Trickling Filter System

Trickling Filter System

	Trickling Filter System This is a fixed film sewage treatment method. It is a simple method but very expensive. It works on the principle of filtration. Sewage is distributed by a sprinkler revolving over a bed of porous material which is normally an artificially constructed bed consisting of broken stones, bricks or other suitable material. The aerobic life that flourishes on the surface of such material oxidises and nitrifies the organic matter present.
Whenever sewage flows over a contact surface, aerobic bacteria lying dormant in the liquid, become active and start breeding readily in favourable conditions and form a film called the zooglial layer on the surface. Sewage percolates the porous bed and the effluent is collected at the bottom. Dense slimy bacteria grow and coat the porous material. Zooglea armigera has a principal role in generating slime matrix through secretion of exopolysaccharide which accumulates a heterogeneous microbial community absorbs and mineralises the dissolved organic nutrients in the sewage thus reducing the BOD of the effluent. Aeration is passively provided by the porous material. A food web is established based upon the microbial biofilm. Insects consume the excess biomass generated (only when the sprinkling is shout off). Sewage is re-circulated several times through the same filter to further clear the sewage.
Drawbacks Nutrient overload may lead to excess microbial slime reducing aeration and percolation rates and leads to removal of trickling filter bed. Trickling filter method cannot be used during cold winters when the temperature is very low since the growth rate of the organisms becomes very low.

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