MICROFILTRATION SYSTEM AS A PRETREATMENT FOR RO UNITS - TECHNICAL ANDECONOMIC-ASSESSMENT

Microfiltration (MF) seems to be a very attractive pretreatment techni que that is increasingly being used in drinking water, seawater, and w astewater applications. Recently, it has been used as a pretreatment i n reverse osmosis applications. This paper presents the results of a r esearch project on the viability and the economics of MF as a pretreat ment technique for a seawater reverse osmosis (SWRO) system. The overa ll performance of the MF unit indicates that the SDI of the surface se awater feed ranges between 0.26 and 3.10% with an average SDI value of 2.24. SDI of surface seawater feed is above 6.5%. Average filtrate fl owrate is 3.20 m(3)/h. The optimal backwash interval is 10 min at vari able feed flowrate. The MF unit is capable of reducing COD and BOD val ues and producing good quality water suitable as a feed for RO systems . The techno-economic study revealed that the total unit water costs p roduced by beachwell, MF and conventional surface pretreatment systems are 11.082, 12.264 and 28.153 fils/m(3),(dagger) respectively. It is clear that the beachwell system is the most cost-effective among the t hree available techniques for seawater pretreatment. If for some reaso n the beachwell system is not technically feasible, then the MF system is the next most cost-effective system for seawater pretreatment. It has the added advantage of better water quality.