Impact of Optimised Control of the Pre‐coagulation Regime During Ultra‐filtration Treatment of Raw Upland Waters

Abstract

The effect of controlling the pre‐coagulation regime on downstream ultrafiltration of raw upland waters has been investigated. It has been shown that zeta potential can be used to detect changes in the coagulation process and hence to determine appropriate dosage levels. This is important, as incomplete coagulation has a detrimental effect on ultrafiltration membrane performance, particularly in terms of fouling caused by excess iron. Submerged hollow‐fibre membrane units yield superior performance with pre‐coagulation and sufficient slow mixing of coagulant guarantees high permeate flow recovery after backwashing. Fouling by natural organic matter can be remedied by conventional cleaning techniques. However, fouling due to excess iron can only be removed by heating the cleaning solution. The associated costs are thus two‐fold; that of excess coagulant and that of cleaning.

Effect of Time in Chemical Cleaning of Ultrafiltration Membranes

“…Here, we relate between the cleaning time t and the concentration of the cleaning agent C and show that Ct is an important operational parameter in chemical cleaning of ultrafiltration membranes [6,7]. Through a series of fouling and cleaning experiments with polyethersulfone (PES) and polyvinyldifluoride (PVDF) membranes, it is proved that cleaning performed with a cleaning intensity Ct between 0.5 and 1.0 g h L -1 improves the membrane functionality.…”