The object of this investigation was to determine, by the concept of specific resistance, the effect of certain variables on the filterability of calcium sulfate sludge resulting from lime neutralization of synthetic, return sludge seeded, sulfuric acid samples, The variables investigated were rate of mixing, rate of lime addition, degree of neutralization, return sludge loadings and acid concentration. Mixing rate and lime addition rate are factors effecting the characteristics and filterability of calcium sulfate sludge. Slow lime addition provided a more effective return sludge than did rapid lime addition. Slow sample mixing produced a more filterable sludge than did rapid mixing for a given lime addition rate. The degree of sample neutralization appeared to have only a minor effect on the filterability of the sludge, with the filter ability improving as the final pH of the sample decreased. The sample return sludge dosage appeared to have only a minor effect on the filterability of the resulting sludge with filterability decreasing as return sludge loadings increased. A complete evaluation of the effect of return sludge loading cannot be made, however, until these studies are expanded to include the optimum return sludge loading for the given acid-lime system. The values of specific resistance obtained were influenced by the resistance of the filter paper. For samples with similar dry solids concentration the effect is approximately the same; however, the amount of filter paper interference decrease with increased sample dry solids concentration. For varying acid concentrations there was a minor decrease in specific resistance as the acid concentration, and dry solids concentration, of the samples increased. This decrease was thought to be due to decreasing amounts of filter paper interference rather than improved sludge filterability. / Master of Science

Equilibrium powdered activated carbon (PAC) concentrations of 20, 160, and 280 mg/L in activated sludge reactors treating cellulose acetate manufacturing wastewater were found to enhance substrate removal. The improved substrate removal as measured by COD averaged 20 percent. The apparent mechanism of improved removal was the stimulation of greater biomass growth. PAC addition increased the oxygen uptake rate (OUR), the observed cell yield coefficient (Ybbs) and the first order substrate removal coefficient (Kb) of the activated sludge system, which were operated at a temperature of 18°C and a biological solids retention times of fourteen days. The addition of PAC also improved the sludge settleability but this resulted in higher effluent suspended solids concentration because zone settling Velocity was the primary factor affecting effluent suspended solids. A type of activated sludge bulking, known as jelly formation, plagued the biological reactors but nitrogen addition appeared to solve the problem / Master of Science / incomplete_metadata

The purpose of this study was to investigate selective operational parameters and their effect on activated sludge settling and dewatering rates. Several laboratory scale reactors were used in this study and fed with various synthetic substrates. The sludges produced from these reactors were used to examine sludge settling and dewatering characteristics as the selected operational parameters were varied. This study intended to determine if: (1) qualitative shock loadings affect sludge dewatering and settling and will biological systems recover quickly under various conditions; (2) aeration basin dissolved oxygen concentration affects sludge settling and dewatering characteristics; (3) biopolymer content can be correlated with sludge dewatering rates such that biopolymer content can be used as a parameter to monitor sludge dewatering characteristics. Results from this study indicated that the shock loadings considered here significantly alter the sludge settling and dewatering characteristics of an activated sludge population. Shock loadings may cause shifts in the bacterial population, allowing undesirable microorganisms to predominate but activated sludge systems can recover from shock loadings caused by the introduction of a different substrate. Also, it was seen that activated sludge dewatering is directly affected by the dissolved oxygen level in the aeration basin and the minimum level required is 2.0 mg/L in a completely-mixed system. A definite relationship was noted between biopolymer production and sludge dewatering with high biopolymer content correlating with poor sludge dewatering and low biopolymer content correlating with good sludge dewatering. / Master of Science / incomplete_metadata

The activated sludge (AS) process used for treating high-strength cellulose acetate wastewater of Celanese Corporation, Pearisburg, Virginia, produces a sludge with poor flocculation and settling characteristics, particularly during the periods of shock organic loadings. Pilot-scale treatment units were set up to study the effects of a fixed film pretreatment on the stability of the AS process, using a new type of trickling filter (TF) media consisting of long plastic strips. The pretreated activated sludge (PAS) unit was compared with a control activated sludge unit (CAS). Different hydraulic and organic loadings were applied to the TF. The study confirmed the ability of a TF to provide greater stability to subsequent AS processes during periods of shock organic loading. The TF did not significantly improve the PAS system effluent quality and organic removal performance, even though the PAS sludge had better settle ability in terms of Sludge Volume Index and had less filamentous growth than the CAS system. The TF pretreatment confirmed its ability to act as a roughing filter. During the study, it reduced the organic loading on the AS system by 26 to 43 %, oxygen requirement of AS system by 38 to 62 %, the aeration volume requirement by 17 to 47 %, and the sludge production by 0 to 37 %. The PAS system required fewer nutrients than the CAS system. / Master of Science

Combined activated sludge-fixed film media treatment systems are an interesting innovation in treatment technology. By adding media into the aeration basin, increased biomass concentrations may be maintained with little or no increase in solids loading to the clarifier. The ideal combined system can treat higher organic and ammonia loadings than a conventional system, and is more resistant to temperature changes and shock loadings. Overloaded plants can be outfitted with media as an alternative to plant expansion, and initial designs of combined systems can result in smaller aeration basins and clarifiers in places of land scarcity. / Master of Science

A debate currently exists concerning whether or not oxygen uptake rate is a valid control parameter for monitoring the activated sludge process. A laboratory study was conducted to attempt to shed light on the controversy. Two bench-scale reactors were operated at steady state and under shock load. Oxygen uptake rate (OUR) was measured with the BOD bottle technique and with an on-line respirometer. The reliability of the results obtained from the BOD bottle technique was also of interest. No relationship could be deduced between effluent quality and oxygen uptake rate thereby suggesting that the latter would not be useful as a control parameter. As was concluded from the shock load data, the oxygen uptake rate varies very inconsistently at high organic loadings. It was found that the BOD bottle technique completely failed at very high organic loadings and gave meaningless results. The on-line respirometer, in spite of its high sensitivity, gave more realistic and consistent results. / M.S.

The effects of varied concentrations of a natural sewage grease on the oxidative activities of activated sludge were investigated in an effort to determine the feasibility of using activated sludge as a treatment method for wastes high in grease content. The method employed to measure the oxidative activities of the activated sludge was the standard Warburg respirometer technique. Cumulative net BOD curves were plotted to determine the magnitude of the oxidation. Total grease analyses were performed throughout the test period to establish a definitive pattern of depletion by oxidation. The experimental results indicated that the grease was completely assimulated within 24 hours and that there were no adverse pH changes during the course of oxidation. On the basis of the experimental evidence activated sludge shows great promise as a treatment method for wastes high in grease content. / Master of Science

The effect that the COD:TKN ratio had on total nitrogen removal efficiency. as well as, the effect on COD removal efficiency, nitrogen distribution in the effluent streams, and total system mixed liquor suspended solids concentrations in the activated sludge process as a function of the mean cell residence time (θ_c) were examined in this investigation. A definite relationship was shown to exist between the influent COD:TKN ratio, mean cell residence time, and nitrogen removal efficiency by operating two bench scale activated sludge reactors under continuous feeding. Theoretical data, which were generated by applying biokinetic equations and stoichiometric relationships, were compared to laboratory obtained data to evaluate the validity of using stoichiometric relationships to establish design and operational criteria. The mean cell residence time was used as the control parameter in this investigation. It was demonstrated that nitrogen removal efficiency increased via waste sludge incorporation as θ_c was decreased. It was also shown that nitrogen removal efficiency increased with an increase in the influent COD:TKN ratio by both experimental results and theoretical data. Optimum nitrogen removal efficiencies were found to occur at decreasing mean cell residence times and increasing COD:TKN ratios. / M.S.

The effect of phosphorus limiting conditions on process performance was investigated using laboratory scale activated sludge units. Data were collected for COD:P ratios of 287:1, 212:1, 87:1 and 56:1 at several mean cell residence times. Data collected at COD:P ratios of 287:1 and 212:1 produced sludge with extremely poor settling characteristics and data were collected for only one mean cell residence time at each ratio; Data for COD:P ratios of 87:1 and 56:1 were used to estimate kinetic coefficients. These kinetic coefficients were used to develop predicted values of process performance subject to phosphorus limiting conditions utilizing mathematical and stoichiometric relationships. Predicted values were compared to laboratory data. For both predicted values and laboratory data, a phosphorus limitation resulted in decreased COD removal efficiency, nearly 100 percent phosphorus removal efficiency, decreased reactor solids concentrations, solids with poor settling characteristics, decreased sludge production and artificially high F/M ratios. / M.S.

In the recent past more and more attention has been given by sanitary engineers to the problem of nitrogen removal in sewage treatment. This attention is brought about by several problems associated with nitrogen. First, in some locations, such as our southwest United States, there is both an essentially constant supply of water and an increasing demand for water. This calls for water recycling. or reuse, as a means of meeting the demand for potable water. An accumulation of impurities, such as compounds of nitrogen, can limit the recycling of water. One such substance is nitrate nitrogen, which when in excess of ten parts per million can cause the disease methemo-globinemia in bottle-fed infants. / Master of Science