The sensitivity of SDI analysis: from RO feed water to raw water Original Research Article

The water characterisation is generally challenging regarding the pre-treatment operation up-stream reverse osmosis. The classical parameters are not applicable due to analytical limitations, and/or the sensibility of those parameters is too low compared to the water fluctuation behaviour measured on full-scale water treatment plants. The evaluation of the water fouling potential could be a more sensible parameter, supplementing the analytical tools actually used for design purpose. The silt density index (SDI) is a parameter characterising the fouling potential of water. It is one of the most important parameter for the design and operation of RO membrane process. SDI analytical protocol is standardized in the ASTM D 4189-95 (Reapproved 2002). This method evaluates the quantity of matter in water, based on fouling variation of a 0.45-μm membrane during a filtration time. It is typically applied on low fouling potential water such as pre-treated water feeding reverse osmosis or nanofiltration (SDI15 min < 5).