The primary goal of this study was to evaluate a new device and system, designed to optimize the performance of standard low pressure air diffusers in two types of aerated systems (activated sludge and aerobic sludge digestion) and to decrease overall energy consumption. Aerated treatment systems are very important in the treatment of wastewaters and management of sludges. The activated sludge process is widely used to treat wastewater from both industrial and municipal sources. However, they are costly to operate because oxygen is marginally soluble in water and standard low pressure (8 psig) diffusers provide marginal mixing and minimum retention. The newly patented device is referred to as TotalMix and is a type of pneumatic mixing system. TotalMix introduces air under high pressure at regular fixed intervals. During the tests the frequency of air delivered, the pressure, and the period of pressured air delivery was varied manually or through feedback control to optimize oxygen transfer and the interaction with a regular aeration system. Various chemical parameters, most importantly dissolved oxygen, were measured and compared to the new approach, using the TotalMix in combination with standard diffuser systems. The new System was tested in different sized tanks (17,000 L and 380,000 L), different concentrations of total solids (TS), using different airflow rates and different diffusers (membrane fine bubble diffusers, ceramic fine bubble diffuser, and course bubble diffuser). The statistical evaluation of the experiments indicates an increase in oxygen transfer rate with a concomitant decrease in energy consumption at low airflow rates. / Master of Science

M.S.

This research involves design and implementation of computer program for simulation of a wastewater treatment plant. The program has the capability to be interfaced with an existing analog wastewater plant process flow training board which is equipped with meter readouts of key process variables and adjustable control valves. It is planned that the total system simulator could be used to train wastewater treatment plant operators to afford them hands-on dynamic experience in plant operations. The wastewater treatment process modeled is the activated sludge process. Beginning with the known plant design stead-state equations for this particular process an algorithm was developed to simulate the treatment process through probable system dynamics. All assumptions are presented in a logical manner and used to develop the necessary transient equations. The success of this project demonstrates that a simulation program which emulates a waste treatment process is possible; however, it is suggested that further research is needed to provide deeper insight into variable changes during system transients.

The presence of biologically-active estrogenic endocrine disrupting compounds (EDCs) in treated effluents from biological wastewater treatment facilities has prompted wide-spread interest in the behavior of these contaminants during the activated sludge process. The yeast-estrogen screen (YES) was used to quantify the estrogenic activity of samples taken from different areas of three wastewater treatment facilities. An estrogenic mass-balance around these facilities revealed that the majority of influent estrogenic activity was removed in the activated sludge process, but the main route for EDC discharge to the natural environment was via the treated effluent. The estrogenic activity in the effluent from a membrane bioreactor (MBR) was lower compared to a fully aerobic activated sludge process using secondary clarification, suggesting that enhanced removal of particulate and colloidal material may improve EDC removal efficiency. Colloidal material was obtained from settled mixed liquor suspended solids (MLSS) collected from a pilot MBR and a full-scale activated sludge process that included anoxic and aerobic zones. The MLSS was sized fractionated by filtration, and used to quantify the sorption coefficients for pyrene, 17&#946;-estradiol (E2), and 17α-ethinylestradiol (EE2) by fluorescence quenching. The MLSS-derived colloidal organic carbon (COC) sorption coefficient (Kcoc) for pyrene ranged from (< 1 to 80) L/kgcoc, indicating a similar affinity for pyrene compared to natural organic matter. Kcoc coefficients for E2 ranged between (< 1 to 158) L/kgcoc for E2 and (< 1 to 228) L/kgcoc for EE2, and are the highest E2 and EE2 sorption coefficients reported in the literature to date. There was a strong correlation between the Kcoc coefficients and molar extinction coefficient at 280 nm (e280) for pyrene and E2, suggesting that the interaction of the π;-electrons is an important factor in determining overall sorption behavior. There was no such correlation for EE2. Based on the Kcoc coefficients and COC concentrations of the samples, between 1 and 50% of the aqueous E2 and EE2 concentrations were associated with colloidal material. In a novel application of the YES bioassay, the bioavailability of colloid-associated E2 was quantified by comparing the EC50 values of the dose-response curves generated in the presence and absence of size fractionated COC. An increase in EC50 values as a function of COC concentration was attributed to a reduction in bioavailability of E2, suggesting that MLSS-derived COC can reduce, but not eliminate, the biological impact of EDCs. However, there was a high degree of variability in the EC50 values, and estimates of the colloid-associated E2 fraction based on the Kcoc-e280 correlation were unsuccessful in accurately predicting increases in EC50 values. Nevertheless, the YES bioassay may represent a powerful tool in determining the bioavailability of EDCs in complex environmental samples. Results from this research effort suggest that the colloidal phase derived from activated sludge systems represents an important transport vehicle whereby EDCs and other trace organic compounds can enter into the natural environment. Consequently, wastewater treatment plants discharging to sensitive ecosystems or involved with direct water reuse programs should optimize the treatment process to remove colloidal material. / Ph. D.

Utilization of the activated sludge process is widespread although many of the mechanisms that make it work are still relatively misunderstood. Recent studies have indicated that dual substrate limitations may occur in the process. Several misconceptions in the basic fundamentals regarding the rates and mechanisms involved in oxygen transfer to wastewater systems also exist. This research investigation examined the effects of the mean cell residence time and wastewater stoichiometry on the operation of the completely mixed activated sludge process under a dual substrate limitation. At low mean cell residence times (θ_c) the system was growth C limited with respect to carbon and at high mean cell residence times the system was oxygen limited. Oxygen transfer studies were conducted to ascertain the relationship between the steady state oxygen transfer coefficient (K_La) and the oxygen uptake rate of the mixed liquor (R). The objectives of this research were accomplished by operating two continuous flow bench scale activated sludge units at COD:TKN ratios of 6.07:1 and 0.65:1. Reactor-1 was operated at a COD:TKN = 6.07:1 and was always growth limited with respect to organic carbon while Reactor-2 was operated at a COD:TKN = 0.65:1 and was carbon limited at low mean cell residence times and oxygen limited at high θ_c values. Mean cell residence time served as the primary control parameter during the laboratory studies and was varied form approximately 2.5 to 21.0 days. Theoretical studies were also conducted in which biokinetic and stoichiometric equations were used to develop a model to simulate the process operating under carbon and oxygen limitations. The model was found to yield results that were similar to the actual experimental data collected. Further refinement of the model by including inhibition functions would result in a model with better predictability. Examination of the experimental data collected during the laboratory study revealed several interesting conclusions. Operation of the activated sludge process at a low COD:TKN ratio (0.65:1) and under an oxygen limitation at high mean cell residence times can result in high levels of free ammonia and nitrite that will lead to a deterioration in effluent quality. Increased removal efficiencies for COD, TKN and NH₃-N can be achieved by operating the process at a high COD:TKN ratio (6.07:1). Steady state oxygen transfer coefficients determined in the mixed liquor of the reactors indicated there was a direct relationship to the oxygen uptake rate of the activated sludge (R). This observation is quite significant since standard aeration theory states that K_La is constant for a given aeration device. Nonsteady state K_La values determined on the effluent from each reactor indicated that K_La was a constant. Alpha and beta coefficients determined from nonsteady state tests on wastewater effluent from each reactor showed no trend with the mean cell residence time. / Ph. D.

This study compared the sludge characteristics of a lab-scale Air Products (A/O) and a conventional activated sludge system. The sludges were analyzed for operational properties and the exocellular biopolymers of each sludge was characterized. Operational analysis mainly consisted of measurements of settling (SVI) and dewatering (specific resistance, CST) parameters at each sludge age. Biopolymers were measured using pH extraction followed by gel filtration and subsequent analysis for carbohydrate and protein concentrations. The results showed a high degree of similarity between the two systems both operationally and with respect to biopolymer characteristics. The A/0 system did produce a lower effluent soluble COD at sludge ages below 5 days. Also, the A/O system showed some consistent differences in the distribution of bound and unbound fractions of protein and carbohydrate ECP but these had no discernible· effect on sludge operational characteristics. In addition relationships between unbound ECP and effluent BOD, bound HMW ECP and SVI, and phosphorus and Mg uptake were observed, with varying degrees of consistency, in this study. / Master of Science

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 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