This thesis discusses the mechanisms associated with the removal of organic matter, nitrogen and phosphorus in wastewater-fed high rate algae ponds (HRAP) designed to operate as triplicates. Research was conducted at the San Luis Obispo Water Reclamation Facility (SLOWRF) as a pilot-scale study of nine 30-square meter ponds one foot in depth. During period of study, triplicates were operated at hydraulic retention times (HRT) of 4, 3 or 2-days. Main objectives for the study were to determine minimum HRTs required to achieve secondary and tertiary treatment. Experimental conditions such as CO2 supplementation, nighttime aeration and operation of ponds in series were employed to evaluate optimal conditions for efficient nutrient removal. Ponds were continuously fed primary effluent with the following water quality characteristics: 5-day total biochemical oxygen demand (TBOD5) of 124mg/L, 5-day soluble carbonaceous biochemical oxygen demand of 67mg/L (scBOD5), total suspended solids (TSS) of 66mg/L, volatile suspended solids (VSS) of 65mg/L, total ammonia nitrogen (TAN) of 34mg/L-N, oxidized nitrogen of 1.1mg/L-N, total K̇jeldahl nitrogen (TKN) of 42mg/L-N and dissolved reactive phosphorus (DRP) of 3.3mg/L-P. Nutrient removal efficiencies were compared between summer months (April – October) and winter months (November – February). Average pond temperatures during summer and winter were 20.4 °C and 14.9 °C, respectively. Average TAN removal efficiencies of 2-day HRT ponds ranged from 62% in winter to 78% in summer. Operation of ponds at an increased 3-day HRTs resulted in corresponding seasonal increases of TAN removal by 14% and 12%. In 4-day HRT ponds operating in series after a 3-day HRT set, TAN removal efficiency was 98% in winter and 99% in summer. Aeration increased nitrification and nitrate concentrations in 2-day HRT ponds to10mg/L-N ± 4.4mg/L-N. DRP concentrations and BOD removal efficiencies within replicate ponds were similar throughout seasonality. DRP was 1.2mg/L-P ± 0.66mg/L-P at a 4-day HRT operating in series, 2.2mg/L-P ± 0.57mg/L-P at a 3-day HRT and 2.6mg/L-P ± 0.58mg/L-P at a 2-day HRT. Aeration had no measureable effect on BOD removal. BOD removal efficiency was 97% at a 4-day HRT in series with a 3-day HRT and 95% at 3-day and 2-day HRTs.

In order to meet increasingly stringent total nitrogen limits, supplemental carbon must be added to improve the performance of the biological nutrient removal process. An industrial by-product that contained ethylene glycol and propylene glycol was used as a substitute carbon source for methanol in this study. The objectives of this study were to investigate the efficiency of using the glycol mixture as carbon source, including the calculation of denitrification rate and yield at two different initial concentrations of glycols. Possible inhibition effect on nitrification was also investigated. Three SBR reactors were operated by adding methanol, a low dosage of glycol, and a high dosage of glycol into the reactors. The low dosage glycol reactor exhibited the best performance, with the highest denitrification rate of 11.55 mg NOx-N/g MLVSS"h and the lowest yield of 0.21 mg VSS/mg COD. Small nitrite accumulation was observed in the low dosage glycol reactor (COD=185"•15 mg/L), but effluent quality was not influenced. Excess glycol in the reactor caused deteriorated performance. The high dosage glycol reactor (COD=345"•20 mg/L) performed with the lowest denitrfication rate of 8.56 mg NOx-N/g MLVSS"h and the highest yield of 0.55 mg VSS/ mg COD. The reactor with the high dosage of glycol also inhibited the lowest nitrification rate of 1.15 mg NH3-N oxidized/g MLVSS"h, which indicated that excess glycol may cause nitrification inhibition. / Master of Science

Tableau d’honneur de la Faculté des études supérieures et postdoctorales, 2007-2008. / Les transformations de l'azote pendant l'hiver et le potentiel des pertes à l'environnement pendant l'hiver ont été peu étudiés. Une incubation avec 15N a été effectuée pour mesurer l'effet des températures basses (-6 à 10 °C) sur la nitrification, la dénitrification et l'immobilisation de l'ammonium après épandage d'un lisier de porc avec ou sans ajout de paille de blé. Les nitrates, marqués et non marqués, se sont accumulés dans les sols à des températures > -2 °C, ce qui confirme une nitrification active dans les sols légèrement gelés. Une immobilisation nette de l'azote a été observée seulement dans les sols avec paille, mais a cessé entre -2 et 2 °C. La nitrification était le processus principal sous 0 °C. La nitrification dans les sols gelés augmente le risque d'accumulation et de perte d'azote par lessivage et dénitrification et ne semble pas pouvoir être atténuée par l'ajout de paille de blé. / Overwinter nitrogen transformations and the consequent potential for loss of slurry nitrogen to the environment have not been studied in depth. An incubation study using an N isotope was undertaken to measure the effect of cold temperature (-6 to 10 °C) on nitrification, denitrification and immobilization of ammonium in the soil following slurry application in the presence or absence of wheat straw. Labelled and unlabelled nitrate increased in soils incubated at temperatures > -2 °C, confirming active nitrification in lightly frozen soils. Net immobilization was observed only in soils with straw incorporation, but ceased between -2 and 2 °C. Nitrification was the predominant process below 0 °C. Nitrification in frozen soils increases the risk of nitrogen build-up and loss by leaching and denitrification and seems not to be mitigated by the addition of wheat straw.

New possibilities of nutrients removal by additions of magnesium compounds were studied in primary treatment and supernatant of side stream in wastewater treatment. The precipitation product from this method is magnesium ammonium phosphate (MAP) socalled struvite. High efficiencies on NH4-N and PO4-P removals have been demonstrated up to over 90 % respectively in side stream from dewatering of digested sludge. In order to find out the nutrient removal efficiency in raw wastewater and the feasibility of MAP recycling in wastewater treatment, the postulations of combining MAP and nitrification-denitrification process, and MAP and partial nitritation-anmmox process were carried out by experimental works in the laboratory at Land and Water Resources Department, KTH. It was found that 92-97 % of PO4-P and 57 % of NH4-N were removed from raw wastewater by Mg2+ addition at pH10 to pH10.5. The research work revealed that recycling of MAP by nitrification-denitrification and partial nitritation-anmmox processes may be a feasibly process combination. In MAP and nitrification -denitrification process, the released ammonium was mostly oxidized to nitrate in nitrification phase and ready for denitrification. Based on presented results on MAP and partial nitritation-anmmox process, it was found that the released ammonium was consumed by anammox bacteria.

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This research first examined nitrification inhibition caused by different classes of industrially relevant chemicals on activated sludge and found that conventional aerobic nitrification was inhibited by single pulse inputs of every chemical tested, with 1-chloro-2,4-dinitrobenzene (oxidant) having the most severe impact, followed by alkaline pH 11, cadmium (heavy metal), cyanide, octanol (hydrophobic) and 2,4-dinitrophenol (respiratory uncoupler). Of the different chemicals tested, the oxidative and hydrophobic chemicals showed severe nitrification inhibition relative to other treatment processes and therefore deserved further investigation. For oxidative chemicals, we hypothesized that the more severe inhibition was because nitrifying bacteria lack one or more of the microbial stress response mechanisms used to mediate the toxic effect of oxidative chemicals. During these experiments, we showed that a rapid (minutes) antioxidant potassium efflux mechanism does not exist in two nitrifying bacteria, Nitrosomonas europaea and Nitrospira moscoviensis. Furthermore, we showed that another important antioxidant molecule, glutathione, was not oxidized as readily as in a non-nitrifying bacterium. Furthermore, we hypothesized that hydrophobic chemical-induced nitrification inhibition recovered more quickly because of the presence of membrane modification stress response mechanisms. While testing this hypothesis, we showed that N. europaea modified its cell membrane in response to hydrophobic chemicals using a long-term (hours) membrane modification mechanism that required the synthesis of new fatty acids, but it did not contain a short-term (minutes) response mechanism involving a cis/trans isomerase. Therefore, investigating these nitrifier stress responses showed that nitrifiers lack short-term stress responses that may be used to rapidly detect inhibition, indicating that conventional methods of detecting nitrification inhibition, like differential respirometry and nitrate generation rate (NGR), are still the fastest and easiest methods to use. Because several conventional methods exist, we also investigated differences between differential respirometry and a UV method we developed to measure NGR. During these tests, we showed that the UV NGR method provided a more reliable measure of nitrification inhibition than differential respirometry, and that the time to maximum nitrification inhibition depended on the properties of the chemical toxin, which implies that longer exposure times may be needed to accurately predict nitrification inhibition. / Ph. D.