TABLE 11-1 Membrane Terminology Term Definition Array,train,or pass Multiple interconnected stages in series by concentrate staging or permeate staging Asymmetric A membrane that varies in density or porosity across its structure,and having a varying consistency throughout Backwash The intermittent residual stream from a MF or UF membrane system Brine Concentrate stream containing a TDS concentration greater than seawater (approximately 35,000 mg/L total dissolved solids) Brackish water Water having a TDS concentration ranging from approximately 1000to15.000mg/L Chemical cleaning or clean in place The periodic application of a chemical solution to a membrane system to remove accumulated foulants in order to maintain productivity and retum the membrane to baseline operation levels Concentrate,reject,retentate, The membrane output stream that contains higher TDS (NF,RO) residual,or blow-down stream or higher TSS (MF,UF)than the feed stream Concentration-polarization A phenomenon that occurs when dissolved and/or colloidal materials concentrate on or near the membrane surface in the boundary layer Conventional MF or UF process A treatment system consisting of a configured group of pressure-or vacuum-driven membranes contained in modules or basins consisting of a pretreatment strainer,air and reverse filtration discharges,filtrate tankage and associated appurtenances,including chemical feed for posttreatment Conventional RO or NF process A treatment system consisting of acid and/or scale inhibitor addition for scaling control,cartridge filtration for pretreatment, the RO or NF membrane treatment process,including the processes of aeration,corrosion control stabilization and pH adjustment,and disinfection for posttreatment (Continued)Tongji University