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

Colloidal gas aphrons (CGAs) are typically a 55 to 70% dispersion of 50 +/- 40 micron-sized air bubbles in water. Generation of CGAs has proceeded to allow continuous production of up to 80 liters per minute. Previous laboratory testing has demonstrated the effectiveness of CGA flotation for removing fine particulates, such as coal fines, food wastes, phosphate slimes, algae, as well as oils from contaminated solutions. This study involved comparing CGA flotation versus dissolved air flotation (DAF) in a wastewater treatment sludge media. Initially, laboratory tests were conducted to see if field testing was warranted, and to screen possible surfactant chemicals to be used in any such field testing. Three surfactants were tested individually; sodium dodecylbenzene sulfonate (NaDBS), alkyl dimethyl benzyl ammonium chloride (BTC-824), and cetyl pyridinium chloride (CPC). From the laboratory results and observations, it appeared that the CGA flotation tests using both NaDBS and CPC were more effective than DAF. Tests using BTC-824 were inconsistent due to bubble instability. Overall, the laboratory results and observations seemed encouraging, and field testing was initiated. Next, four field tests were conducted at Pepper's Ferry Regional Wastewater Treatment Authority (PFRWTA) in which CGA flotation was used to try and enhance the performance of a DAF system. Tests were conducted by adding CGAs directly into the sludge influent line of PFRWTA's DAF system. Although CPC gave the best laboratory results, NaDBS was used in the field testing due to its availability and cost. Results from all four field tests showed that a more concentrated effluent sludge was obtained when CGA flotation was used to enhance DAF. The field test results for the raffinates were inconclusive. Overall, the results from the field testing seem promising. From these tests, CGA flotation appears to be an improvement over DAF in producing more concentrated effluent sludges when tested in a wastewater treatment sludge media. CGA flotation could enhance and/or possibly replace DAF in certain industrial applications. / Master of Science

The effects of in-basin storage of sludge on the iron, manganese, and TOC removal of water treatment plant (WTP) clarifiers and on the dewatering characteristics of sludge were examined. The use of chlorine dioxide as a preoxidant to retard observed detrimental effects was also investigated. Sludge samples that were stored over a period of 120 days were found to release up to ten times the original supernatant concentration of iron and manganese from the sludge into the overlying supernatant liquor when sludge redox potential values decreased below +100 mV. Organic carbon also increased in the supernatant but to a lesser extent. Sludge dewatering characteristics as measured by specific resistance and capillary suction time were found to improve when sludge redox potential readings remained over 100 mV but varied greatly when readings were below this level. Field monitoring and sampling of the clarifiers at Lee Hall WTP and Harwood's Mill WTP from April to July showed that the removal efficiencies of the clarifiers was not related to in-basin sludge storage. This conflicted with a later portion of the study and was thought to be due to the lack of standardized sampling techniques. The final phase of the investigation dealt with the use of chlorine dioxide to retard the negative effects of in-basin storage of sludge. Sludge accumulation in clarifiers resulted in decreased iron and manganese removal efficiencies when chlorine dioxide was not used. Addition of chlorine dioxide improved the iron and manganese removal efficiencies of the clarifiers. Sludge dewatering characteristics were found to improve with the use of chlorine dioxide as a preoxidant. / Master of Science

The disposal of pulp and paper industry sludge has become a significant problem in recent years. Increasing costs and regulatory constraints associated with landfilling and incineration have caused the industry to look for viable alternatives for the disposal of their wastes. In September of 1988, a nutrient-enriched, combined (primary/secondary) paper mill sludge was surface applied to a 4-year-old and a 6-year-old red pine (Pinus resinosa Ait.) plantation in central Wisconsin at rates of 10, 20 and 40 dry Mg ha⁻¹. Red pines measured 10 and 22 months following sludge application did not show a significant volume growth response to increasing sludge rates. Nonetheless, some biologically significant trends did occur following the first growing season, namely, diameter growth in the younger plantation decreased by 27%, 36% and 39% with increasing rates of sludge application. Reductions in height, crown width and volume growth were seen as well. Increased absorption of moisture among the heavier application rates coupled with already dry conditions is believed to be the cause of the growth reduction. Tree growth in the older plantation was more variable, possibly reflecting the greater degree of establishment and reduced susceptibility to moisture deficits. By the end of the second growing season, there was some indication that the trees were responding to sludge application in both plantations, with the greatest growth occurring among the 40 Mg ha TM treatment plots for all growth parameters. Red pine fascicles examined 12 months following sludge application showed significant increases in foliar concentrations of N, P, Ca, Mg and S with increasing rate of sludge application. This corresponded with a significant increase in fascicle biomass relative to application rate in the younger plantation. Fascicle biomass was not affected by sludge application in the older plantation. Analysis of nutrient response, in general, indicated luxury consumption taking place among all nutrients with the exception of boron, which decreased in foliar concentration, to low or deficient levels, and content in sludge amended plots in both plantations. Analysis for nutrient concentrations and dry matter production of Carex spp. (sedge), the predominant herbaceous understory component, showed increasing foliar N levels with sludge application 21 months following treatment in above-ground tissue, with a corresponding increase in above-ground biomass relative to controls of 22%, 33% and 85% among the 10, 20 and 40 Mg/ha treatments, respectively. An assessment of woody vegetation using a competing vegetation assessment system (CVAS) showed essentially no response by hardwood competition to sludge application for either study site. Total weed control, consisting of 0.140 kg ha⁻¹ a.i. of Oust™ and 1.3 kg ha⁻¹ a.i. of Garlon™ was performed in August of 1989 and resulted in significantly reduced coverage of herbaceous and woody competing vegetation in both plantations the following growing season. Analysis of red pine volume growth between weed control treatments did not show a significant response relative to sludge application for either plantation one year following herbicide application. Additionally, there was evidence of reduced weed control efficacy with increasing sludge application rate in the younger plantation. This suggests that weed control efficacy may be greater if weed control is performed prior to sludge application; however, given the apparent sequestering ability of the herbaceous vegetation, removal of this component may contribute to elevated levels of undesirable leachates in soilwater and groundwater. / 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

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

Lime-stabilized and chemically-fixed sludges have been inadequately characterized for utilization as amendments to acid soils. Laboratory incubation studies were employed to evaluate calcium carbonate equivalence (CCE) and nitrogen (N) mineralization rates of these sludges when applied to three acid Typic Hapludults from Virginia. Greenhouse studies were conducted to evaluate the effect of increasing sludge application rates on growth of corn. The CCE of the lime-stabilized and chemically-fixed sludges were 30. 9 and 58.1%, respectively. Application of sludges to soils resulted in rapid neutralization of soil acidity. Added organic-N was mineralized at an average rate of 32% in surface soils. Based on N mineralization, application rates of lime-stabilized and chemically-fixed sludges will be limited by CCE for most soils. Corn yields on the Glenelg and Tatum soils were improved by addition of the sludges and remained within 95% of maximum at 118 and 160%, respectively, of the rate predicted to raise soil pH to 6.5. Zinc deficiencies were induced at the highest sludge application rates. Corn yields were higher when soils were amended with lime-stabilized or chemically-fixed sludges than when amended with CaC03 because the sludges contained Zn and other nutrients. Lime-stabilized and chemically-fixed sludges are good sources of lime which will supply N at the rate of approximately 32% of applied organic-N but overapplication of these sludges to meet the N needs of corn will probably result in Zn deficiency on all but the most acid soils. / M.S.

Experiments were performed on samples of alum and activated sludges to determine if these sludges, conditioned with polymers under high-stress, would achieve favorable dewatering rates. Tests were conducted using a variable high speed mixer with root mean square velocity gradient (G) values ranging from 560 - 2000 sec⁻¹ with both anionic and cationic high molecular weight polymers. Capillary suction time (CST) was used to measure relative changes in dewatering rates. Results indicated that readily dewatered sludges can be obtained when subjected to high-stress mixing conditions. The most significant parameters governing high-stress conditioning were determined to be polymer dose and total mixing energy input (Gt). It was discovered that as Gt increases, polymer dose requirements increase as well, so as to maintain an optimum dewatering rate. Also, the activated sludges tested in the study appear to be resistant to the effects of polymer overdosing. / M.S.

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