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

Several available methods of measuring sludge bound water content in the laboratory were examined. The effect of polymer conditioning on the bound water content of biological sludge samples was measured using the dilatometric method. The effects of mechanical dewatering on the bound water content of biological sludge samples and on chemical sludge samples was measured using the same method. The controlled drying method was used to measure the effect of polymer conditioning and mechanical dewatering on the chemically bound water fraction. The relationship between bound water content and cake solids concentration was examined, as well as the relationship between cake solids concentration and sludge bulk density. The role of apparent sludge floc density was examined. The dilatometric method was found to be the most accurate and most convenient method for measuring the chemically bound water fraction. Polymer conditioning was found to release significant volumes of bound water. Further bound water release was produced by mechanical dewatering. The amount of bound water released increased with the degree of mechanical dewatering pressure applied. The chemically bound water fraction was not affected by polymer conditioning or mechanical dewatering. A reduction in bound water brought about a corresponding increase in cake solids concentration. Sludge bulk density increased with cake solids concentration. Apparent sludge floc density of the unconditioned, underwatered sludge sample was predictive of ultimate dewatering performance in many cases. / Master of Science / incomplete_metadata

A high strength industrial wastewater was treated in a bench-scale activated sludge reactor modified by the addition of biomass support media to the aeration tank. Two experimental biomass support systems (BSS) and one conventional activated sludge system were operated at different mean cell retention times (mixed liquor MCRTs). Three separate media were tested, NOR-PAC and Linpor used as free-floating supports, and BIONET used as a fixed-bed support. The effect of the media on substrate and oxygen utilization, and solid-liquid separation was investigated. Substantial attached growth did not occur on the NORPAC and BIONET media. The attached biomass concentration in the Linpor systems increased with increased media concentration. The ratio of attached volatile solids to total volatile solids (attached volatile solids + MLVSS) decreased with increased mixed liquor MCRT. The advantages of the BSS would occur at low mixed liquor MCRTs. Both the BSS and control systems achieved greater than 94% COD removal and substrate utilization rates (mg/h) did not significantly change during the experiments. Therefore, both systems were substrate limited. The substrate limitations caused decreased oxygen uptake rates of the attached biomass with increased mixed liquor MCRT. The sludge settling of the Linpor systems was a function of mixed liquor MCRT, filamentous upsets, and the presence of the media. Enhanced settling was observed in the Linpor system only at the 3 day mixed liquor MCRT experiment. / Master of Science

The effects of lime and sodium hydroxide on gas production from stored sewage sludge were examined. The impact of calcium on gas production was also investigated. The rate and volume of gas production and change in pH over time were monitored in all the reactors in an effort to study the relationship between chemical dose, pH, and gas production. The duration of inhibition of gas production increased with the lime dose. Gas production was initiated only after the pH in the reactors decreased to near 8.0. A decrease in pH was observed in all the lime dosed reactors with an initial pH less than 12.0. An initial pH greater than 12.0 was required to completely arrest organic acid and gas production. For the sludge used in this study, a quick lime dose of 0.36 Ib/lb of dry solids, which elevated the pH to higher than 12.0, was required for complete inhibition of gas production. Gas production and pH patterns observed in sodium hydroxide dosed reactors were similar to those in lime dosed reactors. A decrease in pH by nearly 2 pH units was observed in these reactors after calcium chloride addition. This was thought to be primarily due to the precipitation of calcium carbonate. Gas production after elutriation was observed in all the reactors with an initial pH less than 11.5. The volume of gas produced after elutriation decreased with increase in initial pH. An NaOH (19N) dose of 0.29 Ib/Ib of dry solids was required for permanent prevention of gas production. Calcium alone was not capable of arresting gas production but it reduced the total gas production in the reactors with a pH less than 7.5. At pH values greater than 7.5, calcium had little effect on gas production. / Master of Science

An essential step in producing "drinking" water is to precipitate the suspended and dissolved colloids through the addition of flocculents such as lime, ferric chloride, aluminium sulphate and/or poly-electrolytes. The by-product of this process is termed water treatment sludge (WTS) and contains mainly silt, clay and some organic matter. Previously this material was disposed of in landfill but more recently, alternative methods for its disposal are being evaluated. A potential disposal option is land treatment. In this system of waste disposal the inherent properties of the soil are used to assimilate the waste. Although the effect of the land disposal of WTS on soil chemical quality is gaining increasing research attention, few studies have investigated the effects on soil physical quality. This study was originally commissioned by a local water utility to evaluate the effects of the land disposal of sludge produced at their works, on soil quality. At this plant organic polymers are used to both flocculate the material and to thicken the sludge in the water recovery process. Fresh sludge has a consistence approaching that of slurry but dries to angular shaped aggregates of extremely high strength. Nevertheless, sludge aggregates comprise a network of micro-pores and channels and are therefore porous. Because of these properties, the potential use of WTS as a soil conditioner was considered.. Since lime, gypsum and polyacrylamide are wellrecognised soil conditioners, these were included as reference treatments in the study. Two field trials (Brookdale and Ukulinga) and laboratory experiments were designed to investigate the influence of WTS on soil in terms of water retention, hydraulic conductivity, evaporation, aeration, aggregation and strength. Seven rates of WTS are represented at the . Brookdale trial but research efforts were concentrated on the 0, 80, 320 and 1280 Mg ha' treatments. WTS was also applied as a mulch (without incorporation into the soil) at the 320, 640 and 1280 Mg ha" level. Gypsum was applied at rates of 5 and 10 Mg ha", lime at 2 and 10 Mg ha' and anionic polyacrylamide at 15 and 30 kg ha'. At the Ukulinga trial, WTS was mixed with the upper 0.2 m of the soil at rates of 0, 80, 320 and 1280 Mgha'. Only the high rates of gypsum, lime and anionic polyacrylamide being tested at the Brookdale trial are represented at the Ukulinga trial. All treatments in this study were maintained fallow. The laboratory study features an additional two soils to those from the field experiments, chosen to produce a range in clay contents. WTS influenced several soil physical properties. Soil bulk density decreased following the addition of sludge to soil. This caused an increase in porosity (particularly macro-porosity) and therefore water retained at saturation, but only of statistical significance at the 1280 Mg ha" level. Equally an increase in water retention at the wilting point (-1500 kPa matric potential) also occurred, owing to the high microporosity of sludge aggregates. Despite these effects very little change in both the plant available and readily available water content occurred. Neither, gypsum nor lime caused any significant change in water retention. Aslight improvement was noted on the polyacrylamide treatment at the Brookdale site but this effect did not persist for very long after the trial was established. Although in situ field measurements were influenced strongly by natural spatial variability, WTScaused a marked increase in the saturated hydraulic conductivity (Ks). The reasons for this relate to the higher porosity and the inherently stable nature of the sludge aggregates, which imparts a more open structure to the soil and reduces the extent of pore blockage. This finding was corroborated in a laboratory study in which strong positive correlations between sludge content and Ks was found. The water retention curve and saturated hydraulic conductivity was used to predict the unsaturated hydraulic conductivity function (Kw)using the RETe computer model of van Genuchten et al., 1991. The results showed a decrease in Kw on the sludgeamended treatments the extent of which increased with sludge content. This finding was tested in an evaporation study conducted under controlled environmental conditions. More water was conserved on the sludge-amended treatments than the control, because of its lower Kw. The application of the sludge as a mulch was more effective in conserving water than incorporating the sludge with soil. The air-filled porosity at field capacity (-10 kPa matric potential) of the sludge-amended soil remained within a favourable aeration range of 10-15%, which suggests that aeration should not be a limiting factor for plant growth. Air-permeability nevertheless improved substantially. Attempts at using the size distribution of dry soil aggregates to evaluate the influence of the sludge on aggregation proved unsuccessful. Saturated soil paste extracts for selected soil depths beneath the mulch layers at the Brookdale trial, nevertheless, showed significant increases in Ca2+ and Mt+ concentrations, which is encouraging from a soil stability perspective. Due to the inherently strongly aggregated nature of this soil, no meaningful change in aggregate stability, however, was measured. Significant improvements in soil stability were, nevertheless, found when fresh sludge was mixed with soil. If the sludge is not allowed to dry fully beforehand the polymer that it contains remains active and available for bonding of the soil particles together. Upon drying, these polymers become irreversibly attached to the soil substrate and win not become reactivated even upon re-wetting of the soil. This also explains why sludge aggregates found below only a few centimetres of the soil surface maintained their strongly aggregated nature. This suggests that although WTS consists of mainly silt and clay, the risk of this constituent fraction becoming released and clogging water conductive soil pores are, at present, low. Despite the high strength of the sludge aggregates the penetrometer soil . strength (PSS)within the tilled layer was non-significantly different from the control treatment. Below the tilled layer, however, the PSS on the sludge-amended treatments were lower owing mainly to wetter soil conditions. The research completed to date suggests that land treatment as an environmentally acceptable disposal option for water treatment sludge shows promise since soil conditions tend to be improved. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2001