Full Description

The use of low-pressure membrane systems has experienced exponential growth over thepast five years due to their abilities to deliver drinking water and wastewater that exceedmore stringent standards. With their modular design and sophisticated automation,membrane plants are now being built to deliver safety and flexibility with minimaloperator intervention. Another driving force for the popularity of membranes is that theircosts have never been lower. Lower costs are spurred by more efficient process operation,expanded manufacturing capacity and increased competition. The most important factorthat dictates the membrane plant size or the number of membranes is the membrane'sability to handle fouling. A well-designed membrane, with high porosity and permeability,will inherently provide better flux and economics. However, to make use of those physicalproperties, membrane fouling must be controlled in a practical and economical manner.Pretreatment of the feed water usually has a quantifiable benefit on the sizing of membranesystems. However, pretreatment carries an associated cost and is typically applied whenadditional contaminant removal is required. For example, coagulation prior to membranefiltration is applied to reduce TOC in raw water.An alternative option to control fouling is through the judicious use of an "enhanced fluxmaintenance" (EFM) strategy that effectively increases the membrane flux, therebyreducing the cost of membranes quite significantly. Keeping the membranes clean as oftenand as long as possible allows the most efficient use of the membranes area and porosity.This paper presents the causes of fouling and the details of the application of the EFMprocess for full-scale facilities. Case histories of successful implementation of EFM's areprovided.Present worth costs for normal flux and enhanced flux are given for a 36-mgd membraneplant design. Operating membranes at enhanced flux using EFM resulted in 30% savingsin lifetime costs and 20% smaller footprint. The benefits of lower membrane capital andreplacement costs greatly exceed costs associated with increased use of chemicals tomitigate fouling and energy to maintain a higher flux. Includes 4 references, tables, figures.

Product Details

Edition: Vol. - No. Published: 03/05/2003 Number of Pages: 9File Size: 1 file , 620 KB