An attapulgite nano-scale (NS) membrane was prepared on the clay-fly ash ceramic substrate. Based on this NS membrane, a membrane filter was developed for the problem of energy waste, thermal and phosphorus pollution resulting from the high blowdown rate of medium-pressure boilers. Mounting this membrane filter on the boiler blowdown pipe, it could separate both particles and ions, which are larger or smaller than the membrane pore size. The quality of treated water met the requirements of feed water standards in medium-pressure boilers. Recycling treated water to the feed water system could reduce the boiler blowdown rate to less than 1%. (C) 2013 Elsevier B.V. All rights reserved.