Effect of Using Different Types of Coagulant on Sludge Conditioning at Different Temperatures
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Sludge dewaterability is an important process in wastewater treatment before disposal. Solids removal is a primary objective of wastewater treatment. There are many coagulants that are commonly used in this process and the most widely used is aluminum sulfate (alum). Filtration without coagulation will not remove the fine particles if the filter medium is too coarse. Coagulation is required to agglomerate the fine particles, thus making the wastewater more suitable for filtration and also resulting in much of the coagulated matter to settle out prior to filtration. This project aims to study the effect of sludge conditioning using two types of sludge conditioning, Aluminum sulfate and cationic polymer (PRAESTOL). Possible effect of temperature is also studied. Sludge samples were collected from local municipal wastewater treatment plant and were stored at 4C. Then conditioning of these samples was investigated using two types of conditioners: aluminum sulfate and cationic polymer (PRAESTOL) at three different temperatures (10, 20, 30 C). The optimal dose of each type of conditioner was estimated at each temperature. Physical and chemical properties were measured including chemical oxygen demand(COD), Biochemical oxygen demand (BOD), total solid (TS), total suspended solid (TSS), pH, flock structure, turbidity and viscosity. The conditioned samples were dewatered using capillary suction time test (CST). The data was analyzed using statistical methods, such as t-test and regression. The results showed that the optimum alum conditioner dosages at 30, 20, 10 C were, 300, 150, and 120 mg/L, respectively. Similarly, the optimum polymer conditioner concentrations were 0.236, 0.634, and 0.72 mg/L at 30, 20, and 10 C, respectively. The relationship between optimal conditioner concentrations and temperature was quadratic for both alum and polymer but in opposite direction. So the optimum concentration of alum increased with the increase of the temperature but optimum concentration of polymer decreased with temperature increase.