Thesis. 1977. Ph.D.--Massachusetts Institute of Technology. Dept. of Mechanical Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Vita. / Includes bibliographical references. / Ph.D.

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 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.

This research study examined the effect operational parameters, dissolved oxygen (D.O.) and food to microorganism ratio (F:M ratio) had on the thickening and dewatering from laboratory-scale and full-scale activated sludge treatment processes. Differences observed in sludge thickening and dewatering at CWWTP and BWWTP were investigated. Data was collected and operational parameters at full-scale facilities monitored. A laboratory-scale activated sludge reactor was constructed and operated on line with the CWWTP, which experienced filamentous bulking conditions since startup and operational parameters of the reactor monitored. Laboratory-scale experiments involved varying mixed liquor D.O. concentration and mean cell residence time (MCRT) and observing the resultant sludge thickening and dewatering characteristics. Increase in mixed liquor D.O. concentration, F:M ratio and reduction of MCRT at CWWTP resulted in improved sludge thickening and dewatering performance. Results showed sludge thickening characteristics were enhanced at D.O. concentrations greater than 3.0 mg/1 and less favorable at D.O. concentrations less than 2.0 mg/1. No trend correlation existed between aeration basin D.O. concentration and sludge dewatering resistance in the range of 3.0 to 7.0 mg/1. Correlation between laboratory-scale and full-scale activated sludge systems demonstrated that laboratory-scale reactor units can be. utilized to predict plant operational changes in relation to sludge thickening and dewatering performance. / M. S.

O estudo apresenta os principais aspectos da operação de secagem térmica de lodos gerados em estações de tratamento de esgotos, os tipos de equipamentos disponíveis no mercado que podem ser utilizados para esse fim e o comportamento da sorção de umidade pelo material seco quando em contato com o ar ambiente. A operação de secagem térmica é uma alternativa para a diminuição do peso e volume de lodos, com conseqüente diminuição dos custos de transporte e disposição final. É considerada, também, um processo de melhoria da qualidade do lodo, pois elimina os microrganismos patogênicos e, ao mesmo tempo, preserva a matéria orgânica presente no lodo, aspectos de importância fundamental quando o lodo/biossólido seco vai ser utilizado na agricultura. Os equipamentos para secagem térmica podem ser diretos ou indiretos. Os principais tipos são: secador rotativo, de soleiras múltiplas, de leito fluidizado, por transporte pneumático e transportadores de esteira. Cada tipo possui vantagens e desvantagens em relação aos demais. A eficiência do processo de secagem térmica é influenciada por uma série de fatores, como: consumo específico de energia, tipo de equipamento utilizado e teores de umidade inicial e final do material. Nos ensaios de laboratório, mediu-se os teores de umidade de equilíbrio do lodo produzido na ETE Baureri, localizada na Região Metropolitana de São Paulo, sob diferentes condições de umidade relativa do ar ambiente. Com esses valores, obteve-se a curva de umidade de equilíbrio do material. Como resultado dessa experiência conclui-se que para cada umidade relativa do ar ambiente há um teor de umidade de equilíbrio do lodo. / The study presents the main aspects of a thermal drying operation of the sludge produced by wastewater treatment plants, the types of equipment likely to be used for this purpose and the sorption behavior of the water contents by the dry material when in contact with the air. The thermal drying operation is an alternative to reduce the weight and volume of the sludge production with a resulting decrease in transportation and final disposal costs. It is also deemed to be a process that improves the sludge quality because includes the elimination of pathogenic microorganisms while preserving the existing organic matter of the sludge, which are aspects of the utmost importance whenever the dry biosolid will be used as fertilizer in agriculture. The thermal drying equipment can be direct or indirect. The main types are: rotary dryers, multi-tray dryers, fluid bed dryers, flash dryers, and conveyor dryers. Each type presents advantages and disadvantages when compared to one another. The efficiency of the thermal drying process is affected by several aspects, such as specific consumption of energy, type of equipment used, and initial and final water contents of the material. The laboratory tests measured the equilibrium moisture contents of the sludge produced by Barueri Wastewater Treatment Plant, located in the São Paulo Metropolitan Region, under different conditions of environment relative humidity. Based on these measurements, an equilibrium moisture curve of the material was obtained. The major conclusion of the experiment was that to each environment relative humidity there is a corresponding equilibrium moisture of the sludge.

O estudo apresenta os principais aspectos da operação de secagem térmica de lodos gerados em estações de tratamento de esgotos, os tipos de equipamentos disponíveis no mercado que podem ser utilizados para esse fim e o comportamento da sorção de umidade pelo material seco quando em contato com o ar ambiente. A operação de secagem térmica é uma alternativa para a diminuição do peso e volume de lodos, com conseqüente diminuição dos custos de transporte e disposição final. É considerada, também, um processo de melhoria da qualidade do lodo, pois elimina os microrganismos patogênicos e, ao mesmo tempo, preserva a matéria orgânica presente no lodo, aspectos de importância fundamental quando o lodo/biossólido seco vai ser utilizado na agricultura. Os equipamentos para secagem térmica podem ser diretos ou indiretos. Os principais tipos são: secador rotativo, de soleiras múltiplas, de leito fluidizado, por transporte pneumático e transportadores de esteira. Cada tipo possui vantagens e desvantagens em relação aos demais. A eficiência do processo de secagem térmica é influenciada por uma série de fatores, como: consumo específico de energia, tipo de equipamento utilizado e teores de umidade inicial e final do material. Nos ensaios de laboratório, mediu-se os teores de umidade de equilíbrio do lodo produzido na ETE Baureri, localizada na Região Metropolitana de São Paulo, sob diferentes condições de umidade relativa do ar ambiente. Com esses valores, obteve-se a curva de umidade de equilíbrio do material. Como resultado dessa experiência conclui-se que para cada umidade relativa do ar ambiente há um teor de umidade de equilíbrio do lodo. / The study presents the main aspects of a thermal drying operation of the sludge produced by wastewater treatment plants, the types of equipment likely to be used for this purpose and the sorption behavior of the water contents by the dry material when in contact with the air. The thermal drying operation is an alternative to reduce the weight and volume of the sludge production with a resulting decrease in transportation and final disposal costs. It is also deemed to be a process that improves the sludge quality because includes the elimination of pathogenic microorganisms while preserving the existing organic matter of the sludge, which are aspects of the utmost importance whenever the dry biosolid will be used as fertilizer in agriculture. The thermal drying equipment can be direct or indirect. The main types are: rotary dryers, multi-tray dryers, fluid bed dryers, flash dryers, and conveyor dryers. Each type presents advantages and disadvantages when compared to one another. The efficiency of the thermal drying process is affected by several aspects, such as specific consumption of energy, type of equipment used, and initial and final water contents of the material. The laboratory tests measured the equilibrium moisture contents of the sludge produced by Barueri Wastewater Treatment Plant, located in the São Paulo Metropolitan Region, under different conditions of environment relative humidity. Based on these measurements, an equilibrium moisture curve of the material was obtained. The major conclusion of the experiment was that to each environment relative humidity there is a corresponding equilibrium moisture of the sludge.

Separation of liquid from solids is a necessary step in the ultimate disposal of wastewater sludges. Most commonly, sludges are dewatered by pressure-filtration methods. Mathematical models of the physics of the sludge dewatering process would provide the ability to predict dewatering performance and optimize the design and operation of dewatering facilities.

The differences in pollutant export from identical land areas treated with fertilizer and/or composted domestic wastewater sludge (compost) were evaluated. Three plots were constructed with a Glenelg silty clay soil and seeded with Falcon fescue (Festuca 'Falcon'): Plot 1 received conventional fertilizer; Plot 2 received a combination of compost and reduced conventional fertilizer; and Plot 3 received only compost. Runoff was collected and analyzed for soluble orthophosphate as P, total soluble phosphorus as P, total phosphorus as P, soluble ammonia as N, soluble Kjeldahl nitrogen as N, total Kjeldahl nitrogen as N, nitrite plus nitrate as N, total suspended solids, chemical oxygen demand, cadmium, copper, lead, nickel, zinc, chromium, and iron. Compost was found to improve moisture retention in the soil and crop, sustain plant growth during excessive dry periods, improve the quality of the crop, reduce runoff, and reduce soil erosion. The export of all pollutants was reduced by the use of compost. The use of fertilizer in combination with the compost did not provide any observable benefit. Instead, the fertilizer provided excessive soluble orthophosphate, total soluble phosphorus, and oxidized nitrogen which were subsequently exported from the test plot. The increased export of soluble Kjeldahl nitrogen may have been caused by excess insoluble N from the fertilizer application, which may have reacted with the organic matter, forming soluble organic nitrogen. The use of compost as a soil amendment significantly reduced the pollutant export which, in turn, reduced the potential impact on receiving waters. / 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.

Experiments were performed on alum, anaerobically digested and aerobically digested sludges to determine the optimum polymer conditioning for a belt filter press The optimum polymer dosages for all three zones of a belt filter press were compared with each other to determine the best overall conditioning. The requirements of all three zones of a belt filter press were the same. However, the gravity rate of drainage seems to under predict the dosages for optimum belt filter press performance. In addition the total mixing energy, G (the shear) and t (the mixing time), that represents the laboratory belt filter press was found to be approximately 45,000. Using a mixing energy input of 45,000 and a standard Buchner funnel apparatus the correct polymer dose for the belt filter press can be predicted. / Master of Science