| Traditional WWTP management has faced several problems that the cost of power consumption for oxygen aeration and of operation maintenance is high, and activated sludge are susceptible to water quality, water quantity, and temperature change which may lead to poor stability. Most of the energy saving research focused on aeration equipment and device, but rarely on sludge itself. In the study, aerobic activated sludge are collected from aeration tank of different sewage treatment plants and from the aeration tanks of two improved A2/O process in the laboratory. Oxygen consumption demand of the sludge selected with different density and its energy saving features were study. On the other hand, under certain conditions, short term impacts on stability of the selected sludge were analyzed. The results of the studies are as follow:(1) Through setting an biological phase selector in the aerobic pool of an traditional A2/O reactor, the average particle size of sludge in the improved reactors,R1 and R2, can reach 295.5 μm and 269.2μm, respectively. And the SVI which refers to sludge sedimentation performance, can reach 37~42 ml/g and 28~38 ml/g respectively during stable operation. As well as can be seen from morphological perspective, granular sludge have been successfully developed in two improved A2/O reactors.(2) By choosing activated sludge called Sludge A, B, C, D, E from different sewage treatment plants and aeration tanks of two improved A2/O process in the laboratory respectively, oxygen consumption demand of the sludge selected with different density and its energy saving features were study. Results shows that when the sludge density of the Sludge A, B, C, D, E are 1.0013 g/mL, 1.0006 g/mL, 1.0017 g/mL, 1.0041 g/mL and 1.0033 g/mL, respectively, sludge density present D>E>C>A>B, both oxygen consumption rate of Sludge D and E were higher than Sludge A, B and C. it concludes that active sludge with high density is more activate. Oxygen consumption process of the selected Sludge with different density were studied, it shows that oxygen consumption ratio,actual oxygen demand(cod) divided by the theoretical demand, of Sludge A, B, C, were 1.44, 1.69, 1.38, respectively, while the ratio of Sludge D and E were 0.42 and 0.61, respectively, in a certain density range, It shows that the sludge with higher density consumed less dissolved oxygen on degradation of certain pollutants and has better energy-saving performance.(3) In short term impacts on stability of the selected sludge were analyzed, results show that Sludge A and B had not changed in shape while sludge aggregations with high density in Sludge C reduced obviously. Analyze on particle size of the selected sludge shows that the particle size of Sludge A and B increased while Sludge C declined.(4)The experiment of short-term impact on selected sludge shows that in the unsteady environment, for the sludge density of Sludge C,A and B is C>A>B,the endogenous respiration rate is C<A<B. Energy of Low density sludge is mainly used in basal metabolism and less in growth metabolism, which turns to high stability. On the contrary,energy in the sludge with high density is mainly used for growth and less used in basal metabolic, which turns to poor stability. |
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