Upgrading coagulation with hollow-fibre nanofiltration for improved organic matter removal during surface water treatment

Rising organic matter concentrations in surface waters in many Nordic countries require current drinking water treatment processes to be adapted. Accordingly, the use of a novel nanofiltration (NF) membrane was studied during a nine month period in pilot scale at a large drinking water treatment plant in Stockholm, Sweden. A chemically resistant hollow-fibre NF membrane was fed with full scale process water from a rapid sand filter after aluminum sulfate coagulation. The combined coagulation and NF process removed more than 90% of the incoming lake water dissolved organic carbon (DOC) (8.7 mg C L−1), and 96% of the absorbance at 254 nm (A254) (0.28 cm−1 incoming absorbance). Including granulated active carbon GAC) filter, the complete pilot plant treatment process we observed decreases in DOC concentration (8.7–0.5 mg C L−1), SUVA (3.1–1.7 mg−1 L m−1), and the average nominal molecular mass (670–440 Da). Meanwhile, water hardness was practically unaffected (