INTERMEDIATE TREATMENT- ROUGH FILTER

 It has long been known that a flowing stream purifies itself, especially if the stream flows over moss-covered rocks. This purification has been associated with slime on rocks and the oxygen in the water. This process has also been adapted to the wastewater treatment in the trickling filter process, where wastewater is allowed to trickle or flow down through a bed of rocks. The name of the process is misleading, however, as no filtration actually occurs.

The specifications and characteristics of the roughing filters are: 152’ in diameter, 7’ media depth, using rocks that are 2-5 inches in diameter as the media. The rotary distributors arms that apply the wastewater to the rock media are 150’ in diameter.

The roughing filters are fixed growth biological systems using a crushed rock media to support biological growths. As the rotating distributor arms sprinkle primary effluent over the surface of the rock, biological organisms grow forming a slime layer which covers the rocks. The biological organisms consist mainly of bacteria, protozoa, and fungi that feed on the organic matter in the wastewater. Finely suspended solids are also removed by the filters by adsorption onto the slime layer. As the biological organisms grow, the thickness of the slime layer increases and is eventually sloughed off by the applied wastewater and a new layer of growth begins.

The treated wastewater and biological solid are collected in a system of filter under drains and discharged to the intermediate pump station.