Reduction of haloacetic acids in natural surface water by integrated treatment: coagulation and membrane processes

The objectives of this research were to study the elimination of dissolved organic carbon (DOC) and the reduction in the formation of haloacetic acid potential (HAAFP) when natural water from La Pedrera reservoir was treated with a single process of coagulation or filtration membrane, and a combined process (coagulation followed by treatment with membranes). In this research two coagulants, aluminium sulfate and polyaluminium chloride, and four membranes, two nanofiltration membranes (NF 90 and DESAL HL) and two ultrafiltration membranes (PES 5000 and PES 10000) were studied. The highest reduction in DOC was obtained when the natural water underwent the combined treatment of coagulation followed by NF90 membrane filtration. With this combined treatment the values of DOC rejection were over 82% independently of the coagulant used. For the single treatment with nanofiltration membranes, HAAFP rejection was 81% for NF 90 and 76% for Desal HL. However, a single treatment with coagulation or ultrafiltration membranes showed results for HAAFP rejection of under 35% and 26%, respectively. When a combined treatment of aluminium sulfate followed by ultrafiltration with the PES 5000 membrane was used, HAAFP rejection reached values of 80% approximately. These values are very similar to the results obtained from a single treatment with NF 90 but with the advantage that the flux of PES 5000 is 4,000 times the flux of the NF 90 membrane. Therefore, this treatment should be given due consideration.