The dewatering characteristics of sludges produced by water and wastewater treatment plants bear heavily on the methods chosen to treat and dispose of the sludge, as well as on the costs associated with handling the large volumes of sludge produced at these facilities. This study investigated why different sludges dewater to different dry solids concentrations, how sludge structure affects dewatering, and how sludge structure changes during gravity thickening and during different types of mechanical dewatering. It is generally thought that sludge can be described as having a three-tiered structure: (1) primary particles, (2) floc particles, and (3) aggregate particles. To investigate sludge structure in relation to sludge dewatering, this study has defined sludge structure using several sludge particle micro properties. A laboratory technique incorporating isopycnic centrifugation in gradients of Percoll^R media was developed to measure one micro property known as floc particle density. Six field and laboratory sludges were subjected to a series of dewatering tests: gravity thickening, centrifugation, and vacuum filtration. Each sludge was analyzed for macro- and micro properties through each stage of dewatering. It was concluded that improvements in thickening and dewatering characteristics were heavily dependent upon increases in sludge floc density and decreases in aggregate water content. / Master of Science

The activation energy of Douglas fir wood char gasified in carbon dioxide was determined. Activation energies were found for chars that had been pyrolyzed in nitrogen at 600, 750, and 900°C. A thermogravimetric analyzer provided the weight versus temperature data used to obtain the activation energies. The Coats-Redfern integral method of kinetic analysis was used to extract the activation energies from the data. This method can be used to obtain an activation energy from a single weight versus temperature trace for a constant heating rate. An overall apparent activation energy of 723 ± 60 kl/mole and a natural log of the pre exponential factor of 68.8 ± 6.2 was determined from the data collected for all three chars. The different char preparation temperatures did not appear to affect the activation energy. / Master of Science

Twelve different powdered activated carbons (PACs) were screened under laboratory conditions to determine their performance in the removal of chlorite ions (ClO₂⁻) and in the production of chloride ions (Cl⁻) and chlorate ions (ClO₃⁻) during that removal. All screenings were conducted in reagent water, at pH 7.0 ± 0.2 pH units, with a standard concentration of 20 mg/liter of powdered activated carbon (PAC) added in each case, and with the process and samples protected from light. One set of screening experiments was conducted with both ClO₂⁻ and chlorine added with the PAC, while the other set contained only ClO₂⁻, and PAC. The chlorine and ClO₂⁻ were added to concentration levels which might be expected in disinfection practice in water treatment plants. Periodic samples were drawn as the mixtures were stirred over a 24 hour period. Each sample was analyzed for Cl⁻, ClO₂⁻, and ClO₃⁻ concentrations utilizing ion chromatography. All PACs were found to reduce ClO₂⁻ to Cl, and ClO₃⁻ was never detected when chlorine was absent. The data provided no consistent significant evidence of ClO₃⁻ formation even when chlorine was present. The rate of ClO₂⁻ removal was most rapid in the first two hours of contact, but slowed to rates below 6 percent per hour after 4 hours of contact. Rates of ClO₂⁻ removal varied with PAC type. The overall rate of ClO₂⁻ removal was also slower, with the total percentage of ClO₂⁻ removal less, when chlorine was present in the mixture. / Master of Science

The concentrations of chlorine dioxide (CI02), chlorine, chlorite (CIO2), and chlorate (CI03) were evaluated following pretreatment of raw water by CI02 at water treatment plants in New Castle, Pennsylvania; Charleston, West Virginia; Skagit, Washington; and Columbus, Georgia. Chlorite and chlorate concentrations were unaffected by any of the water treatment processes and did not vary as a function of time of travel in the distribution system. Chlorine dioxide, which was analyzed on-site at two water treatment plants, reformed in the clear well and in the distribution system following post chlorination. The chlorite-removal capability of powdered activated carbon (PAC) was evaluated in both laboratory- and pilot-scale studies. Chlorite removal by PAC in laboratory studies decreased with increasing pH over a range from pH 5.5 to 7.5 and varied with the type of PAC. Chlorite was reduced to chloride at pHs ranging from 5.5 to 7.5, but CI03- formed at the pH 5.5 through 6.0. The pilot plant study; which was conducted at Newport News, Virginia; evaluated CI02 removal by PAC enmeshed in a floc blanket in a pulsed-bed, solids-contact clarifier. An average of 27 percent of the CI02 was removed when the PAC dose was 10 mg/L PAC and 57 percent when it was 20 mg/L PAC. Chlorate was not removed by PAC, but the concentrations could be reduced if the CIOz generator was properly operated. / Master of Science

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 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

2, 3, 7, 8-Tetrachlorodibenzo-p-dioxin is well known for its immunotoxic effects on the thymus, as well as on B and T lymphocyte functions. Previous studies suggested that TCDD exerted immunotoxic effects only on cells differentiating in response to antigenic challenge. To this date, no work has been done to characterize the long-term effects of TCDD on the activated cells. Additionally, no studies have been done to determine whether TCDD has any effect on resting T cells. In the current study, therefore, we investigated the effects of TCDD on activated and resting cells within the same animal. T cells in the popliteal lymph node cells were activated by rear footpad immunizations with anti-CD3 antibodies. Distally-located axillary lymph nodes were chosen as a source of naive and resting T cells. Our results demonstrate that TCDD acted at the time of cell differentiation to suppress the immune responses of activated T cells, but failed to suppress, and at times, enhanced the immune responses of resting T cells. The TCDD-induced immunomodulations were temporary; responsiveness of both activated and resting T cells from TCDD-treated animals returned to normal by two weeks post-treatment, suggesting that TCDD does not affect memory cells. Futhermore, we provide direct evidence that the TCDD-induced immunosuppression in activated cells is due to increased apoptosis of CD3+ T cells. TCDD also induced significant changes in cell surface markers expressed by naive and activated T cells. Together our data suggested that TCDD suppresses the proliferative responsiveness of only the activated, but not naive, T cells and that this is accomplished by induction of increased apoptosis of activated T cells. These studies shed new light on the mechanism through which TCDD induces increased susceptibility to infections and cancer in the vertebrate host. / 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