ITT's Place in the Cycle of Water - Water Solutions

The Cycle of Water: Clean WaterMembrane FiltrationFiltration is the process of holding back impurities ina liquid by passing it through a permeable barrier.Traditionally, this has often been achieved usingbeds of sand through which the water is allowed topercolate, usually preceded by coagulation, flocculationand settlement stages to reduce the load of impuritiesrequiring filtration and to enhance the removal ofvery fine particles. Other types of media can be usedin place of (or in combination with) sand to addressspecific impurities, an example being the use ofCASE STORY:Nanofiltration Perfect Fit forCooper City, FloridaWhen the municipal water supplier inCooper City, Florida was faced with a challengeto meet regulations imposed by theEnhanced Surface Water Treatment Rule, itbegan the process of implementing a newtechnology called nanofiltration. With productsand technical support from ITT, theywere able to successfully implement a newand cost effective water filtration technologythat enabled them to conform to thenew regulations.activated carbon to absorb chemical contaminants.This type of filter is typically cleaned by backwashing,whereby the flow of water is reversed to lift depositsout of the bed. Introducing air into the backwashwater enhances the scouring effect. Media filters canbe operated using a head of water or can be containedin pressurized vessels.Membrane technology is increasingly being used toseparate contaminants from both drinking water andwastewater, with various drivers having an influence,such as reduced plant footprints, ease of integrationinto existing infrastructure, protection againstpathogens and superior treatment performance.Four categories are commonly recognized, which arebased on the size of particle or molecule retained –microfiltration (MF), ultrafiltration (UF), nanofiltration(NF) and reverse osmosis (RO). RO is the finest form ofmembrane separation, retaining most dissolved speciesincluding monovalent salts. The pressure in RO systemsmust exceed the osmotic pressure of the dissolvedspecies to force the liquid fraction across the semipermeablemembrane. NF bridges the gap between ROand UF, as it is capable of retaining solutes greater than300 Daltons, such as organic carbon and divalent salts.UF covers a relatively broad spectrum of particle sizes,retaining macro-solutes, colloids and viruses. MF is thecoarsest form of membrane filtration, bordering onconventional particle filtration, and provides a barrierto turbidity, cryptosporidium and bacteria.Developments in system design and membranematerials are continuing to increase the efficiency andperformance of membrane technology, reducing wholelife costs and increasing throughput.ITT’s Place In The Cycle of Water: Everything But The Pipes