Pretreatment of primary sludge, waste activated sludge, and comingled sludges has become of substantial interest for the improvement of the rate limiting hydrolysis step during anaerobic digestion. As primary sludges are already easily degraded, waste activated sludges provide the most noticeable improvements in anaerobic digestion (AD) as a result of sludge pretreatment (SPT). A vast literature and theory review was conducted to establish high-potential treatment and result ranges. The average wastewater compositions for total chemical oxygen demand (COD) and total solids (TS) were 16-43 and 13-40 g/L, respectively. Sludge pretreatment percent solids solubilisation ranges for all common SPT technologies were 13-42% for both particulate COD and total suspended solids (TSS). Subsequent anaerobic digestion enhancement ranges were percent reductions in total COD and TS of 24-55 and 22-46%, respectively, as well as biogas production increases of 9-43%. The ranges shown here were fairly representative of those observed for all SPTs. Additional SPT technology information for full-scale design was also gathered. A MS Excel spreadsheet wastewater treatment plant model (referred to herein as PretrAD) capable of comparing control and SPT incorporation scenarios was created. The PretrAD output was verified against a third party commercial model. PretrAD allows the user to input data on performance of all unit processes found in a typical biotreatment wastewater treatment plant (WWTP). Various return flow paths and other attributes of a WWTP can be specified and provide versatility and comprehensiveness. A database of typical performance data for all unit processes was compiled and used in PretrAD and for comparing performance of WWTPs with and without SPT. The stirred ball mill, high pressure homogenizer, and ultrasound technologies were mechanical processes with sufficient comparable data for inclusion in PretrAD. Conventional heating and microwave heating technologies were included as thermal processes. Alkaline and ozone technologies were included as chemical processes. Finally, the common conventional heating + alkaline (thermochemical) technology was also included alongside a purely financial assessment of a proposed microwave heating + alkaline technology incorporation scenarios. PretrAD was then used to evaluate treatment benefits by varying a number of performance parameters with and without SPT. Operating parameters that were changed were normal and low heat recoveries at the anaerobic digester, normal and doubled sludge disposal distances, low-peak influent flow regimes, and low to high SPT energy demands (evaluated with identical solubilisation results). Control and SPT scenarios were performed for all variables and both mesophilic and thermophilic AD. Overall net WWTP treatment costs based on energy inputs and recoveries along with chemical inputs were compared for the various scenarios. It was found that an all average influent flow regime represented (within 5%) all annual flow regime combinations of low, average, and high flows and their associated quality variations. Following the basic comparisons of control and SPT scenarios, additional runs were conducted with increases of 25 and 50% for the energy demands of each SPT. Mesophilic AD scenarios always had lower final costs than thermophilic AD scenarios under identical treatment parameters. Practical (cost-effective) and impractical (higher than control costs) scenarios were found for all SPTs except thermal and thermochemical processes. Thermal and thermochemical processes were always practic31 and always impractical, respectively, when compared to control scenarios using identical conditions. When different scenario conditions were compared, both thermal SPTs were deemed impractical when high cost results were compared to low cost results. Solids loadings and heat recoveries were the most cost-influential variables of PretrAD. Other important qualitative results were not incorporated into the evaluation. They include but are not limited to dewatering improvements, pathogen reduction, anaerobic digester vessel size reduction, and hydraulic residence time reductions for the anaerobic digester. Inclusion of these parameters could render some SPTs practical for scenarios where they were deemed impractical on a pure cost of treatment basis. Furthermore, full-scale incorporation drawbacks such as additional unit costs, operation and maintenance demands, and actual throughput capacities could render some practical scenarios impractical. The constructed PretrAD model has been proven effective for the rapid determination of treatment plant costs related to SPT incorporation. A tool such as this is vital for the site-specific analysis of SPT technologies.

The use of membrane processes in drinking water treatment has increased exponentially in the last few years. However, one of the shortcomings that hinders their wider application is the propensity of membranes to become fouled, causing the permeate flux to decrease with time. One of the main membrane foulants is the natural organic matter (NOM) present in water sources. Membrane characteristics and performance are affected by membrane preparation conditions. The objective of this thesis was to investigate the impact of hydrophobic surface modifying macromolecule (SMM) addition and other manufacturing conditions on the membrane characteristics and performance of polyethersulfone (PES) membranes. As it was necessary to test numerous membrane coupons prepared under many different conditions, during the first stage of this study a membrane test protocol was established. Small test cells gave very similar results to those produced by a larger test cell, which is recommended by USEPA for membrane testing. The test protocol was relatively short in duration and required a small amount of test solution. Moreover, as membrane compaction rate depends on the material, it was important to incorporate a precompaction step into the test protocol in order to quantify the contribution of membrane compaction when fouling was studied. The second stage of the study evaluated the impact of different membrane preparation conditions (i.e., solvent evaporation time and PES concentration) and the impact of three different SMM formulations. The three SMMs differed only in the polyol used in their synthesis. SMM41, the most miscible SMM, proved to be the most promising SMM. In general, the increase of PES concentration and/or evaporation time, together with the surface modification, produced tighter membranes with improved TOC removals, decreased NOM deposition on top of the membranes and decreased flux reduction, but also resulted in a reduced permeation rate. The best SMM41-modified membranes performed as well as their unmodified counterparts in terms of pure water permeation rate, TOC removal, and final flux. SMM41 modification significantly reduced the amount of NOM deposited on the membrane surface, and in general reduced the percentage of flux reduction. Thus, the effect of surface modification on the membrane performance was positive but marginal. Membranes prepared with PVP had higher porosities and consequently, larger permeation rates than the membranes prepared without PVP, and similar TOC removals. In this case the effect of the SMM41-modification was statistically insignificant. When different fractions of NOM were used as feed solutions a significant effect was observed for all the response variables. Low-molecular-weight NOM, as that present in most groundwaters and coagulated surface waters, caused less fouling, having a higher permeate flux at the end of the experiment; however, smaller TOC removals were observed. In general, there is a compromise between the TOC removal that the membrane can achieve and the permeation rate. Higher TOC removal is achieved by membranes with smaller permeation rate.

Improvement of biodegradability of waste activated sludge (WAS) depends on enhanced disintegration of the floc structure of sludge and increasing the accessibility to both intracellular (within the microbial cell) and extracellular (within the polymeric network) materials before WAS is sent to anaerobic digesters. This study proposes microwave (MW) technology as a new and an alternative pretreatment method to disintegrate the floc structure of secondary sludge, to enhance the hydrolysis and to improve the anaerobic digestion of WAS in comparison to existing pretreatment methods such as, chemical, mechanical and conventional heating (CH) techniques. In the first stage of the study, the effects of MW pretreatment on disintegration and hydrolysis of WAS by soluble chemical oxygen demand (COD), soluble protein, soluble sugar and nucleic acid leakage detection experiments were investigated. The effects of three variables [MW temperature (T), MW intensity (I), WAS concentration (C)] and the effects of four variables [T, I, C and volume percentage of WAS pretreated (PT)] were investigated on WAS solubilization and biogas production in two multilevel factorial statistical designs containing 24 solubilization runs and 54 mesophilic batch reactors, respectively. In a low temperature range (50-96°C) using a household type (1250 W, 2450 MHz) MW oven, pretreated WAS samples resulted in 3.6 +/- 0.6 and 3.2 +/- 0.1 fold increases in soluble COD/total COD ratios at high [5.4% total solid (TS), w/w] and low (1.4% TS, w/w) sludge concentrations, respectively. WAS, pretreated to 96°C, produced the greatest improvement in biogas production with 15 +/- 0.5 and 20 +/- 0.3% increases over the controls (unpretreated) after 19 d of digestion at low and high WAS concentrations. In the second stage of the study, two different pretreatment temperatures (50 and 96°C) were further tested in a total of 10 semi-continuous digesters at sludge retention times (SRTs) of 5, 10 and 20 d. Digesters using CH WAS were also run to investigate thermal and athermal effects of MW pretreatment. In general, incremental increases in total solid (TS), volatile solids (VS) and total COD removal efficiency of pretreated digesters compared to controls dramatically increased as SRT was gradually shortened from 20 to 10 to 5 d. WAS pretreated to 96°C by MW and CH achieved 29 and 32% higher TS and 23 and 26% higher VS removal efficiencies compared to controls at SRT of 5 d, while similar reactors at SRT of 20 d had only 16% higher TS and 11 and 12% higher VS removals than those of controls, respectively. Ultrafiltration (UF) was also used to characterize the soluble molecular weight (Mw) distributions of control, CH and MW irradiated WAS at 96°C. Soluble CODs of CH and MW irradiated WAS were 361 +/- 45 and 143 +/- 34% higher and resulted in 475 +/- 3 and 211 +/- 2% higher cumulative biogas productions relative to the control at the end of 23 days of mesophilic batch anaerobic digestion, respectively. Depending on the Mw fraction, the range of substrate volumetric utilization rate increases from anaerobic digesters was between 94-184% for the CH and 26-113% for the MW compared to the control for the first 9 days of the digestion. Digesters treating high Mw materials (Mw > 300 kDa) resulted in smaller first-order biodegradation rate constants, k, indicating that microorganisms require a longer time to utilize high Mw fractions which are most likely the cell wall fragments and exopolymers. MW studies under the boiling point (100°C at 1 atm) have promised a significant potential to disintegrate the floc structure and to enhance the hydrolysis and biodegradability of WAS in full-scale digesters.

One of the problems associated with the disposal of solid wastes in landfills, particularly in high precipitation areas, is the pollution caused by the production of the often highly contaminated leachate. This study was initiated to investigate the treatability of a low-strength municipal landfill leachate using aerobic digestion followed by activated carbon polishing, so that the most cost effective treatment system could be determined. Sludge desorption and leachate toxicity assessment were also included in the study. The aerated lagoon process alone was very effective in treating the leachate to a quality that is nearly acceptable for discharge to a receiving water. Only SO₄ and Fe in the settled effluent significantly exceeded the local requlatory standards for specific discharges. Carbon adsorption greatly improved the settled effluent quality in terms of color, Fe and COD. However, the addition of this polishing process for combined treatment may not be cost effective. For an influent COD of 1,600 mg/1 and with MLVSS concentrations ranging between 360 and 560 mg/1, the settled effluent COD removal increased from 82.6% to as high as 90.1% when 9C was increased from 2 to 10 days. For the corresponding influent BOD5 of about 1,000 mg/1 and with θ[sub c] greater than 3 days, the BOD5 removal efficiencies averaged 99.1% and the settled effluent BOD5's were no greater than 10 mg/1. This indicates that the raw leachate can be almost completely biodegraded by aerobic digestion. The metal removal efficiency in aerobic treatment was greater than 95% for Fe and Mn, better than 90% for Zn and Pb, and about 80% for Al. Metals expected to be mainly or significantly removed by chemical precipitation due to pH change during treatment included Ca, Fe, Mn, Zn and Pb. Analysis of the kinetic parameters associated with the biological treatment indicated that the concentrations of pollutants, such as heavy metals, in the leachate were not great enough to cause significant inhibition of biological growth. It also showed that this leachate could very likely be added to a domestic sewage, in a high percentage, for aerobic treatment without producing adverse effects. From a treatment efficiency point of view, the optimum solids detention time was found to be 7 to 10 days for leachate BOD₅ ranging from 1,000 to 3,000 mg/1. However, since the predicted θ[sub c] for failure was 0.42 day at 22°C for a 1,000 mg/1 BOD₅ leachate, a θ[sub c] of 2 to 4 days seems possible in the field. On the other hand, the effects of winter temperature on BOD₅ removal and sludge settleability, as well as many other unknown factors on the overall biological treatment efficiency must be considered. It was, therefore, felt that a solids detention time of 5 days or more would be the more realistic approach for a full-scale treatment system, despite the fact that an economic analysis favored a shorter θ[sub c]. / Applied Science, Faculty of / Civil Engineering, Department of / Unknown

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Civil and Sanitary Engineering, 1935. / Vita. / Includes bibliographical references (leaf 102). / by Rolf Eliassen. / Sc.D.

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