Multistage Drinking Water Filtration

Abstract Multistage drinking water filtration is a combination of roughing filter and slow sand filter unit processes that broadens the use of these passive treatment methods to include source water whose turbidity is higher than that normally suitable for biological filtration. Slow sand filtration is one of the oldest surface water treatment techniques, but it is easily compromised by source water with high turbidity caused by erosional or meteorologic events in the upstream watershed. By providing roughing filter pretreatment, suspended solids are decreased and the biological integrity of the slow sand filter is maintained with a concomitant extension of the filtration period. Slow sand filtration is still a viable method of water treatment most suitable for raw water sources low in turbidity and suspended solids. Multistage filtration has been shown to be an efficient and effective drinking water treatment technique for source water with high turbidity, organic matter, and suspended solids.