ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Chemical pretreatment of feed water for membrane distillation

Marek Gryta

Institute of Chemical and Environment Engineering, Szczecin University of Technology, ul. Pułaskiego 10, 70-322 Szczecin, Poland

E-mail: marek.gryta@ps.pl

Received: 30 March 2007  Revised: 29 June 2007  Accepted: 11 July 2008

Abstract: Membrane distillation was used to produce demineralized water from ground water. The influence of feed water pretreatment carried out in a contact clarifier (softening with Ca(OH)₂ and coagulation with FeSO₄ · 7H₂O) followed by filtration, on the process effectiveness was evaluated. It was found that the chemical pretreatment decreased the membrane fouling; however, the degree of water purification was insufficient because precipitation of small amounts of deposit on the membrane surface during the process operation was still observed. The permeate flux was gradually decreasing as a result of scaling. The morphology and composition of the fouling layer were studied using scanning electron microscopy coupled with energy dispersion spectrometry. The presence of significant amounts of silica, apart from calcium and magnesium, was determined in the formed deposit. The removal of foulants by heterogeneous crystallization performed inside the filter (70 mesh), assembled directly at the module inlet, was found to be a solution preventing the membrane scaling.

Keywords: membrane distillation - fouling - scaling - water pretreatment

Full paper is available at www.springerlink.com.

DOI: 10.2478/s11696-007-0085-5

Chemical Papers 62 (1) 100–105 (2008)