A viable sludge management alternative is land application of waste sludge. However, it is necessary to implement efficient monitoring and analysis of land applied sludges in order to assess potential health risks associated with this means of disposal. The State of Virginia is considering a proposal that requires land-applied wastewater sludges to undergo analysis by EPA's Toxicity Characteristic Leaching Procedure (TCLP) (EPA, 1986b) to determine if the sludge exhibits hazardous characteristics, which preclude land application as a management alternative. The method currently used for the analysis of hazardous wastes is the Extraction Procedure (EP) Toxicity Test. Both of these test methods analyze for trace organic chemicals and heavy metals. However, the TCLP is designed to analyze for volatile organic chemicals to a greater extent than the EP. Because of the added complexity and the current expense of the TCLP, the State is concerned that the TCLP may not be warranted for the analysis of trace organic chemicals in land-applied sludges. This research was designed to compare the abilities of the EP and TCLP for the analysis of trace organic chemicals in wastewater sludges. Samples from three municipal wastewater treatment plants that utilize secondary biological treatment, aerobic digestion and land-apply waste sludge were evaluated by both EP and TCLP methods. Both tests utilize a weak acid extraction to remove organic chemicals from the wastewater sample. The weak acid extract was subjected to liquid-liquid extraction (EPA Method 625) to partition and concentrate the organic chemicals into methylene chloride; this methylene chloride extract was then subjected to GC and GC/MS for quantitative analysis and qualitative identification of targeted and nontargeted organic chemicals. In order to assess recovery and extractability efficiencies of each test, surrogate standards were added prior to the test procedure. These standards were bromoform, 1-chlorooctane, DDT, ethylene dibromide (EDB, a volatile fungicide), fusarex (tetrachloronitrobenzene), and heptachlor. Control samples were run for both EP and TCLP, in addition to a sludge samples with no surrogates added. Analysis indicated that both the TCLP and EP tests showed high variability for the recovery of the sludge surrogates. The recoveries of the surrogate standards were low and varied between zero and 30 percent depending on the standard and the matrix. Surrogate recoveries were evaluated with respect to various physical/ chemical properties of the individual standard, the sample site, and the test method utilized. Although the TCLP recovered the volatile surrogate standards only slightly better than the EP, there was no statistically significant difference between the TCLP and EP for the recovery of the non- and semi-volatile surrogate standards. Specific trace organic chemicals identified in the sludges included dimethylpentanol, dichlorodimethoxybenzene, 4-methylphenol, and tetrabutylphenol. Other chemicals, such as contaminants and artifacts resulting from laboratory processing and background contamination in the reagents, were also identified in the blank control samples as well as the sludge samples. / Master of Science

The purpose of this investigation was to determine what effect agitation had upon the biochemical oxygen demand of sewage. In order to determine the effect of agitation, the composition of the sewage, the seed source, the temperature and the dilutions were held constant. / Master of Science

Conditioning studies were conducted on several water and wastewater sludges using polymers to determine the effect of high-intensity mixing on floc formation and breakup. Mechanisms acting in particle coagulation were also investigated. A rapid mixing apparatus was used in conditioning the sludge to simulate the high velocity gradients encountered in most dewatering equipment. Anionic and cationic polymers of varying molecular weights and an inorganic coagulant were chosen as the conditioning agents. Dewatering rates were measured by the capillary suction time (CST) apparatus. The effect of rapid mixing on the polymer efficiency was evaluated by premixing the polymer, using the same mixing apparatus, prior to applying it to condition the sludge. Data analyses revealed the great impact the primary floc breakup has on the sludge dewatering rate, although this was shown to be dependent on the nature of the sludge particles. Some minor changes were imparted to the polymer chains by intense mixing but there was no evidence that particle polymer bonds were fractured. The mechanisms of coagulation were observed to be related to sludge type. Overall, successful conditioning of sludges by polymers requires a proper determination of the sludge characteristics, a correct choice of polymer type and dose, and a knowledge of the mixing intensities. / Master of Science

The operation of three continuous flow units as modified activated sludge models using mean cell residence time as a principal operational parameter has led to the following conclusions: 1. Lower mean cell residence times result in higher phosphorus removal efficiencies in biological reactors. 2. Higher mean solids residence times result in higher phosphorus removal efficiencies in strictly chemical reactors. 3. Calcium-phosphate precipitation can occur in continuous flow reactors in a normal activated sludge pH range (7.5-8.5) given sufficient Ca++ concentrations. 4. Calcium-phosphate precipitation can occur in the activated sludge process without hindering COO removal efficiency. 5. The phosphorus sludge content only exceeded the one to two percent range in the biochemical and chemical units, where phosphorus precipitation was the predominate phosphorus removal mechanism. 6. The anaerobiosis and acid stripping procedure, as used in this investigation, is not effective in enhancing either a biological or chemical unit's ability to remove phosphorus. / Master of Science

The effects of coagulation pH and influent turbidity on aluminum and ferric hydroxide sludge macro-and micro-properties were investigated. To reduce the number of variables, sludges were produced under specific operating conditions in a 400 L/day continuous-flow pilot-plant. The effluent turbidity was monitored to evaluate process modifications. Sludge thickening and dewatering characteristics improved with reductions in the coagulation pH, increases in the influent turbidity levels, and/or reductions in the coagulant dose/influent turbidity ratio. Sludge floc/ aggregate density was the dominant sludge micro-property; sludges with superior thickening and dewatering characteristics were composed of higher density flocs/aggregates. A trade-off appeared to exist between improved sludge characteristics and effluent quality; however, verification will require additional research. / M.S.

The objective of this research was to determine whether or not variations in dissolved oxygen concentration above the critical dissolved oxygen concentration affect the kinetic coefficient and settleability of activated sludge. Synthetic substrate loadings of 0.25, 0.50, 0.75 were applied to bench scale activated sludge reactors with average mixed liquor volatile suspended solids concentrations of 2000 mg/1. The substrate removal rate coefficient, oxygen uptake coefficients, yield coefficients, and sludge settling properties were evaluated at dissolved oxygen concentrations of 2, 4, 8, and 10 mg/l. The kinetic coefficients were different at each dissolved oxygen concentration investigated but the differences could not be correlated with dissolved oxygen concentration variations. Instead, the variations in the coefficients appeared to be distributed in a random manner due to inaccurate test methods and fluctuating environmental conditions. Sludge settling properties as measured by the sludge volume index and the initial settling velocity were independent of dissolved oxygen concentration. The results of the study indicated dissolved oxygen concentration has no noticeable effect upon the kinetic coefficients and sludge settleability in activated sludge systems operated at loading levels and solids concentrations similar to the ones employed in this study. / Master of Science

The problems of sludge handling and disposal have significantly increased in the past decade because of more stringent discharge limits which create more disposable sludges and because regulations have been enacted which control the ultimate disposal of sludge residues. These problems have resulted in a need for producing sludges with both good dewatering characteristics and low water content so as to minimize the ultimate volume of disposal solids. Because of the need for more information concerning sludge dewatering this project was undertaken. The objectives of this study were to quantify the physical properties of sludges following chemical conditioning by a variety of conditioning chemicals. Water and wastewater sludge samples from full-scale Blacksburg water and wastewater treatment plants were used. The iron sludge was made in the laboratory. Each one of these samples was subjected to dewatering studies using laboratory-scale vacuum filtration equipment and sand drying beds. This study indicated that the best conditioner for activated sludge is ferric chloride. Addition of ten percent ferric chloride (on dry solids basis) enhanced the dewatering process and slightly increased the shear strength. Polymer was also an excellent conditioner for activated sludge. A polymer dose of 0.6 percent on a dry solids basis increased the shear strength slightly and increased the dewatering rate of activated sludge. The increase in solids concentration of activated sludge conditioned with polymer was smaller than that by conditioning with ferric chloride. Since the volume of sludge to be disposed has an impact on economics, polymer conditioning might be preferred over ferric chloride conditioning. Lime conditioning of activated sludge appeared to be useless. Conditioning with a mixture of 15 percent lime and 5 percent ferric chloride on dry solids basis did not improve the dewatering rate of activated sludge but conditioning with 20 and 25 percent lime and 5 percent ferric chloride for each mixture appeared to modestly improve the dewatering rate and greatly increase the shear strength of activated sludge. However, conditioning with mixture of lime and ferric chloride appears to be unreasonable when ten percent ferric chloride alone can produce a better-conditioned sludge. Polymer appeared to be an excellent conditioner for alum and iron sludges. / Master of Science

The technical and economical problems associated with sludge handling and disposal have significantly increased in the past years due to: (1) the introduction of more stringent water and air pollution regulations, often requiring the use of processes that produce large quantities of sludge as by-products; and (2) the development of regulations stipulating the means of ultimate disposal of sludge residues. These problems have resulted in a need for producing sludges with both good dewatering characteristics and low water content so as to minimize the ultimate volume of solids which must be disposed of. Recognizing the need for further work in this area of research, the objectives of this study were to examine the fundamental parameters which affect sludge dewatering characteristics. Included in this investigation were an analysis of both sludge dewatering and sludge handling characteristics. Parameters of interest were floe size, shape, and density, sludge viscosity and shear strength, and floc compressibility. The experimental investigation involved the collection of both water and wastewater sludge samples from full-scale treatment plants in the Commonwealth of Virginia. These samples were analyzed for each of the parameters previously mentioned; in addition, each was subjected to dewatering studies using laboratory-scale vacuum filtration, sanbed, and filter press equipment. The experimental results showed clearly that particle size distribution was a key parameter for describing the response of sludges to each of the dewatering methods utilized. For biological sludges, other factors such as biopolymer content were felt to have a major effect on dewatering characteristics. Sludge floc density was shown to have a direct correlation to the ultimate solids concentration obtained by vacuum filtration. Sludge handleability was conveniently evaluated through the use of the standard Atterburg liquid limit test procedure. Finally, the use of high-pressure filtration was found to provide much more appropriate information regarding water content than the centrifugation method proposed by Vesilind (1979). / Master of Science

Bench scale activated sludge reactors were acclimated to dextrose and then to low levels of pentachlorophenol. The metabolic activity of activated sludge was evaluated by its specific rate of dextrose uptake, Δs/Δt/X (measured by COD removal). Depression of the specific uptake rate, resulting from batch experiments in which the activated sludges were spiked with priority pollutants, indicated the relative inhibition caused by that toxin dosage. This study intended to determine if: (1) acclimation to low levels of PCP would provide any protection to the biomass against detrimental effects of higher shock loads of pentachlorophenol; (2) PCP-acclimation would decrease the inhibitory effect of related priority pollutants; (3) PCP would be consistently and efficiently degraded in the reactors. The practicality of this study was twofold. First, to determine the feasibility of introducing small concentrations of a toxin to the biological system of a treatment facility in order to gain protection against shock loads of that and related toxic chemicals. Secondly, to develop a rapid and easy method for evaluating the effects of a chemical load on activated sludge. The procedure was found to be applicable and it showed that acclimation of activated sludge to PCP provided protection against shock loads of pentachlorophenol as well as phenol, 4-nitrophenol, 2-chlorophenol, and 2,4,6-trichlorophenol. Gas chromatography analysis showed very little disappearance of PCP in the 1 mg PCP/L reactor; however, in the 15 mg PCP/L reactor, the penta concentration decreased to virtually zero for about a week and then it began to gradually increase. / Master of Science

This research effort involved the application of indirect- and direct-contact, freeze-thaw conditioning techniques for improving the dewatering characteristics of both wastewater and water treatment sludges. Sludges tested included waste activated sludge, primary sewage sludge, waste activated/primary sewage sludge mixtures and alum sludge. The direct-freeze methods examined were the use of a secondary refrigerant (butane) evaporated in the sludge and the use of gas hydrate or clathrate formation by addition of Freon 12 under appropriate temperature and pressure conditions. Sludges were also frozen solid using indirect freezing methods, thawed and tested for comparative purposes. Particle size distribution and floc density measurements were used to determine changes in particle characteristics; specific resistance values and dewatered dry solids concentration were used to assess dewatering characteristics. Results of direct- and indirect-contact, freeze-thaw conditioning were compared to the effects of polymer conditioning. The results indicated that direct-freeze methods do not appear technically or economically competitive with currently accepted conditioning methods. The superior results obtained with the indirect-contact, freeze-thaw process when compared to the direct-contact processes suggested that the extent and rate of freezing may greatly influence the particle characteristics of the conditioned sludge, and thus its dewatering characteristics. / Ph. D.