The nanofiltration(NF)process was used to treat the circulating water discharged from coal-fired power plants.The experimental results show that

the removal rates of Ca~(2+)

Mg~(2+)

Ba~(2+)

Sr~(2+)

SO_4~(2-)and other divalent ions by the NF treatment were all over 85%

and that of the organic matter are over 83%.When the NF membrane recovery ratio was between 15% and 85%

the desalination rate of the NF membrane was over 75%

while the retention rate of Na~+

Cl~-and other monovalent ions were low.As the water supply of the boiler feed water

the NF effluent could ensure the safe and stable operation of reverse osmosis system.For the power plants using stainless steel pipes(except 304 and 304L)as the cooler tube materials

the NF effluent can be reused as the circulating water supplement water

to reduce the water intake quantity of the power plant.