The feasibility of ultra- and microfiltration depends strongly on the achieved net flux. Direct treatment of surface water frequently results in low net fluxes and high cleaning frequencies. Experiments have been conducted at constant flux on surface water with an ultrafiltration pilot plant with direct filtration, in-line coagulation and pre-coating (EPCE) with ferric hydroxide flocs. The aim was to control and reduce the rate of fouling. With the use of a pre-coat at the beginning of the filtration cycle a stable ultrafiltration process was obtained. This is contrary to the use of in-line coagulation and direct filtration which resulted, due to a very high fouling potential of the feed water, in high fouling rates at low fluxes. The result of this exploratory research is an important step towards a higher feasibility of micro- and ultrafiltration.

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