ABSTRACT
A trickling filter consists of a bed of coarse media, usually rocks or plastic, covered with microorganisms. The wastewater is applied to the media at a controlled rate, using a rotating distributor arm or fixed nozzles. Organic material is removed by contact with the microorganisms as the wastewater trickles down through the media openings. The treated wastewater is then collected by an underdrain system.
The trickling filter is usually built into a tank which contains the media. The filter may be square, rectangular, or circular.
The trickling filter does not provide any actual filtration, the filter media provides a large amount of surface area that the microorganisms can cling to and grow in a slime that forms on the media as they feed on the organic material in the wastewater.
The slime growth on the trickling filter media periodically sloughs off and is settled and removed in a secondary clarifier which follows the filter.
Key factors in trickling filter operation include the following concepts52:
– Hydraulic loading rate, gal/day sq/ft = Flow, gal/day ( including recirc . ) Media top surface, sq/ft https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780203734216/4406a4e1-8626-47b2-b2d2-ea441a87fc3d/content/eq10.tif"/>
– Organic loading rate, lbs/day 1,000 cu/ft = BOD into filter, pounds per day Media volume, 1,000 of cu/ft https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780203734216/4406a4e1-8626-47b2-b2d2-ea441a87fc3d/content/eq11.tif"/>
– Recirculation ,ratio = Recirculation flow , MGD Average influent flow, MGD https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780203734216/4406a4e1-8626-47b2-b2d2-ea441a87fc3d/content/eq12.tif"/>
