  K  L  = mass transfer coefficient  a = interfacial area between the gas and liquid phases  The "alternate best fit log deficit method" requires that equation 8 descibed by Baillod and Paulson (1986) be written in the following logarithmic form.  log(C - C) = log(C - C ) - (K a/2.303) t R  R  0  L  This equation is fit to the data by performing a linear regression of the log of ( C - C) R  versus time. K a is then determined from the slope of the regression. C values used L  R  for the aeration tests were based on pure water at 20°C and 1 atmosphere.  As C  R  cannot be measured by a membrane probe and many wastewaters contain substances that interfere with the Winkler method, C values were based on total dissolved solids R  (TDS) concentrations given by Baillod and Paulson (1986).  In this method, chloride  concentrations from Standard Methods are converted to T D S .  For example, a  wastewater with a TDS concentration of 9100 mg/L is calculated to have a C of 8.6 R  while a water with no TDS is calculated to have a C of 9.07. R  The data for K a values L  was obtained during the react period of the SBR cycle and after the D O in the reactor had stabilized.  This method was categorized as a batch endogenous test (without  wastewater flow), as the rate of change of D O was momtored during the react period. A limitation of this method is that a shut down in aeration results in inadequate mixing of the wastewater and may lead to erratic results upon resumption of aeration (Boon,  21  1983).  Alpha, Beta, and Theta Factors (a, [3, and 0). Alpha factors were determined using the unsteady-state aeration method described in the methods for K a determination. L  C  R  values for beta factors were calculated based on the total dissolved solids (TDS) measurements at 20°C described by Baillod and Paulson (1986).  Theta factors were  taken to equal 1.024 for this study.  6. Microbial Identification  Aerobic  Plate  Counts.  Viable  aerobic  plate  counts  were  obtained  using procedures described in Standard Methods (American Public Health Association, 1985).  Additional aerobic plate counts were completed on R2A  medium described by Reasoner (1985). incubated at 28°C for 5 to 7 days.  Plates using the R2A medium were  A l l plates and media were autoclaved at  121°C for 15 minutes.  Coliform Identification. Most Probable Number (MPN) tests were carried out to the completed stage using the multiple tube fermentation technique as described in Standard Methods (APHA, 1985).  The identification of fecal  coliforms was completed using Standard Methods (APHA,  1985).  Fecal  coliforms were isolated using E C medium and were incubated at 44.5°C for 24 hrs.  Salmonella Identification.  Salmonella sp. were isolated using the methods  described by Parry et al. (1982).  Salmonella were concentrated in peptone  water, enriched in tetrathionate broth, and selected on Salmonella-Shigella agar 22  and TSI agar. All positive TSI agar slopes were subjected to serological testing identifying the O, V i , and H antigens.  Differential Procedures for Microbial Identification.  All  coliforms  selected  through the completed stage of the M P N test were further identified to the genus level according to Bergey's Manual of Systematic Bacteriology (1974) and the Manual of Clinical Microbiology (Lennette, 1985). Specific tests included the following.  1.  Catalase Reaction.  bacteria  catalyses  the  The release  enzyme of  catalase  oxygen  from  produced  by  hydrogen  some  peroxide.  The organism to be tested is grown on a nutrient agar slant for 18 to 25 hours at 35°C.  To test for catalase, approximately 1 ml of hydrogen peroxide is poured  over the slant. The presence of gas bubbles indicates a positive test.  2. Motility Tests. To test for motility, nutrient agar slants containing 0.4% agar were used. The slants were inoculated by stabbing into the top of the agar to a depth about 5 mm. The tubes were incubated for 2 days at 35°C.  If the results  were negative, the slants were incubated a further 5 days.  3. Spore Stains. Heat fixed bacterial isolates were stained with malachite green and  counterstained with carbol fuchsin.  Spore were identified under oil  immersion magnification.  4.  Gram Stains. Heat fixed bacterial isolates were stained with crystal violet  solution and counterstained with safranin. Under magnification, gram-positive organisms appear blue while gram-negative organisms appear red.  23  5. Culture  Media.  All culture media (MacConkey, etc.) was formulated  according to the Manual of Clinical Microbiology (Lennette, 1985) except for the R2A medium described by Reasoner (1984).  24  Results and Discussion  1. Waste Characterization.  Wastewater samples obtained from an egg processing facility were analyzed for pH, BOD, C O D , solids, settleability, nitrogen, and phosphorus. The pH varied from 7.34 in lagoon 1 to 8.93 from the influent line. Figure 5 illustrates the C O D and BOD of the wastewater as it proceeded through the system.  The influent had a C O D and  BOD of 5105 mg/L and 2572 mg/L, respectively. After an approximate retention time of 4.5 days in lagoon 1, the C O D was reduced by 40% while the BOD was reduced by 54%. A n additional 6.7 day retention in lagoon 2 resulted in a total reduction of 55% for C O D and 68% for B O D .  As aerobic lagoons are usually designed for B O D  removals of 80-95% (Branion, 1992), the present removal rate of only 68% through the two lagoons was not deemed adequate. In this case, food to microorganism ratios (F/M = kg B O D applied/kg mixed liqour volatile suspended solids (MLVSS) x d) for C O D and B O D were 0.53 d and 0.27 d 1  lagoon 2, respectively.  1  for lagoon 1 and 0.55 d and 0.21 d for 1  1  Usual F / M ratios for BOD range from 0.2 to 0.6 d" (Metcalf 1  and Eddy, 1991) for completely mixed activated sludge systems. Figure 6 shows the reductions in total and suspended solids. As illustrated, the TS decreased by only 15% and the M L V S S actually increased from 312 mg/L to 1372 mg/L (336%) in the first lagoon and to 1222 mg/L in the second lagoon. likely the result of the increase in biomass.  The increase in M L V S S was most  Typical activated sludge systems contain  biomass in the region of 1500 to 5000 mg/L. The settling velocity of the effluent (figure 7) was determined to be 1.04 m/h. Branion (1992) reports that solids with good settling characteristics have settling velocities ranging from 1.52 to 7.62 m/h. T K N decreased 26% from 170 mg/L to 125 mg/L while ammonia nitrogen increased substantially from 6 mg/L to 119 mg/L (figure 8). Here, the increase in ammonia  25  .60005000 r-  VZA  COD  ES3 B O D  4000 mg/L  3000 2000 1000 Influent  Lagoon 1 0 = 4.5 d  Lagoon 2 0 = 6.7 d  F i g u r e 5. BOD a n d COD R e d u c t i o n s ' f o r Egg P r o c e s s i n g Wastewater T r e a t e d b y an A e r o b i c Lagoon S y s t e m  •6000  WA  TS TDS  5000 h  MLVSS  m g / L  1000 0 L  Influent  Lagoon 1 0 = 4.5 d  Lagoon 2 0 = 6.7 d  Figure 6. Solids R e d u c t i o n s f o r Egg P r o c e s s i n g Wastewater T r e a t e d b y a n A e r o b i c Lagoon S y s t e m  26  B o •A  '3D •i—I CP  PC CD CJ  0)  10  20  30  40 Time  50  60  70  80  100  (min)  F i g u r e 7. S e t t l i n g V e l o c i t i e s for Egg P r o c e s s i n g T r e a t e d by an A e r o b i c Lagoon S y s t e m  27  90  Wastewater  V7A I^Xl  200  TKN Ammonia Ortho Phosphates  1 50  mg/L  100  50  0 L  Influent  Lagoon 1 Lagoon 2 0=4.5 d 0 = 6.7 d  F i g u r e 8. TKN, A m m o n i a , a n d O r t h o p h o s p h a t e V a l u e s f o r Egg P r o c e s s i n g Wastewater. T r e a t e d by A e r o b i c Lagoons  28  nitrogen was most likely a result of the biodegradation of organic nitrogen to ammonia nitrogen.  Figure 8 also shows that the concentration of orthophosphate was reduced  54% from 41 mg/L to 19 mg/L. While total nitrogen levels above 85 mg/L, ammonia levels above 50 mg/L, and organic phosphorus concentrations above 5 mg/L are considered "strong" for a wastewater (Metcalf and Eddy ,1991), these levels are not too high if the wastewater is further treated through land application.  Loehr (1984)  reports that an alfalfa crop over its growth cycle can remove 504 kg nitrogen/ha and 39 kg phosphorus/ha.  A n effluent  of  100  mg/L total  nitrogen  and  19 mg/L  orthophosphate would result in a mass loading at 2.0 x 10 L/yr of approximately 2000 7  kg nitrogen/yr and 380 kg orthophosphate/yr.  Therefore, if one crop is grown per  year, a land base of 10 hectares is required.  2. Sanitary Chemicals and Treatment Efficiency  To determine if the cleaning chemicals were responsible for the low D O levels in the lagoon system at the egg processing facility, a number of batch digests were monitored for D O levels after chemical additions. Figure 9 represents the phenomenon that is occurring in the first lagoon.  Influent wastewater was aerated over a 24 hour  period. After 7 hours the D O dropped from a high of 8.2 mg/L to 0 mg/L and stayed at 0 mg/L for the remainder of the testing period.  Figure 9 exhibits the D O levels  when a simulated egg wastewater is combined with the eight sanitary chemicals. Without the presence of chemicals, the D O falls from approximately 8 mg/L to 6 mg/L over a 24 hour period. This consumption of oxygen is normal for wastewater actively undergoing microbial degradation.  After 24 hours, the eight sanitary chemicals were  added to the active digest (figure 9).  Within 14 hours, the D O dropped from  approximately 6 mg/L to 0 mg/L and stayed at this level for the remainder of the monitored time. A n aerobic plate count of this wastewater revealed approximately 10  7  29  (A)  10  a CD  x .o Influent  • j>. Kl  m  10  15  20  25  30  Time (hrs) (B) 1 0  on  r  S i m u l a t e d Wastewater (Whole Egg)  CP  S i m u l a t e d Wastewater  O  + Chemicals  T3  j> "o  m m ' -i—i  O  • 20 .  30  Time ( h r s ) F i g u r e 9. Dissolved Oxygen Levels of (A) Egg P r o c e s s i n g Wastewater a n d of (B) S i m u l a t e d Egg P r o c e s s i n g Wastewate and S a n i t a r y C h e m i c a l s Over Time  30  cells/ml, indicating that the sudden drop in D O could not be due to the microbes utilizing the substrate. Batch digests were also initiated using the cleaning chemicals in combination with distilled water.  Figure 10 shows that the D O remained fairly  constant over a 27 hour period. As the egg fraction must be present for a sudden drop in D O , wastewaters were prepared which contained either egg whites or yolks plus chemicals (figure 10). It was found that the egg whites and yolks must both be present for a sudden drop in D O to occur. When digests were run using each individual chemical, the following chemicals resulted in sudden D O drops with most reductions occurring within 15 hours. 1. 2. 3. 4.  Sodium hypochlorite Ovaclean Procid acid D-Foam  5. Bolt (figure 7) All the experiments evaluating the effects of disinfecting chemicals on D O were done prior to establishing a microbial population. Therefore, any sudden reduction of D O could not be attritubed to microbial oxidation. Therefore, the cause of the high oxygen demand is though to be due to surfactants and chemically oxygen demanding substances which are added prior to entering the waste treatment system.  For example, many of  the disinfecting agents added during processing where chlorine based. Middlebrooks et al. (1982) found that the C O D of pond effluents can increase as the concentration of free chlorine increases. This was attributed to the oxidation of SS by the free chlorine. The oxidation of SS created an oxygen demand which did not allow sufficient oxygen for the growth of the biomass. In addition, the presence of surfactants or surface active agents may reduce the ability for gas exchange by decreasing the surface renewal at the gas-liquid interface.  However, by allowing for the microbial population to be  established over a two week period, aeration rates of 1.0 L/min adequately supported growth and resulted in good reductions in C O D . 31  It is believed that a population was  '(A)-  •  10  r  Distilled Water + Chemicals  4  5 - 1 0  15  Time  20  25  30  25  30  (hrs)  Egg Whites + Chemicals  8  ; ^  e  e  e  e  e  % e e e e o €  W  Egg Yolks + Chemicals  0  10  -15-  Time  20  (hrs)  F i g u r e 10. T h e E f f e c t of S a n i t a r y C h e m i c a l s o n t h e D i s s o l v e d O x y g e n L e v e l s of (A) D i s t i l l e d W a t e r a n d (B) D i f f e r e n t E g g F r a c t i o n s  32  established which was successful at eliminating or reducing the chemicals responsible for the increase in oxygen demand. Overall * the cost of providing additional aeration to the reactors can be expensive and it may be more cost effective to remove the chemicals from the wastewater prior to treatment.  3. Aeration Requirements  Aeration  Rates.  In an attempt to achieve a D O level between 2 and 3 mg/L in both SBRs, various aeration rates were studied with the lab scale reactors. At an aeration rate of 0.2 L/min for both reactors (figure 11), the D O levels remained at 0.0 mg/L over the 24 hour test. When the aeration rate was increased to 0.6 L/min (figure 11), the D O level did not improve in the first reactor but increased to 4-6 mg/L in the second reactor over 24 hours. To achieve more appropriate D O levels, the aeration rate was adjusted accordingly.  When the aeration rate was raised to 1.0 L/min in the first  reactor and decreased to 0.5 L/min in the second reactor (figure 12), the D O level in the first reactor increased to a high of 2 mg/L and varied between 1 and 4 mg/L in the second reactor. As the D O level was still low in SBR 1 for the first 12 hours of the digest, an attempt to further increase the aeration rate was made.  A n increase to 1.5  L/min improved the D O concentrations in the first reactor (figure 12) to between 1 and 4 mg/L.  While the D O levels improved with higher aeration rates, the initial addition  of influent (fill stage) to the reactors resulted in a sudden drop in D O (figure 12B). In all cases, an improvement in the D O levels was not realized until approximately 10 hours after the initial fill period. This effect was evident during all aeration rates. As was discussed in the section "Sanitary Chemicals and Treatment Efficiency", it is believed that the chemicals added for disinfection process during processing are  33  (A)  8  f  Of)  d . CD  >, fx! O X)  j>  Reactors 1 & 2 (0.2 L / m i n )  m m  10  15  Time (B)  .20  25  30  (hrs)  8 Reactor 2  (0.6 L / m i n )  a CD  >, X O  T3 CD  j>  'o  m co  Reactor 1  (0.6 L / m i n )  0 >St» o o 6"°o o cft°X> o cffio.o t 5. 10 15 20 %  0<  Time  25  30  (hrs)  F i g u r e 11. Dissolved Oxygen Wastewater at the A e r a t i o n for R e a c t o r s 1 & 2 a n d (B) 1 & 2.  34  >0<::>  Levels of Egg Processing Rates of (A) 0.2 L / m i n 0.5 L / m i n for R e a c t o r s :  (A)  8  6  R e a c t o r 2 (0.5 L / m i n )  •  4  Q  P  p..  'O' 0 A"oo6ooo 0 5 10  A ooo • .ooo • Reactor 1 • (1.0 L / m i n )  J  15  I  L  20  25  :  30  I  25  30  .' Time ( h r s ) 8 R e a c t o r 2..(0.5 L / m i n )  4  0  •P A A  / o  Reactor 1 (1.5 L / m i n )  10 , 15 20 Time (hrs)  F i g u r e 12. Dissolved Oxygen Levels of Egg P r o c e s s i n g Wastewater at "the" A e r a t i o n Rates of (A) 0.5 & 1.0 . L / m i n f o r t h e F i r s t a n d S e c o n d Reactors, R e s p e c t i v e l y a n d (B) 0.5 a n d 1.5 L / m i n f o r t h e F i r s t a n d S e c o n d Reactors, Respectively. 35  creating a high oxygen demand. In the earlier chemical batch tests (figures 11 and 12), the D O remained at zero over the 24 hour testing period.  In the aeration testing  period, the reactors were placed in a continuous mode and were allowed to achieve "steady state" over a period of two months.  It is believed that a population was  established which was successful at eliminating or reducing the chemicals responsible for the increase in oxygen demand.  However,  by reducing or eliminating these  chemicals before they enter the waste stream, a more cost effective aeration system can be utilized. The efficiency of the digests were also evaluated through C O D , B O D , and solids reductions (table 4). At an aeration rate of 1.0 L/min for SBR 1 and 0.5 L/min for SBR 2, the efficiency appears to reach a plateau. As the efficiency did not increase substantially when the aeration rate was increased to 1.5 L/min in the first reactor, all subsequent digests employed an aeration rate of 1.0 L/min for the first reactor and 0.5 L/min for the second reactor.  Final reductions of 86% C O D and 98% B O D were  reached (Table 4). The efficiency greatly improved from the lagoon system which only achieved reductions of 55% and 68% for C O D and B O D , respectively (figure 5). Reductions of solids were less dramatic with only a 10% reduction in TS and a 65% reduction in TSS at the aeration rate of 1.0 mg/L. However, this compares favourably to the lagoons at Vanderpols which only achieved a reduction of 15% for TS and actually had an increase in TSS (figure 6).  During the testing period, the p H varied  from an average of 8.1 in the first reactor to 7.6 in the second reactor. At aeration rates of 1.0 L/min and 0.5 L/min, the air supplied on a daily basis for the first and second reactors was 0.036 ftVmin and 0.018 ftVmin, respectively.  For comparison,  activated sludge systems with lower strength wastewater have been found to require approximately 1500 ftVlb BOD (Tchobanoglous and Franklin, 1991). If applied to the experimental SBR system, the air requirments are 0.028 ftVmin for the first reactor and 0.014 ftVmin for the second reactor.  36  Table 4. BOD and C O D reductions for various aeration rates  1  Percent Reductions Aeration  Reactor  Rate (L/min)  Number  0.45  COD  BOD  Lagoon 1  40  55  0.23  Lagoon 2  55  68  0.2  1  40  57  0.2  2  59  75  1.0  1  73  96  0.5  2  86  98  1.5  1  77  95  0.5  2  88  99  2  Notes: 1. 2.  Aeration  Values for C O D and BOD reductions represent the best values achieved through the study at the prescribed aeration rate Lagoons 1&2 refer to the system located at Vanderpols' Egg Ltd.  Performance.  The ability of the aeration system to dissolve oxygen in wastewater and clean water was determined using the unsteady state method described in the methods and materials section. The K a of egg processing wastewater was determined to be 5.0 h r  1  L  (figure 13) while the K a of clean water was determined to be 10.8 h r . 1  L  wastewater had a TDS concentration of 4496 mg/L, C mg/L.  R  As the  was calculated to be 8.83  The D O in the liquid phase (C) was set at 2.0 mg/L. The a factor, which  relates the ratio of K a of wastewater to clean water, was determined to be 0.46. L  As a  values have been reported between 0.3 and 1.9 (Barnhart, 1986), a value of 0.46 seems quite reasonable. A (3 value of 0.97 was established using TDS values obtained during the aeration studies.  This value also seems very reasonable in that Metcalf and Eddy  (1991) state that |3 values vary between 0.7 and 0.98 while a value of 0.95 is  37  Wastewater K a = log 9:08 - log 5.5 6 min L  = 5.0 h r "  (2.303)  1  h Clean Water K a = log 9.08 - log 2.9 L  (2.303)  6 min = 10.8 h r  _ 1  2  0  3 , 4 Time (min)  Figure 13. K a Determination for Egg Processing Wastewater and Clean Water L  38  commonly used for domestic wastewater.  Coefficients a' and b'. While the oxygen requirements for B O D metabolism and endogenous respiration can be determined through aeration studies, the requirements can also be expressed through the following equation (Balasha, 1974):  0  2  = a'ASQ + b ' X V  (eq. 9)  where: 0  2  = oxygen requirement in the aeration system, kg0 /day 2  a' = oxygen consumed per unit substrate removed b' = endogenous rate coefficient, day~l AS = S - S , mg/L 0  e  X = M L V S S , mg/L V = volume of aerated basin, m  3  Q = volumetric flow rate, m /d 3  By plotting 0 / X V versus AS/Xt, the values of a' and b' can be presented graphically. 2  Using the unsteady-state aeration method (ASCE, 1984) and equation 8, described in the materials and methods section, the overall mass transfer coefficient (K a) for egg L  processing wastewater was determined to be 5.0 h r (figure 13). 1  volume of 4 litres, the mass of 0  2  At an operating  transferred per unit time was calculated to be 3394  mg 0 / d using the following equation. 2  0 / V - dC/dt = K a (C - C) 2  L  R  (eq. 10)  This was based on maintaining an aeration basin with a D O of 2 mg/L. The plot of  39  0 / X V versus AS/Xt (figure 14) resulted in the following values for a' and b'. 2  a' = 0.68 g 0 /g BOD removed 2  b' = 0.32 d  1  Table 5. Results of SBR aeration study  Series Parameter X  1  (mg/L MLVSS)  2  3  4  5  6  922  850  1315  965  1620  1340  AS (mg/L BOD)  2862  2790  2195  2375  2692  2797  0 / X V (days )  0.79  0.85  0.55  0.76  0.45  0.54  HRT (days)  4  4  4  4  8  8  AS/XHRT  0.77  0.82  0.50  0.73  0.21  0.26  1  2  The parameter a' represents the fraction of substrate removed for energy during the respiration process while b' represents the mass of 0  2  utilized during endogenous  respiration. By determining the values a' and b' for a particular wastewater in a labscale system, these values can later be useful in developing the aeration system at a larger scale.  While a' and b' are well documented in the literature for domestic  wastewaters, the values for wastewaters such as egg processing wastewater are not known.  For domestic wastewater, typical values for a' vary from 0.36 to 0.63 while  typical values for b' vary from 0.13 to 0.28.  While the values for a' and b' for egg  processing wastewater are slightly higher than the values given for domestic wastewater, this is expected as the strength of egg processing wastewater is much higher than that of domestic wastewater.  For example, typical B O D levels for  domestic wastewater vary from 110 mg/L to 400 mg/L while the egg processing  40  •1.0 0.9 0.8  - 0 . 3 6 + 0,68  s  5*-  Xt  XV  0.7' 0.6 0.5 0.4  •0.3 0.2 0.1 0.0 0.0  b' .= 0.32 d  0.2  0.6  0.4 S/Xt  (d  X  0.8  .0  )  F i g u r e 14. D e t e r m i n a t i o n of the Coefficients a' a n d b'  41  wastewater used in this study varied from 2516 mg/L to 2952 mg/L.  Case Study. If the lagoons at Vanderpols (table  6) are to be upgraded to an SBR  system, the oxygen requirements can be calculated using the coefficients a' and b'. Using equation 9, oxygen requirements for the first SBR is 7916 kg/h and the second SBR is 4126 kg/h. Assuming air contains 21 % 0 by volume and has a density of 1.27 2  g/L, the volume of air required in the first and second SBRs is 448 mVmin and 233 mVmin, respectively. Furthermore, the aeration intensity for the first and second SBRs is calculated to be 105 g 0 / m h and 37 g 0 / m h , respectively. In the first SBR, fine 3  3  2  2  bubble diffusers are recommended as they have a maximum aeration intensity of 200 g 0 / m h while coarse bubble diffusers with a maximum aeration intensity of 100 g 3  2  0 / m h can be used in the second SBR (Boon, 1986). 3  2  Table 6. Characteristics of Egg Processing Lagoon System  Q (m /d)  V(m )  S (mg/L)*  M L V S S (mg/L)*  1  55  246  2619  1169  2  55  364  131  808  Lagoon  3  3  * Lab Scale Results  For comparison, a system comprised of two lagoons in series would use considerably less aeration. Using equation 2, described in the introduction, the maximum theoretical oxygen demand in a completely suspended lagoon is as follows:  R o = 6.24 x 10' Q S  (eq. 2)  5  2  0  Middlebrooks (1982) recommends that the maximum value (RQ ) should be multipled 2  by 1.5 to allow for peak flows. With a flow rate of 55 m /d and an influent BOD of 3  42  2952 mg/L, the oxygen required in the first lagoon is 10.4 kg 0 /h. A reduction in the 2  B O D to 300 mg/1 after the first lagoon reduced the oxygen requirement in the second lagoon to 1.0 kg 0 /h. 2  Using equation 3, the total power required is 13hp in the first  lagoon and 1.3 hp in the second lagoon. In addition, to maintain a completely mixed basin, the power requirements are 6.8 hp in the first lagoon and 4.6 hp in the second lagoon.  Balasha and Sperber (1974) report that the power required to maintain  complete mixing can vary from 3-4 W/m for larger lagoons (above 10,000 m ) to 20 3  3  W/m for smaller lagoons (500m ). The aerators now in place (10 hp and 5 hp) meet 3  3  the requirements for mixing in both lagoons but do not supply the oxygen demand determined during the lab scale experiments.  If a higher oxygen transfer rate is  required submerged aerators can be placed on the bottom of the lagoon or attached to the sides.  5. Determination of Kinetic Constants  The results of five series of digests, under different operational conditions (Table 7), were studied to determine the kinetic constants k, K,., Y , and k . d  Using the  Lineweaver-Burk plot (figures 15 and 16), the following values were obtained.  k =  1.98 d  1  K = 822 mg/L s  Y = 0.32 k = d  0.07 d  1  While the values for k, Y , and k fall well within the range of constants established for d  other food processing wastewaters (table 2), the value for K seems high. However, K s  s  values up to 500 mg/L have been reported for wastewaters for poultry processing. 43  0 1 .  2  3  4  5 6  7  8  9.  10  J _ ( 1 0 " ) (mg/L) 3  S  e  ,  F i g u r e 15. D e t e r m i n a t i o n of the Coefficients K, a n d k  44  45  Nonetheless, additional testing is needed to determine the accuracy of the kinetic coefficients established in this study for egg processing wastewater.  Table 7. SBR Results for the Determination of Kinetic Coefficients Test Series 1  Parameter  2  4  3  2952  2952  2952  2952  e (mg/L BOD) M C R T (days)  340  320  135  145  5  10  20  20  HRT (days)  4  4  8  8  X (mg/L MLVSS)  965  1315  1222  1115  X0/S -S  1.47  1.99  3.5  3.2  1/S (mg/L)(xl0 )  2.9  3.1  7.4  6.8  1/9 (days )(xlO- )  0.20  0.10  0.05  0.05  S„-S„ / X-0 (days )  0.68  0.50  0.29  0.31  s  o (mg/L  BOD)  s  o  (days)  e  3  e  1  2  C  1  6. Mean Cell Residence Time  To increase the efficiency of the biomass, solids recycle was incorporated into the lab scale SBR system.  Aeration rates were maintained at 1.5 L/min for reactor 1  and 0.5 L/min for reactor 2 through the testing period. Retention times of 5, 10, and 20 days were examined.  After adjusting the M C R T , the SBR system was run  continuously for two weeks before testing resumed. This was to allow the microbial population to stabilize after a change in the M C R T .  Figure 17 and 18 illustrate the  differences in the D O over 24 hours for a M C R T of 5, 10, and 20 days. Each increase in the M C R T from 5 days to 10 days and from 10 days to 20 days resulted in a digest higher in D O .  A M C R T of 10 days results in a digest with D O levels in the  recommended levels of 1 to 3 mg/L.  The settling velocity of the sludge improved from  46  10  MCRT = 5 days  6  Reactor 2 Q . = 0.5 L/min  •• • • Reactor 1 Q = 1.5 L/min air  5  10  15  20  25  30  Time (hrs) 10 MCRT = 10 days  Reactor 2 Q = 0.5 L/min air  Reactor 1 Q = 1.5 L/min air  o 10  15  20  Time .(hrs)  Figure 17. Dissolved Oxygen Levels of Egg Processing Wastewater for a Mean Cell Residence Time of (A) 5 . days and (B) 10 days 47  Figure 18. Dissolved Oxygen Levels of Egg Processing Wastewater for a Mean Cell Residence Time of 20 days.  48  0.5 m/h (5 d MCRT) to 2.0 m/h (10 d MCRT). By increasing the M C R T to 20 days from 10 days, there was little change in the settling velocity. The minimum 0 , the C  residence time at which the biomass cannot reproduce faster than they are wasted from the system, can be calculated using the following equation.  •  1  =(Y)  kS„  Qcmin  K  1 0  -  c m i n  +  S  (eq. 11)  o  1.98 d x 2952 mg/L 1  - 0.07 d  1  822 mg/L + 2952 mg/L  cmin  0  s  (-k„)  =  0.67 days  Using the parameters kinetic constants as determined from figures 14 and 15, the 0  c m i n  equals 0.67 days. If the SBR system is operated at a 20 day M C R T , the system would have a process safety factor (SF) of approximately 30 days. higher than expected, the 0  C m i n  expected.  was  , calculated from equation 10, was much lower than  Tcholbanoglous and Franklin (1991) recommend that biological treatment  systems should be operated with MCRTs treatment.  As the value for  from 2 to 20 days to ensure adequate  In addition, Branion (1992) recommends an M C R T of between 3 and 15  days for a sludge with good settling characteristics. From personal experience, a M C R T of 0.67 days and a SF of 30 days does not seem reasonable and this value would be expected to cause a washout of the biomass.  49  7. Pathogens.  As egg processing wastewater has the potential for supporting the growth of pathogenic microorganisms, the wastewater was analyzed for the presence of coliforms, fecal coliforms, and  Salmonella. Multiple tube fermentation for the determination of  coliforms resulted in an average of 3500 MPN/100 mis for the influent and an average of 80 MPN/100 ml for the effluent.  Salmonella were zero. were identified  In all samples, the presence of fecal coliforms and  Confirmed coliforms, later isolated on nutrient agar slants,  on the basis of colony  morphology,  microscopic  morphology,  biochemical tests, and growth on selected media. Two distinct bacteria were isolated in the influent and effluent wastewaters.  The first isolate resulted in typical orange  colonies of approximately 3 mm in length.  The second isolate resulted in typical  colonies of white colour with diameters ranging from 1-2 mm.  As the result of  additional testing using differential procedures (table 8), the isolates were identified as  Bacillus sp. and Micrococcus sp.  Table 8. The Determination of Bacterial Isolates  Recognition Factor  Isolate 1  Isolate 2  Gram Reaction  +  +  Size (microns)  3.0  1.0-2.0  Shape  bacilli  cocci  Orientation  singular, chains  pairs,tetrads,clusters  Spore Stain  +  Catalase Reaction  ++  Motility Growth on Plate Count Agar  orange-pink  Growth on MacConkey Agar Growth at 45°C  orange-pink  50  white-yellow  As these two genera are common to microorganisms found on egg shells (Frazier and Westhoff, 1988), their presence is not a surprise. While the tests confirmed the abense of coliforms, some species of both these genera do cause minor skin infections (Lennette et al, 1985), though both have been traditionally minimized in clinical microbiology. Furthermore, as most egg processing facilities use their wastewater for irrigation, the likelihood of disease transmission from these two genera is unlikely. By using the M P N test for coliforms and the fecal coliforms test as an indicator of Salmonella, the bacterial safely of the discharged effluent should be ensured.  51  Conclusions  Based on the data obtained during this study, a number of conclusions and recommendations can be drawn.  1.  The upgrading of a lagoon system to a SBR system for the treatment of egg  processing wastewater resulted in an effluent suitable for irrigation purposes.  The  following effluent levels are possible.  a) C O D  500 mg/L  b) BOD  30 mg/L  c) TSS  334 mg/L  2. Many of the sanitary chemicals used in egg processing facilities reduce the D O in the lagoons causing poor digestion performance by increasing the oxygen demand of the wastewater.  Once a microbial population is established in the SBR system, the D O  can be maintained between 1 and 3 mg/L. However, the D O does not reach these levels until approximately 10 hours after the fill period.  By reducing or elmiinating  these chemicals in the influent stream, D O levels in the range of 1 to 3 mg/L are possible throughout the treatment process.  3.  Aeration rates of 1.0 L/min and 0.5 L/min for the first and second reactors  respectively maintained D O levels between 1 and 3 mg/L. The coefficients  a' and b' were found to be 0.68  g 0 /g 2  B O D and 0.36 d , 1  respectively. The K a for egg processing wastewater using submerged, diffused aeration was 5.0 hr L  52  1  while the K a for clean water was 10.8 h r . 1  L  The a value was calculated to be 0.46  while the (3 value was calculated to be 0.97.  4. The kinetic coefficients for the aerated biodegradation of egg processing wastewater were found to be:  a)  = 822 mg/L  b) k =  1.98 d .  c) k = 0.07 d  1  1  d  d) Y = 0.32  5. A M C R T of 10 days resulted in a system which maintained a D O between 1 and 3 mg/L  and a sludge with good settling characteristics.  The minimum M C R T was  calculated to be 0.68 days using the kinetic coefficients Y , k, K , and k . The process s  d  safety factor was calculated to be 30 days.  6.  The influent had an average coliform count of 3500 MPN/100 mis while the  effluent had an average of 80 MPN/100 mis. Tests for the presence of  Salmonella and  fecal coliforms indicated an absence of both in the influent and effluent.  Further  differential testing of confirmed coliforms indicated the absence of coliforms and the  presence of Bacillus sp. and Micrococcus sp..  53  Recommendations for Further Study  1. As the kinetic coefficients were based on a small group of samples, additional testing is needed to confirm the accuracy of the coefficients obtained in this study.  2. While it has been concluded that the sanitary chemicals used in egg processing facilities results in an increased oxygen demand on the wastewater system, additional studies are needed to determine the specific chemical interactions of each chemical within the wastewater.  54  References American Public Health Association (APHA), 16th Ed. (1985) Standard Methods for the Examination of Water and Wastewater. Washington, D . C . Arora M L et al. (1985) Technology Evaluation of Sequencing Batch Reactors. J.WPCF. 57,8: 867-875. A S C E (1984) A Standard for the Measurement of Oxygen Transfer Systems. Amer. Soc. of Civ. Eng., Oxygen Transfer Standards Committee. Baillod R C and Paulson W (1986) Proposed Standard for Measurement of Oxygen Transfer in Clean Water. In Aeration Systems - Design, Testing, Operation, and Control (Editor William C Boyle), pp. 300-348. Park Ridge, New Jersey. Balasha E , Sperber H (1974) Treatment of Domestic Wastes in an Aerated Lagoon and Polishing Pond. Water Research. 9: 43-49. Boon A G (1983) Aeration Methods. In Oxidation Ditches in Wastewater Treatment (Editors D Barnes, C F Forester, and D W M Johnstone), pp. 173-187. London, England. Branion R (1992) Notes for the course C H M L 572. University of British Columbia, Vancouver, Canada. Bartch E H and Randall C W (1971) Aerated Lagoons - A Report on the State of the Art. JWPCF. 43,4: 699-708. Bulley R N et al. (1973) Biological Treatment of Egg Processing Wastewater. In Food Processing Waste Management, pp. 306-315. Syracuse, New York. Campbell, Jr. HJ (1986) Oxygen Transfer Testing Under Process Conditions. In Aeration Systems - Design, Testing, Operation, and Control (Editor William C . Boyle), pp. 349-367. Park Ridge, New Jersey. Dennis GB (1979) Lagoons and oxidation ponds. J . WPCF. 51,6: 1197-1200. Favero MS (1985) Sterilization, Disinfection, and Antisepsis in the Hospital. In Manual of Clinical Microbiology (Editors Lennette E H et al.) , pp. 129-137. Washington. Fernandez et al. (1992) Effect of Different Factors on the Die-Off of Fecal Bacteria in a Stabilization Pond Purification Plant. Wat. Res. 26,8: 1093-1098.  55  Frazier W C and Westhoff D C (1988) Contamination, Preservation, and Spoilage of Eggs. In Food Microbiology, pp. 255-267. New York. Galil N et al. (1991) The Influence of Mixing on the Physical Characteristics of Biological Floes. J. W P C F . 63,5: 768-772. Helmer et al. (1991) Public Health Criteria for the Aquatic Environment: Recent WHO Guidelines and their Application. Wat. Sci. Tech. 24,2: 35-42. Irvine R L et al. (1983) Municipal Application of Sequencing Batch Treatment. J.WPCF. 55,5: 484-488. Irvine R L et al. (1985) An Organic Loading Study of Full-Scale Sequencing Batch Reactors. J. WPCF. 57,8: 847-853. Isenberg H D et al. (1985) Collection, Handling, and Processing of Specimens. In Lennette E H (ed.), Manual of Clinical Microbiology (4th Ed.). Washington, D.C. Kormanik R A (1972) Design of Two-Stage Aerated Lagoons. J . WPCF. 451-457. Kouzeli-Katsiri A (1987) Design Optimization for Dual Power Aerated Lagoons. J.WPCF. 59,9: 825-832. Lo K V , Bulley NR, and Kwong E (1985) Sequencing Aerobic Batch Treatment of Milking Parlour Wastewater. Agricultural Wastes. 13:131-136. Loehr RC (1984) Land-Treatment Systems. In Pollution Control for Agriculture, pp.760-803. New York. Middlebrooks JE et al. (1982) Wastewater Stabilization Lagoon Design, Performance, and Upgrading. New York. Minet J et al. (1991) Salmonella Detection in Sewage Waters using Fluorescent Antibodies. Wat. Sci. Tech. 24,2: 373-376. Nemerow N L , Dasguptu A (1991) Economics of Waste Treatment. In Industrial and Hazardous Waste Treatment, pp. 81-100. New York. Okada Met al. (1990) Removal of Nutrients and B O D from Soybean Fermentation Wastewater in a Ten-Year-Old Sequencing Batch Reactor Activated Sludge Process. Wat. Sci. Tech. 22,9: 85-92.  56  Orhon D et al. (1986) Substrate Removal Mechanism For Sequencing Batch Reactors. Wat. Sci. Tech. 18,6: 21-33. Parry et al. (1982) A Manual of Recommended Methods for the Microbiological Examination of Poultry and Poultry Products. New York. Reasoner DJ and Geldreich E E (1985) A New Medium for the Enumeration and Subculture of Bacteria from Potable Water. Appl. and Envir. Micro. 49,1: 1-7. Rich L G (1985) Mathematical Model for Dual-Power Level, Multicellular (DPMC) Aerated Lagoon Systems. In Mathematical Models in Biological Waste Water Treatment, pp. 154-198. (Editors Jorgensen SE and Gromiec MJ). Amsterdam. Scheiter et al. (1993) Sludges for Cold Regions Lagoons. Wat. Env. Res. 65,2: 146155. Schumann G E , Stanley M A , Knudsen D (1973) Automated Total Nitrogen Analysis of Soil and Plant Samples. Proc.Soil Sci.Soc.of America. 37: 480-481. Shertzer R H (1986) Wastewater Disinfection - Time for a Change. J.WPCF. 58,3: 174-180. Silverstein and Schroeder E D (1983) Performance of SBR Activated Sludge Processes with Nitrification/Denitrification. J . WPCF. 55,4: 377-384. Sneath et al. (1974) Bergey's Manual of Systematic Bacteriology - Volume 2. Baltimore Sobsey M D (1989) Inactivation of Health-Related Microorganisms in Water by Disinfection Processes. Wat. Sci. Tech. 21,3: 179-195. Tchobanoglous G , Franklin B L (1991) Wastewater Engineering: Treatment, Disposal, and Reuse (3rd. Ed.). New York. Tekippen RJ, Bender R H (1987) Activated Sludge Clarifiers: Design Requirements and Research Priorities. J. WPCF. 59,10: 865-870. United States Environmental Protection Agency (1971) Design Guides For Biological Wastewater Treatment Processes. Water Pollution Control Research Series T1010 ESQ 08/71. Washington, D . C . World Health Organization (1975) Joint F A O / W H O Expert Consultation Microbiological Specifications for Foods. Food and Agriculture Organization of the United Nations document EC/Microbiol/75/Report 1. F A O , Rome.  57  


Citation Scheme:


Citations by CSL (citeproc-js)

Usage Statistics



Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            async >
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:


Related Items