AWWA MTC53839

Pilot plant experiments were performed to investigate a novel microfilterretentate water thickener in a membrane water treatment system which uses Japan's Sagami River water as the raw water source. The membrane filter thickener, which showed the concentration polarization phenomenon in the submerged dead-end filtration process, was proved to be applicable to the thickening of the physical washing retentate water, which has a mean turbidity of 100 NTU and a maximum turbidity of 400 NTU at a filtration flow rate as high as 0.5 m/day. The raw water recovery rate of the preceeding membrane filtration system was increased in excess of 99% by the new thickener. However, extra high turbidity (over 420 NTU) caused a rapid increase in filtration resistance. Higher flow rates (0.5 m/day) maintained lower resistance than lower flow rates (0.3 m/day) becauseturbid water was pushed down to a concentration cone faster at higher flux. Particle size distribution analysis showed that particles finer than 3 um tend to remain and accumulate in the thickening basin, and therefore attach to the surface of membranes and lead to increased filtration resistance. Includes 5 references, tables, figures.