Study on the effect of chemical conditioning method on the dewatering effect of biochemical sludge

In view of the high water content of biochemical sludge in urban sewage treatment plants, which was not conducive to the following treatment, the sodium hypochlorite oxidation method, Fenton oxidation method and Fenton + calcium oxide combined method were used to dewater the sludge, respectively, combined with single factor analysis to optimize external conditions. The experimental results showed under the optimized conditions, the sludge moisture content could be reduced from 89.90% to 78.44%, and the filtrate quality was about 50% of the initial sludge quality, when sodium hypochlorite was selected as the oxidant. The moisture content of sludge could be reduced to 65.32%, and the filtrate quality increased to 60% in Fenton oxidation system. After combined with calcium oxide, the moisture content of sludge could be further reduced to 51.06%, and the filtrate quality was about 56% of the initial sludge quality. The addition of calcium oxide promoted the hydrolysis of iron ions, and iron hydroxide-calcium sulfate and excess calcium sulfate crystallized. The rigid skeleton constructed could form a large number of water-permeable channels in the sludge, and thus improve the dewatering performance of biochemical sewage. Considering the sludge dewatering effect and chemical cost, Fenton + calcium oxide combined method was found to be the best conditioning method.