Trickling filter

A trickling filter is a type of wastewater treatment system that uses a bed of media to remove organic matter from sewage. The media, often made of rocks, gravel, or specially designed plastic shapes, provides a surface for microorganisms to grow and form a biofilm. As wastewater is distributed over the media, the microorganisms break down the organic pollutants.

File:Benfleet Sewage Treatment Plant, Filter Bed - geograph.org.uk - 1450096.jpg

A trickling filter at Benfleet Sewage Treatment Plant

History

The concept of trickling filters dates back to the late 19th century. They were first developed in England and Germany as a method to treat sewage by allowing it to trickle over a bed of stones. The process was found to be effective in reducing biochemical oxygen demand (BOD) and suspended solids in wastewater.

Design and Operation

Trickling filters consist of a bed of media over which wastewater is distributed. The media can be made of various materials, including rocks, gravel, or plastic. The choice of media affects the efficiency and cost of the system.

File:Trickle Filter.svg

Diagram of a trickling filter system

Wastewater is distributed over the media using a rotating arm or fixed nozzles. As the water trickles down, it comes into contact with the biofilm on the media. The microorganisms in the biofilm consume the organic matter, converting it into carbon dioxide, water, and biomass.

Advantages and Disadvantages

Trickling filters are known for their simplicity and low operational costs. They do not require complex machinery and can operate with minimal energy input. However, they can be less effective in cold climates and may require large land areas.

Applications

Trickling filters are used in various settings, from small municipal wastewater treatment plants to large industrial facilities. They are particularly useful in areas where land is available and energy costs are a concern.

File:Trickle Filter Cross-section.png

Cross-section of a trickling filter

Maintenance

Regular maintenance of trickling filters involves cleaning the distribution system and monitoring the growth of the biofilm. Excessive growth can lead to clogging, while insufficient growth can reduce treatment efficiency.

Related Pages

• Wastewater treatment
• Biological treatment processes
• Sewage treatment

References

• Metcalf & Eddy, Inc. (2003). Wastewater Engineering: Treatment and Reuse. McGraw-Hill.
• Tchobanoglous, G., Burton, F. L., & Stensel, H. D. (2003). Wastewater Engineering: Treatment and Reuse. McGraw-Hill.

File:Collapsed trickling filter at the WWTP in Norton (6845984347).jpg

Collapsed trickling filter at a wastewater treatment plant