Wash water in waterworks: contaminants and process options for reclamation

Reclamation of clean water from filter backwash water was studied through pilot-scale experiments. The pilot plant consisted of clarification, sand-filtration, and ultrafiltration modules in sequence, with a provision to bypass the sand filter. Clean water that conformed to World Health Organization (WHO) guidelines on Potable Quality was reclaimed. Turbidity, aluminum and iron were found to be critical contaminants in process selection and design. Clarification, followed by sand filtration, was found to be the minimum requirement for recycling filter backwash. However, membrane filtration would enhance reclaimed water quality as the membrane acts as an additional barrier against Giardia and Cryptosporidium.