A trickling filter is designed to remove

Explanation:

Trickling filters are designed primarily to remove dissolved organic matter from wastewater. This is achieved through the biological activity of microorganisms that form a biofilm on the filter media, effectively breaking down and oxidizing the organic pollutants.

Trickling Filters Work:

1. Structure and Design: A trickling filter consists of a bed of media (such as rocks, gravel, or specially designed plastic media) over which wastewater is distributed. The media provides a large surface area for microorganisms to attach and grow.

2. Microbial Biofilm: As wastewater trickles over the surface of the media, a thin layer of microbial biofilm develops on the media. This biofilm is composed of bacteria, fungi, and other microorganisms that are effective in degrading organic matter.

3. Flow of Wastewater: Wastewater is distributed over the surface of the media using a rotating arm or another distribution system, ensuring even coverage. The wastewater then trickles down through the media bed, contacting the microbial biofilm.

4. Biological Oxidation: The microorganisms in the biofilm consume the organic matter present in the wastewater as a food source. The organic matter is oxidized to carbon dioxide, water, and new microbial cells. This process reduces the biochemical oxygen demand (BOD) of the wastewater, which is a measure of the amount of organic matter present.

5. Effluent Collection: After passing through the media, the treated water is collected at the bottom of the filter and directed to a secondary clarifier. In the clarifier, any remaining solids (including sloughed-off biofilm) are settled out before the water is discharged or subjected to further treatment.