Treatment concept for future drinking water production

摘要

A new concept for drinking water treatment is investigated on pilot scale. The treatment process consists of fluidized ion exchange (FIEX) to remove multivalent positive ions like calcium, ultrafiltration (UF) for removing suspended solids and pathogens, nanofiltration (NF) for removing pathogens, trace organic contaminants and to increase biological stability, marbel filtration to condition the water and granular activated carbon (GAC) filtration to remove apolar trace contaminants. The pilot research is aiming at membrane fouling prevention in both ultrafiltration as well as nanofiltration. Also the effectiveness of the combination nanofiltration and GAC with respect to the removal of trace organic substances is investigated. The UF-experiment was conducted without inline coagulation at constant flux (65l/h.m2) for 14 days. The results showed that during dose 14 days UF performance is stable if the FIEX-effluent is used as the feed and NaOH was used in the enhanced backwash. Because of the absence of multivalent positive ions there was no scaling in the NF , even at high recovery (97%). NF-scaling was investigated at various recoveries with constant recycle flow velocity (0.12 m/s). For the effectiveness of the whole process, different pharmaceuticals and pesticides are dosed in front of NF and measured in the effluent of both the nanofiltration as well as the GAC. The micro pollutants were efficient removed by the combination NF/GAC also because of the absence of pre-loading on the GAC. The polar substances (eg. MTBE) with molecule weight smaller than 100 daltons were not retained by the treatment process. The concept is promising to produce high quality drinking water, and the cost (50 euro cents per cubic meter) is competitive with conventional treatment concepts.