Digitized by Kansas Correctional Industries

Com o objetivo de estudar a redução na geração de resíduos sólidos no processo por lodo ativado por meio de adição química, foi montada uma Estação de Tratamento Piloto na área do Centro Tecnológico de Hidráulica, situado dentro do Campus da Universidade de São Paulo, na cidade de São Paulo. A ETE Piloto é composta de dois sistemas em paralelo, e idênticos, de tratamento por lodo ativado convencional em mistura completa. A pesquisa foi realizada em três fases distintas e consecutivas. Em todas as três etapas, o primeiro sistema de tratamento da ETE Piloto (Sistema I) recebeu a adição do produto Dosfolat XS, com a intenção de verificar se esse provocaria realmente, a redução do lodo gerado, em comparação com o segundo sistema (Sistema II) que não recebeu Dosfolat XS. As três fases da pesquisa consistiram, respectivamente, na operação dos dois sistemas, em paralelo, durante 94, 79 e 133 dias efetivos, com alimentação de esgoto decantado na vazão de 5 m3/dia nas duas primeiras etapas e com esgoto bruto na vazão de 2m3/dia na fase final. Ao longo das três fases do experimento, foram verificadas as condições de sedimentabilidade, as concentrações de sólidos em suspensão totais e voláteis do lodo dos reatores biológicos, e as eficiências de remoção de DBO, DQO, Nitrogênio Total e Fósforo dos dois sistemas paralelos. Os resultados obtidos nessa pesquisa somente indicaram eficiência do produto Dosfolat XS na redução da geração de lodo no tratamento de esgoto por lodo ativado, em relação ao tratamento por lodo ativado sem a adição de Dosfolat XS. / Aiming to study the reduction in waste production in the activated sludge process, a Treatment Pilot Plant was built at Centro Tecnológico de Hidráulica, situated at the campus of Universidade de São Paulo, in São Paulo. The Pilot Plant was composed of two parallel and identical systems, that were operated in the conventional activated sludge process with complete mixing. This study was conducted in three different and successive phases. In each phase, the first system received addition of Dosfolat XS, in order to verify if this product would decrease the quantity of produced sludge, in comparison with the second system, which did not receive any addition. The three phases above mentioned were consisted in the operation of those two systems during 94, 79 and 133 effective days respectively. There was, in the first and second phases, primary effluent feeding at 5m3/day flow and, in the third phase, raw wastewater feeding at 2m3/day. During this three phase experiment, its several parameters were monitored: settleability parameters, total and volatile suspended solids concentration of the sludge in the biologic reactors, and the removal efficiency of BOD, COD, TKN and Phosphorus for those two parallel systems. The results of this study indicated only the efficiency of Dosfolat XS to decrease the quantity of produced sludge in wastewater treated by activated sludge process, in comparison with the activated sludge process without Dosfolat XS addition.

From June to November 2007, a microscopic analysis was conducted on the activated sludge from eleven selected wastewater treatment plants (WWTP's) belonging to the City of Cape Town. The primary objective was the identification of the dominant and secondary filamentous organisms. Other important criteria included were the floe character, diversity, filament index (Fl) and identification of the protozoan and metazoan communities. The operational data determined from routine analyses of the sludge, influent and effluent were used to assess the relationship of the filamentous population to wastewater characteristics and to compare this with previous findings. Fl values of >3 and dissolved sludge volume indices (DSVI's) of >150 were chosen as representing the possibility of bulking conditions being present. The five most prevalent dominant filaments were Type 0092, Type 1851, actinomycetes, Microthrix parvicella and Type 021N, being present in 74%, 31%, 22%, 17% and 14% of samples respectively. Type 0092 did not appear to be associated with bulking in any of the WWTP's, although it was often incidentally present as a co-dominant species when bulking conditions existed. All three WWTP's with the Modified Ludzack-Ettinger configuration harboured Type 1851 as the major dominant species, irrespective of whether the plants treated domestic or industrial effluent. Conditions suggestive of bulking were present in two of these WWTP's. Contrary to expectations, Type 1851 was often found as a dominant species where domestic waste was the primary influent. Type 021N and actinomycetes were strongly implicated when bulking occurred. The overgrowth of these filaments appeared to be related to factors such as nutrient deficiency (Type 021N) or the presence of large amounts of low molecular weight substances in the influent. Microthrix parvicella did not cause major bulking problems. There was a strong association between low levels of nitrates/nitrites in the clarifier supernatant and good phosphorous removal, irrespective of the configuration of the WWTP. The converse was also true. / Thesis ((M. Environmental Science))--North-West University, Potchefstroom Campus, 2009.

HT biomass sonicated at ES inputs < 56KJ/gTS decreased floc size by 41% and enhanced its metabolic activity by 50-250% compared to control. ES inputs >118 KJ/gTS caused HT biomass solubilization and irreversible loss of its metabolic activity and reflocculation ability. During continuous activated sludge processing (ASP) of real primary effluent the observed yield (Yobs) decreased by 20% compared to control ASP at SF (stress factor) of 1 (biomass exchanged without USPT). At SF of 0.5, 1 and 1.5 (biomass exchanged with USPT) the Yobs further decreased by 33, 25 and 44% respectively as compared to control. This indicated that combining biomass anoxic exposure with USPT enhanced sludge reduction by increasing microbial maintenance metabolism likely in combination with microbial flora shift in the ASP depending on SF.

Anaerobic membrane bioreactors may provide a sustainable technological solution for digestion of waste activated sludge due to their capacity to achieve substantial volatile solids (VS) destruction and positive energy balances with reduced digester volumes. However, membrane integrated anaerobic systems may have limitations that are imposed by membrane fouling and a decrease in biomass activity due to possible exposure of biomass to high shear conditions. This study characterised bioprocess and membrane performance under varying conditions, identified foulant type and origin and mechanism of fouling, and developed fouling control strategies by using low cross flow velocity and pressure anaerobic membrane systems. The study employed a pilot scale anaerobic digester integrated with negative and neutral tubular membranes; pilot and bench scale control digesters supported with bench scale filtration unit parametric studies. The membranes were polyvinylidene difluoride based with an average pore size of 0.02 micron and were operated at a constant cross flow velocity of 1 ms-1 and constant trans-membrane pressure of 30 kPa. Four operating conditions consisting of different combinations of HRT and SRT were evaluated. By integrating membranes into the digesters it was possible to simultaneously enhance digestion and increase throughput of the digesters without affecting its performance. The anaerobic membrane digester showed 48-49% volatile solids destruction at 30 days SRT under conventional and higher loadings of 1.2±0.4 and 2.1±0.6 kg COD m-3day-1. This was a 100% increase in performance compared to a control digester subjected to higher loading. This result was supported by the associated specific methane generation. The control digesters operated at a relatively higher SRT showed comparable VS destruction and gas generation to the anaerobic membrane running at a similar SRT. However the extra gas generated didn’t compensate heat required to maintain larger volume of the digester. In case of anaerobic membrane digesters due to the high rate feeding, increase biogas production and co-thickening, the energy balance increased by 144 and 200% under conventional and higher loading conditions respectively. Characterization of membrane performance showed that the average sustainable flux was 23.2±0.4 and 14.8±0.4 LMH during HRT-SRTs of 15-30 and 7-15 days respectively. The critical fluxes were in the range of 30-40, 16-17 and 20-22 LM-2H-1 during HRT-SRTs of 15-30, 7-30 and 7-15 days respectively. The decline in membrane performance at a higher loading was associated with the formation of cake layers on the membrane surface that led to reversible fouling. The additional decline in performance at extended SRT was attributed to irreversible fouling. The colloidal fraction of the sludge showed an overall higher fouling propensity during the long term pilot studies and short term filtration tests. The suspended solids fraction of the sludge showed a positive impact at concentration below 15 g/L but resulted in a decrease of membrane performance at higher concentrations. Further studies of foulant origin through a series of microscopic, membrane cleaning and sludge characterization studies showed that the colloidal proteins, soluble carbohydrates and inorganic materials such as iron, calcium and sulfur and their interaction to have a significant impact on membrane fouling. To control anaerobic membrane fouling by the digested sludge, integration of membrane relaxation techniques in the filtration cycle were found effective. By incorporating a unique relaxation technique to tubular membranes, it was possible to increase the sustainable flux to 29.2±1.8 and 34.5±2.5 LM-2H-1 for neutral and negative membranes during 15-30 HRT-SRT process condition. Addition of cationic polymers and sequential mechanical-citric acid membrane cleaning, that targeted both reversible and irreversible fouling was also found effective.

In this study, a laboratory-scale activated sludge reactor and a biotrickling filter were constructed to study the removal of methyl tert-butyl ether (MTBE) from air vented from contaminated sites. The activated sludge tank (0.4 m¡Ñ0.4 m cross-sectional area, 3.0 m height, and 480 L total volume) was made by acrylic resin. A mixed liquor suspended solids (MLSS) concentration of 2000-3000 mg/L was maintained in the experimental mixed liquor and the sludge was acclimated for 30 days under selected conditions of a Food to Microorganism Ratio (F/M) of 0.3 g BOD/(g MLSS¡Dday) and an influent gas MTBE concentration (C0) of 180 mg/Am3 (@27oC). Results on performance tests show that an average MTBE removal efficiency of 93.6% was obtained with the operation conditions of C0 of 610 mg/Am3 (@27oC), volumetric aeration rate of 0.063 m3/m3¡Dmin, MLSS of 2600 mg/L, and submerged liquid depth of 1.0 m. The biotrickling filter was made by combining two same type of acrylic resin columns (each 0.2 m inner diameter, 2.0 m height, and packed with 900 pieces of polypropylene Pall rings to a height of 1.35 m) in series for the test gas flow and in-parallel for the trickling liquid flow. Each test was operated for 8 hours to reach a steady state for a set of selected conditions (gas flow rate 0.050 m3/min and superficial gas velocity 0.027 m/s, trickling liquid flow rate 0.004 m3/min and pH: 6.8-7.2, and liquid/gas flow ratio: 80 L/m3). Results show that the MTBE removal efficiencies from the influent gas were 40%, 22% and 15%, respectively, with C0 of 50,100 and 230 mg/Am3 (@27oC).

It has been confirmed that vented gases from swine manure compositing operations contain biodegradable ammonia and amines as main odorous compounds. The thesis focuses on the odor-removal performance from the gases by sparging them into an activated sludge aeration liquor in which the odorous compounds can be absorbed and biodegraded. An acrylic column (0.20 m i.d.¡Ñ1.2 mH) was used as the activated sludge aeration tank and a wooden case (1.0 mL¡Ñ0.6 mW¡Ñ0.6 mH) as a swine manure compositing tank. Seed sludge for the odor removal experiments was obtained from a swinery wastewater plant located at southern Taiwan. Both swine manure from the swinery and a pre-fermented composite sample obtained from a compositing plant located at East-southern Ping-Dong County were used for the odorous gas generation. Experiments were conducted at mixed liquor suspended solid (MLSS) concentrations of 2,250-2,750 mg/L, liquid pH of 6.4-6.6, and aeration intensities of 0.1-0.5 m3/m3.min. Results show that the experimental removal efficiencies for both ammonia and amines with, respectively, 18-50 and 180-250 ppm in the influent gas were greater than 80% with aerated activated sludge liquid depths of greater than 0.60 m within the tested aeration intensities. Keeping the activated sludge at around 25oC favored the biodegradation of the absorbed ammonia and amines and resulted in the removal of the compounds to around 85-95%. Temperatures of lower than 15oC shifted the removal to as low as 50-60% because of the limitations in both the biological growth and activity. Results from the study confirm that the activated sludge bioscrubbing approach should be applicable to odor control for the compositing plants.

published_or_final_version / abstract / toc / Civil Engineering / Master / Master of Philosophy

published_or_final_version / abstract / toc / Civil Engineering / Master / Master of Philosophy

published_or_final_version / Civil Engineering / Master / Master of Philosophy