Kroftas Continuous Backwash Sand Filter or KS Filter is a tertiary treatment option to reduce total suspended solids after primary and secondary treatment. Its key feature is the ability to maintain consistent flow of filtered water while simultaneously cleaning the filter media so as to prevent choking of the filter media.

It is equipped with a unique double sand backwash device that allows flexibility and reliability in operation. For the backwash of the sand, the sand is taken from the bottom and is pumped by an airlift to the washing chamber, after which it falls back into the sand bed. It is highly efficient in removing suspended solids and turbidity along with other impurities.