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Study on Conditioning and Deep Dewatering of Sewage Sludge

Author: LiHaiFeng
Tutor: ZhouXiaoLong；YuGuoXian
School: East China University of Science and Technology
Course: Chemical processes
Keywords: sewage sludge chemical conditioning deep dewatering ultrasonic conditioning
CLC: X703
Type: Master's thesis
Year: 2012
Downloads: 476
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Abstract

If deep dewatering of it can be obtained, then the sludge volume can be reduced greatly, and costs of management, transportation and treatment can be lowed, and it will be helpful for the utilization of the dewatered sludge as resource. Chemical and physical conditioning means of sewage sludge are the most efficient and commonly used methods used to improve its dewatering performance. Polyacrylamide is one of the most used conditioners, however, there are a lot of disadvantage in economic and environmental benefits for it. Thus, GLT conditioner was prepared with biomass wastes, and effects of GLT and ultrasonic irradiation on dewatering performance of sewage sludge and related action mechanism were investigated. The main conclusions obtained are as follows:GLT conditioner prepared with biomass wastes, is an incompressible solid particles with abundant surface groups containing oxygen. GLT can absorb fine sludge particles when added to the sewage sludge with 99%wt of water content, and exchange ions with bio-cells in sewage sludge, and Ca2+ and Mg2+ exchanged from it caused chemical environment in the cells to lose balance, which led to extracellular polymer degradation. As GLT addition dosage increased, specific resistance (SRF) of the conditioned sludge dropped, Water ratio of the sludge can be reduced to 58.98%wt which is down by 10.47% compared with the blank experiment.Cationic polyacrylamide (CPAM) can markedly improve the sedimentation properties and the filtration speed of the sludge, and some degree reduction of SRF was obtained by moderate dosage. But CPAM had no effects on the sludge particles structure in the aqueous phase, and it was difficult in obtaining deep dewatering of the sludge.GLT had a good synergistic effect with the CPAM. The synergistic effect not only improved the sludge settling properties, but also had effect on surface structures of sludge flocs, which caused degradation of some organic matter, and release of calcium and magnesium ions, and thus improved sludge dewatering performance. Under the experimental conditions, water ratio of the conditioned sludge after deep dewatering, was down to 55.85%wt.Ultrasound had strong breaking action on cell wall in the sludge. The ultrasonic parameters had significant effects. The higher ultrasound power or the longer action time was, the more extracellular polymers degraded, and the higher concentrations of Ca2+ and Mg2+ and COD in the aqueous phase were. In the case with no conditioners, SRF and deep dewatering performance of the irradiated sludge first reduced and then increased with the increase of the sludge degradation.

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