Commercial RO System
This reverse osmosis system contains a preservative solution to prevent microbiological growth and freezing which if ingested may cause irritation of the gastrointestinal tract, colic, diarrhea or other symptoms. Therefore, approximately 5 gallons of water must be drawn from the tap to flush out the preservative solution before using the system. This volume of water represents approximately two days of production. The water flushed should be disposed of to the drain.The water that flows through the filter during this first time will not be clean enough for human consumption and should be discarded or put through another filter until a sufficient schmutzdecke has formed. Slow sand filters require a more or less continuous flow of water to avoid drying out the biolayer and to ensure a continuous flow of nutrients to support the microorganisms in the biolayer. As the filter is used, the schmutzdecke will grow bigger and consequently will reduce the flow rate of the filter. When flow rate becomes too low, the filter has to be cleaned by emptying the filter and scraping off the top layer of sand.9 Because slow sand filters are slow, the water needs a long time to get through the sand and capacity is limited, although they are relatively easy to manage. Below is a diagram showing a slow sand filter.