Pretreatment filtration system membrane

Membrane Fouling. Pretreatment of the membrane or feed solution prior to filtration may be desirable within allowable limits. The various treatment options are discussed in Sec. 6.3. At the start of a filtration run, the solute or solids concentration is relatively small and progressively builds as the permeate is removed from the system. If a substantial flux decline is observed at low solids concentration, membrane fouling aspects are believed to be important. A flux decrease with an increase in solids concentration is largely due to concentration polarization and can be minimized through efficient fluid hydrodynamics and/or backpulsing. PH221123)... 

The thermal brine from local desalination plant was pretreated using a two-step filtration system (1pm + granular activated carbon) to remove particulates and organic contaminants present in the feed stream that could potentially affect the hydrophobicity of the membranes. This conservative pretreatment gave both systems the best chance of success. 

Membrane Pretreatment Filtration The most common membrane pretreatment process uses hoUow-fiber MF or UF membranes to separate suspended solids and particles (including microorganisms) from the soiuce seawater. MF and UF membrane systems have been shown to be very effective for turbidity and silt removal. Turbidity can be lowered consistendy below 0.1 NTU, and filter effluent typically has SDI levels below 3 over 90% of the time. 

Field evaluation of a hybrid membrane system consisting of an UF membrane pretreatment unit and an RO seawater unit was conducted by Glueckstem et al. [56]. For comparison a second pilot system consisting of conventional pretreatment and an RO unit was operated in parallel. The conventional pretreatment unit included in-line flocculation followed by media filtration. The smdy showed that UF provided a very reliable pretreatment for the RO system independent of the raw water quality flucmations. However, the cost of membrane pretreatment was higher than conventional pretreatment. This suggested that membrane pretreatment for RO desalting systems is only economic for sites that require extensive conventional pretreatment or where wide flucmations in the raw water quality are expected. 

One of the possible configurations for the pharmaceutical water purification system is shown in Fig. 3. The first three stages in that system (multimedia filtration, softening, and carbon filtration) are considered pretreatment steps for the RO unit that conducts final purification. The cartridge filter shown before the RO is provided to protect the membranes from the fine carbon particles. There are many variations of the treatment systems sometimes carbon filter is placed before a softener, sometimes it is eliminated completely. 

Nanofiltration (and its sibling technologies reverse osmosis, ultra filtration, and microfiltration), is a fully developed, commercially available membrane technology with a large number of vendors. Nano-filtration relies on the ability of membranes to discriminate between the physical size of particles or species in a mixture or solution and is primarily used for water pretreatment, treatment, and purification). There are almost 600 companies in worldwide which offering membrane systems. 

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