The quality of effluent water from original pretreatment system in shangdu power plant can't satisfy the requirements stipulated in design from begining to end

leading to serious blockage in disc-type filter and on the ultra filtration membrane.Combining with the characters of intake water quality

i.e.low temperature and low turbidity

a retrofit scheme of the pre-treatment system has been put forward and implemented;(1)additionally installing inclined pipes in the clarifying pond with mechanical agitation;(2)adding dosing points of coagulant aids;(3)adding multi-medium filters after the said clarifying pond.After retrofitling

the results of test in operation show that the quality of effluent water from said clarifying pond and from the multi-medium fiter is good

realizing the requirement of taking the surface water as the water source of make-up water for boilers.