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120 Compendium of Sanitation Systems and Technologies .10 Functional Group T: (Semi-) Centralized Treatment collection filter support feed pipe filter sprinkler T8: TR 2.5 m deep, but filters packed with lighter plastic filling filling packed plastic lighter filters with but deep, m 2.5 to 1 usually is filter The Design Considerations or anaerobic. anoxic be may layers inner the and biomass the within air.toHowever, exposeddepleted and oxygenis dosed being of cycles through goes media filter the way, this In sprinkler. of arotating use the with e.g., filter, the over ‘trickled’ is wastewater pre-treated incoming The ing new biomass. wastewaterwater,dioxideand tocarbon generat- while the in load organic oxidizethe media the of surface the over biofilm thin the in grow that Organisms formation. biofilm for area large a provides surface A specific high media. filter plastic pre-formed special PVC or shredded bottles, gravel, rocks, as such material, area surface specific a high with filled is filter trickling The film coveringthe filter material. pores of the filter, organics are degraded bythe bio- the through migrates water the As filter. the over tled wastewater is continuously ‘trickled’ or sprayed operates under (mostly) aerobic conditions. Pre-set- A trickling filter is a fixed-bed, biological reactor that Application Level: Trickling Filter Trickling   City Neighbourhood Household IC KLI NG FIL TE R 99 Management Level:  Household Public Shared 90 to 150 m 150 to 90 Inputs: Outputs: slough off. High-rate loading conditions will also cause cause also will conditions loading High-rate off. slough will and attached stay to ability its lose will state, nous layeroxygen;deprivedof be will enterwill it endoge an - With time, the biomass will grow thick and the attached and flushingof the filter material. improveeffluent theto for pattern wetting recirculation a with designed usually is filter trickling The collected. be to sludge excess and effluent the filter, allowing the of bottom the supports slab perforated A rate. filling maximum the at air for passageway a provide should ment performance and prevent odours. The underdrains Adequate air flow is important to ensure sufficienttreat- efficienttreatment. ensure to and clogging prevent to essential also is treatment Primary circulation. air good for provide and clogging to prone less are packing) plastic in (as pores Larger ic surface ic area surface between 45 and 60 m diameter between 7 and 10 cm. A material with a specif- ticles should be uniform and 95% of them should have a par The option. cheapest the is gravel or rock crushed light, and allows air to circulate. Whenever it is available, is ratio, volumeto surface high a has durable, and cost low- is filter material to12ideal up The be deep. can m Brownwater 2 /m Effluent Effluent 3 for plastic packing is normally used. used. normally is packing plastic for Greywater Systems 1,6-9 Applicable to: Blackwater Sludge 2 /m 3 for rocks and air outlet - must must be handled by backwashing and periodic flooding. and filters trickling with associated well are problems flies known filter and biofilm the on grazing Snails there power are failures. when or reduced is flow water the when night at atic - problem be may This kept moist. be must packing The should bedetermined the from fieldoperation. frequency filter. flushing the and rates dosing Optimum flush to used be can doses) (flushing rates loading lic ging and keep the biofilm thin and aerobic. High - hydrau filter must be periodically washed away to prevent clog- the on accumulates that sludge The problems. of case in pump the repair and filter the monitor to required is operator skilled A Operation &Maintenance solids treatment, all of which can still pose health risks. and discharge effluent treatment, primary and pre- for taken be must measures Appropriate businesses. and homes from away built be filter the that require lems - prob fly and Odour Health Aspects/Acceptance but specialadaptations for coldclimates required. are environments, all almost in built be can Tricklingfilters settlements. rural large, or peri-urban for suited best still are they although compact, are filters trickling T.5), Ponds, tion Stabiliza - Waste (e.g., technologies other to Compared ous supplyofpower andwastewater isrequired. continu- a general, in but designed, be can system ling trick (gravity) low-energy A clog. filter to the cause will loading solids high since clarification primary following Appropriateness andthe dischargeperature, requirements. tem- ambient the media, filter of type wastewater,the the of characteristics the on based determined is filter) the to applied be can wastewater much how (i.e., rate lodged from the filter. The hydraulic and nutrient loading mayhavethatdis- to remove anybiomass tank settling sloughing. The collected effluent should be clarified in a This technology can only be used used be only can technology This ------+ + + Pros &Cons _ Tchobanoglous, F. G.,Burton, L.andStensel, H.D.(2004). Reading References &Further EPA_ U.S. (2000).Wastewater Technology Fact Sheet. Trickling (Ed.),Reuter, A. _ Ulrich, S.(Ed.),Gutterer, B.(Ed.),Sasse,L., Eddy, 4 Wastewater Treatment Engineering: andReuse, Metcalf & (Detailed description andexample calculations) 890-930. includingtipsfor shooting) trouble (Design summary Available at: www.epa.gov cy, Washington, D.C.,US. Filters. 832-F-00-014. U.S. Environmental Protection- Agen ough University, UK. Leicestershire, Developing APractical Countries. Guide.WEDC, Loughbor Wastewater Treatment Systems (DEWATS) andSanitation in Panzerbieter, T. andReckerzügel, T. (2009).Decentralised Not all parts and materials mayNot belocallyavailable allparts treatment andprimary Risk ofclogging,dependingonpre- problematic often are Flies andodours wastewaterstant flow Requires andcon- ofelectricity source aconstant sonnel Requires andmaintenance operation by skilledper ly, the dosingsystem particular Requires designandconstruction, expert costs High capital wetlands to compared required Small landarea constructed (ammoniumEfficient nitrification oxidation) loading rates Can beoperated atarange oforganic andhydraulic th New York, Ed.(Internat. Ed.).McGraw-Hill, US.pp. - - - POST

121 Compendium of Sanitation Systems and Technologies T Functional Group T: (Semi-) Centralized Treatment .10