EFFECT OF TEMPERATURE, PH AND DO CONCENTRATION ON FILTERABILITY AND COMPRESSIBILITY OF ACTIVATED-SLUDGE

This study investigates the effect of aeration basin temperature, pH and dissolved oxygen (DO) concentration on filterability and compressibility characteristics of activated sludge. Laboratory-scale semi-continuous reactors, fed with synthetic wastewater were used. Effects of temperatures of 15, 20, 25, 30, 35°C; pH values of 5.7, 7.2, 8.2, 9.0 and DO concentrations of 0.5, 1.0, 1.5, 2.0, 5.0 ml/l were studied by keeping all the other parameters constant in each case. Results indicated that as the operating temperatures of reactors were increased, specific resistances to filtration also increased. Up to 25°C a decrease in compressibility of the sludges was observed and above 25°C the sludges became more compressible. Similarly, as the operating pH of the reactors were increased, sludge filterabilities decreased. Increases in the pH of the reactors caused the sludges to become more compressible. On the other hand, low aeration basin DO concentrations reduced the filterability of sludges; and caused the formation of low compressible sludges, and poor effluent qualities. At higher DO concentrations higher filterabilities, better effluent qualities and more compressible sludges are resulted.