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The purpose of this study was to investigate the effects of copper on the treatment of an abandoned landfill leachate by a Modified Ludzack Ettinger (MLE) single-sludge, activated sludge treatment system. MLE systems are designed to accomplish nitrification and denitrification, and at least two systems were used: one to which copper was added, and one maintained as a control. The system that did not receive copper additions gave an indication of the treatability of the leachate by an MLE system. Copper was added at concentrations of 1.0, 2.0, 2.5, and 5.0 mgCu/L in the influent and the sludge age was varied from 8 to 30 day. It was determined that copper did inhibit nitrification and denitrification. A strong linear relationship was shown to exist between the specific copper loading on the system, that is the total copper entering the system within a day divided by the total biomass within the system, and the soluble copper concentration within the system. The adsorption of copper by the activated sludge, and the resulting soluble copper concentration in the mixed liquor, could be generally described by the Freundlich Isotherm. Intermittent inhibition of nitrification unrelated to copper addition also occurred during treatment of the landfill leachate which was obtained from the abandoned Dixie Caverns Landfill near Roanoke, Virginia. The inhibiting substance was not identified during this study. It did not significantly inhibit denitrification, but did cause elevated effluent suspended solids concentrations. An additional treatment step would be needed for reliable treatment of the leachate. Copper additions caused inhibition of both nitrification and denitrification. The degree of nitrification and denitrification inhibition was a strong function of the soluble copper to ML VSS ratio in the reactors, i.e., the toxin -to -microorganism (TIM) ratio. Nitrification and denitrification appeared to be equally sensitive to copper. Both were severely inhibited at a soluble copper to ML VSS ratio of 0.001 in aerobic and anoxic reactors, respectively. Nitrosomonas species were more strongly inhibited by copper concentrations than were the Nitrobacter species. The denitrifiers appeared to be as sensitive to copper as the Nitrosomonas species. / Master of Science

The extracellular polymers produced by bacteria play an important role in bacterial aggregation or bacterial flocculation in secondary waste treatment. The mechanisms responsible for this floc formation are thought to be polymer induced adsorption and interparticle bridging among bacterial cells or between bacterial cells and inorganic colloids. The efficiency of the processes following flocculation in the treatment line such as sedimentation, sludge thickening, and sludge dewatering depends on the extent of this bacterial flocculation. In this research, sludge samples from under various substrate conditions were examined for type, molecular weight, physical characteristics„ and quantity of extracellular polymers so that the general characteristics of the various polymers could be established. An attempt was made to determine if a relationship exists between the state of bacterial aggregation and the polymer characteristics. This research also investigated the sludge physical properties. The effect of various parameters such as pH, divalent cation (mixture and concentration), and mixing (period and intensity) on dewatering properties were studied. A major goal of this study was to develop a flocculation model for activated sludge. This model could be used to determine if plants can increase the efficiency of waste treatment and sludge thickening and sludge dewatering processes. / Ph. D.

M.S.

The purpose of this investigation was to conduct batch and continuous flow laboratory experiments with bench scale activated sludge units to determine the effects of nickel on the completely mixed activated sludge process. The model units were located in a constant temperature room maintained at 20±2°C. The batch reactors were operated under acclimated and shock loaded condition with various nickel concentration to determine its effects on the rate of COD removal. The continuous flow units were operated until steady state conditions were obtained at each mean cell residence time studied and then data were recorded for an approximate 7 days period and averaged to obtain one steady state data point. Nickel was added to the waste water at various concentration to determine its effects on COD removal efficiency, degree of nitrification and on the biokinetic constants Ymax and kd. / Ph. D.

The effects of a continuous dose of 0.5 mg/l nickel on activated sludge performance at varying COD:TKN ratios were investigated. Continuous flow, complete mix, bench-scale reactors were operated over a range of mean cell residence times, and COD removal efficiency, biokinetic coefficients, extent of nitrification, and nickel removal evaluated at each. Data from two earlier studies, in which 0.5 and 1 mg/l nickel doses were applied to similar units, were included for comparison. Organic removal efficiency was not impaired for the nickel doses considered. Biokinetic coefficients and nitrate production were also unaffected by 0.5 mg/l nickel. In contrast, one mg/l nickel sharply inhibited nitrification, caused an apparent decrease in reactor solids concentration, and related biokinetic changes in coefficients. Nickel removal was erratic. / Master of Science

This study investigated the influence of nitrogen and sludge age change in reactor performance and biopolymer production in activated sludge systems. The qualitative and quantitative analyses of the naturally occurring biopolymers were performed and the results were correlated to sludge a settling characteristic and effluent quality. In order to obtain the sludge samples for the analyses, two completely mixed, continuous flow activated sludge systems were maintained during this research. Raw wastewater from the Celanese Fiber Plant located at Narrows, Virginia was utilized as the influent. Nitrogen was added in the feed solution as ammonium sulfate. The sludge age was changed from ten to five days for both systems. Biopolymers were extracted from the sludge floc matrix using pH-adjustment technique followed by centrifugation. The total biopolymer contents were analyzed for protein and carbohydrate concentrations. High molecular weight biopolymers were also analyzed following gel filtration. The sludge settling characteristics were measured in terms of Sludge Volume Index and effluent quality in terms of effluent turbidity. The results indicated that the relationship between total biopolymer concentrations and sludge settling characteristics is culture specific. No consistent relationship was observed between total biopolymer concentrations and effluent turbidity and/or SVI. Additional nitrogen in a reactor system promoted production of high protein content biopolymers. However, no significant improvement in effluent quality of the reactor was noticed by the additional nitrogen. Deficiency of nitrogen in a reactor system promoted the production of high carbohydrate content biopolymers. The high concentration of carbohydrate biopolymers seemed to correspond directly to the high effluent turbidity. / M.S.

The purpose of this research was to conduct a laboratory study to determine the effects of nickel on the completely-mixed activated sludge process. Continuous-flow bench-scale reactors were operated at COD:TKN ratios of approximately 1.0:1 and 0.5:1 by varying the nitrogen concentrations in the feed solutions. Each unit received a COD concentration of 400 mg/l and was dosed continuously with a nickel concentration of 0.77 mg/l. The mean cell residence time was utilized as the operational control parameter to assess the influence of nickel on organic removal efficiency, on the degree of nitrification, and on the maximum yield and the microbial maintenance energy coefficients, Y_max and k_d. The results obtained in this study indicated that the soluble COD removal efficiency of the heterotrophic microorganisms was not affected by the 0.77 mg/l nickel concentration. The low continuous nickel dose to the reactor, however, appeared to stimulate the heterotrophic growth or to cause a replacement of the bacteria with a species of nickel-tolerant microorganisms. At the same time, the nickel appeared to stress the heterotrophs and to cause an increase in their maintenance energy requirement. Nitrification was found to be inhibited by the low nickel concentration, and this inhibition was not reduced by operating the reactors at lower COD:TKN ratios. / Master of Science

The effect that mean cell residence time (MCRT) had on the dewaterability of biological sludges was examined in this study. Aeration basin sludge and waste activated sludge from a full scale domestic wastewater treatment facility, in addition to sludges produced from two laboratory scale reactors fed with a synthetic substrate and a primary effluent-dog food mixture, respectively, were used to perform dewatering tests. The sludges were evaluated at various MCRT values for optimal dewatering resistances, optimal conditioning requirements, and optimal compressibility conditions. Specific resistance determinations were made using a 3uchner funnel apparatus to evaluate all of the above mentioned parameters. Also particle size analyses were performed on all sludges to investigate how particle size affected dewatering resistance and conditioner requirements, and also to investigate how MCRT affected particle size. All particle size determinations were made using a HIAC PC-320, twelve channel particle size analyzer. Results from the study revealed that plants can operate under extended aeration and still maintain good sludge dewatering characteristics. Likewise, by varying MCRT shifts in particle size distribution and corresponding changes in dewatering resistance were noted in the laboratory reactors. However, no optimum MCRT with respect to dewatering could be founded. Particle size proved to be the most important parameter affecting dewatering, and it was affected by conditioning, periods of anaerobiosis, and MCRT in the laboratory reactors. / Master of Science

A high strength industrial wastewater was treated in a bench-scale activated sludge reactor modified by the addition of biomass support media to the aeration tank. Two experimental biomass support systems (BSS) and one conventional activated sludge system were operated at different mean cell retention times (mixed liquor MCRTs). Three separate media were tested, NOR-PAC and Linpor used as free-floating supports, and BIONET used as a fixed-bed support. The effect of the media on substrate and oxygen utilization, and solid-liquid separation was investigated. Substantial attached growth did not occur on the NORPAC and BIONET media. The attached biomass concentration in the Linpor systems increased with increased media concentration. The ratio of attached volatile solids to total volatile solids (attached volatile solids + MLVSS) decreased with increased mixed liquor MCRT. The advantages of the BSS would occur at low mixed liquor MCRTs. Both the BSS and control systems achieved greater than 94% COD removal and substrate utilization rates (mg/h) did not significantly change during the experiments. Therefore, both systems were substrate limited. The substrate limitations caused decreased oxygen uptake rates of the attached biomass with increased mixed liquor MCRT. The sludge settling of the Linpor systems was a function of mixed liquor MCRT, filamentous upsets, and the presence of the media. Enhanced settling was observed in the Linpor system only at the 3 day mixed liquor MCRT experiment. / Master of Science