ABSTRACT

The major drawback of ultrafiltration water treatment technologies is the membrane fouling. The membranes are fouled due to blockage of membrane pores because of particulate adsorption present in feed water over the surface or inside of membrane pores. It results the decline of permeate flux and increase of trans-membrane pressure. The membrane fouling decreases the plant performance, increases energy demand due to increase of trans-membrane pressure and operating cost. Fouling mechanism mainly depend on the raw water quality such as PH, total dissolved solids, turbidity, ionic
strength (magnesium ions, calcium ions, carbohydrates), and total hardness. The physical and operational parameters including trans -membrane pressure, pore size and temperature also contribute membrane fouling. The purpose of this study was to examine the performance of an installed ultrafiltration water treatment plant Nawabshah to investigate the major cause and mechanism of membrane fouling. For that. different quality parameters of feed product water and physical and operational parameters were investigated. The methods used and techniques adopted as per standards of American Public Health Association, United State Environmental Protection Agency and American Society for
Testing and Materials.

The results revealed that the level of all quality parameters of product water such as pH, turbidity, TDS, EC, hardness, magnesium, calcium, chloride, sodium, and sulphate were within World Health Organizations standards. It was found that the trans-membrane pressure was directly proportional to the rate of membrane fouling and inversely proportional to the permeate flux. The membrane fouling became less at lower feed water temperatures and pre-treated feed waters. The membranes fouling were reduced by adopting some changes in time period of backwashes, chemical enhanced backwashes and clean in place methods. The proposed mechanism was examined before and after adopting the changes in operational parameters of the plant.
The permeate fluxes of the plant were found 200m3/h and 209m3/h, rejection fluxes.
12m3/h and3m3/h, and trans membrane pressure 0.9 bar, and 0.6 bar before and after modifications respectively. The above results confirmed that the proposed changes are effective as these are not only decrease the rate of membrane fouling but also increase the plant performance. lt is suggested. that the membrane fouling can also be reduced by pre -treatment of feed water and lowering the level of feed water temperature. In addition, the increasing time period of air scouring, forward flush and decreasing time interval of operating cycle can also decrease the chance of foulant deposition over membrane pores.