The enigma of anaerobic sludge granulations is still exciting the minds of both experimental scientists and modeling experts. A unique combination of mechanical, physiochemical and biological forces influence granulation during processes of anaerobic digestion. However, knowledge of potential driving forces of granulation has not been transformed into a comprehensive model of anaerobic granulation. In this computational experiment, we address the role physiochemical and biological processes play in granulation and provide a literature-validated working model of anaerobic granule de novo formation. The model developed in a cDynoMiCs simulation environment successfully demonstrated a de novo granulation in a glucose fed system. The simulated granules exhibit experimental observations of radial stratification: A central dead core surrounded by methanogens then encased in acidogens. Practical applications of the granulation model was assessed on the anaerobic digestion of low-strength wastewater by measuring the changes in methane yield as model parameters were systematically swept. This model will be expanded in the future to investigate the influence of mechanical forces on the de novo granulation and the application of a model to anaerobic digestion of a complex protein-carbohydrate rich feedstock.

The potential of enhancing lipid accumulation in municipal sewage activated sludge via fermentation of lignocellulose biomass hydrolyzate was investigated. The overall objective was to increase the levels of feedstock lipids in the activated sludge biomass and increase its biodiesel yield via in situ or ex situ transesterification; and improve its cost competitiveness as an abundant feedstock source for biofuels production. To reduce production costs and maintain environmental sustainability, influent wastewater and waste lignocellulose biomass hydrolyzate were used as cultivation media and substrate, respectively. However, lignocellulose hydrolyzates also contain degradation by-products such as furfural and acetic acid that are known to exert inhibitory effects on microorganisms; hence their effects on the fermentative performance of activated sludge were investigated and fermentation strategies were proposed and evaluated to counteract the microbial toxicity of these compounds. The utilization rate and efficiency of xylose by activated sludge microorganisms for lipid production was also evaluated as pentose sugars such as xylose usually constitute a major percentage of lignocellulose hydrolyzates. Furthermore, variations in the population profile of activated sludge microbiota were determined via 16S rRNA sequence analysis to determine the effect of sugar fermentation at different initial conditions. Results show that activated sludge lipid contents and biodiesel yield could be enhanced by fermentation of sugars at a high initial C:N ratio (70:1). Furfural was found to be highly inhibitory to microbial growth and lipid accumulation while high initial acetic acid concentrations enhanced biomass production but not lipid formation. Xylose was also utilized more efficiently than glucose by the activated sludge microorganisms for biomass and lipid production albeit at relatively slower rates; hence sugar mixtures derived from lignocellulose could be utilized for the process. Semicontinuous and continuous fermentation modes were proposed and evaluated as strategies to reduce inhibitory effect of furfural and acetic acid and improve lipid productivity, but the lack of nutrient supplementation prevented the cultures from sustaining microbial growth and lipid production, leading to cell death and washout. Finally, the reduction in the diversity of the activated sludge microbiota could point to specific microbial strains that are mainly responsible for lipid accumulation.

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Upset events due to the inflow of toxic chemicals are a critical issue for wastewater treatment facilities. Understanding the source-effect relationship of toxic chemicals can facilitate the prevention or improved reaction to upset events. Part one of this study was conducted to investigate the source of upset events at a regional industrial wastewater treatment plant (WWTP). Part two of this study determined the process performance effects of two chemical shocks, cyanide (zinc-cyanide complex) and pH, on nitrifying and non-nitrifying activated sludge. A modified respirometric assay protocol was developed to allow the industrial WWTP to screen industrial wastewaters for inhibitory properties. All five industrial wastewaters tested revealed inhibitory properties. Large day-to-day variations were found, illustrating the need for a large database of results for comparison over time. Additionally, a small volume contributor, that was thought by the utility to be an unlikely source of problems, contributed significantly to the wastewater oxygen demand and demonstrated inhibitory properties. The modified respirometric procedure enabled the WWTP to identify possible industrial sources that could cause an upset event. Lab-scale sequencing-batch reactors were used to determine the effects of cyanide and pH shock on activated sludge. Three reactors were shocked with increasing weak-acid complexed zinc cyanide or pHs of 5, 9, and 11. The resulting effects were compared to an un-shocked control reactor. It was found that respiration and nitrification were affected by the zinc cyanide complex, while COD removal, effluent TSS and dewaterability were not. Recovery was seen in less than 2 X solids residence time (SRT) for the nitrifying biomass and within 3 X SRT for the non-nitrifying biomass. The results of the pH experiment showed that the pH 11 shock affected the settleability, nitrification, COD removal, and effluent TSS levels of the reactors, while pH 5 and pH 9 shocks had no effect. Recovery was seen within 3 X SRT for both the nitrifying and non-nitrifying systems. / Master of Science

Impact of Sludge Volume and Water Quality on DBPs in a Full-Scale Water Works The goal of this research was to determine the role of settled sludge on the formation of disinfection by-products in a full-scale water treatment plant. The occurrence of disinfection by-products in chlorinated drinking water has become a major concern to treatment facilities in their effort to comply with strict regulations set by the United States Environmental Protection Agency. Water samples were tested for trihalomethanes and haloacetic acids at both ends of the sedimentation process to evaluate formation over the length of the basin. Sludge volume and other important water quality parameters were also measured at the time of sample collection. Statistical analyses were used to analyze contributions from the sludge and to determine influential factors leading to disinfection by-product formation. The treatment plant incorporated chlorine dioxide into the treatment process seasonally, and effects were evaluated. Predictive models were developed from the data to be used under various treatment methods. The models created for trihalomethanes and haloacetic acids require measurements of chlorine dose, reaction time, total organic carbon, pH, water temperature, and sludge volume. The models performed well in predicting actual trihalomethane and haloacetic acid concentrations and could serve as a valuable tool in the control of disinfection by-products. DBP Formation Potential of Settled Sludge in a Full-Scale Water Treatment Facility It is still a common occurrence for water treatment facilities to store sludge in sedimentation basins for extended periods, rather than relying on mechanical collection equipment. The goal of this research was to characterize contributions from settled sludge to the formation of disinfection by-products (DBPs), and determine whether continuous removal is essential in the control of DBPs. Samples were taken from top and bottom sludge layers in the sedimentation basin and water was extracted either by draining or centrifugation. The water was analyzed for trihalomethanes and haloacetic acids and water quality measurements were recorded. Concentrations of both DBPs were very high in top-layer sludge; trihalomethanes ranged from 321.5 μg/L to 568 μg/L and haloacetic acids ranged from 74.6 μg/L to 409.8 μg/L. Evidence of biodegradation was observed in the bottom-layer sludge. The water samples were dosed with 4 mg/L chlorine, the United States Environmental Protection Agency's maximum residual disinfectant level, to determine if further DBP formation was possible. The extracted water from the bottom-layer sludge was shown to form high trihalomethane concentrations when chlorinated, and haloacetic acid concentrations were observed to increase when samples from the top-layer sludge were chlorinated. / Master of Science

<p> Although both steady state and dynamic simulation studies of the activated sludge process are available, the data bases employed have traditionally been: derived from bench scale studies, derived from historical monitoring data, synthetic based on mathematical functions. Actual plant operating data, if available, would reflect full scale operation and would provide a much better data base to judge existing or future process models. This study was designed to provide a more comprehensive data base than presently existed on a full scale municipal activated sludge system. Both flow and component concentrations were continuously measured on two hour intervals for two periods of 10 days and 5 days duration. Streams sampled included the plant influent, the primary clarifier effluent, the aeration tank effluent, the secondary clarifier effluent, the activated sludge recycle and the waste sludge line. Based on total nitrogen and total phosphorus, the data were examined for mass flow closure around the aeration tank. A time dependent mixing model based on two unequal volume stirred tank reactors in series was found to adequately describe the observed variation in aeration tank input-output data. The measured aeration tank inflow and outflow was corrected to give a hydraulic balance using a statistical procedure which generates flow corrections based on expected measurement error. The resulting total nitrogen and total phosphorus material balances were found to improve based on a reduction of the residual sum of squares.</p> / Thesis / Master of Engineering (MEngr)

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Recent advances in activated sludge facilities operations utilize sludge recycle flow rate control to minimize adverse effects on the clarifier during peak solids loading situations. Although this control action is directed at the thickening function, there has been speculation that the elevated recycle rates may be responsible for an increased effluent solids concentration. To evaluate the significance of recycle rate to the steady-state effluent suspended solids concentration, identical side-by-side settling columns were operated with recycle rates spanning the range of normal practice. The studies were conducted so that each side-by-side unit received identical activated sludge feed slurries. Replicate experimental units operating at identical recycle rates and receiving identical feed slurries were used to determine experimental error. The experimental design facilitated a statistical determination of the significance of the effect of recycle flow rate. An analysis of variance procedure was pursued, with the conclusion that recycle rate does, in fact, influence suspended solids removal. Ramifications for facilities design and operation is also reviewed.