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<!{|style="float: left;"|{{Language-- table at top of page with logo, picture, Application level, Management level, and input-output tables -->box|english_link=Trickling_Filter|french_link=Lit_bactérien|spanish_link=Filtro_Percolador|hindi_link=coming soon|malayalam_link=coming soon|tamil_link=coming soon | korean_link=coming soon | chinese_link=Coming soon | indonesian_link=Coming soon | japanese_link=Coming soon}}|}{|width="100%"|style="width:50%;"|{{santablesantable_new|

sys2=[[Blackwater Treatment System with Infiltration|56]]|sys3=[[Blackwater Treatment System with SewerageEffluent Transport|67]]|sys4=[[Blackwater Transport to (Semi-) Centralized Treatment System |78]]|sys5=[[Sewerage System with Urine Diversion |89]]|

Input1=Blackwater|Input2=Greywater |Input3= Brownwater | Input4= Effluent |Input5=|

[[Image:Icon_trickling_filter.png |right|95px80px]]'''A Trickling Filter is a fixed bed, biological filter that operates under (mostly) aerobic conditions. Pre-settled wastewater is ‘trickled’ or sprayed over the filter. As the water migrates through the pores of the filter, organics are degraded by the biomass covering the filter material.'''

The Trickling Filter '''A trickling filter is filled with a high specific surfacefixed-area material such as rocksbed, gravel, shredded PVC bottles, or special pre-formed filter-material. A material with a specific surface area between 30 and 900m2/m3 is desirablebiological reactor that operates under (mostly) aerobic conditions. Pre-treatment is essential to prevent clogging and to ensure efficient treatment. The pre-treated settled wastewater is continuously ‘trickled’ or sprayed over the surface of the filter. Organisms that grow in a thin bio-film over As the water migrates through the surface pores of the media oxidize filter, organics are degraded by the organic load in biofilm covering the wastewater to carbon dioxide and water while generating new biomassfilter material.'''

<br>The trickling filter is filled with a high specific surface area material, such as rocks, gravel, shredded PVC bottles, or special pre-formed plastic filter media. A high specific surface provides a large area for biofilm formation. Organisms that grow in the thin biofilm over the surface of the media oxidize the organic load in the wastewater to carbon dioxide and water, while generating new biomass. The incoming pre-treated wastewater is sprayed ‘trickled’ over the filter , e.g., with the use of a rotating sprinkler. In this way, the filter media goes through cycles of being dosed and exposed to air. However, oxygen is depleted within the biomass and the inner layers may be anoxic or anaerobic.

===Design Considerations=== The filter is usually 1 to 3m 2.5 m deep , but filters packed with lighter plastic filling can be up to 12m 12 m deep. The ideal filter material is low cost and durable, has a high surface to volume ratio, is light, durable and allows air to circulate. Whenever it is available, crushed rock or gravel is the cheapest option. The particles should be uniform such that and 95% of the particles them should have a diameter between 7 and 10cm. Both ends of the filter are ventilated to allow oxygen to travel the length of the filter10 cm. A perforated slab that allows the effluent material with a specific surface area between 45 and 60 m2/m3 for rocks and excess sludge 90 to be collected supports the bottom of the filter150 m2/m3 for plastic packing is normally used.

With time, the biomass will grow thick Larger pores (as in plastic packing) are less prone to clogging and the attached layer will be deprived of oxygen; it will enter an endogenous state, will lose its ability provide for good air circulation. Primary treatment is also essential to stay attached prevent clogging and will slough offto ensure efficient treatment. High-rate loading conditions will also cause sloughingAdequate airflow is important to ensure sufficient treatment performance and prevent odours. The collected effluent underdrains should be clarified in provide a settling tank to remove any biomass that may have dislodged from passageway for air at the filter. The hydraulic and nutrient loading maximum filling rate (i.e. how much wastewater can be applied to A perforated slab supports the filter) is determined based on the characteristics bottom of the wastewaterfilter, allowing the type of effluent and excess sludge to be collected. The trickling filter media, is usually designed with a recirculation pattern for the ambient temperature, effluent to improve wetting and flushing of the discharge requirementsfilter material.

- Can be operated at a range of organic and hydraulic loading rates. <br> - Efficient nitrification (ammonium oxidation) <br>- Small land area required compared to Constructed Wetlands. constructed wetlands| con=- High capital costs and moderate operating costs <br> - Requires expert design and construction. , particularly, the dosing system <br>- Requires operation and maintenance by skilled personnel <br> - Requires a constant source of electricity and constant wastewater flow. <br> - Flies and odours are often problematic. <br> - Risk of clogging, depending on pre- and primary treatment <br>- Not all parts and materials may be locally available locally. <br> - Pre-treatment is required to prevent clogging. <br> - Dosing system requires more complex engineering.

==Adequacy=Appropriateness=== This technology can only be used following primary clarification since high solids loading will cause the filter to clog. A low-energy (gravity) trickling system can be designed, but in general, a continuous supply of power and wastewater is required. Compared to other technologies (e.g., [[Waste Stabilization Pond|Waste Stabilization Ponds]], T.5), trickling filters are compact, although they are still best suited for peri-urban or large, rural settlements. Trickling filters can be built in almost all environments, but special adaptations for cold climates are required.

This technology can only be used following primary clarification since high solids loading will cause the filter to clog. A skilled operator is required to monitor ===Health Aspects/Acceptance=== Odour and repair fly problems require that the filter be built away from homes and the pump in case of problemsbusinesses. A lowAppropriate measures must be taken for pre-energy (gravity) trickling system can be designedand primary treatment, but in generaleffluent discharge and solids treatment, a continuous supply all of power and wastewater is requiredwhich can still pose health risks.

Compared ===Operation & Maintenance=== A skilled operator is required to monitor the filter and repair the pump in case of problems. The sludge that accumulates on the filter must be periodically washed away to other technologies prevent clogging and keep the biofilm thin and aerobic. High hydraulic loading rates (eflushing doses) can be used to flush the filter.gOptimum dosing rates and flushing frequency should be determined from the field operation. [[Waste Stabilization Pond|WSPs]]), trickling filters are compact, although they are still are best suited for peri-urban or large, rural settlementsThe packing must be kept moist. Trickling Filters can This may be built in almost all environments, although special adaptations for cold climates problematic at night when the water flow is reduced or when there are requiredpower failures.

The odour ===References===* Tchobanoglous, G., Burton, F. L. and fly problems require that the filter be built away from homes Stensel, H. D. (2004). Wastewater Engineering: Treatment and businessesReuse, Metcalf & Eddy, 4th Ed. (Internat. Ed.). There must be appropriate measures taken for preMcGraw-treatmentHill, effluent discharge and solids treatmentNew York, all of which can still pose health risksUS.pp. 890-930. (Book; Detailed description and example calculations)

The sludge that accumulates on the filter must be periodically washed away to prevent clogging* U. High hydraulic loading rates can be used to flush the filterS. The packing must be kept moistEPA (2000). This may be problematic at night when the water flow is reduced or when there are power failures[https://www3.epa.gov/npdes/pubs/trickling_filt_nitrification.pdf Wastewater Technology Fact Sheet. Trickling Filters]. 832-F-00-014. U.S. Environmental Protection Agency, Washington, D.C., US. (Design summary including tips for trouble shooting)

===Acknowledgements===