Trickling filter is also referred as trickling biofilter or biological filter or biological trickling filter. The other term such as intermittent filter, percolating filter, fixed film process, packed media bed filter, alternative septic system, roughing filters and attached growth process also refers trickling filter. Usually trickling filter includes lava, gravel, rocks, slag, moss, ceramic, coke, peat moss and or plastic media where there is a waste water percolating downwards. Layer of microbial film covers the packed bed of media. The aeration to trickling filter is by splashing or diffusion of air or by forcing the air to pass through the porous bed.
Working of Trickling Filter:
The organic compounds with layer of microbial film can be removed either by adsorption or absorption. The selection of filter media should be ideal depending on the high surface are to volume ratio. The filter media should be porous in nature and should have internal surface area in addition to external surface area. The waste water flows and biological film requires organic compounds to be oxidized. The oxidation of organic compounds release carbon dioxide, water and other byproducts as a result. If the thickness of biological film increases, then treated effluent is sloughed off as a part of secondary sludge treatment plant. The treatment of waste water with trickling filter is followed by sedimentation tank and or clarifier for effective separation and removal of the contaminants. It is one of the oldest water treatment technologies still in practice.
Types of Trickling Filter:
Following are basic classification of trickling filter.