Research On The Dewatering Characteristics Of Sludge In Municipal Sewage Treatment Plant By Physical-Chemical Method

With the treatment of the wastewater, a large quantity of sludge will be produced. Its amount is about 0.3%～0.5% of the total water quantity (according to the containing water rate 97%). There are abundant harmful and poisonous material, useful vegetable nutriment (nitrogen, phosphor, and potassium), organic matter and humidity etc. One of the indispensable work in Municipal sewage treatment plant is sludge treatment and disposal, whose purpose is to make the sludge reducing volume, stabilization, harmlessness and synthetical use etc. Combining the process craft of Chongqing Tang Jia-qiao wastewater treatment plant, this text adopts chemical regulating method on different sludge, improving the dehydration performance of the sludge.The test process is as follows:Firstly, take analysis of three kinds of sludge.Secondly, take complete experiments, and choose four kinds of polymer coagulants to make coagulant experiment with three kinds of sludge (primary settling sludge, thickening sludge and digested sludge) respectively. Sludge dewatering is often characterized by the sludge filterability, expressed as the specific resistance to filtration (SRF). Most SRF values are based on filtration plots of the inverse filtration rate (dt/dV) versus the accumulated filtrate volume (V). Such plots yield linear relationships during filtration of non-compressible structures. Under the stable pressure condition, the specific resistance of sludge is tested. According to the dosage, we can conclude the optimum coagulant with its optimum dosage.Then we shall choose three factors that are very important to the specific resistance of the sludge (the filtration pressure, pH value and the mixing rate) to test their influence on the dewatering characteristic. Then we can determine the optimum experimental scope of each factor. Based on the above-mentioned results, the study uses orthogonal design test on thickening sludge (fresh sludge) and digested sludge to make a further step determining an optimum operative condition of the optimum coagulant.Through the experiment analysis, the study makes the following conclusions: 1) Four kinds of coagulants all can decrease the specific resistance of the sludge and improve the dewatering character. Compared with their dosage and market price, GPF-2 is the best. 2) Four kinds of coagulants all can lower the concentration of TP and COD in the filtrate. Of which, PAC's effect on phosphorus removal is best,and GPF-2 reduce the concentration of COD well.3) The optimum operation condition of thickening sludge is that the dosage of GPF-2 is 0.08 g/l, filter pressure is 400 g/cm2, quick mixing rate is 250 r/min, and slow rate is 70r/min. The optimum operation condition of digested sludge is that the dosage of GPF-2 is 0.18 g/l, filter pressure is 400 g/cm2, quick mixing rate is 200 r/min, and slow rate is 60r/min.