Removal of natural organic matter (NOM) in drinking water treatment by coagulation-microfiltration using metal membranes

Drinking water sources in Norway are characterized by high concentrations of natural organic matter (NOM), low pH, low alkalinity and low turbidity. The removal of NOM is therefore in many cases a general requirement in producing potable water. Drinking water treatment plants are commonly designed with coagulation direct filtration or with NF spiral wound membrane processes. This study has investigated the feasibility and potential of using inorganic metal microfiltration membranes in a submerged membrane configuration with coagulation pre-treatment for drinking water production. Variations in operating modes and conditions were tested, from dead-end operation to semi sequencing batch operation using air scouring and backwashing cycles for membrane cleaning and fouling control. Fluxes around 180 LMH at transmembrane pressures below 0.3 bar where achieved over production cycles in excess of 50 h. Treatment efficiencies in general showed >95% colour removal, ∼85% UV removal, 65-75% TOC removal and <0.2 NTU turbidity and non-detectable suspended solids in the permeate. The initial results show that MF metal membranes is an interesting alternative to sand filtration in coagulation/direct filtration for treating drinking water.