Fecal coliforms suspended in a natural stream water were exposed to rhodamine WT dye, chlorine and both in combination. Samples were analyzed for coliforms by three enumeration techniques. Statistical analyses of data by the paired-t test showed that for non-chlorinated samples no significant difference (0.10 level) was found between the recoveries by the three enumeration techniques. For chlorinated samples the standard membrane filter technique (Std-MF) yielded significantly lower recoveries (0.05 level) than the standard MPN procedure. A modified membrane filter technique employing a two-layer agar and a five hour 35°C preincubation period (Mod-MF) was found to yield recoveries consistently greater (0.05 level) than the standard MF technique. The data showed that exposing fecal coliforms to 100 to 1,000 ppb of rhodamine WT dye for 30 minutes, did not inhibit the recovery or enumeration of the organisms by any of the three assay methods. The number of fecal coliforms that survived exposure to 0.2 to 0.3 ppm of chlorine and 10 to 100 ppb of dye was not significantly different from the number enduring contact with similar concentrations of chlorine alone. / Master of Science

M.S.

The purpose of this study was to investigate the interaction between colloidal substances and activated sludge and attempt to relate this information to the performance of activated sludge processes, particularly the contact stabilization process. Protein and carbohydrate organic colloids and a combination substrate were separately studied to determine if the type or classification of substrate colloids is a factor in the colloid-sludge interaction. Albumin, potato starch, and jack bean meal were the substrates chosen. Two series of studies were performed. The first involved monitoring metabolic uptake of the colloidal substrates alone and then with glucose supplementation. The second series used mercury poisoned activated sludge to investigate the physical-chemical removal of different loadings of the colloidal substrates. During these experiments, conditions of pH, ionic strength, and cationic valence were varied to determine their role in the physical interactions between the colloids and the sludge. Data obtained from the metabolic studies were monitored for unusual responses in substrate and oxygen utilization. Other factors determined included yield and oxygen utilization constants, substrate removal rates, and initial removal capacities of the sludge. Physical studies on the metabolically inactive sludge yielded data on the facility of organic colloid removal by activated sludge under a variety of different environmental conditions. Removal capacities were recorded as well as any particle size variations of the activated sludge after colloid addition. Further information was obtained on the settleability of the colloid-sludge mixtures. An adsorption and release phenomenon was observed for the two carbohydrate containing substrates while a two step oxygen utilization was observed for albumin and starch. Glucose addition was hypothesized to repress extracellular enzyme production thereby decreasing the sorption capacities of the activated sludge. Studies with the metabolically inactive sludges indicated that variations in pH, ionic strength, and cation valence play important roles in the physical removal of organic colloids by activated sludge. Sorption capacities of sludge varied with MLSS concentration. Unit sorption capacities for all three substrates decreased as MLSS levels increased. Total sorption capacities increased for albumin and jack bean meal with an increase in MLSS; the starch removal capacity however still decreased. The type of sorption occurring (adsorption or enmeshment) was believed to be important for these variances. Better quality supernatants were noted after substrate colloid addition. It was hypothesized that dispersed bacteria in the supernatant were coagulated by the organic colloids. Finally, carbohydrate colloids responded in a manner consistent with contact stabilization theory. Specifically the carbohydrates exhibited better sorption characteristics as .wel1 as an adsorption and release phenomenon. / Ph. D.

Benzo-a-pyrene, a carcinogenic polycyclic aromatic hydrocarbon, was injected into the aeration tank of an activated sludge pilot plant in an investigation to determine the ability of activated sludge to effectively treat this compound. The method employed to segregate Benzo-a-pyrene from other organics was a modified Soxhlet technique followed by gas chromatographic analysis. The amount of Benzo-a-pyrene detected in the effluent, supernatant, sludge filtrate and sludge cake was tabulated to determine the mechanism of removal. The experimental results indicated that adsorption appeared to be.the primary mechanism of removal. The concentration of Benzo-a-pyrene in the effluent collected from the pilot plant was below the level of detection by gas chromatography. On the basis of the experimental evidence activated . sludge provides satisfactory treatment for wastes containing low concentrations (i.e. 0.5 mg/l) of Benzo-a-pyrene, a carcinogenic polycyclic aromatic hydrocarbon. / Master of Science

The objective of this study was to investigate what effect the concentration of microorganisms would have on substrate removal, microbial substrate storage, and oxygen utilization at a constant food-to-microorganism ratio. Batch experiments were conducted, under aerated and completely mixed conditions, using a domestic wastewater, a paper mill wastewater, and a food processing wastewater. A series of three batch experiments were run for each of these wastes. The food-to-microorganism ratio for each series was kept constant while the mixed liquor suspended solids concentration was varied for each of the experiments within the series. The following analyses were conducted on samples that were withdrawn at specified time intervals: filtered and settled COD, oxygen uptake, mixed liquor volatile suspended solids (MLVSS), pH, protein concentration and carbohydrate concentration. No significant uptake and subsequent release of organic substrate was observed for any of the wastewaters studied. For the same F/M ratio, the rate of removal of organic substrate and the degree to which it was removed in the activated sludge system was found to be a direct function of the MLVSS concentration. The change in the cellular carbohydrate to cellular protein ratio in the activated sludge during substrate metabolism was a function of the MLVSS concentration. As the MLVSS concentration increased, the carbohydrate to protein ratio, which is an indicator of substrate storage, also increased, even though the F/M ratio was held constant. / Master of Science

The capability of the activated sludge process to operate with sea water included in the influent substrate. Sea water was added at various percentages from 5-40. The study concluded that from a biological standpoint the activated sludge process could operate successfully. However, rapid settling problems because of a build up of total solids became the limiting factor. / Master of Science

Treatment of municipal and industrial wastewaters results in the production of wastes in the form of sludge. Since the quantity and characteristics of sludge depend upon the degree of treatment, the upgrading of treatment facilities has had the effect of increasing sludge production. Since the quantity of sludge is a function of the type of treatment provided, any attempt to minimize sludge handling should begin at the source. The hydrolytic assist activated sludge process provides positive control of the mixed liquor solids and is effective in the disposal of organic sludge created in the wastewater treatment process. In theory, this modification involves the hydrolysis of waste activated sludge by acid addition to a pH of 1.0 or with base addition to a pH of 13.0. Hydrolysis is followed by autoclaving at 15 psi and 121°c for a period of five hours. This treatment will solubilize most of the cellular material which can then be reintroduced to the aeration tank after pH neutralization. No sludge is wasted; it is all recycled as hydrolyzed sludge. The main objective of this research was to operate laboratory activated sludge units over a range of Qc values to determine effects and differences in process performance and operation for the hydrolytic assist mode. Results obtained during this study indicate that COD removal efficiency for the hydrolytic assist is compatible with the conventional process. In addition, the hydrolytic assist process proved to be an effective disposal method for sludge produced in the activated sludge process. / M.S.

Handling and disposal of residual solids from wastewater treatment plants is an expensive and difficult task. The acid hydrolytic assist activated sludge process is one method of minimizing sludge production from a biological wastewater treatment process. Acid hydrolysis of waste sludge involves pH adjustment to 1.0 or less followed by heat treatment. The hydrolyzed sludge can then be adjusted to a neutral pH and recycled to the treatment process as soluble organic material. In effect, hydrolysis promotes cellular autodigestion by artificially inducing the normally difficult metabolic steps. The use of hydrolysis in the extended aeration process allows periodic sludge wasting for control purposes but avoids the problem of ultimate sludge disposal. Previous research was limited to the use of hydrolysis in the extended aeration process. The effect of mean cell residence time, Θ_c, on an activated sludge process utilizing hydrolysis had not been evaluated. Also, only limited information is currently available regarding the kinetics of wastewater treatment with the hydrolytic assist activated sludge process. The purpose of this research was to gain additional insight into the hydrolytic assist activated sludge process with regard to mean cell residence time and the kinetics of wastewater treatment. Determination of the relative effect of hydrolysis on nitrification in the activated sludge process was a secondary objective of this study. Mathematical and stoichiometric equations were used to predict process performance characteristics. A laboratory investigation was then conducted to obtain actual operational results for comparison. A description of the investigative procedures and results is included along with a review of the literature. / Master of Science

The sludge blinding coefficient, β, was evaluated in this experimental study, to determine if β could be used as a useful characterization parameter for sludge filterability. Fresh activated sludge, activated sludge aged at room temperature, primary sludge, alum sludge, and a calcium carbonate slurry were filtered using a Buchner funnel apparatus and varying size filter media at various pressure differentials. Particle size measurements were also performed on the above mentioned sludges using an automated particle size analyzer to examine the impact of particle size and size distribution on β. Effects of conditioning, elutriation, supernatant removal, and replacement on β were also studied. In general, β correlated well with the average specific resistance, indicating that it could be useful in predicting a sludge filtration pattern. β was found to increase as the mean particle size of a sludge decreased, or the particle size distribution of a sludge widened. Conditioning, elutriation, supernatant removal, and replacement were found to reduce β by improving the mean particle size of a sludge and narrowing a sludge particle size distribution. In addition, β was found to increase by the applied pressure differential and filter media pore sizes for a few sludges. / Master of Science

Nearly 700,000 Virginians depend on septic tanks and other wastewater treatment systems for treatment of household wastes. The Joint Subcommittee Report HJR 7 1987 reported that sixty percent of Virginia's residential septic “systems and drainfields are operating improperly. With the demand for rural and suburban development increasing, a viable alternative to septic systems and drainfields is needed. One proposed alternative is single family package treatment systems. One vital concern is that a majority of these systems discharge directly into surface waters. Thus, the objective of this study was to evaluate the performance of aerated package treatment systems (APTS). Five APTS located in southwest Virginia were chosen. Each site was visited three times during 1990 and 1991, and various parameters were monitored from the primary settling chamber, aeration chamber, and effluent. Systems were sampled in the morning, afternoon, and night. Also, two dye studies were conducted to evaluate hydraulic displacement. The results indicated that overall field performance was poor due to unreliable maintenance by homeowners, an ineffective chlorinator/dechlorinator system, inadequate biological treatment, and mechanical malfunctions. Eighty-one percent and 62% of the effluent samples were found to have five day Biochemical Oxygen Demand (BOD,) and total suspended solid (SS) concentrations exceeding 30 mg/L, respectively. Effluent dissolved oxygen values were less than 5 mg/L, the state's standard for small package treatment systems. Sixty-four percent of the effluent samples were found to contain more than 200 fecal coliforms/100 mL. In five instances where disinfection was evident, chlorine residuals were detected in the effluent, which also violates state standards. / Master of Science