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Effect of turbulence, light and turbidity on the standard BOD test Morissette, Denis G. 1976

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EFFECT OF TURBULENCE, LIGHT AND TURBIDITY ON THE STANDARD BOD TEST by DENIS G. MORRISSETTE B.A.Sc, University of Ottawa, 197^ A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE i n the Department of C i v i l Engineering We accept this thesis as conforming to the required standard The University of B r i t i s h Columbia A p r i l 1976 I n p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r an a d v a n c e d d e g r e e a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r a g r e e t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e H e a d o f my D e p a r t m e n t o r by h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . D e p a r t m e n t o f C i v i l Engineering The U n i v e r s i t y o f B r i t i s h C o l u m b i a 20 75 Wesbrook P l a c e Vancouver, Canada V6T 1W5 D a t e A p r i l 12/76 ABSTRACT The currently used BOD test attempts to predict ox-ygen l e v e l depletion i n a given environment, e.g. a moving stream, and i s also a parameter for the design and operation of b i o l o g i c a l processes. It i s run under conditions s i m i l a r to those occurring i n nature, but i t has been reported that the oxidation rate i n a stream i s higher than the corresponding rate obtained from the laboratory BOD test. This study was undertaken to observe the e f f e c t of turbulence, l i g h t and t u r b i d i t y , separately and i n combina-tions, on the standard BOD test, using raw sewage samples. Mixing was found to increase the BOD,, by an average of 15$. reduce the lag period and increase the ultimate BOD value. Light did not show any appreciable change on the standard BOD test, since only an average 4% increase i n BOD^ was found. However, t u r b i d i t y demonstrated an average reduc-t i o n of 25% on BOD,, values. When the above physical changes were observed i n combinations, the results were not additive. As an example, l i g h t and t u r b i d i t y , i n combination, did not reduce the BOD,-decrease to 21% (25%-k%). Instead, the decrease i n BOD^ v a l -ue was 5%. This c l e a r l y points out that physical changes to the BOD test should not only be studied separately, but also i n combinations. Therefore, this study appears to expose the inade-quacy of the present BOD test f o r actual stream conditions. It has also shown that without further research, extrapola-t i n g from the e x i s t i n g standard BOD t e s t , y i e l d s questionable r e s u l t s . Inclusion i n the BOD test, of the physical charac-t e r i s t i c s of the stream, i s a possible s o l u t i o n to obtaining r e l i a b l e r e s u l t s . TABLE OF CONTENTS Page LIST OF TABLES v i LIST OF FIGURES v i i ACKNOWLEDGMENT v i i i CHAPTER I INTRODUCTION 1 II LITERATURE REVIEW 4 2.1 BOD Progression Equation and Parameters . 4 2.2 N i t r i f i c a t i o n . 5 2.3 Ba c t e r i o l o g i c a l Growth Curve 6 2.4 Temperature E f f e c t s 7 2.5 Turbulence Effects 8 2.6 Light Effects 10 2.7 Conclusions 11 III RESEARCH RATIONALE 12 IV MATERIALS AND EXPERIMENTAL TECHNIQUES . . . . 14 Mixing Apparatus 14 4.2 Choice of Lamps 15 4.3 Temperature Control 17 4.4 BOD Test With Mixing 18 4.5 BOD Test With Light . 20 4.6 BOD Test With Turbidity 22 4.7 Summary 23 V EVALUATION OF BOD PROGRESSION CONSTANTS . . . 24 VI ANALYSIS OF THE RESULTS 29 6.1 E f f e c t of Turbulence on BOD 29 6.2 E f f e c t of Light on BOD 41 6.3 E f f e c t of Turbidity on BOD 46 6.4 Combination Testing and Summary 53 i v V VII IMPROVING THE BOD TEST 57 VIII CONCLUSIONS AND RECOMMENDATIONS 63 8.1 Conclusions 63 8.2 Recommendations f o r Further Studies . . . . 65 IX REFERENCES 67 X APPENDICES 70 Appendix A Measuring Light Intensity with a Camera Meter 71 Appendix B Computer Programs and Flow Charts for the Three Modified Methods . . . 74 Appendix C Results of Individual BOD Test Runs 88 Appendix D Calculated BOD Progression Constants 98 Appendix E The Correct Mixing Rate from F i e l d Conditions 104 LIST OF TABLES Table Page I Sunlight Intensities 16 II Calculated Lag Period Values 25 III Variations i n Rate Constants as a Function of the Lag Period 27 IV BOD Progression Constants of the BOD Test with Mixing 31 V Comparison of BOD,- of Mixed and Quiescent Runs r 34 VI Variations i n k as a Function of L at 600 rpm 38 VII Variations i n k as a Function of L at Different Mixing Rates 39 VIII Percent Change i n BOD,- Due to Light and Turbidity ? 42 IX Variations i n k as a Function of L i n Tests with Light and Turbidity 42 X Percent Change i n BOD^ Values of Tests with Turbidity ? 47 XI Variations i n k as a Function of L i n Tests with Turbidity 47 XII Variations i n Lag Period 48 XIII Summary of the Results 53 v i LIST OF FIGURES Figure Page 1 Error i n the Rate Constant as a Function of the Lag Period 28 2 Typical BOD Progression Curves 33 3 Variations i n BOD^ Changes 35 4 Change i n k as a Function of L at 600 rpm . . 37 5 Change i n k as a Function of L at Various Mixing Speed 40 6 Change i n Constants of BOD Test with Light and Turbidity ». . . . 45 7 Percent Change i n BOD^ Values 50 8 Change i n t as a Function of Turbidity . . . 51 9 Change i n Constants i n BOD Test with Turbidity 54 v i i ACKNOWLEDGMENT The author i s g r a t e f u l to his supervisor, Dr. D.S. Mavinic, f o r his guidance and encouragement during the completion of this study. His advice was invaluable. The author i s gr a t e f u l to Mrs L i z a McDonald, head lab technician, f o r her help and assistance. Her advice saved many hours of hard labour. The author i s also g r a t e f u l to Dr. Ken H a l l f o r his help and constructive c r i t i c i s m . F i n a n c i a l support f o r t h i s work originated from the National Research Council of Canada, under grant numbers A8945. A7986 and a one year scholarship to the author. v i i i CHAPTER I INTRODUCTION The increasing concern about the p o l l u t i n g strength of domestic and i n d u s t r i a l wastewaters has warranted the need for improved methods of analysing affected waters. The cur-rent measure of p o l l u t i o n a l strength of bio-oxidizable matter i s the biochemical oxygen demand, BOD. This test measures the amount of oxygen required by microorganisms to s t a b i l i z e decomposable organic matter under aerobic conditions. It i s used to predict oxygen l e v e l depletion i n a given stream and is also a parameter for the design and operation of b i o l o g i -c a l processes. The presently accepted BOD test i s one i n which a sample i s incubated at 20°C i n the dark, with no mixing, over a f i v e day period. Theoretically, an i n f i n i t e time i s required to completely s t a b i l i z e the organic matter, but f o r the most p r a c t i c a l purposes, the reaction may be considered complete a f t e r 20 days. But t h i s i s a long waiting time. Experience had shown that, a f t e r f i v e days, a large portion of the organic matter was oxidized and that the values ob-tained were reproduceable. Consequently, a f i v e day incuba-. t i o n period was adopted. Although the f i v e day BOD y i e l d s useful r e s u l t s f o r the control of sewage treatment plant operation, i t i s generally conceded that the ultimate BOD and the rate at 1 2. which i t i s being exerted, with respect to time, must be known i n order to measure the b i o l o g i c a l treatment process effectiveness and to predict subsequent oxygen depletion i n a stream. The BOD test i s run under conditions s i m i l a r to those occurring i n nature, but i t has been reported (1),(2) that the oxidation rate i n streams i s higher than the corre-sponding rate obtained from the laboratory test. This d i f f e r -ence i s due to biophysical differences between laboratory te s t procedures and r i v e r c h a r a c t e r i s t i c s . For example, the turbulence found i n streams i s not reproduced i n the standard BOD test? the temperature of the stream may d i f f e r from the 20°C used i n the test? the amount of sunlight received i n the stream i s not reproduced i n the incubator where the bottles are kept i n the dark; the b i o l o g i c a l population d i f f e r ; the oxygen concentration of the BOD bottle d i f f e r s from that of t the stream, since the l a t t e r i s continually replenished; and i t was also found that, i n some r i v e r s , the bottom becomes covered by a slime formation, thus providing some treatment for the r i v e r by acting i n a s i m i l a r way to a t r i c k l i n g f i l -t e r . Although some of these factors, such as temperature, have been studied closely, many others remain which have been given l i t t l e or no attention. This study was undertaken to gain a better under-standing of the e f f e c t of turbulence, a r t i f i c i a l l i g h t and tu r b i d i t y , both separately and i n combination, on the standard-BOD test. An attempt was made to duplicate, as c l o s e l y as possible, natural receiving water conditions. CHAPTER II LITERATURE REVIEW 2.1 BOD Progression Equation and Parameters The progressive exertion of the BOD of f r e s h l y p o l -luted water normally breaks down into two stages: f i r s t , oxidation of the carbonaceous material and secondly, n i t r i -f i c a t i o n of the waste matter, namely ammonia. In 1925. Streeter and Phelps, (3) proposed that the rate of b i o l o g i c a l oxidation of carbonaceous organic matter, dL/dt, i s proportional to the remaining concentration of un-oxidized substances L^ .. Therefore, theeequation f o r b i o l o g i c a l oxygen demand, y, exerted i n time t becomes, y = (L-L t) = L ( l - e " K t ) = L ( l - 1 0 - l c t i ...1 where L = Ultimate oxygen demand due to carbonaceous matter i n mg/1 K or k = Rate c o e f f i c i e n t of BOD removed i n day" 1 t = Time i n days. Although several investigators (4), (5 ) 1 (6), (7), have rec-ognized and discussed the p o s s i b i l i t y of compound reactions e x i s t i n g i n the progression of oxygen u t i l i z a t i o n i n waste-water, t h e i r BOD data are s t i l l best formulated by the above f i r s t order equation. Numerous studies (4), (5). (8), (9). have been conducted on the progression of BOD with synthetic substrate 4 and domestic and i n d u s t r i a l wastewater samples. These tests were performed by f i r s t d i l u t i n g the samples, then seeding i f necessary and incubating at a fi x e d temperature f o r a fixed period of time. Both L and k (base 10) i n the Streeter and Phelps Equation 1 were found to depend on temperature and the nature of the sample. It was also determined (10) that k (base 10) could vary from te s t to test with the same sample, sometimes by a factor of as much as two. Orford and Ingram (5) had concluded that not only was the monomolecular equation a poor expression f o r the analysis of b i o l o g i c a l oxidation, but the k and L values varied with time and thus showed very l i t t l e physical or bio-l o g i c a l s i gnificance as a measure of oxidation or strength. Gannon (1) showed that the values obtained f o r k (base 10) and L depended on the method of c a l c u l a t i o n . Zanoni (11) reported that the values of k (base 10) and L depended considerably on the time period chosen f o r the c a l c u l a t i o n . 2.2 N i t r i f i c a t i o n I t has been reported (12) that the presence of organic matter, p a r t i c u l a r l y amino compounds i n excessive concentrations, i n h i b i t s the growth and r e s p i r a t i o n of n i t r i -f y i n g organisms. N i t r i f i c a t i o n i s an important contributory factor i n the depletion of oxygen from sewage and polluted waters, but i t ' s a c t i v i t y i s delayed u n t i l a suitable environ-ment fo r n i t r i f y i n g organisms develops (13)' N i t r i f y i n g bacteria are usually present i n r e l a t i v e l y small numbers i n raw domestic wastewater and t h e i r populations do not become 6. s u f f i c i e n t l y large to exert an appreciable demand f o r oxygen, u n t i l about 10 days or more have elapsed i n the regular BOD test. Protozoa and other plankton also are present i n sewage or surface water, but since t h e i r growth rate i s much less than the growth rate of bacteria, t h e i r d i r e c t influence upon the decomposition rate of organic matter i s small. How-ever, t h e i r influence can be detected i n d i r e c t l y through the depredation of b a c t e r i a l populations (13). 2.3 B a c t e r i o l o g i c a l Growth Curve Under controlled environmental conditions, the growth curves for pure bacteria cultures generally follow a predictable and reproduceable pattern. The f i r s t stage begins with a lag period, during which the organisms are adjusting to the substrate and physical conditions. Then, the micro-organisms enter a stage of progressive exponential m u l t i p l i -cation. When the number of bacteria approaches the satura-t i o n l e v e l , the m u l t i p l i c a t i o n rate decreases u n t i l i t reaches a period of stationary growth, i n which the number of organisms remains r e l a t i v e l y constant. F i n a l l y , the cultures enter a death phase, with a continuous decrease i n the viable population (14). The experimental r e s u l t s of Bhatla and Gaudy (15). using glucose as a substrate and seeded with sewage, showed that the number of bacteria i n BOD bottles rose r a p i d l y to the saturation value with a l i n e a r trend. This saturation value was usually reached within 1.5 "to 3 days and was followed 7. d i r e c t l y by a rapid decline i n the viable b a c t e r i a l count. They also noticed that the break i n the oxygen uptake was marked by a rapid increase i n the protozoan population. 2.4 Temperature Effects Temperature af f e c t s the rate of substrate u t i l i z a t i o n i n a b i o l o g i c a l system. The r i s e i n temperature speeds up the b i o l o g i c a l process, i . e . causes an appreciable increase i n the rate of biochemical consumption of oxygen. The e f f e c t of temperature on substrate u t i l i z a t i o n i s assumed to be p r i -marily a thermo-chemical phenomenon. This assumption i s made on the basis-that oxidation of organic materials by micro-organisms involves a series of enzymatic reactions which are temperature dependent. The most commonly used empirical equation was developedSby Streeter and Phelps (3)» f o r the e f f e c t of temperature on the value of the deoxygenation constant, k, of polluted waters, , (T -T) ^ r p / k i p — 6 ... 2 • t Q where k T = Reaction v e l o c i t y at temperature T i n C k^ = Reaction v e l o c i t y at temperature T i n °C 0 = The thermal c o e f f i c i e n t , with a value of 1.047 f o r temperatures ranging from 10 to 37°C. Theriault (16) confirmed th i s value of Q experimen-t a l l y using samples collected from the Ohio River. Gotaas (8) observed that the above equation was applicable while using glucose as a substrate. He also concluded that over tempera-ture ranges 5 - 15°C, 15 - 30°C, and 30 - 40°C, the value of 8. 9 was d i f f e r e n t . Bewtra and Charan (9), i n a detailed study on raw sewage samples, observed that the rate constant, k, between 12 - 37°C, was increasing with the increase i n temperature, but the rate of increase decreased as the temperature i n -creased. They proceeded to conclude that a separate equation i n the form (T - 20) ^rp/^20 = ® • • • 3 could be applied to describe the change i n k values i n tem-perature ranges of 12 - 20°C, 20 - 37°C and 37 - 40°C. Moore (10) conducted BOD experiments on d i l u t e d domestic sewage, with both bicarbonate and phosphate d i l u t i o n waters and on undiluted samples from two streams containing moderate p o l l u t i o n of remote o r i g i n . The value of 0 f o r sewage, obtained by Moore, was 1.145 f o r a temperature range of 0.5 - 5 &C, and 1.065 f o r a temperature range of 5 - 20°C. On the other hand, the value of © f o r the r i v e r water, f o r a temperature range of 0.5 - 20°C, was 1.026. Thus, i t i s ap-parent that, using a formula to estimate the value of k at one temperature from i t s value at another temperature, i s not re-l i a b l e unless the formula i s derived from experimental data on the waste being studied. 2.5 Turbulence E f f e c t The e f f e c t of turbulence, applied to a b a c t e r i a l system, has been of considerable i n t e r e s t to a number of i n -vestigators. As a re s u l t , the understanding of the e f f e c t of a g i t a t i o n on microbial systems has been improving continuously. 9. Tsao and Kempse (17) observed that an increase i n the oxygen uptake by Pseudomonas ovalis occurred as the system's turbu-lence was increased, by increasing the rate of mechanical mixing. Rincke (18), c i t i n g the work of Imhoff (19) and Von der Emde (20), has stated that the rate of oxygen uptake and substrate u t i l i z a t i o n increases i n the activated sludge, with an increase i n the rate of mixing. Zahradka (21) found that a d e f i n i t e r e l a t i o n s h i p existed between the mechanical energy supplied to an activated sludge p i l o t plant and the p u r i f y i n g a b i l i t y of the sludge. Recently, Richard and Gaudy (22) have reported that, at a very low rate of oxygen supply, the variations i n the rate of oxygen supply to a microbial system caused a change i n the v e l o c i t y gradient and the viable count increased l i n e a r l y with the rate of addition of oxygen. They also observed a decrease i n the b i o l o g i c a l s o l i d s y i e l d s with an increase i n the amount of mixing energy input and a t t r i b u t e d i t to an increase i n the r a t i o of r e s p i r a t i o n to synthesis. Lordi and Heukelian ( 2 3 ) , using sewage f i l t e r e d through glass wool, have shown an increase i n the rate constant with mixing. Busch, Kehrberger, Norman and Schroeder (24), conducted some preliminary experiments i n BOD bottles, with t h e i r contents continuously mixed by using magnetic s t i r r e r s . More recently, Gannon (1) determined the influence of mixing on the BOD rate constant f o r the Clinton River water, located between Pontiac and Rochester, Michigan. Certain BOD bottles were sealed and the contents were s t i r r e d 10. using magnetic s t i r r e r s . It was observed that the BOD rate constant under continuous s t i r r i n g was more, than ten times the rate constant obtained under quiescent conditions. Most of the previous studies have been conducted eithe r on synthetic, soluble substrates or on r i v e r water. In recent years, the influence of mixing on raw, s e t t l e d , and b i o l o g i c a l l y treated wastewaters has been studied by A l i (25). In his work with primary effluent, he proposes the following r e l a t i o n , k /k = 1.035 + 3.404 x 10'^ N ...4 s q where, k = Rate constant f o r the s t i r r e d sample, day - 1 S k^ = Corresponding rate from the quiescent test, day""1 N = S t i r r e r ' s speed i n revolution per minute. Furthermore, A l i has also found that mixing reduces the lag period of the substrate being studied. The ultimate BOD under s t i r r e d or quiescent conditions was about the same. 2.6 Light Effects The effects of turbulence on BOD progression i s now better understood, but the e f f e c t of sunlight s t i l l remains somewhat of a mystery. Hoch, Owens and Kok (26) have found that i l l u m i n a t i o n influences oxygen uptake by two mechanisms. Oxygen uptake was found to be i n h i b i t e d at low l i g h t inten-s i t i e s and accelerated at medium to high i n t e n s i t i e s . Golterman (27) demonstrated that the oxygen consumption was higher when BOD bottles are kept i n the l i g h t instead of i n the dark. Unfortunately, none of the above studies mention the absolute value of the l i g h t i n t e n s i t i e s used, but rather describe them as being low, medium and high i n t e n s i t i e s . How-ever, these studies indicate that, as the l i g h t intensity-increases, so does the oxygen consumption. 2.7 Conclusions Much work has been done to develop the BOD t e s t to what i t i s today. Unfortunately, i t does not f u l f i l l the r e -quirements of modern sanitary engineering. The BOD progression dynamics are f u l l y documented and so i s the temperature e f f e c t . Much has come from the recent studies on turbulence. Clearly, turbulence, l i g h t and t u r b i d i t y , separately and i n combination, stand out as being a possible next step i n the BOD test anal-y s i s . CHAPTER III RESEARCH RATIONALE The BOD test i s well accepted as a t o o l f o r the design of sewage treatment plants, where i t provides a meas-ure of treatment e f f i c i e n c y . The test can e a s i l y meet th i s demand, since only r e l a t i v e r e s u l t s are required. However, when the absolute value of the BOD i s needed, f o r natural r e -ceiving water conditions, the test i s not well accepted. It was conclusively shown (1), that the r e s u l t s of laboratory t e s t i n g were not i n accordance with f i e l d values. This means that the standard BOD te s t does not adequately re-produce f i e l d conditions. There are two solutions to th i s problem, and here i s the seed of an important controversy between researchers. The f i r s t s olution i s to replace the e x i s t i n g BOD test with another type of test. Unfortunately, every new technique developed has i t s own drawbacks. However, some researchers, e.g. P e i l and Gaudy (28), are presently working toward a solution. U n t i l such a so l u t i o n i s found, we w i l l have to r e t a i n the e x i s t i n g BOD test. The second s o l u t i o n would be to improve the current test. The amelioration i s only possible i f the t e s t i s sub-mitted to physical changes, i n order to develop better cor-r e l a t i o n between laboratory and f i e l d conditions. Obviously, before any changes could be made, t h e i r e f f e c t s have to be 12 known. The author prefers the second solution, to the con-troversy on the BOD test, because i t yie l d s an immediate, possible s o l u t i o n to the problem. This study w i l l look into the e f f e c t of turbulence, l i g h t and t u r b i d i t y and combination thereof. Turbulence has been studied recently, (see Chapter 2) but s t i l l has not been analysed i n combination with other factors. Light and t u r b i d i t y have had l i t t l e , i f any, re-search done on them., In past studies, very l i t t l e attention was given to combinations of factors, which i s what occurs i n streams. \ CHAPTER IV MATERIALS AND EXPERIMENTAL TECHNIQUES In t h i s investigation, raw sewage samples were tested to determine the influence of mixing, l i g h t and t u r b i d i t y , on t h e i r bio-oxidation rates. Raw sewage was chosen because i t i s the worst type of discharge of domestic wastewater possible. The samples were co l l e c t e d from Lion's Gate Sewage Treatment Plant, i n North Vancouver. This plant receives about 75% do-mestic waste and 25% i n d u s t r i a l waste. 4.1 Mixing Apparatus The mixing apparatus consisted of three four-unit magnetic s t i r r e r s , "Magne-4" model 4820-10, manufactured by the Cole-Parmer Instrument Company. Although these units were advertised as having speed control from 50 to 1600 rpm, i t was found impossible to operate them below 250 rpm. No c a l i b r a t i o n chart was available with the units, thus, i t was necessary to determine the mixing speed at various settings. Furthermore, i t was necessary to re c a l i b r a t e the mixers once they were "broken i n " . In general, checking the c a l i b r a t i o n and o i l i n g the mixers once every other week was found to be quite s a t i s -factory f o r speed control. n II To complement the mixers, twelve 1-1/2 x 5/16 hexagonal shaped, t e f l o n covered, 1.8 ml volume magnetic bars were used. Although the mixers were advertised as remaining 14 cool, heat was created a f t e r some length of time. Thus, as-bestos pads were placed between the mixers and the BOD bottles to minimize the heat transfer. 4.2 Choice of Lamp In t r y i n g to f i n d the material necessary to expose BOD-bottle to l i g h t , many problems were encountered. Deter-mining the type of lamp required to reproduce sunlight, i s quite a d i f f i c u l t task, since no e x i s t i n g lamp w i l l reproduce a l l the wavelengths contained i n the sunlight spectrum. We know that infrared i s absorbed near the surface of the water and therefore i s not required. Fluorescent l i g h t i n g w i l l produce a l i g h t , with very l i t t l e heat production, but these lamps produce l i g h t i n narrow wavelength bands and therefore do not reproduce the spectrum desired. The next p o s s i b i l i t y was to use incandescent l i g h t -ing, which produces l i g h t i n a wide band of wavelengths. A l i g h t source w i l l not emit l i g h t f o r a l l the sunlight spectrum, but incandescent l i g h t i n g does reproduce much larg e r wave-length bands than the fluorescent l i g h t s . I t was therefore decided that incandescent l i g h t would be used. Unfortunately, incandescent l i g h t s have the d i s t i n c t disadvantage of heating, something to be avoided i n an incubator. The l i g h t i n t e n s i t y to be used also had to be de-cided. The i n t e n s i t y of sunlight, i n cloudy or c l e a r sky, was measured with a Weston Master IV l i g h t meter and the re s u l t s are given i n Table I. I t i s not necessary to have a l i g h t meter, l i k e the Weston, which reads i n foot-candles. Any 1 6 . ordinary camera meter w i l l give l i g h t i n t e n s i t y i n foot-candles, provided the f/stop, ASA and exposure timecare known. Appendix A explains how to use a camera meter to f i n d the i n t e n s i t y of l i g h t i n foot-candles. TABLE I SUNLIGHT INTENSITIES Type of Sky Intensity (foot-candles) Clear (summer) 10,000 Clear (winter) 8,000 Cloudy 3,000 Overcast 1,000 Rainstorm 400 The values of Table I are only approximations of the true value of l i g h t i n t e n s i t i e s i n various weathers. The i n -t e n s i t i e s were measured by the author. They were followed as guidelines, f o r the i n t e n s i t y required from the l i g h t source. Most l i g h t sources are c a l i b r a t e d f o r t h e i r l i g h t production and i t i s possible to f i n d out, from any lamp manufacturer, the output of t h e i r lamps i n "lumens". The lumen i s defined as the rate at which l i g h t f a l l s on a one square foot area surface, which i s equally distant one foot from a & source whose int e n s i t y i s one candle. One foot candle i s the ill u m i n a t i o n on one square foot of surface, over which i s evenly d i s t r i b u t e d one lumen. Therefore, one foot-candle i s equal to one lumen per square foot (29), (30)« 17. The e f f i c i e n c y of a l i g h t source i s given as lumens per watt and may vary from 10 to 130 lumens/watt. It i s need-less to say that the more e f f i c i e n t a l i g h t source i s , the more expensive i t i s . In t h i s study, the heat produced had to be minimized, to reduce the heating of the BOD bottle contents. This can only be done by reducing the wattage of the lamp used, with an increase i n e f f i c i e n c y . Also the lamp had to be operative on 110 volts, f o r convenience. For reasons of economics and ease of handling, a 500 watt quartz lamp, with a tungsten filament giving 10,000 lumens, was used i n t h i s study. Such a lamp has an e f f i c i e n c y of 20 lumens/watt, which i s low, but represents a d i s t i n c t advantage over using about 10, 100 watt bulbs at an e f f i c i e n c y of 10 lumen/watt. The spectrum produced by t h i s lamp i s very s i m i l a r to sunlight's, but i s lacking i n the u l t r a v i o l e t range. 4.3 Temperature Control It was found possible to maintain good temperature control of 20 + 1GC, even with the three mixers i n one incu-bator. However, the incubator was incapable of handling the heat generated by the lamp. Therefore, a room with constant temperature was developed and the experiments, with the l i g h t , c a r r i e d out therein. Because of the heat generated from the lamp, i t was impossible to work i n the higher range of l i g h t i n t e n s i t y , unless an a i r fan was provided to help i n c i r c u l a t i n g the a i r . Even with such a fan, the maximum l i g h t i n t e n s i t y produced 18. could not be 10,000 foot-candles, but rather 8,000 foot-candles. In order to ensure good temperature control, a Honeywell temperature recorder was i n s t a l l e d i n the room. This recorder had three probes, so that the temperature of the room and the temperature of the BOD bottles could be monitored. The temperature variances could e a s i l y be adjusted i n the room. However, i t was found impossible to adequately con-t r o l the temperature when the lamp and the mixers were used simultaneously. For such tests, a walk-in incubator was used. Unfortunately, this s p e c i a l incubator was only available f o r a short period of .time during the author's research work; thus, li m i t e d data concerning mixing and l i g h t i n combination, i s to be found i n t h i s report. 4.4 BOD Test With Mixing Unless otherwise stated, a l l tests were conducted using the procedures suggested i n the Standard Methods (31)• In order to evaluate the influence of mixing on BOD progres-sion, two sets of BOD bottles were inoculated for each experi-ment. The f i r s t set was kept under the standard quiescent condition, as described i n Standard Methods (31) and two bot-t l e s were removed each day and analysed f o r dissolved oxygen by the Winkler Method, using the Azide Modification. Four blanks were also kept i n th i s set, two of which were analysed at the beginning of the run and two at the end. The second set consisted of twelve bottles kept under continuous s t i r r i n g by the magnetic mixers described previously. This number of twelve bottles was l i m i t e d by the a v a i l a b i l i t y of mixers. Normally, i t i s found that i n unmixed bottles, n i t r i f i c a t i o n occurs a f t e r about 10 days. It was observed that i n the mixed samples, t h i s period was short-ened! to about seven days. It was therefore decided to use a BOD test period of 6 days. This permitted the use of two bot-t l e s a day and, therefore, gave an average of the d a i l y r e s u l t s . Similar to the f i r s t set, the two d a i l y bottles were tested f o r dissolved oxygen by the Winkler T i t r a t i o n Method. A l i (25) proposed to take the dissolved oxygen readings of the mixed bottles with an oxygen probe. The dissolved oxygen readings were taken by t i g h t l y i n s e r t i n g the oxygen probe i n the BOD bottle at predetermined time i n t e r v a l s . Simultaneously, the temperature of the bottle contents was read with a thermistor. A f t e r having taken the readings, the bottle was stoppered again and kept under continuous s t i r -r ing. Proper care was taken to prevent loss or gain of oxy-gen between the bottle contents and the environment, while measuring dissolved oxygen and temperature. The v a l i d i t y of t h i s method was checked and the results were found to be i n accordance with the Winkler Method. Because i t i s possible to analyse the same BOD bottle many times i n one run, the t o t a l number of bottles required i s much le s s . By using the Winkler Method, f o r the dissolved oxygen analysis, the twelve mixing places could only provide room for one BOD run. By using an oxygen probe, the same twelve places would s u f f i c e f o r three simultaneous runs. However, an oxygen probe was not available at the beginning of t h i s study, 20. and was only used f o r the study of t u r b i d i t y . In this study many mixing rates were studied, the range being 300 - 900 rpm, at 100 rpm increments. The lowest mixing rate of 300 rpm was chosen because the mixers would not operate at much lower rates. On the other hand, the mixers could operate much fas t e r than the stated maximum, but at 900 rpm, the magnetic bars would s t a r t jumping i n the bottles. This action of jumping i s i n i t i a t e d when the magnetic bar, because of the curved bottom of the bottle, travels towards, then h i t s the side of the bo t t l e , with such force that i t can no longer remain f l a t on the bottom. Therefore, the results obtained at the 900 rpm mixing rate are not completely r e l i a -ble. 4.5 BOD Test With Light The standard BOD test i s performed i n the dark to eliminate algae growth. In thi s study, since l i g h t was pro-vided to the bottles an algacide had to be added. DCMU ( 3i ( 3 t^-dichlorophenyl) - 1,1-dimethylurea), obtained from K Sc K Laboratory of C a l i f o r n i a , has been shown by previous investigators to i n h i b i t photosynthesis at concentrations of 10~^M (27). Hoch and Owens (26) showed that DCMU has no i n -fluence on oxygen uptake i n the dark, but i n h i b i t e d an enhanced oxygen uptake at very high l i g h t i n t e n s i t i e s . To have 10"^M of DCMU present i n the BOD bottles, 46.6 mg was added to 20 1 of the d i l u t i o n water. To control the l i g h t i ntensity, two techniques were used simultaneously. By increasing or decreasing the distance 21. between the l i g h t source and the BOD bottles, i t was possible to control the amount of l i g h t reaching the b o t t l e s . With such a technique i t would be impossible to illuminate the bottles, with as l i t t l e an i n t e n s i f y as 1,000 foot-candles, because of the distance involved. For such low i n t e n s i t i e s , the author reverted to the standard lower wattage bulbs. Simultaneously, t u r b i d i t y was created with bentonite clay i n the bottles, to simulate actual r i v e r t u r b i d i t y . For a section of the study on l i g h t , no mixers were used, therefore not l i m i t i n g the number of BOD progressions which could be matched by a control. It was decided that three BOD runs plus a control could be used. The three runs consisted of approximately 3.0 Jackson Turbidity Units (JTU), 200 JTU and 400 JTU. The sets of experiments were exposed to 1,000 ft-candles, 3,000 ft-candles and 8,000 ft-candles l i g h t i n t e n s i t y . When the mixers were used i n conjunction with l i g h t , the tests were performed i n the walk-in incubator. Since the incubator was only available f o r a short period of time, very l i t t l e data was obtained f o r t h i s combination, as discussed e a r l i e r . The simultaneous tests performed on a single raw sewage sample consisted of a control, one BOD t e s t with l i g h t only, l i g h t and t u r b i d i t y , mixing and l i g h t , mixing and l i g h t and t u r b i d i t y , and t u r b i d i t y only. The l i g h t used had a 3,000 ft-candles intensity, the t u r b i d i t y was 200 FTU and the mixing rate was 600 rpm. 22. 4.6 BOD Test With Turbidity To set some guidelines as to the amount of t u r b i d i t y to study, i t was decided to use, as a maximum, the t u r b i d i t y found i n the lower Fraser River near Vancouver. This t u r b i -dity, considered high, represented a maximum of approximately 500 FTU (Formazin Turbidity Unit). Turbidity was measured by a Hach Turbidimeter Model 2100A. One FTU i s equivalent to one standard JTU (Jackson Turbidity Unit), as reported by the Hach manufacturer. The t u r b i d i t y was always added to the bottles i n the same way. F i r s t about 300 mg of bentonite clay was mixed with 1 l i t r e of BOD d i l u t i o n water. Then the d i l u t i o n r a t i o of t h i s mixture was determined, to obtain the desired t u r b i d i t y . The dissolved oxygen of the mixture was always measured before i t was added to the BOD bottles. In studying the e f f e c t of t u r b i d i t y , separately or i n conjunction with mixing, the method employed was as described i n section 4.4, using the oxygen probe. The oxygen probe i s a YSi 54 probe, manufactured by Yellow Springs Instrument Co. Limited. The general set up of t h i s section was to have three runs of d i f f e r e n t turbid values mixing, while three others of the same turbid values were kept quiescent. This l e d to observations of t u r b i d i t y e f f e c t s on the BOD t e s t and the e f f e c t of t u r b i d i t y i n conjunction with mixing. Also, as explained e a r l i e r , one single run was performed on one sample, with many possible combinations, 23. employing l i g h t and mixing. There was only one run performed f o r the combinations of l i g h t and mixing, l i g h t and mixing and t u r b i d i t y , because of the afore-mentioned time constraint on the walk-in incubator. 4.7 Summary The e f f e c t of turbulence, l i g h t and t u r b i d i t y , on the standard BOD test, was studied, separately and i n combinations. Turbulence was studied at 300, 400, 500, 600, 700, 800 and 900 rpm, while another set of experiments was conducted at 600 rpm with many d i f f e r e n t raw sewage samples. Light was studied at 1,000, 3,000 and 7.000 ft-candles and t u r b i d i t y at 160, 3^0, 430 and 570 JTU. The combinations are as follows! f i r s t , l i g h t and tu r b i d i t y , at 1,000 ft-candles l i g h t i n t e n s i t y with 270 and 410 JTU, at 3,000 ft-candles with 260 and 510 JTU, at 7.000 ft-candles with 250 and 360 JTUj secondly, turbulence and tu r -b i d i t y , at 600 rpm with 160, 3^0, 430 and 570 JTU; t h i r d l y , l i g h t and turbulence, at 3,000 ft-candles with 600 rpm and f i n a l l y , l i g h t and turbulence and t u r b i d i t y , at 3,000 ft- c a n -dles with 600 rpm and 200 JTU. Although some problems were encountered with temper-ature when using the lamp, these were countered with the use of an a i r fan. However, the problem remained when using the lamp and the mixers simultaneously. It seems imperative that any work involving l i g h t and mixing, as a combination, be performed i n a large incubator. CHAPTER V EVALUATION OP BOD PROGRESSION CONSTANTS In order to evaluate the e f f e c t of a physical v a r i a -t i o n on the BOD test, the ultimate BOD (L), the progression rate constant (k base 10) and the lag period ( t Q ) must be known. The values of the constants have been calculated f o r each sample by d i f f e r e n t modified methods: the Slope Method, the Moments Method and the Graphical Method. The Slope Method does not allow f o r the p o s s i b i l i t y of the existence of a lag period or an i n i t i a l oxygen demand which, i f present, would give misleading k and L values. Therefore, t h i s method has been modified to take into consir deration the influence of the l a g period and i n i t i a l damand (25). The requirements of the Moments Method i s that BOD determination should be made on a r i g i d time schedule. This procedure i s modified by adopting a t r i a l and error analysis, so that i t can be applied r e a d i l y to data gathered at regular, as well as i r r e g u l a r time i n t e r v a l s . Moreover, the procedure takes into consideration the existence of the lag period (25). The Graphical Method has the e f f e c t of the l a g period included i n i t s procedure. By means of a mathematical oper-ation, the lag period, t Q , was eliminated from the monomolec-u l a r equation, which s t i l l allows f o r i t ' s existence. A simple modification was proposed to f i n d t (25). Table II shows the 24 25-calculated t Q values of the three modified methods. Appendix B gives the computer programs and flow charts f o r the three modified methods. TABLE II CALCULATED LAG PERIOD VALUES Run # Slope (days) Moments (days) Graphical (days) Average (days) 1 0.2500 0.3722 0.1389 0.2537 2 0.4500 0.4302 0.7809 0.5537 3 0.1000 0.1606 0.0719 0.1108 4 0.4500 0.4302 0.7809 0.5537 5 -0.2500 -0.3557 -0.2376 -0.2811 6 0.0000 -0.1806 0.0976 -0.0277 7 -0.3500 0.0428 -0.3291 -0.2121 8 -0.3000 -0.3103 -0.2978 -0.3027 9 -0.3000 -0.2931 -0.2854 -0.2928 10 -0.0500 -0.0917 -0.0581 -0.0666 11 -0.3500 -0.1714 -0.2395 -0.2536 12 0.1500 0.3088 0.0112 0.1567 13 0.2000 0.2159 0.1802 0.1987 14 0.1000 0.2224 0.0784 0.1334 Gannon (1) ca r r i e d out both laboratory and f i e l d studies on BOD rate constant f o r selected samples from the Clinton River, Michigan. He computed the BOD rate constants by using several mathematical and graphical methods, i n c l u d -ing the Moments and the Slope Methods, without any modifica-t i o n . In t h i s study, the Slope Method yielded k (base 10) v a l ues s i g n i f i c a n t l y d i f f e r e n t than those obtained by the Moments Method and he concluded that the method of analysis d e f i n i t e l y 26. influences the r e s u l t i n g k value. Table III and Figure 1 i l l u s t r a t e the error i n using the Slope Method without the modification f o r the l a g period, when c a l c u l a t i n g the BOD progression rate constant. It i s observed that both methods, with or without modifications, agree when there i s no lag period. The equation of the l i n e i n Figure 1 was found by the l e a s t squares method. In general, the modifications resulted i n a better consistency between the values. However, a noticeable v a r i a -t i o n i n the re s u l t s , obtained by the i n d i v i d u a l methods, was observed occasionally. Therefore, comparisons based on the average of the values obtained by three d i f f e r e n t methods, rather than by one alone, give greater confidence i n conclu-sions drawn from these data. Consequently, the average values have been used f o r discussion. 27. TABLE I I I VARIATION S I N RATE CONSTANTS AS A FUNCTION OF THE LAG PERIOD Run # Average t_ (days) 0 k s l o p e . ( d a y s " 1 ) k s l o p e m o d i f i e d ( d a y s " 1 ) k s l o p e k s l o p e m o d i f i e d 1 0.2537 0.1093 0.1570 O.6962 2 0.5537 0.1467 0.3098 0.4735 3 0.1108 0.1513 0.1855 0.8156 0.5537 0.1467 0.3098 0.4735 5 -0.2811 0.1459 0.1459 1.0000 6 -0.0277 0.1607 0.1641 0.9793 7 -0.2121 0.1015 0.0572 1.7745 8 -0.3027 0.1047 0.0661 1.5840 9 -0.2928 0.1538 0.1134 1.3563 10 -0.0666 0.1442 0.1440 1.0014 11 -0.2536 0.0431 0.0559 0.7710 12 0.1567 0.1601 0.1917 0.8352 13 0.1987 0.2344 0.2795 O.8386 14 0.1334 0.2161 0.2344 0.9219 l - 6 - r Figure I - ERROR IN THE RATE CONSTANT AS A FUNCTION OF THE LAG PERIOD . -0.3 0 Lag Period ( days) 0.3 0.6 CHAPTER VI ANALYSIS OF THE RESULTS In th i s chapter, the re s u l t s discussed are derived from the observations found i n Appendix C. However, f o r convenience, a l l the calculated values of the BOD progression constants may be found i n Appendix D. 6.1 E f f e c t of Turbulence on BOD This study included many mixing rates. At the higher mixing rates, i t was observed that bubbles were formed i n the bottles but would disappear a f t e r about 48 hours. This unusual occurence was c l e a r l y observed at 700 rpm and faster, because of the vortex that the gas would form i n the bottles. At f i r s t the bubbles were thought to be the r e s u l t of supersaturation of oxygen i n the d i l u t i o n water. However, a pH of 4.5 was measured i n the bottles with bubbles and a f t e r 48 hours, when the gas bubbles had apparently redissolved, a pH of about 6.8 was measured. Oxygen cannot change the pH of a solution, i f the photosynthesis process i s eliminated and was therefore doubtful as a possible explanation. Possibly the gas was C0 2 < This gas i s a by-product of the b i o l o g i c a l r e s p i r a t i o n and thus i s being continually produced. The following chemical equation shows how C0 2 , af f e c t s the pH. C0 2 + H 20 ^ H 2 C 0 3 ^ L HC0~ + H + ...5 As C0 2 i s introduced i n the d i l u t i o n water, the pH decreases. 29 30. However, the phophate buffer i n the d i l u t i o n water should control any pH s h i f t s . Apparently, the buffer was not work-ing properly. What a c t u a l l y occurs i n a BOD bottle i s somewhat of a mystery, since only a handful of reactions, among scores, are known to happen. It i s beyond the scope of t h i s study to determine what i s causing the pH changes. Such a determi-nation represents a f u l l study of the i n t e r a c t i o n between the buffer systems present i n the BOD bottles. It i s possible, that the gas formed may be due, at l e a s t p a r t i a l l y , to zones of high and low pressures created i n the bottles by the r o t a t i n g mixers. The high pressure zones would increase the p a r t i a l pressure of oxygen and carbon dioxide and therefore, the gases would come out of solution. As oxygen i s used i n the microbial r e s p i r a t i o n , i t would re-dissolve. As the b i o l o g i c a l r e s p i r a t i o n decreases a f t e r a few days, the pH i s then raised to 6.8. Simultaneously, the free C0 2 i n solu t i o n i s changed to C0^ and KCOy thus permit-t i n g the gas to redissolve. It appears that turbulence accelerates the production of gas, which cannot be handled immediately by the d i l u t i o n water, but which i s eventually controlled when the b i o l o g i c a l action reduces to a lowerrrate. As shown by A l i {25), mixing accelerates every b i o l o g i c a l process i n the BOD bottle, e.g. a larger b i o l o g i c a l population and a reduced l a g period i n the mixed runs as compared to the control. This production of gas bubbles also occurs at lower 31. mixing rates, but closer observation during the f i r s t 24 hours i s required to detect them. Under quiescent conditions, no gas bubbles were observed. The results of the runs with mixing, i n terms of tha l a g period ( t Q ) , ultimate BOD (L) and the rate of BOD progression (k) are given i n Table IV. Every mixing run i s paired with a control run, because only one of these mixing tests could be performed at a time. TABLE IV BOD PROGRESSION CONSTANTS OF THE BOD TESTS WITH MIXING Run # Mixing Rate L(mg/1) k(days" 1) t Q(days) (rpm) 1 300 218.2 0.1723 0.2537 2 0 173-3 0.3079 0.5537 3 400 227.9 0.1847 0.1108 4 0 173.3 0.3079 0.5537 5 500 194.2 0.1425 -0.2811 6 0 I83.O 0.1555 -0.0277 7 600 320.7 0.0821 -0.2121 8 0 311.4 0.0644 -0.3027 9 700 260.1 0.1166 -0.2928 10 0 209.8 0.1384 -0.0666 l l 800 326.0 0.0665 -0.2536 12 0 166.6 0.2131 0.1567 13 900 207.3 0.2752 0.1987 14 0 194.1 0.2461 0.1336 It was observed that the ultimate BOD of the mixed run was usually higher than that of the quiescent run. This 32. increase i n available substrate i s believed to be the r e s u l t of the breaking up of the organic f l o e s e x i s t i n g i n the raw sewage and also the reduced l a g period. The reduced l a g p e r i -od indicates the p o s s i b i l i t y that some substrates, which would normally be c l a s s i f i e d as having a low bi o d e g r a b i l i t y , are now being u t i l i z e d by the microorganisms. The BOD progression rate, k, was lower, i n many cases, when turbulence was supplied i n the bottle. This ob-servation contradicts what has been reported i n a recent inves t i g a t i o n (25), but was also noted by Gaudy (31). It would be erroneous to conclude that mixing reduces the bio-l o g i c a l a c t i v i t y . Mixing increases the microorganisms to substrate contact and helps i n removing the b i o l o g i c a l wastes from the immediate surroundings of the microorganisms. By close inspection of Table IV, i t w i l l be noted that, although the progression rate, k, was lower, i n many o cases, when turbulence was supplied, at the same time, the ultimate BOD value was also much greater i n the mixed bottles. Therefore, at any time during the BOD progression test, a l -though the rate constant can be lower i n mixed bottles as compared to quiescent ones, more BOD can a c t u a l l y be exerted because of the aforementioned higher ultimate BOD values. Typical BOD progression curves are given i n Figure 2,. The oxygen consumption was always greater i n the mixed samples. As shown i n Table V, a comparison between mixed and quiescent runs reveals that mixing increased the BOD^ by an average of 15% and ranged from 6.k% to 21.7%. 33. Time ( d a y s ) Figure 2 - T Y P I C A L BOD PROGRESS ION C U R V E S . 34. TABLE V COMPARISON OF B0D„ OP MIXED AND QUIESCENT RUNS Mixing (rpm) Rate BOD^ Mixed BODc Quiescent (mg/1) (mg/1) Percent Increase 300 183.1 159.8 14.6 400 194.4 159.8 21.7 500 159.6 149.8 6.5 600 200.9 167.6 19.9 700 198.0 166.2 19.1 800 177.7 151.8 17.1 900 192.8 181.2 6.4 Average 15.0% Figure 3 shows how the increases i n BOD^ are varying with the mixing speed. At f i r s t , as the mixing rate i s i n -creasing, the e f f e c t of turbulence i s also increasing. The maximum increase occurs at 630 rpm above which, the mixing speeds are decreasing t h e i r influence on BOD^ values. This decrease i s believed to be the r e s u l t of "floe shearing" by the turbulence. Also, as the mixing rate increases, more gas bubbles are being produced i n the BOD bottles and simultaneous-l y the pH drops. This low pH may i n h i b i t the normal b a c t e r i o l o -g i c a l r e s p i r a t i o n . At 900 rpm, the magnetic bars no longer remained at the bottom of the bottles and therefore, there was much less mixing i n the bottles. The results presented i n Table V and Figure 3 are comparable to that of A l i (25). His results also show much less v a r i a b i l i t y . The high v a r i a -b i l i t y found i n t h i s study i s the r e s u l t of using a d i f f e r e n t 3.6. sample for every run. Each sample i s affected d i f f e r e n t l y by mixing. Since the ultimate BOD value and the progression rate constant were not comparable to other investigations, i t was decided that further research was needed. Therefore, a series of BOD runs were done on d i f f e r e n t raw sewage samples, at the same mixing rate of 600 rpm. The results of these runs are given i n Table C2. The BOD progression constants were calculated and they are given i n Table D2. Since the same mixing rate of 600 rpm was used i n a l l the runs of thi s section, the variations i n ultimate BOD values between mixed and quiescent runs seem to depend on the sample. The sample used f o r these runs was raw sewage and consequently, the amount and siz e of organic f l o e varied f o r every weekly samples; Since i t i s thi s breaking up of the fl o e which determines the changes i n ultimate BOD values, i t is expected that performing BOD tests, with mixing on d i f f e r e n t samples, w i l l r e s u l t i n many values f o r the r a t i o of mixed to quiescent ultimate values. As explained previously, when the r a t i o of mixed to quiescent rate constant i s low, the ultimate BOD of the mixed bottles was higher than i n the control run. The o v e r a l l BOD exerted at any time was always greater i n the mixed bottles. Figure 4 and Table VI present the change i n the rate constant as a function of the ultimate BOD value. I t i s ob-served that the ultimate BOD value may as much as double i n value i n mixed conditions. L q - Ultimate BOD Values under Quiescent Conditions ( mg/ I ) L s - Ultimate BOD Values under Mixing Co n di t i ons ( mg/I ) 2.2h-in _ J 8 ka - Progression Rate Constant under , Quiescent Conditions (days ) k, - Progression Rate Constant under Mixing Conditions (days ) , 4 h 0 0.2 0.6 1.0 k s / k q .4 Figure 4 - CHANGE IN k AS A FUNCTION OF L AT 600 rpm. 38. TABLE VI VARIATIONS IN k  AS A FUNCTION OF L AT 600 RPM Run # L /L s' q k / k s q 7.8 1.030 1.275 15.16 1.347 0.595 17.18 1.020 1.475 19,20 2.442 0.274 21,22 5.549 0.513 35.38 1.440 0.510 41,44 1.576 0.541 As the value of L„/L„ decreases, the value of k / k s q s' q increases. However, the change i n L_/L_ never dropped below s q 1.0. This i s understandable, since, i f mixing increases the ultimate BOD value, the worst case i s when the increase i s n e g l i g i b l e , i n which case L/L„ i s equal to 1.0. s q As the ultimate BOD value of quiescent and mixed conditions become similar, the rate constant of mixed samples, as compared to quiescent samples, increases. In other studies where primary effluent or f i l t e r e d raw sewage was used, i t was found that the ultimate BOD value was the same between mixed and quiescent conditions and therefore, greater rate constants were found i n the mixed conditions. However, f o r actual c r i t i c a l stream conditions, where raw sewage i s d i s -charged into a receiving stream, the sewage i s not free of floes and therefore, the studies using f i l t e r e d sewage or primary e f f l u e n t may not be r e a l i s t i c . 39. In t h i s study, many mixing rates were u t i l i z e d to determine the e f f e c t of mixing. The res u l t s of many BOD tests involving d i f f e r e n t mixing rates are given i n Tables Cl and DI. Figure 5, Table VI and Table VII contain a l l of the values of the BOD progression rate constants and the ultimate BOD of a l l tests with varying mixing rates. I t i s e a s i l y observed that a l l of the results f i t the same curve. However, no pat-tern i s found f o r the d i f f e r e n t mixing rates. Nevertheless, i t i s believed that f o r the same sample, as the mixing rate increases, the ultimate BOD value w i l l increase because of the breaking up of organic f l o e s . TABLE VII VARIATIONS IN k AS A FUNCTION OF L  AT DIFFERENT MIXING RATES Run # Mixing Rate (rpm) L / L s q k A s q 1,2 300 1.259 0.560 3A 400 1.315 0.600 5,6 500 1.061 0.916 7,8 600 1. 030 1.275 9,10 700 1.240 0.842 11,1'2 800 1.957 0.312 13,1^ 900 1.068 1.118 In general, whatever may be the sample or the mixing rate, the BOD exerted at any time w i l l be higher i n the mixed runs as opposed to the quiescent one. Also, the ultimate BOD of the mixed run i s always equal to or greater than the corre-Figure 5 - CHANGE IN k AS A FUNCTION OF L AT VARIOUS MIXING RATES. 41. spending control run, but never l e s s . The lag period i s usual-l y reduced by mixing and the immediate oxygen demand i s usually greater. The BOD progression rate constant, k, may be l a r g e r or smaller than the rate constant of the control run and varies as a function of the r a t i o of mixed to quiescent u l t i -mate BOD values. This intimates that sample "quality", even domestic sewage, profoundly a f f e c t s the standard BOD test and associated values and constants. This implies separate t e s t -ing f o r each effluent, to be absolutely c e r t a i n of rate con-stants and BOD exertion. 6 « 2 E f f e c t of Light on BOD This study consisted of the i l l u m i n a t i o n of BOD bottles at d i f f e r e n t high l i g h t i n t e n s i t i e s of 1,000 ft-candles, 3,000 ft-candles and 7.000 ft-candles. To control the inten-s i t y , the l i g h t source was moved towards or away from the bottles while, simultaneously, t u r b i d i t y was created i n the bottles. Tables VIII and IX give the results of the obserr vations. In Table IX, L L i s the ultimate BOD value of the sample submitted to l i g h t , L Q i s the ultimate BOD value of the sample i n the dark, k^ i s the BOD progression rate constant of the sample i n the l i g h t and k Q i s the BOD rate constant of the sample i n the dark. By examining the percent change i n the BOD^ values fo r the t e s t with li"ght only, i t i s apparent that l i g h t by i t s e l f does not seem to a f f e c t the r e s u l t s . At the most, i t could be said that l i g h t only s l i g h t l y enhances the oxygen TABLE VIII PERCENT CHANGE IN BOD DUE TO LIGHT AND TURBIDITY Run # Turbidity (JTU) Light Intensity (ft-candles) % BOD^  Change 24 0 1,000 +6. 3 25 270 1,000 -4.0 26 410 1,000 +2. 2 28 0 3,000 +6.4 29 260 3,000 -2.3 30 510 3,000 -2.5 32 0 7,000 -0.8 33 250 7,000 34 360 7,000 -14.9 TABLE IX VARIATIONS IN k AS A FUNCTION OP L IN TESTS WITH LIGHT AND TURBIDITY Run # V L D V k D 23, 24 1.308 0.626 23,25 1.206 0.586 23,26 1.101 0.847 27,28 1.516 0.564 27,29 1.008 1.001 27,30 1.811 0.377 31,32 0.954 1.220 31.33 0.914 0.951 31,34 0.761 1.618 43-uptake. It should be kept i n mind that the maximum increase i n BOD,-, due to l i g h t , of 6.4% i s not very s i g n i f i c a t i v e , since the BOD tes t i n i t s e l f contains a Sf» error margin. Similar to section 6.1, i t was impossible i n t h i s section to use the BOD rate constant as the comparison para-meter, because the ultimate BOD value of the standard t e s t and the t e s t with l i g h t and t u r b i d i t y was usually d i f f e r e n t . Since the BOD rate constant i s dependant on the ultimate BOD value, i t follows that one parameter must be kept constant i f the other i s to indicate the ef f e c t s of physical changes on the standard BOD test. On the other hand, i t i s i n t e r e s t i n g to speculate on how the physical changes could a f f e c t the ultimate BOD values. In the case of turbulence, i t i s e a s i l y understood how the organic floes can be broken up to increase the u l t i -mate BOD. However, l i g h t does not have s i m i l a r e f f e c t s . The illum i n a t i o n does not break up anything, nor does i t reduce the lag period. The increase must then be due to a greater a b i l i t y of the microorganisms to u t i l i z e the less biodegra-dable material under l i g h t conditions. This greater a b i l i t y of the microorganisms, i s believed to be the r e s u l t of "exci t a t i o n " of c e r t a i n microorganisms by l i g h t . Certain photosynthetic pigmented bacteria exhibit phototactic- behaviour? that i s , t h e i r movements are influenced by l i g h t (32) . The. reason f o r the increase i n ultimate BOD may also reside, at lea s t p a r t i a l l y , i n the light-induced oxidation of organic matter (27) . However, t h i s auto-oxidation of organic 44. matter may indeed be very small. No c o r r e l a t i o n was found between the increase i n BOD^ and the increase i n l i g h t i n t e n s i t y nor was there a c o r r e l a t i o n between an increase i n the rate constant and an increase i n l i g h t intensity. However, repeating t h i s l i g h t study with a single sample, f o r every l i g h t i n t e n s i f y , may reveal otherwise. Since, i n t h i s case, only one l i g h t source was available, only one run could be followed at a time. A sample could hardly be kept more than a week. Therefore, d i f f e r e n t samples had to be used. This may explain the lack of c o r r e l a t i o n of the r e s u l t s . It was also observed that, at a chosen l i g h t inten-s i t y , the ultimate BOD of the t e s t i n the l i g h t , compared to the one i n the dark, would decrease as the added t u r b i d i t y was increased. This reduction may be p a r t i a l l y due to the reduc-t i o n i n the l i g h t i n t e n s i t y received by the bottles, but i s mainly the r e s u l t of t u r b i d i t y , as discussed i n section 6.3. Figure 6 represents the results of the BOD tests with l i g h t and t u r b i d i t y . Since many samples were used to determine the points of the curve and since these samples were obviously d i f f e r e n t i n c h a r a c t e r i s t i c s , i t i s expected that l i g h t and t u r b i d i t y w i l l a f f e c t each sample d i f f e r e n t l y . A detailed observation of Table VIII, IX and Figure 6 reveals that no c o r r e l a t i o n exists between the l i g h t i n t e n s i t i e s and the e f f e c t on ultimate BOD. However, there i s a d e f i n i t e r e l a t i o n s h i p between L L / L D and kj/kp. I f l i g h t and t u r b i d i t y increases the ultimate BOD Figure 6 - CHANGE IN CONSTANTS OF THE BOD TEST WITH LIGHT AND TURBIDITY . 46. of a sample, the l e a s t e f f e c t they could have would be when l i g h t and t u r b i d i t y i s absent, i n which case the bottles would be i d e n t i c a l to the control run. Following t h i s reasoning, the lowest value f o r L J / L Q should be l.G. Figure 6 presents two d i f f e r e n t curves, the f u l l l i n e being the experimental r e s u l t s obtained and the dotted l i n e representing the results of t h i s section i f the "ques-tionable" point i s omitted. The presence of the "questionable" point makes the f u l l l i n e decrease below a value of 1.0 f o r V L D ' However, that point may be the r e s u l t of a BOD test performed-, on a sample with a large dose of i n d u s t r i a l waste. Possibly some photo-sensitive chemicals i n that waste reacted under the influence of l i g h t to produce a product which i n -h i b i t e d the normal functioning of b a c t e r i o l o g i c a l r e s p i r a t i o n . The same reaction may have not occurred i n the control bottles because they were i n the dark. In summary, l i g h t s l i g h t l y increased the BOD^ value of the standard BOD test. However, t h i s increase i s small and comparable to the 5% error generally at t r i b u t e d to the stan-dard BOD test. 6.3 E f f e c t of Turbidity on BOD Since t u r b i d i t y i s always present, to a varying degree, i n streams, but usually almost absent i n the standard BOD test, i t was decided to investigate i t ' s e f f e c t . To do so, many BOD tests were performed with t u r b i d i t y ranging from 0 JTU to 600 JTU under mixing or quiescent conditions. The 47. r e s u l t s of thi s study are given i n Tables X, XI and XII. TABLE X PERCENT CHANGE IN BOD,- VALUES OF TESTS WITH : TURBIDITY Run # Turbidity Mixing Rate % B0De Change " (JTU) (rpm) j 44,45 160 0 -19.4 44,46 340 0 -26. 0 38,39 430 0 -23.5 38,40 570 0 -25.8 44,41 2 600 15.4 44,42 160 600 -25.3 44,43 340 600 -24.6 38,36 430 600 -32.3 38,37 570 600 -30.5 TABLE XI VARIATIONS IN. k AS A FUNCTION OF L IN TESTS WITH TURBIDITY Run # 44,45 2.8775 0.1663 44,46 2.0807 0.1916 38,39 3.4426 0.0943 38,40 5.7106 0.0705 44,41 1.5764 0.5414 44,42 2.7154 0.1262 44,43 3.0238 0.1111 38,36 6.1369 0.0410 38,37 2.4545 0.1167 48. In Table XI, L T i s defined as the ultimate BOD value of tests with t u r b i d i t y , L c i s the ultimate BOD value of con-t r o l tests, k,p i s the BOD progression rate constant f o r the tests with t u r b i d i t y and k c i s the BOD progression rate con-stant f o r the control tests. TABLE XII VARIATIONS IN LAG PERIOD Run # Turbidity Mixing t Q ( c l e a r ) t Q ( t u r b i d ) (JTU) Rate (days) (days) ^OC'^OT^ * (rpm) (days) 4 4 , 4 5 1 6 0 0 - 0 . 1 6 3 5 -0.4867 0 . 3 2 3 2 44,46 3 4 0 0 - 0 . 1 6 3 5 -0.6817 0 . 5 1 8 2 38,39 4 3 0 0 0.0434 - 0 . 6 5 3 6 0 . 6 9 7 0 38,40 5 7 0 0 0.0434 -O .8O36 0 . 8 4 7 0 44,41 2 600 -O . I 6 3 5 - 0 . 4 7 8 9 0 . 3 1 5 4 4 4 , 4 2 1 6 0 6 0 0 - 0 . 1 6 3 5 - 0 . 7 8 9 8 0 . 6 2 6 3 44,43 340 600 -O . I 6 3 5 - 0 . 9 0 4 5 0.7410 3 8 , 3 6 4 3 0 600 0.0434 - 1 . 2 3 8 2 1 . 2 8 1 6 3 8 , 3 7 5 7 0 600 0.0434 - 1 . 0 5 1 8 1 . 0 9 5 2 It was observed that, often, i n a' turbid test, the ultimate BOD was much higher than the control test 's BOD, the rate constant was very small and the immediate oxygen demand was very large. A l l these factors, together, indicate perhaps, that the microorganisms of some t u r b i d i t y BOD tests were undergoing endogenous r e s p i r a t i o n . The very small BOD progression rate constant i s representative of the endogenous state, where the rate of 4 9 . oxidation i s very slow. The very large ultimate BQD repre-sents, not the substrate avai l a b l e , but rather the stored food of the microorganisms. The large ultimate BOD value i s not the r e s u l t of orgahics i n the bentonite, which was tested and found to contain very l i t t l e usable organic matter. The endogenous r e s p i r a t i o n i s due to the large amount of t u r b i d i t y which "masks" the substrate from the micro-organisms. This e f f e c t can e a s i l y be observed i n Figures 7 and 8. The BOD^ decreased as t u r b i d i t y increased. This e f f e c t i s noticed up to 200 JTU and then l e v e l s o f f , so that above 200 JTU, a 26% decrease i n BOD^ i s expected. Also, the immediate oxygen demand increased with t u r b i d i t y i n a l i n e a r fashion. It i s i n t e r e s t i n g to note, i n Figure 7. The d i f f e r -ence between mixed and unmixed samples. In both cases, above 30 JTU the e f f e c t was a decrease i n BODy as compared to the control runs. This means that l i t t l e t u r b i d i t y i s required to counteract the e f f e c t of turbulence. The percent BOD^ decrease i n mixed and unmixed samples tapers o f f at approximately the same value at high t u r b i d i t y l e v e l s . The unmixed samples have les s negative e f f e c t , but one should keep i n mind that some bentonite was deposited at the bottom during the t e s t and therefore l e s s t u r b i d i t y was e f f e c t i v e l y present i n the bottles. Also con-si d e r i n g the error inherent to the BOD test, i t seems reason-able to assume that, above 80 JTU, there was no difference i n 50. 0 2 0 0 4 0 0 6 0 0 Turbidity (JTU) Figure 7 - PERCENT CHANGE IN B0D 5 V A L U E S . 51. O Turb id i ty + M i x i ng O T u r b i d i t y (JTU ) Figure 8 - C H A N G E IN f 0 AS A FUNCTION OF TURBIDITY. 52. the BOD exerted a f t e r f i v e days, under turbid conditions, whether the sample be mixed or quiescent. It appears that t u r b i d i t y n u l l i f i e s the e f f e c t of mixing. Looking at what happens i n the BOD bottle, i t i s observed that mixing increases the p r o b a b i l i t y of contact bet-ween the substrate and the microorganisms and therefore a c c e l -erate the whole process of BOD progression. However, when t u r b i d i t y i s present, the p r o b a b i l i t y of a microorganism entering i n contact with a bentonite p a r t i c l e i s also increased. After enough bentonite i s added to the bottle, the t u r b i d i t y l i m i t s the substrate to microorganisms contact, to the same amount as i f i t was unmixed. I t i s also i n t e r e s t i n g to observe the e f f e c t of t u r b i d i t y on the lag period.': As the t u r b i d i t y increases, so does the immediate oxygen demand. In a separate t e s t , the bentonite did not show any oxygen demand. This indicates again that the t u r b i d i t y "masks" the substrate from the micro-organisms. The high immediate oxygen demand indicates that the microorganisms want to oxidize the substrate but the small rate constant indicates that they cannot get to i t . The reduction i n lag period due to mixing i s c l e a r l y i l l u s t r a t e d i n Figure 8. This figure seems.to indicate a smal-l e r reduction i n l a g period i n the mixed samples. However, ad-ding turbulence to a bottle usually resulted i n a negative l a g period or immediate oxygen demand. Since we are considering the difference between the mixed condition and the control, t h i s difference w i l l be greater when the samples are mixed as 53. compared with the sample with t u r b i d i t y only. Since the two li n e s are almost p a r a l l e l , i t i s reasonable to assume that the decreased l ag period due to mixing w i l l always be present at any t u r b i d i t y . Figure 9 demonstrates again the re l a t i o n s h i p of the ultimate BOD value and the BOD progression rate constant. The ultimate BOD value i n the turbi d bottles may be as high as s i x times the corresponding control bottle, at which time the rate constant of turbid tests i s very low as compared to the control. Again i t i s seen that l>rj/^c w i l l never go below 1.0. 6.4 Combination Testing and Summary This study consisted of the analysis of the BOD test, subjected to three d i f f e r e n t physical changes, namely mixing, l i g h t and t u r b i d i t y . The t o t a l d i f f e r e n t combina-tions possible with those three changes i s seven. Table XIII presents the res u l t s of a l l the studied combinations. TABLE XIII SUMMARY OF THE RESULTS Physical Change Minimum Change Maximum Change Avg Change (*) if") (f>) Mixing 6.4 21.7 15.0 Light -0.8 6.4 4.0 Turbidity -19.4 -26.0 -23.7 Mixing + Turbidity -24.6 -32.3 -28.2 Turbidity + Light 2.2 -14.9 -5.7 Mixing + Light (No max. and min. available 15.3 Light+Turb+Mixing since there with these was only one run combinations) -26.4 54* 7.0 6.0 5.0 4.0 3.0 2.0 0 Ultimate BOD of Turbid Test,(mg/I) Ultimate BOD of Clear Test,(mg/1) Rate Constant of Turbid Test,(days ') — Rate Constant of Clear Test,(days ') 0.1 0.2 0.3 0.4 k T / k c 0.5 0.6 Figure 9 - CHANGE IN CONSTANTS OF BOD TEST WITH TURBIDITY. 55. As mentioned e a r l i e r , mixing increased the BOD^ by 1 5 % , l i g h t by 4.0% and t u r b i d i t y reduced the BOD^ by 23.7%. These ef f e c t s were not additive. For example, mixing and tu r b i d i t y , i f they had additive e f f e c t s , would have reduced the BOD^ value by 8.7% (15.0 - 23.7). From Table XI, we f i n d t h i s experimental value to be 28.2%. The reason f o r t h i s d i f f e r -ence was explained e a r l i e r , as being due to the n u l l i f i e d e f f e c t of mixing when t u r b i d i t y was added. When t u r b i d i t y and l i g h t were added to the standard BOD test, there was a s i m i l a r occurrence. Light and t u r b i d i t y , i f they had additive e f f e c t s , should have resulted i n a de-crease of BOD^ of 19.7% (4.0-23.7). However, the experimental value of t h i s combination was a decrease i n BOD^ of 5«7%. No explanation, to date, has been found f o r this difference. One should keep i n mind, however, that temperature variations i n the illuminated bottles are possible. On the other hand, i t i s not believed that the small possible changes i n temperature would cause such a large difference. The two other combinations have only the res u l t s of one run, because the BOD test was performed i n a large walk-in incubator, available only a short period of time (explained e a r l i e r ) . However, many runs with d i f f e r e n t physical changes to the BOD tes t were performed simultaneously. The re s u l t s of the runs are given i n Table C5 and D5. The changes i n B0D<-, as compared to the control run, due to the various physical changes, are as follows: l i g h t 4.0%, t u r b i d i t y -20.2%, t u r b i d i t y and l i g h t -13.3%, mixing and l i g h t 15«3%» mixing 5 6 . and l i g h t and t u r b i d i t y - 2 6.4%. Comparing the e f f e c t on the BOD^ of the control of the f i r s t three combinations stated above, with the re s u l t s of Table XIII, indicates that the sample and runs were t y p i c a l . Since the same sample was used f o r a l l the combinations, i t i s then expected that, the r e s u l t s of mixing and l i g h t , mixing and l i g h t and t u r b i d i t y , are also t y p i c a l . There was no difference between mixing and l i g h t , and p l a i n mixing. The e f f e c t of l i g h t i s so small that i t was l o s t i n the e f f e c t of mixing. The e f f e c t on BOD^ of the combination of l i g h t , t u r b i d i t y and mixing was very s i m i l a r to the e f f e c t of mixing and t u r b i d i t y . Again the e f f e c t of l i g h t was l o s t with the e f f e c t of mixing. However, i t could have been e a s i l y expected that l i g h t would have a greater e f f e c t because of the t u r b i -d i t y present. The large e f f e c t of l i g h t i n the presence of t u r b i d i t y was not demonstrated. CHAPTER VII IMPROVING THE BOD TEST Oxygen balance studies, to determine stream capacity i n a s s i m i l a t i n g organic p o l l u t i o n , are based primarily on the Streeter-Phelps equation (4)« k..L —k« t —k~t —k^t D = tr Ir ( 1 0 ~ 1 0 ) + D 10 * ...6 K2 1 0 where D = Dissolved oxygen d e f i c i t , mg/1 k^ = BOD reaction rate constant, day" 1 L & = F i r s t stage BOD at the upstream end of the stretch, mg/1 k 2 = Reaeration rate constant, day t = Time of flow i n the stretch, days D Q = The dissolved oxygen d e f i c i t at the point of d i s -charging the waste, mg/1. Equation 6 i s based on the assumption that only two main pro-cesses are taking place i n the stream; f i r s t oxygen removal by b i o l o g i c a l oxidation and second oxygen supplied by r e -aeration. Dobbins (33) modified the Streeter-Phelps equation to include the following a d d i t i o n a l sources of oxygen supply and demand: a. the removal of BOD by sedimentation or adsorption b. the removal of oxygen from water due to benthal demand 57 58. c. the removal of oxygen by plant r e s p i r a t i o n d. the addition of oxygen by photosynthesis Following i s Dobbins' equationj - ( k . ,+ lOt - k p t k2 - (k 1 + k 3 ) - k 9 t + D 0 10 c ...7 where k^ = Rate constant f o r the removal of BOD by sedimen-t a t i o n or adsorption or both, day"* = Rate of addition of BOD due to bottom deposits along the stretch, mg/1 per day Dfi = Net rate of addition of oxygen due to photosyn-thesis and plants r e s p i r a t i o n , mg/1 per day. The reaeration constant k 2 has been defined by the following general r e l a t i o n s h i p i C U n k„ = .. .8 2 2.3 H m where U = The average stream v e l o c i t y , fps H = The average stream depth, f t . Depending on the stream conditions, d i f f e r e n t values f o r C, n and m have been reported by several investigators (34), (35), (34). C h u r c h i l l , Elmore and Buckingham (34) have 59. proposed the following equation» 5 026 U 0 , 9 6 9 (T-20) k 2 = 5 1.673 { U 0 2 k ) •'• 9 H i n which T denotes the temperature i n °C. The value of the BOD reaction rate constant, k^, should be determine i n the laboratory. The rate of oxida-t i o n found from the standard BOD t e s t i s used frequently, instead of the actual rate constant k^ i n the stream, even when the value of has been reported to be several times greater than k (1). In t h i s study, i t was shown that the two values may i n f a c t be very d i f f e r e n t . Other research (25) has extrapolated from the standard BOD test to f i e l d conditions. In t h i s study, i t was found impossible to correlate the change i n the rate constant and the mixing speed because of the varying ultimate BOD v a l -ues. However, i t i s possible to measure the turbulence i n the stream and to reproduce the same amount i n the BOD bot-t l e s . The same i s true f o r t u r b i d i t y , temperature and l i g h t . It appears that reproducing the r i v e r conditions i n the bottles, instead of extrapolating from the BOD test, i s an i n t e r e s t i n g p o s s i b i l i t y . F i e l d surveys may help to determine kg. k^, and Dfi leaving the value of kj and L & to be determined i n the laboratory. It was shown i n t h i s study that ^ and L a de-pended on the physical c h a r a c t e r i s t i c s of the r i v e r , such as turbulence, t u r b i d i t y , possibly l i g h t and also on the type of 60. waste being discharged. Because of the complexity of the ef f e c t s on BOD progression, due to physical factors i n combinations, and also because of the lack of research i n t h i s f i e l d , as much as possible, of the ex i s t i n g c h a r a c t e r i s t i c s of the stream under study, should be added to the standard BOD tes t ; t h i s would eliminate the need f o r extrapolation. The modifications might possibly increase the r e l i a b i l i t y of the BOD test. incubators, capable of d i s s i p a t i n g the large amount of heat created by the lamp. With new design, the lamp could be l o -cated at the top, but outside the incubator. An in f r a r e d screen could then be placed between the l i g h t source and the BOD bottles. Such a screen would absorb the in f r a r e d l i g h t before i t s entrance i n the incubator. The design described above i s an expensive proposition. It seems better to study the effects of l i g h t i n d e t a i l s so that once they are known, l i g h t would no longer be required i n the incubator. Also, the r e s u l t s of t h i s study do not warrant the i n c l u s i o n of l i g h t i n the standard BOD test. lence to a BOD bottle was determined by A l i (25) and the f i nal equation i s as follows i However, adding l i g h t to the te s t would require new The method of adding the correct amount of turbu-10 61. where N = S t i r r e r ' s speed, rpm P y = Power dissipated to a unit volume of r i v e r water, f t - l b / s e c / f t 3 C D - Drag c o e f f i c i e n t , varying with Reynolds number, R /* = Mass density of the r i v e r water, lb-mass/ft 3 J = Ratio of f l u i d v e l o c i t y to the magnetic bar v e l o c i t y b = Thickness of magnetic bar, f t r Q = Half the length of the magnetic bar, f t . In the f i e l d , the power dissipated to a unit volume of r i v e r water, i n f t - l b / s e c / f t 3 , between two stations, L f t apart, i s given byj P v = 3 £ i 9 l T = ^ s U S 2 where a = Cross-sectional area of the flowing stream, f t Q = Rate of flow, f t 3 / s e c h = Head loss incurred by a flow Q, f t w = Unit weight of the f l u i d , l b s / f t 3 g = Gravity constant, f t / s e c U = Mean v e l o c i t y of flow, ft/sec (=Q/a) S = Slope of the water surfaee, f t / f t (=h/L). Reynolds number i s calculated by the following equation i ? Nbr P R = 5.25 * 10"* * —T^— ...1'2 r where JJL - Absolute v i s c o s i t y , l b mass/ft-sec. The observational r e l a t i o n s h i p between Newton's c o e f f i c i e n t of drag, C D, and Reynolds number, R, f o r c i r c u l a r 62. cylinders are given by Pao (37). Typical values f o r J, used by A l i (25) varied between 0.20 to 0.25. Therefore by knowing the c h a r a c t e r i s t i c s of the flowing stream, which include a, \3,f, S and L, the energy dissipated to the f l u i d per unit volume can be obtained from Equation 11. With this value of P f i t i s possible to c a l c u -l a t e N, from Equation 10 and u t i l i z e i t to run the BOD pro-gression test, with continuous s t i r r i n g i n the laboratory. The value of C D w i l l have to be determined from the graph between C D and R (37) by the t r i a l and error method. A t y p i -c a l example i s given i n Appendix E. U n t i l the effects of physical factors, such as temperature, t u r b i d i t y , etc., have been studied i n details i t appears that extrapolating from the present laboratory test to f i e l d conditions i s not possible. Incorporating as much as possible of the stream conditions i n the BOD t e s t would eliminate t h i s need to extrapolate. CHAPTER VIII CONCLUSIONS AND RECOMMENDATIONS 8 . 1 Conclusions This laboratory study has attempted to duplicate as close as possible, actual f i e l d conditions. The changes brought to the standard BOD t e s t consisted of mixing, l i g h t and t u r b i d i t y . Since i t was found by other researchers, that the BOD tes t i n the f i e l d and i n the laboratory yielded d i f f e r e n t r e s u l t s , i t was expected that bringing physical changes to the standard BOD test, would change the r e s u l t s . In fact, there were many differences between the standard BOD test and the modified tests. When mixing was incorporated i n the BOD test, i t was observed that the ultimate BOD increased i n the modified t e s t and that the progression rate constant was ei t h e r higher or lower. It was c l e a r l y shown i n t h i s study that the rate constant i s dependant on the ultimate BOD value. However, examining the changes i n the BOD,- between standard and mixed BOD tests revealed some i n t e r e s t i n g figures. The BOD^ increased i n the range of 6 . 4 % to 2 1 . 7 % with an average of 1 5 % . This increase i s believed to be the re s u l t of the breaking up of organic floes and also the reduced l ag period. At f i r s t , as the mixing rate i s increasing, the e f f e c t of turbulence i s also increasing. The maximum increase occurs at 6 3 0 rpm, above which, the mixing speeds 6 3 64. are decreasing t h e i r influence on BOD^ values. This decrease i s believed to be the r e s u l t of "floe shearing" by the turbu-lence. There was also a reduction i n the l a g period, but no c o r r e l a t i o n was found between the l a g period reduction and the mixing rate. Turbidity influenced the BOD test to a higher degree than expected. It i s i n t e r e s t i n g to note that t u r b i -d i t y at high concentrations n u l l i f i e s the e f f e c t of mixing. In fact, t u r b i d i t y on i t ' s own reduced the BOD^ of the con-t r o l run by 2 3 . 7 % , while t u r b i d i t y and mixing i n combination reduced i t by 28.2%. The difference between the two physical changes, i s probably due to a reduction i n the suspension of the t u r b i d i t y i n the quiescent run. It i s believed that t u r b i d i t y "masks" the substrate from the microorganisms. This was observed by a large imme-diate oxygen demand, which increased as a function of the t u r b i d i t y added, i n conjunction with a very small BOD progres-sion rate constant and large ultimate BOD values. Light had very l i t t l e e f f e c t on the BOD^ of the standard test. In fact, the 4.0% increase i n BOD^ i s well inside the error inherent to the BOD test. The net e f f e c t of t u r b i d i t y and l i g h t , i n combination, i s only a 5 * 7 % decrease i n BOD^. Because t u r b i d i t y was found to reduce the BOD^ by 2 3 . 7 % , i t appears that l i g h t , i n combi-nation with t u r b i d i t y , r e s t r a i n s the reduction i n BODy caused by t u r b i d i t y , by 18.0%. Therefore, l i g h t appears to have much greater e f f e c t i n combination with t u r b i d i t y . 65. Light i n combination with mixing increased the BOD^ of the control by 15.3%. This number i s i d e n t i c a l to the one found with p l a i n mixing. Therefore, under mixing conditions, the l i g h t e f f e cts are probably n u l l i f i e d . Light i n combination with mixing and t u r b i d i t y demonstrated a decrease of 2 6 . 4 % on the BOD^ of the control. This decrease i s s i m i l a r to that which i s found with mixing and t u r b i d i t y , i n d i c a t i n g again that the e f f e c t of l i g h t was n e g l i g i b l e . In conclusion, the BOD te s t has been found to be inadequate f o r f i e l d conditions. It i s c l e a r l y shown i n th i s study that mixing, t u r b i d i t y and l i g h t have a d e f i n i t e e f f e c t on the BOD te s t and should be incorporated i n the standard test. However, before they are incorporated, further knowl-edge i s required i n order to learn i n which proportion every physical change should be made to simulate stream conditions. 8 . 2 Recommendations for Further Studies Many studies are needed i n t h i s f i e l d , to under-stand what i s happening i n streams. This knowledge w i l l be invaluable when the proper corrections are brought to the standard BOD test. Further studies should include one or more of the following subjects: a) Studies on l i g h t with d i f f e r e n t lamps, mainly those with less wavelengths i n the infrared and more wavelengths i n the u l t r a v i o l e t range, to reduce the heat production and increase the s i m i l a r i t y between sunlight and the lamps. 66. b) More studies on combinations of mixing, t u r b i d i t y and l i g h t . These studies should include temperature, since i t ' s e f f e c t i s unknown i n combinations with other physical changes. c) Other tests with longer BOD progression period, since there i s some error i n using only a 6 day period. d) Studies are needed to learn what i s causing the changes i n the ultimate BOD value. I t i s possible that only the break up of organic floes or the presence of i n d u s t r i a l waste i s enough to cause these changes. e) Different types of wastes should also be analysed by BOD progression, to know what e f f e c t s , i f any, they exert on the test. f ) S a l i n i t y e f f e cts are also important i n estuaries, where the BOD t e s t i s often used. Further research i s needed i n t h i s f i e l d . In addition, the physical changes of the above studies should be matched to e x i s t i n g r i v e r types, so that comparison with f i e l d conditions may be possible. REFERENCES 1. Gannon, J.J., "River and Laboratory BOD Rate Considera-tions", Journal of the Sanitary Engineering Divi s i o n , Proceedings of the American Society of C i v i l Engineering, 135-161, SA1, 1966. 2. O'Connor, D.J., "The E f f e c t of Stream Flow on Waste As-s i m i l a t i o n Capacity", Proceedings of the 1 7 t h I n d u s t r i a l Waste Conference, Purdue University, 608-629, 1962. 3. Streeter, H.W., and Phelps, E.B., "A Study of the P o l l u -t i o n and Natural P u r i f i c a t i o n of the Ohio River", Public Health B u l l e t i n 146 III, Washington, D.C, pp. 4-9, p. 19, 1925. 4. Phelps, E.B., Stream Sanitation, John Wily & Sons, New York, pp. 68-71, pp. 76-88, I960. 5. Orford, H.E., and Ingram, W.T., "Deoxygenation of Sewage: C r i t i c a l Review of the Monomolecular Formula", Sewage and Indu s t r i a l Wastes, 2£, 419, (1953) 6. Hoover, S.R., Jasewicz, Lenore, and Porges, N., "An Inter-pretation of the BOD Test i n Terms of Endogenous Respira-t i o n of Bacteria", Sewage and Ind u s t r i a l Wastes, 2£, I I 6 3 , (1953) 7. Busch, A.W., "BODFProgression i n Soluble Substrate", Sew-age and Industrial Wastes, ^0, 1336, (1958) 8. Gotaas, H.B., "Effect of Temperature on Biochemical Oxi-dation of Sewage", Sewage Works Journal, 20, 441, (1948) 9. Bewtra, J.K., and Charan, R., "Effect of Temperature on Biochemical Oxygen Demand", Environmental Health, VII, 143- 164, (1964) 10. Moore, E.W., "Long-Time Biochemical Oxygen Demand Curve", Sewage Works Journal, 13., 61, (1941) 11. Zanoni, A.E., "Waste Water Deoxygenation at Different Temperatures", Water Research, 1, 543, (1967) 12. Thimann, K.V., L i f e of Bacteria, The McMillan Co., N.Y., pp. 353-354, 1955. 13. Sawyer, C.N., and McCarty, P.L., Chemistry f o r Sanitary  Engineers, McGraw-Hill Book Company, New York, pp. 394-410, 1967. 67 68. 14. Brock, T.D., Biology of Microorganisms. Prentice-Hall Inc. Englewood C l i f f s , New Jersey, pp. 92-97. pp. I83-I85, 1970. 15. Bhatla, M.N., and Gaudy, A.F., J r . , "Role of Protozoa i n the Diphasic Exertion of BOD", Journal of the Sanitary Engineering Division, Proceedings of the American Society of C i v i l Engineering, 63-87, S A 3 , 1965. 16. Theriault, E.J., "The Oxygen Demand of Polluted Waters", Public Health B u l l e t i n No. 173, U.S. Public Health Serv-ice, Washington, D.C, 132-I85, 1927. 17. Tsao, G.T.N., and Kempe, L.L., "Oxygen Transfer i n Fer-mentation Systems; I. Use of Gluconic Acid Fermentation f o r Determination of Instantaneous Oxygen Transfer Rates", Journal of Biochemistry and Microbiology Technical Engi-neering, 2, 129, (I960) 18. Rincke, G., Formal Discussion of "The Role of Aeration i n the Activated Sludge Process", In "Advances i n Water Po l l u t i o n Research", Proceedings of the 3rd International Conference on Water P o l l u t i o n Research, Water P o l l u t i o n Control Federation, 2, 72, (1967) 19. Imhoff, K., Process i n Sewage P u r i f i c a t i o n , C a rl Heyman-Verlag, B e r l i n Germany, 1925. 20. Von der Emde, W., "50 Iahre Belegungverfahren", Gas-U Wasserfach, Germany, 105, 755, (1964) 21. Zahradka, V., "The Role of Aeration i n the Activated Sludge Process", In "Advances i n Water P o l l u t i o n Research", Proceedings of the 3rd International Conference on Water Po l l u t i o n Research, Water P o l l u t i o n Control Federation, 2, 53, (1967) 22. Richard, M.D., and Gaudy, A.F., J r . , "Effect of Mixing Energy on Sludge Y i e l d and C e l l Composition", Journal of Water P o l l u t i o n Control Federation, 40, 129-144, (1968) 23. Lordi, D.? and Heukelekian, H., "The E f f e c t of Rate of Mixing on the Deoxygenation of Polluted Waters", Proceed-ings of the 19th I n d u s t r i a l Waste Conference, Purdue University, 530-539, 1964. 24. Busch, A.W., Kehrberger, G.J., Norman, J.D., and Schroeder, E.D., "BOD Progression i n Soluble Substrates - VII Temper-ature E f f e c t s " , Proceedings of the 19th I n d u s t r i a l Waste Conference, Purdue University, 953-964, 1964. 25. A l i , H.I., "Influence of Turbulence on BOD Progression", PhD Thesis, University of Windsor, Windsor, Ontario, 1972. 69. 26. Hoch, G.t Owens, O.V.H., and Kok, B., "Photosynthesis and Respiration", Archives of Biochemistry and Biophysics, 101. 171-180, (1963) 27. Golterman, H.L., "The Determination of Mineralization Losses i n Correlation with the Estimation of Net Primary Production with the Oxygen Method and Chemical I n h i b i -tors", Freshwater Biology, 1, 249-256, (1971) 28. P e i l , K.M., and Gaudy, A.F., J r . , "A Rational Approach f o r Predicting the Dissolved Oxygen P r o f i l e i n Receiving Waters", Biotechnology and Bioengineering, XVII, 69, (1975) 29. Lucalox Lamps, High Pressure Sodium Vapor Lamps. Canadian General E l e c t r i c , Lamp Department Publication LL-8-73, 1973. 30. Light Measurement and Control, General E l e c t r i c , Large Lamp Department Publication TP-118, 1965. 31. Standard Methods f o r the Examination of Water and Waste-water, 13th edition, American Public Health Association, American Water Works Association, Water P o l l u t i o n Control Federation, 1971. 32. Carpenter, P.L., Microbiology, 3rd edition, W.B. Saunders Company, Toronto, Ontario, p.~99, 1972. 33. Dobbins, W.E., "BOD and Oxygen Relationship i n Streams", Journal of the Sanitary Engineering Division, American Society of C i v i l Engineering, 53-78, SA3, 1964. 34. C h u r c h i l l , M.A., Elmore, H.L., and Buckingham, R.A., "The Prediction of Stream Reaeration Rates", Journal of the Sanitary Engineering Division, American Society of C i v i l Engineering, 1, SA4, 1962. 35. O'Connor, D.J., and Dobbins, W.E., "Mechanism of Reaera-t i o n i n Natural Streams", U.S. Geological Survey C i r c u l a -t i o n No. 542, Washington, D.C, I967. 36. Langhein, W.B., and Durum, W.H., "The Aeration Capacity of Streams", U.S. Geological Survey C i r c u l a t i o n No. 542, Washington, D.C, 1967. 37. Pao, R.H.F., F l u i d Dynamics. Charles E. M e r r i l l Books Inc., Columbus, Ohio, 1967. APPENDICES 70 APPENDIX A" MEASURING LIGHT INTENSITY WITH A CAMERA METER 1. Set f i l m speed to ASA 25. 2. Set shutter speed to 1/60 sec. 3. Place the meter close to opaque white paper at a distance no greater than the narrow dimension of the paper. This paper i s to be placed next to the specimen or area under study. 4. Adjust the f/stop u n t i l the meter indicates the correct exposure, (at 1/60 sec.) I f t h i s i s f 2, then i n t e n s i t y = 40 ft-candles f 2.8 = 75 ft-candles f 4 =150 ft-candles f 5.6 = 300 ft-candles f 8 = 600 ft-candles f 11 = 1200 ft-candles f 16 = 2400 ft-candles f 22 = 4800 ft-candles This c a l i b r a t i o n can be expanded by increasing the shutter speed, i . e . at 1/125 sec, f 11 i s equivalent to 2400 ft-candles 1/300 sec, f 11 i s equivalent to 4800 ft-candles 1/500 sec, f 11 i s equivalent to 9600 ft-candles * Reference Time-Life, Encyc. Garden., Foliage House Plants Vol. 71 72. Alternatively, by decreasing the ASA s e t t i n g to 12, shutter speed 1/60 sec, then f 11 i s again equivalent to 2400 ft-candles. Figure Al demonstrates the above technique f o r ASA 25. f / stop APPENDIX B COMPUTER PROGRAMS AND FLOW CHARTS FOR THE THREE MODIFIED METHODS ( 2 5 ) B21 The Slope Method DIMENSION T(20),Y(20),DIFY(20),DIFYY(20),Y2(20),T01(20), 1W(20),V(20),X(20),SUMSQD(38)T0(38),G(20) INTEGER RUN C PROGRAM TO CALCULATE K AND L TO A GIVEN N BOD DATA C GATHERED AT IRREGULAR AS WELL AS REGULAR TIME INTERVALS C LAG PERIOD OR IMMEDIATE DEMAND IS TAKEN INTO C CONSIDERATION. READ(5,101'^ NN 101 FORMAT (115) C NN = NUMBER OF EXPERIMENTS DO 1000 LL=1,NN READ(5.1001i) RUN 1001 FORMAT (115) C RUN = NUMBER IDENTIFICATION OF EXPERIMENTS WRITE (6,2) RUN 2 FORMAT(1H1,6X,31HTHE SLOPE METHOD RESULTS. RUN#,I3) C BOD = 0.0 AT T EQUALS OR VARIES THAN ZERO C T = TIME IN DAYS C BOD = BIOCHEMICAL OXYGEN DEMAND IN MG/L. READ (5,1) N 1 FORMAT (115) C N = NUMBER OF LABORATORY BOD OBSERVATIONS. N = N .+ 1 READ (5,3) (T(I), 1=2,N) 3 FORMAT (8F10.5) READ (5,5) (Y(I), 1=2,N) 5 FORMAT (8F10.5) Y(l) = 0.0 C T0(1) IS THE ASSUMED LAG PERIOD WHICH WILL BE REPLACED C BY THE CORRECT VALUE BY SUCCESSIVE APPLICATION OF THE C METHOD OF LEAST SUM OF SQUARES. T0(1) = -1.0 DO 600 L=l,38 T( l ) = TO(L) NI = N - 1 N2 = N - 2 C DY/DT = DIFY DO 100 1=1,NI DIFY(l) =0.0 IF(I.EQ.Nl) GO TO 150 74 75. DIFYU+1) = ((Y(I+l)-Y(I))*(T(I+2)-T(I+I))/(T(I+l)-T(I) l)+(Y(I+2)-Y(I+l))*(T(I+l)-T(I))/(T(I+2)-T(I+l)))/ l(T(I+2)-T(I)) 150 DIFYY(I) = DIFY(I)*Y(I) Y2(I) = Y(I)**2 100 CONTINUE SUMY = 0 SUMDY = 0 SUMDYY = 0 SUMY2 = 0 DO 200 1=2,Nl SUMY = Y(I) + SUMY SUMDY = DIFY(I) + SUMDY SUMDYY = DIFYY(I) + SUMDYY SUMY2 = Y2(I) + SUMY2 200 CONTINUE AN2 = N2 A = ((SUMY2)*(SUMDY)-(SUMY)*(SUMDYY))/((AN2)*(SUMY2)-1(SUMY)**2) B = ((AN2)*(SUMDYY)-(SUMY)*(SUMDY))/((AN2)*(SUMY2)-1(SUMY)**2) C K = 0.4343*K C AK = K C AL = L AK = 0.4343*(-B) AL = (-A/B) C TO = LAG PERIOD DO 500 J=1,N IF(J.EQ.l) GO TO 77 GO TO 75 77 G(J) = 0.0 X(J) = 0.0 GO TO 501 75 IF(ABS(T(J)-TO(L)).LE.0.005) GO TO 444 GO TO 78 444 G(J) = 0.0 X(J) = 0.0 GO TO 501 78 G(J) = AK*(T(J) - TO(L)) X(J) = AL*(1.0-1.0/10.0**G(J)) 501 CONTINUE 82 FORMAT (F15.5) 500 CONTINUE SUMSQD(L) =0.0 DO 700 1=1, N 700 SUMSQD(L) = SUMSQD(L) + (ABS(X(I)-Y(I)))**2 IF(L.EQ.38) GO TO 600 T0(L+1) = TO(L) + 0.05 600 CONTINUE CALL AMINI (PL,38,KK,SUMSQD) SUMSQD(KK) = PL AKK = KK C DY/DT = DIFY 76. DG 800 1=1,NI T ( l ) = TO(KK) DIFY(K) = 0 . 0 IF(I.EQ.Nl) GO TO 550 DIFY(I+1) = ((Y(I+l)-Y(I))*T(I+2)-T(I+l))/(T(I+l)-T(I)) l+(Y(I+2)-Y(I+l))*(T(I+l)-T(I))/(T(I+2) -T(1+1)))/(T(I+2) l - T ( I ) ) 550 DIFYY(I) = DIFY(I) * Y(I) Y2(I) = Y(I)**2 800 CONTINUE SUMY = 0 SUMDY = 0 SUMDYY = 0 SUMY2 = 0 DO 900 1=2,NI SUMY = Y(I) • SUMY SUMDY = DIFY(I) + SUMDY SUMDYY = DIFYY(I) + SUMDYY SUMY2 = Y2(I) +SUMY2 900 CONTINUE AN2 = N2 A = ((SUMY2)«(SUMDY)-(SUMY)*(SUMDYY))/((AN2)*(SUMY2)-11(SUMY)**2) B = ((AN2)«(SUMDYY)-(SUMY)*(SUMDY))/(4lN2)*(SUMY2)-1(SUMY)**2) C K= 0.4343K C AK = K C AL = L AK = 0.4343*(-B) AL = (-A/B) DO 850 J=1,N IF(J.EQ.l) GO TO 76 GO TO 79 76 G(J) = 0.0 X(J) = 0.0 GO TO 850 79 IF(ABS(T(J)-T0(L)).LE.0.005) GO TO 666 GO TO 74 666 G(J) = 0.0 X(J) = 0.0 , GO TO 850 74 G(J) = AK*(T(J)-TO(KK)) X(J) = AL*(1.0-1.0/10.0**G(J)) 850 CONTINUE WRITE (6,4) 4 FORMAT (/8X,lHT,l4X,iHY,llX,5HDY/DT,8X,7HY*DY/DT,9X,2HY2) WRITE (6,6) (T(I),Y(I),DIFY(I),DIFYY(I), Y2(I), 1=1,NI) 6 FORMAT (5F14.4) WRITE (6,8) T(N),Y(N) 8 FORMAT (2F14.4) WRITE (6,10) SUMY,SUMDY,SUMDYY,SUMY2 10 FORMAT (/3X,11HSUMS(2,N-1),4F14.4) WRITE (6,12) AK,AL,TO(KK) 12 FORMAT (/8X, 2HK=F10. k/Qj., 2HL=F10.4, 4X, 3HTO=Fl 0.4) WRITE (6,16) 16 FORMAT (/19X,1HT,15X,1HX) WRITE (6,18) (T(J),X(J), J=1,N) 18 FORMAT (10X,F15.5,2X,F15.5) 1000 CONTINUE STOP END SUBROUTINE AMINI (PMIN,N,L,RR) C EVALUATION OF THE MINIMUM VALUE DIMENSION R(38),RR(38) 50 FORMAT (2X.E12.3) DO 5 1=1,N IF(RR(I).GT.O.O) GO TO 6 5 CONTINUE 6 PMIN = RR(I) L = I DO 10 I=L,N IF(RR(I).LE.O.O) GO TO 10 IF(PMIN.LE.RR(I)) GO TO 10 PMIN = RR(I) L = I 10 CONTINUE RETURN END |8IME-HSTQN|> /READ* W ~r /READ,N,T(I+1)&Y(1)/ DIFYY (I) =DIFY (I )*Y( I j( Y2=Y(I)**2 3 11=1+1 1-: < o I n i t i a l i z e alJ| sums to zero 3= SUMY =SUMY+Y(I) SUMDY =DIFY(I)+SUMDY S UMDYY=S UMDYY+DIFYY(I} SUMY2 = SUMY2+Y2(I) 1 1=1+1 > 0 1-1 < 0 78. DIFY(I+1)=((Y(I+1)-Y(I))*(T(I+4 -(I+1))/(T(I+1)-T(I))+ (Y(I+2)-Y(I+l)))*(T(I+l) -T(I))/(T(I+2)-T(i+l)))/ T(I+2)-T(I)) |A=((SUMY2)*(SuiDY)-(SUMY)*(SUMDYr 1 )/((N2)*(SUMY2)-(SUMY)**2) B=( (N2 )*(SUMDYY) - (SUMY)*(SUMDY) )/' ((N2)*(SUMY2)-(SUMY)**2) lk=0.4343*(-B) L=(-A/B) J=l ? 0 = 0 G(J)=k*(T(J)-TO(L)) X(J)=L*(1-1/10 **G(J)) [ G W ^ X(J)=0 J=. +1* 0 «T < 0 SUMSQD(L)=0 SUMSQD(L)=SUMSQD(L)+(X(I)+ Y(I))**2 -ji=1+1, T0(L+r)=T0(L +0.05 X Z JBT L=L+1 Zl CALL SU ROUTINE AMINI !! SUMSQD(KK)=P; Flow Chart For The Slope Method DIFY(I+l)=((Y(I+l)-Y(I)*(T(I+2)-T(I+1))/(T(I+1)-T((I)) +(Y(I+2)-Y(I+l))*(T(I+ l)-T(I))/T(I+2)-T(I+l) ))/T(I+2)-T(I)) [G(J)=k*(T(J)-TO(L)) X(J)=L*(1-1/10**G(J) J=J+1 N-J 4 0 /WRITE. k . L > t 0 , T ( J ) , X ( j y STOP _1 1=1 79. T(I)=TO(KKT1 DEFY I £ 0 N l - f DIFYY(I)=DIFY(I)*Y(I) Y2(I)=Y(I)**2 1=1+1 j l - I ~1 0 I n i t i a l i z e a l l sums to zero SUMY=SUMY+Y(I) SUMDY =DIFY(I)+SUMDY S UMDYY=S UMDYY+DIFYY(I) SUMY2 =SUMY2+Y2(I) 1=1+1 0 A= ((SUMY2) * (SUMDY") - ( S U M Y ) *(SUMDYY)/((N2)*(SUMY2) -(SUMY)**2 B=((N2)*(SUMDYY)-(SUMY)* (SUMDY))/((N2)*(SUMY2) -(SUMY)**2) k=0.4343*(-B) L=(-A/B) J=l G(I)=0 X(I)=0 Flow Chart For The Slope Method (Continued) Flow Chart For Subroutine Anine 81. B.2 The Moments Method C THE MOMENTS METHOD C COMPUTER PROGRAM FOR DETERMINING K, LA, AND TO VALUES C FOR A GIVEN BOD DATA GATHERED AT REGULAR OR IRREGULAR C TIME INTERVALS. C K = RATE AT WHICH BOD IS EXERTED IN l/DAY. C L = ULTIMATE BOD OF FIRST STAGE IN MG/L. C TO = LAG PERIOD IN DAYS. DIMENSION Y(20),T(20),ATY(20),S(20),Z(20),X(20),T01(20), 1V(20),W(20) INTEGER RUN READ (5.1001) NN 1001 FORMAT ( 1 1 5 ) C NN = NUMBER OF EXPERIMENTS C AK = K C AL = L DO 1000 LL=1,NN READ (5.101) RUN 101 FORMAT(II5) C RUN= NUMBER IDENTIFICATION OF EXPERIMENTS WRITE ( 6 , 2 ) RUN 2 F0RMAT(1H1,13X,33HTHE MOMENTS METHOD RESULTS? RUN#,I3) READ ( 5.10 N 1 FORMAT (115) C N = NUMBER OF BOD OBSERVATIONS. READ ( 5 , 3 ) (T(I), 1=1,N) 3 FORMAT (8F10 . 5 ) C T = TIME IN DAYS. READ ( 5 , 5 ) (Y(I), 1 = 1 ,N) 5 FORMAT (8F10 . 5 ) C Y = BOD EXERTED IN TIME T IN MG/L. SUMT = 0 SUMT2 = 0 SUMY = 0 SUMTY = 0 SUMT2Y = 0 DO 100 1=1, N SUMT = SUMT + T(I) SUMT2 = SUMT2 +(T(I))**2 SUMY = SUMY +Y(I) SUMT2Y = SUMT2Y + (((T(I)**2)*Y(I)) ATY(I) = (T(I))»Y(I) SUMTY = SUMTY + ATY (I) 100 CONTINUE AN = N WRITE ( 6 , 4 ) 4 FORMAT (/19X,1HT,16X,1HY,16X.2HTY) WRITE ( 6 , 6 ) (T(I),Y(I),ATY(I), 1=1,N) 6 F0RMAT(10X , F 1 5 . 5,2X,F15 . 5.2X,F15 . 5 ) WRITE ( 6 , 8 ) SUMT,SUMY,SUMTY 8 FORMAT ( /6X,9HSUM(1,N)=F10 . 5 ,6X,F11 . 5 ) 82. RAT = (((SUMTY)/(SUMT))-((SUMY)/(AN)))/(((SUMT2Y)/ 1(SUMT2))-((SUMY)/(AN))) C FOR THE FIRST TRIAL K IS ASSUMED = 0.005 AK = 0.005 150 DO 200 J=1,N 200 S(J) = AK * T(J) RATI = 0 RAT2 = 0 RAT3 = 0 DO 300 J=1,N RATI = RATI + 1.0/10.0**S(J) RAT2 = RAT2 + (T(J))/l0.0**S(J) RAT3 = RAT3 + (1.0/10.0**S(J))*((T(J))**2) 300 CONTINUE RATI01 = ((SUMT2)«((-AN)«(RAT2)+(SUMT)*(RAT1)))/ 1((SUMT)*((-AN)*(RAT3) + (SUMT2)*(RAT1))) IF (RATI01 - RAT) 40,50,50 40 AK = AK + 0.01 GO TO 150 50 WRITE (6,10) AK 10 FORMAT (/lOX,2HK=F10.5) RATI02 = ((-AN)*(RAT2) + (SUMT)*(RAT1))/(AN*(SUMT)) CL = ((SUMTY/SUMT)-(SUMY/AN))/RATI02 RATI03 = RATI/AN AL = (RATI03*( (SUMTY/SUMT)-(SUMY/AN))/RATI02) + (SUMY, IAN) C = (CL/AL) TO = (AL0G10(C))/(AK) WRITE (6,12) AL 12 FORMAT (10X,2HL=F10.5) WRITE (6,14) TO 14 FORMAT (10X,3HTO=F10.5) C X= LA(1.0-10.0**-K(T-T0)) DO 400 J=1,N Z(J) = AK*(T(J) - TO) X(J) = AL*(1.0-1.0/10.0*»Z(J)) C X = CALCULATED BOD VALUES EXERTED IN TIME T. 400 CONTINUE WRITE (6,16) 16 FORMAT (//19X,1HT,15X,1HX) WRITE (6,18) (T(J),X(J), J-l.N) 18 FORMAT (10X,F15.5.2X,F15.5) SUMSQ =0.0 DO 800 1=1,N 800 SUMSQ = SUMSQ + (ABS(Y(I)-X(I)))**2 C APPROXIMATE CALCULATION FOR LAG PERIOD TO. WRITE (6,20) 20 FORMAT (//10X,35HAPPROXIMATE VALUE FOR LAG PERIOD TO) DO 500 1=1,N VV = I W(I) = (1.0 - (Y(I))/AL) IF(W(I)) 250,250,500 C Y = LA(1.0 - 10.0**-K(T-T01)) C TO 1 = THE LAG PERIOD IN DAYS. 500 T01(I) = T(I) + (ALOG10(W(I)))/AK GO TO 350 250 VV = I - 1 350 SUMTOl =0.0 NB = VV DO 600 J=1,NB SUMTOl = SUMTOl + T01(J) 600 CONTINUE C AVTO = AVERAGE VALUE FOR THE LAG PERIOD IN DAYS. AVTO = SUMT01/W WRITE (6,24) AVTO 24 FORMAT (/15X,5HAVT0=F10.5) 1000 CONTINUE STOP END 84. &TART DIMENSION lf=T) /READ NN,T(I),Y(I)/ i n i t i a l i z e a l l sums to zero 1=1 SUMT=SUMT + T(I) SUMT2=SUMT2+T(I)**2 SUMY=SUMY+Y(I) SUMT2Y=SUMT2Y+(T(I)**2)*Y(I)) ATY(I)=T(I)*Y(I) SUMTY=SUMTY+ATY(I) 1=1+1 S(J)=k*T(l) J=J+1 RATi=0 RAT2=0 RAT3=0; ZL RATI=RAT1+1/10**S(J) RAT2=RAT2+T(J ) / l 0**S (J |) RAT3=RAT3+(l/l0**S(J)* T(J)**2) . J=J+j > 0 1 RATI01 = ((SUMT2)*((-AN*(RAT2)+(SUMTt )*(RAT1)))/((SUMT)*((-AN)* (RAT3)+(SUMT2)*(RAT1))) RAT=((SUMTY)/(SUMT))-((SUMY)/(N))) /(((SUMT2Y)/SUMT2))-((SUMY)/(N))) -fr=K+0.005 RATI02=((-N)*(RAT2)+(SUMT)*RAT )/(N*SUMT) C L=((S UMTY/SUM)-S UMY/N)RATI02 RATI03=RAT1/AN L=RATI03 *((S UMTY/S UMT)-(S UMY/N ))/RATI02)+SUMY/N) C=(CL/L) t =AL0G(C))/k J=l Z(J)=k*(T(J)-t Q) X(J)=L*(1-1/10**Z(J) ^0 /WRITE,k,L,T(J),X(J) 7 3 7 Flow Chart For The Moments Method 85. B.3 The Graphical Method DIMENSION T(20),Y(20),Z(20),TOl(20),G(20),X(20),W(20), 1V(20) INTEGER RUN READ (5,11) NN 11 FORMAT (115) C NN = NUMBER OF BOD EXPERIMENTS DO 1000 11=1,NN C RUN = NUMBER IDENTIFICATION OF EXPERIMENTS READ (5,20) RUN 20 FORMAT (115) C AK = K C AL = L READ (5,1) N 1 FORMAT (115) C N = NUMBER OF BOD OBSERVATIONS C H = TIME INTERVALS BETWEEN THE OBSERVATIONS H = 1.0 READ ( 5 , 3 ) (T(I), 1=1,N) 3 FORMAT (8F10.5) C T = INCUBATION TIME IN DAYS READ ( 5 , 5 ) (Y(I), 1=1,N) 5 FORMAT (8F10.5) C Y = BOD OBSERVATIONS IN MG/L AN = N Nl = N - 1 DO 100 1=1,N IF(I.EQ.N) GO TO 50 Z(I) = Y(I+1)-Y(I) 100 CONTINUE 50 Z(I) = 0.0 SUMY = 0 SUMZ = 0 SUMYZ = 0 SUMY2 = 0 Do 200 1=1,Nl SUMY = Y(I) + SUMY SUMZ = Z(I) + SUMZ SUMYZ = Y(I)*Z(I) + SUMYZ SUMY2 + Y(I)**2 + SUMY2 200 CONTINUE AN1 = Nl B = ((SUMY2)*(SUMZ)-(SUMY)*(SUMYZ))/(AN1*(SUMY2)-(SUMY) 1**2) C = (AN1*(SUMYZ)-(SUMY)*(SUMZ))/(AN1*(SUMY2)-(SUMY)**2) A = (-B/C) AL = A AK = (1.0/H)*AL0G10(A/(A-B)) WRITE (6,2) RUN 2 FORMAT(1HI,6X,44HTHE MODIFIED GRAPHICAL METHOD RESULTS. 1RUN#,I3) WRITE (6,4) 86. 4 F0RMAT(/15X,1HT,20X,1HY,22X,1HZ) WRITE (6, 6 ) (T(I),Y(I),Z(I), 1=1,N) 6 F0RMAT(10X,F10.4,llX,F10.4,l4x,F10.4) WRITE (6,8) SUMY,SUMZ,SUMYZ,SUMY2 8 F0RMAT(/18X,13HSUMY(1,N-1) =F1G.4,2X,12HSUMZ(1,N-l)= 1F10.4)//18X,13HSUMY(1,N-l)=E10.5//18X,13HSUMY2(1,N-l)= 1E10.5) WRITE (6,10) AK,AL 10 FORMAT(/18X.3HK =F10.4/l8X,3HL =F10.4) C APPROXIMATE CALCULATION FOR LAG PERIOD TO. DO 300 1=1,N VV = I W(I) = (1.0-(Y(I))/AL) IF(W(I)) 350,350.300 300 T01(I) = T(I) + (AL0G10(W(I)))/AK GOfiiTO 450 350 W = I - 1 450 SUMT01 =0.0 NB = VV DO 400 J=1,NB SUMT01 = SUMT01 '+ TOl (J) 400 CONTINUE AVTO = SUMT01/VV WRITE (6,14) AVTO 14 FORMAT(15X.6HAVTO =F10.4) TO =AVTO DO 500 J=1,N G(J) = AK*(T(J)-TO) X(J) = AL*(1.0-1.0/10.0**G(J)) C X = CALCULATED BOD VALUES IN MG/L. 500 CONTINUE WRITE(6,16) 16 F0RMAT(//19X,1HT,15X,1HX) WRITE (6,18) (T(J),X(J), J=1,N) 18 F0RMAT(10X,F15.5.2X,F15.5) 1000 CONTINUE STOP END .87. ISTART DIMENSION, z READ,NN, N, H, T(I &Y(I) 7 1 Z(I)=Y(I+1) H[=I+1 -Y(I) I n i t i a l i z e ai|L sums to zero 3 SUMY=Y(I)+SUMY 3UMZ=Z(I)+SUMZ SUMYZ=Y(I)*Z(I)+SUMYZ SUMY2=Y(I)**2+SUMY2 r — i — 1=1+1 FANI ^ 0 =NTJ <0 B=((SUMY2)*(SUMZ)-(SUMY)*(SUMYZ))| /(AN1*(SUMY2)-(SUMY)**2) C=(AN1*(SUMYZ)-(SUM)*(SUMZ))/(ANl *(SUMY2)-(SUMY)**2) A=(-B/C) L = A k=(l/H)*AL0G10(A/(A-B)) r JLZl v ( i ) = i W(I)=(1-(Y(I))/A) >Q W( T01(l)=T(I)+(AL0Gip (W(l)))/k SO (J)=k*(T(J)-AVT0) bC(J)=A*(l-l/10**G(j|) yWRITEk,L,AVTQ,X(J),T(J)/ AVT0=t 11=11+1 ^0 Flow Chart For The Graphical Method APPENDIX C RESULTS OF INDIVIDUAL BOD TEST RUNS 88 TABLE Cl OBSERVATIONS OF BOD TEST WITH VARYING MIXING RATES Run # 1 2 3 4 5 6 7 8 Mixing Rate (rpm) 300 0 400 0 500 0 600 0 Time (days) BOD (mg/1) 1 57-7 51.8 71.9 51.8 66.6 54.8 64.7 54.8 2 92.6 117.2 121.6 117.2 101.4 95.4 94.7 89.1 3 156.0 143.2 160.7 143.2 132.5 125.8 139.9 124.9 4 168.0 157.9 189.3 157.9 139.3 128.4 176.6 143.6 5 183.1 159.8 194.4 159.8 159.6 149.8 200.9 I67.6 6 193-6 174.5 209.9 174.5 170.5 I65.O 209.4 190.3 * Uneven numbers are the actual mixing runs, while the even numbers are the control runs. Each mixing run has i t s own control run. TABLE Cl (Continued) OBSERVATIONS OF BOD TEST WITH VARYING MIXING RATES Run # 9 10 11 12 13 14 Mixing Rate 700 0 800 0 900 0 (rpm)  Time (days) BOD (mg/1) 1 76.2 60.4 57.5 56.8 81.1 73-9 2 121.2 103.2 88.2 87.2 136.8 123.6 3 144.3 126.4 136.4 132.2 170.2 150.4 4 182.0 153.4 150.0 140.6 193.8 177.9 5 198.0 166.2 177.7 151.8 192.8 181.2 6 210.8 180.4 200.3 153.4 202.0 184.6 TABLE C2 OBSERVATIONS OF BOD TEST WITH A CONSTANT MIXING RATE OF 600 RPM AND DIFFERENT SAMPLES Run # 7 8 15 16 17 18 19 20 Mixing Rate (rpm) 600 0 600 0 600 0 600 0 Time (days) BOD (mg/1) 1 64.7 54.8 103.2 78.8 77.5 70 .5 50.8 42.6 2 94.7 89.I 158.0 133.4 107.6 114.1 78.0 79.6 3 139-9 124.9 194.0 177.6 160.4 154.4 119.8 107.0 4 176.6 143.6 215.0 200.0 208.2 I67 . 6 136 .5 123.7 5 200.9 167 .6 238.7 218.0 214.3 193.6 166.8 131.0 6 209.4 190.3 273.2 234.6 231. 2 225.0 185.0 143.4 TABLE C2 (Continued) OBSERVATIONS OF BOD TEST WITH A CONSTANT MIXING RATE OF 600 RPM AND DIFFERENT SAMPLES Run # 21 22 35 38 41 44 Mixing Rate (rpm) 600 0 600 0 600 0 Time (days) BOD ( mg/1) 1 56.8 51.6 54.9 49.5 47.3 41.9 2 69.2 85-2 89.0 81.7 76.9 67.4 3 123.O 116.2 107.4 104.0 94.2 85-3 4 140.6 139.2 123.9 113.2 112.9 100.7 5 171.7 149.6 142.8 121.5 127.9 110.8 6 I 8 3 .2 178.4 154.2 128.2 145.5 117.6 TABLE C3 OBSERVATIONS OF BOD TEST WITH VARYING LIGHT INTENSITY AND TURBIDITY II* Run # -;23 24 25 26 27 28 29 30 Light Intensity (ft-candles) 0 1000 1000 1000 0 3000 3000 3000 Turbidity (JTU) 2 2 270 410 2 2 260 510 Time (days) BOD (mg/1) 1 32.2 28.2 28.9 24.7 44.0 41.9 40.6 39.9 2 50.8 47.6 44.5 45.8 70.2 67.3 66.6 61.4 3 68.6 63.6 57.8 62.1 92.2 89.7 87.1 81. 2 4 75.0 76.7 72.0 74.6 100.5 109.5 103.5 99.4 5 82.4 87.6 79.1 84.2 119.2 126.8 116.4 116.2 6 91.2 96.6 87.7 91.6 138.4 142.1 126.7 131.6 * There i s one control i n every four runs. TABLE C3 (Continued) OBSERVATIONS OF BOD TEST WITH VARYING LIGHT INTENSITY AND TURBIDITY Run # 31 32 33 34 Light Intensity (ft-candles) 0 7000 7000 7000 Turbidity (JTU) 2 2 250 36O Time (days) BOD (mg/1) 1 43.0 41.6 36.9 37.8 2 68.4 67.8 58.1 62.3 3 81.8 86.1 74.1 77.4 4 95.5 98.7 86.0 86.7 5 108. 5 107.6 95.1 92.3 6 112.7 113.7 101.8 95.8 TABLE C4 OBSERVATIONS OF BOD TEST WITH VARYING TURBIDITY AND CONSTANT MIXING Run # 35 36 37 38 39 40 Turbidity (JTU) 2 430 570 2 430 570 Mixing Rate (rpm) 600 600 600 0 0 0 Time (days) BOD (mg/1) 1 54.9 31.2 32.1 49.5 29.4 29.2 2 89.0 45.6 49.1 81.7 45.3 44.7 3 107.4 56.5 61.2 104.0 59.3 56.9 4 123.9 69.4 71.9 113.2 76.5 72.2 5 142.8 82.2 84.4 121.5 93.0 90.1 6 154.2 94.8 98.7 128.2 103.5 99-1 TABLE C4 (Continued) OBSERVATIONS OF BOD TEST WITH VARYING TURBIDITY AND CONSTANT MIXING Run # 4l 42 43 44 4 5 46 Turbidity (JTU) 2 160 340 2 160 340 Mixing Rate (rpm) 600 600 600 0 0 0 Time (days) BOD (mg/1) 1 47.3 29.3 3 0.6 41.9 26.8 27.4 2 76.9 4 2.3 42.8 67.4 41.8 43.2 3 94.2 54.2 55-0 85-3 54.6 55.2 4 112.9 66.0 69.2 100.7 77.3 70.3 5 127-9 82.8 83.5 110.8 89.3 82.0 6 1 4 5.5 96.4 99.0 117.6 100.4 94.4 TABLE C5 OBSERVATIONS OF BOD TEST WITH MIXING, LIGHT AND TURBIDITY Run # 47 48 49 50 51 52 Turbidity (JTU) 2 200 2 200 200 2 Mixing Rate (rpm) 0 0 600 600 0 0 Light Intensity (ft-candles) 0 3000 3000 3000 0 3000 Time (days) BOD (mg/1) 1 44.8 27.7 53.1 31.4 30.2 44.0 2 70.8 49.8 89.7 46.4 45.3 76.5 3 92.8 70.3 114.2 60.8 62.4 99.7 4 107.8 89.3 130.6 74.8 82.3 116.3 5 123.2 106.8 141.7 88.5 99.2 128.1 6 128.8 123.1 149.0 101.7 105.8 136.5 APPENDIX D CALCULATED BOD PROGRESSION CONSTANTS 98 TABLE Dl PROGRESSION CONSTANTS OF BOD TEST WITH VARYING MIXING RATES Run # k (days' 1) L (mg/1) t Q (days) 1 0.1723 218.2 0.2537 2 0.3079 173.3 0.5537 3 0.1847 227.9 0.1108 4 0.3079 173.3 0.5537 5 0.1425 194.2 -0.2811 6 0.1555 183.0 -0.0277 7 0.0821 320.7 -0.2121 8 0.0644 311.4 -0.3027 9 0.1166 260.1 -0.2928 10 0.1384 209.8 -0.0666 11 0.0665 326.0 -0.2536 12 0.2131 166.6 0.1567 13 0.2752 207.3 0.1987 14 0.2461 194.1 0.1336 TABLE D2 PROGRESSION CONSTANTS OF BOD TEST WITH A CONSTANT MIXING RATE OF 600 RPM Run # k (days" 1) L (mg/1) t Q (days) 7 0.0821 320.7 -0.2121 8 0.0644 311.4 -0.3027 15 0.0966 352.7 -0.6266 16 0.1623 261.8 0.0446 17 0.1143 333.9 -0.0699 18 0.0775 327.4 -O.389O 19 0.0477 384.3 -0.3224 20 0.1744 157.4 0.2107 21 0.0401 1446.6 -0.5661 22 0.0781 260.7 -0.2376 35 0.1072 194.6 -O.36IO 38 0.2100 135.1 0.0434 41 0.0726 218.8 -0.4783 44 0.1341 138.8 -O.I635 101. TABLE D3 PROGRESSION CONSTANTS OF BOD TEST WITH VARYING LIGHT INTENSITY AND TURBIDITY Run # k (days" 1) L (mg/1) t Q (days) 23 0.1358 105.4 -O.I626 24 0.0850 137.9 -O.I654 25 0.0796 127.1 -0 .3923 26 0.1150 116.0 0.0953 27 0.1040 162.7 -O.3636 28 0.0587 246.6 -0 .3730 29 0.1041 164.0 -0.1778 30 0.0392 294.6 -0.6165 31 0.1334 133.0 -0.2857 32 0.1628 126.9 -0 .0598 33 0.1268 121.6 -0.2358 34 0.2159 101.2 0.0496 TABLE D4 PROGRESSION CONSTANTS OF BOD TEST WITH VARYING TURBIDITY AND CONSTANT MIXING Run # k (days" 1) L (mg/1) t Q (days) 3 5 0.1072 194.6 -O.36IO 36 0.0086 829.1 -1.2382 37 0.0245 331.6 -1.0518 38 0.2100 1 3 5 . 1 0.0434 3 9 0.0198 465.1 -O.6536 4o 0.0148 771.5 -O.8O36 41 0.0726 218.8 -0.4789 4 2 O.OI69 376.9 -0.7898 43 0.0149 419.7 -0.9045 44 0.1341 138.8 -0.1635 4 5 0.0223 399.4 -0.486? 4 6 0.0257 288.8 -0.6817 TABLE D5 OBSERVATIONS OF BOD TEST WITH MIXING, LIGHT AND TURBIDITY Run # k (days - 1) L (mg/1) t Q (days) 47 0.1190 159.5 -0.1958 48 0.0259 781.3 -0.3140 49 0.1832 163.O 0.0606 50 0.0132 704.5 -0.9840 51 O.O363 315.6 -0.4627 52 0.1466 158.1 -0.0532 APPENDIX E (25) THE CORRECT MIXING RATE FROM FIELD CONDITIONS The c h a r a c t e r i s t i c s of any r i v e r could be used f o r th i s example. Therefore, the author decided to use assumed c h a r a c t e r i s t i c s . Assume Q = 1500 cfs H M „ = 15 f t mean V = 1 . 0 ft/sec mean ' a = Q/V m a 9 r i = 1500 f t 2 mean where a = Cross-sectional area Width River = 1500/15 = 100 f t Using Manning's equation y = i 4 8 6 m 2 / 3 s l / 2 m n where V = Mean velocity, f t / s e c m n = Roughness factor, 0 .025 f o r earth channel with gravel bottom S = Slope of r i v e r bed, f t / f t m = Hydraulic radius, f t . Rearranging the equation1 S = (nV/l.486 m 2 / 3 ) 2 and S = 3.014 x 10" 5 f t / f t Assuming N = 50 rpm ,-2 . ^oP R = 5.25.x 10 x 104 ' r Q = (3/4) x (1/12) = 6.250 x 1 0 ~ 2 f t b = (5/16) x (1/12) = 2.604 x 1 0 " 2 f t P = 1.94 lb-mass/ft 3 at 20°C JX = 2.106 x IO" 5 lb-mass/ft-sec at 20°C Therefore, R = 393.5 From the R-C^ graph the corresponding C D i s c D = 1.05 Since P = w Q n =/*gV S v a L 6 m Therefore, P„ = I .883 x 1 0 ~ 3 f t - l b / s e c - f t 3 Now, N = 3/ ~z 0 T r V 2.72 x 10 c C g f U - J K b r ^ and assume J = 0.225 Thus, N = 56 .9 rpm, therefore 50 rpm O.K. The turbulence i n the f i c t i t i o u s r i v e r w i l l be reproduced i n the BOD bottle by having the mixers operate u n at 50 rpm with magnetic bars of 1-1/2 x 5/16 . 

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