Experimental Study on Flocculation of Low Temperature and Low Turbidity Water in Huyan Water Treatment Plant

Because the turbidity of finished water from Huyan Water Treatment Plant can not come up to the water quality standard,a series of tests were conducted to solve this problem.The results show that the flocculation efficiency of the raw water into the plant is poor due to its low temperature and low turbidity,and the basic reason of not reaching the standard is that the flocculant dosage is insufficient.The better efficiency of turbidity removal can be attained when polyaluminum chloride(PAC)is chosen as flocculant and activated silica is chosen as coagulant aid.The adding time of activated silica is very important to flocculation.The optimal operation conditions are that the rapid mixing time is 1 min,the dosage of PAC is 15 mg/L,and activated silica(calculated as SiO2)of 0.5 mg/L to 1 mg/L is added after 30 s.The reflux of backwashing water from filters is beneficial to treatment of low temperature and low turbidity water,and both flocculant and coagulant aid can be saved.