Water purification by membrane distillation

Water purification by membrane distillation (MD) has been studied. The expe riments were carried out by using ground water or tap water as the feed. A rapid flux decline was observed during the operation of the MD process. Bas ing on the experiments it was found that CaCO3 was the main foulant of the membrane surface. The initial permeability of the membrane can be restored by cleaning the membrane surface using 2% HCl solution. The thermal pre-tre atment of raw water followed by filtration permits to eliminate the foulant from the feed in the form of deposit before MD process. There was not noti ceable flux decline for the feed pretreated with pH adjustment to 4 by addi tion of HCl, during the MD process. The conductivity of the water purified with MD was with the range of 1-5 muS/cm and TDS did not exceed 2.1 ppm.