| The study mainly focus on the dewatering problems of chemical flocculation sludge generated from the treating of the wasted water in Dongguan Canal by using an enhanced flocculation process in Dongguan Zhangcun Water-purifying Plant. Based on a series of relative scientific experiments,the present study try to analyse the functional mechanism of the coagulants to the chemical flocculation sludge and provide dewatering techniques for the plant.The characteristics of the original chemical flocculation sludge are:pH is 6.5～7.0, solid content is 0.6%～1.5%,VS/TS is 10%～20%,and heat value is too low to be measured.Then through the exhaustive experiment,the study selects the chemical flocculation sludge to make coagulant experiment with 25 different coagulants and several kinds of their dosages,regards the filtration rate,filtrate turbidity as targets, takes the coagulants which can improve the dewatering characteristics of the sludge dramatically as the optimum coagulant.And then using orthogonal test to further determine the best coagulant and the best dosage and the best operating conditions, inspecting the changes of PAM type,dosage,filtering pressure,taking time to filter (TTF),filtrate turbidity and its solid content of sludge cakes as the evaluation indexes. Finally,costs comparison is made on the basis of the 4 better coagulants.The comparative results shows that PAM Z8110 is the best coagulant,the optimum conditions for the effect or advantage of the sludge dewatering is:the pressure 20kPa, dosage 0.05kg·t-1WS,and TTF is 14S,filtrate turbidity is 6.87NTU,solid content is 9.27%,the cost is 2.00yuan·t-1WS.Besides,the results of the function mechanism show that:chemical flocculation sludge contains high content of minerals,small particles with high water content.The sludge characteristics,the sludge conditioning and mechanical dehydration should be regarded as a whole in the dewatering process.The coagulant should not just to improve a sigle particular aspect.That is,the chemical flocculation sludge dewatering rate should be speeden up as much as possible,and at the same time the degree of dehydration in this short period of time can also reach a higher level.
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