Physical Methods

All laundry waste should be strained in a removable basket so that lint does not clog pumps and other equipment in the treatment system.

Plan settling of laundry waste removes the heavier grit particles washed out of clothes. Most biological oxygen demand (BOD) is soluble, therefore settling has little effect on the BOD and chemical oxygen demand (COD) of the waste.

Several types of filtration units are used to treat laundromat wastes. A sand filter efficiently removes particu-late matter. Pressures and filters usually require less space than gravity sand filters. The latter is used following other treatment methods and is little different from filtration through soil. Filtration through diatomaceous earth filter cake is highly recommended, since it removes bacteria and some viruses, and is particularly effective in separating chemical sludges. In diatomaceous earth filtration, prior settling or sand filtration lengthens filter runs but will not result in a better quality effluent.

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