| Water waste including clarifier waste and filter backwash water accounts for 4%～7% clean water produced by a Water Treatment Plant. The account of water waste from Water Treatment Plants is increasing with the number and scale's augment. An important social and environmental problem could be seen for the direct discharge of above mentioned wastewater. The large Water Treatment Plants are required to add wastewater treatment process by Environmental Protection Bureau of China from 2000 years in order to reach wastewater criterion. For this, water treatment plant of zhong-yin carried out to study an appropriate process for its water waste treatment.A concentrated study of the factors affecting sludge thickening property in water treatment plants were involved in this paper. The factors include the raw water property,the solid content of water waste,feeding PAM flocculation,pH value,slow agitation and so on. The experiment uses The Same Direction Flow and Micro-vortex Sludge Coagulation Thickening Process to study the core of water waste treatment process under no feeding chemicals. The results of experiment will have great value for designing parameter choice of water waste treatment process in water treatment plant of zhong-yin.⒈The ratio of feeding PAM will affect performance of sludge thickening process. Based on analysising the sedimentation of coagulation and the turbidity of supernatant, the optimum choice is A778 PAM of anion type. The experiment result shows that the ratio of feeding PAM will be 4.44‰,4.0‰,3.24‰during the low temperature and low turbidity period,the low temperature and high turbidity period and the raw water period respectively.⒉The raw water period and the low temperature and low turbidity period have the similar sludge sedimentation property, and the critical concentration which need to enhance sludge sedimentation is 0.50% more or less; during the low temperature and high turbidity period, the critical concentration is 2.00% more or less. The optimal pH value is 1.8 and up to 12 when the sludge is treated with acid and alkali respectively; when slow agitating, the feasible velocity is 1r/min more or less. The efficacy sequence of above influence factors just like below: feeding PAM flocculation>acid treatment >slow agitating>alkali treatment(pH≥12)>the raw water.⒊The solid content of wastewater discharged from the same direction flow and micro-vortex sludge coagulation thickening tank is up to 2.0%, and they could be dewatered without feeding chamicals before inpouring pressure filter during different periods, but the turbidity of supernatants in thickening tank is 20NTU～30NTU during different periods, and the supernatants should be treated if they were recycled.
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