Treatment of polluted river water with a photocatalytic slurry reactor using low-pressure mercury lamps coupled with a membrane

A novel configuration of a photocatalytic slurry reactor using low-pressure mercury lamps coupled with membrane filtration was proposed, and treatment of polluted river water with a pilot plant of this system was investigated. Both COD and NH+4-N in the river water were simultaneously removed. Under the conditions of a hydraulic retention time of 3.0 h, influent COD strength of 50-80 mg L−1 and NH+4-N of 2-6 mg L−1, 80% COD and 50% NH+4-N were achieved, respectively. The reactor was found to own a higher UV utilization effectiveness than most reported photocatalytic reactors. Intermittent backwash was effective to retard the membrane fouling and enable stable membrane operation for more than 1 month. An adhered catalyst, algae and fungi in the river water were the main contaminants of the membrane, but the membrane permeability could be almost recovered through sequential rinsing by tap water and a sodium hypochlorite solution. After continuous operation for over 1 month, the photocatalytic activity of catalysts was found elevated, which likely resulted from adsorption of hydroxyl-rich alcohols onto the catalyst surfaces.