In water supply treatment, sewage in winter has the characteristics of low temperature and low turbidity. When the water temperature is low, the potential of colloidal particles in the water is high, and the repulsive potential between particles is large, which hinders the agglomeration of particles; when the turbidity is low, the content of colloidal particles in the water is relatively small, the chance of particles colliding with each other and gathering will be reduced, and the clear water area of the clarifier will be white, which is easy to create the illusion of insufficient dosage, so as to increase the dosage of coagulant, but can not achieve the obvious removal effect On the contrary, it causes the increase of chloride ion in water.

In view of the above phenomenon, Lvyuan Environment Group Co.,Limited suggests that the water treatment plant improve the effluent quality of low temperature and low turbidity water from the following aspects. First, strictly control the dosage of coagulant. After a lot of experimental analysis, a small amount of chemicals should be added in the coagulation and sedimentation stage, and an appropriate amount of sludge should be discharged. If necessary, an appropriate amount of loess can be added in the second reaction chamber, which can destroy the colloid in the water and accelerate the precipitation. Second, increase the sludge reflux of mechanical stirring clarifier, discharge sludge reasonably, and control the sludge concentration of the second reaction chamber. It is very important to discharge sludge correctly to ensure the effluent quality of low temperature and low turbidity water. Too much sludge in the reaction chamber will produce crowding sedimentation, resulting in a part of sludge flowing to the clean water area with rising water, damaging the effluent quality; too little sludge can not fully contact with suspended solids and colloidal substances in the raw water, affecting the adsorption bridging effect, resulting in poor coagulation effect, and the effluent quality is not up to standard. Through the analysis of the actual data, the sludge discharge once every four days can better balance the sludge concentration and effluent quality. Third, strengthen the management of filter. Low turbidity water can be removed by micro flocculation and filtration. In this way, a proper flocculation tank is set up before filtration to make the original suspended particles form tiny aggregates, so that they can be better filtered by the filter material layer. In addition, reducing the filtration speed of the filter and increasing the backwashing frequency can improve the filtration efficiency and ensure the effluent quality.