This study focuses on distribution of light pollution water with low turbidity

by adjusting dosage of polyaluminum chloride(PACI)to control floc zeta potential.Influence of backwash water(FBWW)with different coagulation characteristics from filter on coagulation efficiency was also investigated.The results show that FBWW is of good efficiency on turbidity removal as zeta potential close to -11 mV.The maximum removal rate for settled water was 63.81%

and it was higher than that at other potentials by using this processing.And the lowest residual AlP content was found about 0.271 mg稬-1 at this potential.However

excessive backflow(12%)can lead to additional consumption of PACl in this stage

which makes particle matter in raw water to obtain sufficient coagulant difficult and the system to lose stabilization

and so

turbidity

CODMn

AlP

AlD

etc.goes up.When zeta potential is close to 0 mV

the FBWW is also of good effect on CODMn

UV254 and AlP

and AlD can stay in a relative low value as well. If reflux ratio is 9%

the removal rate of CODMn can reach the highest test value

about 34.21%.When zeta potential is placed at close to +4 mV

the reflux of FBWW can cause substantial increase of turbidity

CODMn

AlP and AlD

while removal efficiency for UV245 is improved.This trend was most obvious for the backflow ratio about 12%

at which the highest test value of UV254(60.67%)is obtained.By comparing residual organic matters in filtered and settled water

a significant difference between these organic matters is found.The removal rates of UV254 and CODMn were higher for the filtered water at +4 mV.