| Mechanical dewatering of sludge is part of the difficulty with the removal of water, heating add acid and alkali as a pretreatment method for mechanical dewatering of sludge, which can effectively release bound water within the sludge, the sludge increased the proportion of free water to achieve a good pre-purposes. Heating add acid and alkali can also break the sludge cells.This paper studies the heat treatment on the influence of sludge dewatering properties. After centrifugation in a long time the moisture content of sludge cake can be measured by the degree of dehydration of sludge, with sludge specific resistance to flitration(SRT) of the sludge filtering speed measure. The results show that with increasing temperature, the sludge can increase the degree of dehydration, and SRT decrease.Under the temperature at160℃of hydrolysis, the sludge cake moisture content can be decreased from72.3%of the original mud after centrifugation to61%, SRT decreased from5.21×1012m/kg tol.79×1012m/kg. VSS solution with the water temperature and time increasing, after90min heat hydrolysis in160℃dissolving rate rose to75.35%. After about sludge centrifugal filter out fluid, SCOD with temperature increases the extension of time is continuously increasing, and in160℃heat hydrolysis90min SCOD concentrations reach4574.17mg/L, ammonia nitrogen, total nitrogen concentration increases with temperature rise large, after hydrolysis at150℃the concentration of ammonia reach152.84mg/L5total nitrogen after hydrolysis at160℃to533.18mg/L, coMPared to the original sludge filtrate increased by83.90mg/L,464.09mg/L. PH and alkalinity with heat hydrolysis temperature elevatory slow decline.Acid and alkali sludge can make changes in the distribution of water, improve sludge dewatering properties. Experimental results show that the degree of acid and alkali treatment on the sludge dewatering, filtration speed is not obvious, in the case of pH=1, pH=13the moisture content of cake were69%and70%, after pretreatment of acid sludge dewatering slightly higher than the alkali pretreatment degree. SCOD of filtrate are up in the trend. Acid treatment in the pH=3, maximum SCOD for288.85mg/L; alkali pH=13after the sharp increase in SCOD to568.29mg/L. Total nitrogen and ammonia nitrogen also showed an upward trend,in the pH=13maximum value of TN for105.96mg/L, ammonia nitrogen at pH=3, the maximum value for85.19mg/L. This experimental study of the pH=1acid treatment, sludge at different temperatures of hydrolysis60min situation. By heat treatment after acid pretreatment, can be in relatively low temperature also achieve the sludge particles released internal moisture role.At120℃hot acid pretreatment degree of dehydration of sludge can be greatly improved, the moisture content of cake has fallen to58%, to experimental research purposes.160℃hot acid treatment of the water content of sludge cake was47%, respectively, coMPared to water solution alone, after the moisture content of cake down13.02%. Hot acid treatment of the filtrate water quality better than after heat hydrolysis treatment. By orthogonal experiments, the three factors on the dewatering rate of the extent and dehydration, the importance of three factors were pH, temperature and time. |
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