The characteristics of source water are TSS : >60mg/L; COD : >100mg/L, TOC : >25mg/L; Alkanility : 300 mg/L.CaCO3; TDS : 2000mg/L and pH 6.5-8.5. This is treated with UF membrane with definite backwash frequency.
Dear Jai,
The lifetime between 3-5 years or more.
Qualified Feed Water Quality Parameters :
Parameter Unit Design Basis Maximum Allowable
Turbidity NTU
In my opinion, lifetime should be no less than 5 years to be economically interesting. Regarding the fluxes there are strong variation depending not only in the membrane itself but also in the feed and working conditions (fouling is a key parameter leading to strong flux decline).
Since you have a relative high Organic loading (COD < 100 mg/l) your Flux must probably be kept relative low i.e. 70 - 80 l/m2/h to minimize problems with organic fouling within the pores of the membrane.
The life of your UF membrane will depend on not only water quality, but also membrane type, potting material manufacture, and operation methods. It is not clear whether or not you are using PVDF or polyethersulfone blended with polyvinylpyrrolidone hollow fiber membranes and whether the process is outside-in or inside-out fiber operation, but these membranes when properly designed and maintained can last upwards of 8 years. I agree with the other respondents that operating at lower flux is recommended when treating difficult water; my rule of thumb in operating facilities greater than 3 million gallons per day and larger is to keep flux below 45-50 gallons/square foot-day (
I agree that looking to high COD flux should be lower (about 30 GFD) to reduce fouling tendency. Do you have any pretreatment before UF (looking to TSS value of 60 ppm). If not, flux could be even lesser to avoid solid build up in UF membrane channels.
Thanks a lot for the answers.
@Yashwant : There is no pre-treatment but the source water quality keeps fluctuating.
In addition to the very good comments above, another important aspect to consider is the addition of coagulant upstream the membrane system. Coagulation is efficient to remove colloidal (especially organic) material, transforming it into a pin floc that can be retained by membranes. This will decrease the membrane fouling potential by the colloidal material, resulting in a better operation. However, some coagulants (like polyaluminum chloride) can foul the membranes if overdosed or not dispersed/ reacted correctly in the coagulation process upstream. Good luck.
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