Content of presentation. Long-term effects, maintenance and costs for wastewater treatment wetlands in Sweden. Alhagen - Nynäshamn

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1 Long-term effects, maintenance and costs for wastewater treatment wetlands in Sweden Content of presentation Background Wetlands Treatment results Maintenance Costs Questions, discussion 3-5- Linda Flyckt MSc project at Linköping university for WRS Uppsala AB Background - Seven wetlands for polishing of wastewater Treatment results over time (Tot-N, NH4-N, BOD, TotP) Wetland maintenance Cost efficiency Nitrogen treatment - ha Foto: Energi & Miljö Nitrogen treatment - ha - SBR operating since Nitrogen treatment ha SBR operating since 5 Foto: s kommun Ritning: WRS Uppsala AB

2 Phosphorus- and nitrogen treatment - ha Nitrogen, BOD, pathogens - 5,3 ha Foto: kommun Ritning: s kommun - Örsundsbro - Enköping - - Nitrogen, phosphorus, BOD, pathogens - 2,3 ha Phosphorus and BOD -,6 ha Foto: kommun Bild: Enköpings kommun How large Nitrogen removal has been achieved? The average total-n removal was 32 kg/(ha yr) representing about 3 % of the load Total wetland ha area flow m3/d Hydraulic load mm/d The total-n concentrations were reduced from an average 22 to 3 mg/l Retention time Enköping Örsundsbro ,3 2,3,6 5-9, d Out 6, , 5,9 3 6, 2 6,6 Out 2,6 4,5 9 4,5, 5,8 3 4, 8 Concentration (mg/l) The ammonium-n concentrations were from to.5 mg/l. Tot-N NH4-N 2

3 Wetlandswitha higherarea specificloadhada higherremovalof total-n 3 Removal kg N/(ha yr) 25 5 Örsundsbro Load kg N/(ha yr) Howwellhas phosphorusand BOD been removed? Phosphorus The averageremovalwas46 kg/(ha yr) representing65 % ofthe load. Concentrationsoftotal-P werereducedfrom an averageof.3 to. mg/l. BOD ConcentrationsofBOD werereducedfrom an average of to3.6 mg/l. Total wetland area Hydraulic load Concentrations(mg/l) Differencesbetweenwetlandsin total-p and BOD removal Enköping Örsundsbro ha 5,3 2,3,6,8 mm/d Tot-P,,25,39,3,5,43,,36,52,49,42 Out,,3,,6,6,3,,,,9, BOD 4,6 4,2 35 9, 22 3, 4, 9,5 9, Out 4,2 4,3 3,9 3, 3,9 3,2 5, 3, 3, 3,3 2,2 Total-P concentrationsin the letand Outlet ofthe wetlandsin and mg/l mg/l,6,4,2,8,6,4,2 Ut ,5 3, wetland Ut 2,5 2,,5,,5 wetland, Removal kg P/(ha yr) Wetlandswitha higherloadhada higher removal of total-p y =,688x -,2948 R² = 85 % Load kg P/(ha yr) 3

4 Concentrations of total-p in the inflow and outflow from wetland, mg /l 3 2,5 2,5,5 Ut Maintenance requirements The maintenanceneedsvarieddependingon design and main goal Removalofplants and sediment from canals/ditches on demand (, and ) Sediment removal at inlet(annually in ) Plant cutting(annually in overland flow areas and along the shores and paths for recreational purposes) Costs vestment (capital) costs land, projectdocuments, pumps and pipes, construction.depreciationtime years Operation costs(includes monitoring) Keyfigures(Kr/kg N or P removed) Differences in costs between wetlands Yearof construction Weltandarea ha 5,3 2,3 Capitalcost Mkr 3,5 5 5 Capitalcost-8 Mkr 8 O&Mcosts tkr/år O&M costs (incl. pumping) Pump.costs tkr/år % of total Concluding remarks Wetlandarea ha 5,3 2,3 Annualcosts tkr/yr O&Mtotal % RemovalN kg/yr RemovalP kg/yr 38 6 KeyfigureN kr/kg KeyfigureP kr/kg The function of the wetlands has been good Small maintenance requirements No clear indications of a decreasing actual removal Cost-efficient Good access for public in all wetlands Contribute biodiversity in a dried landscape. Occasional release ofphosphorusseemrelatedtoshiftin the typeofchemicalusedin the P precipitation. Flowvariations areoftenevenedout. 4

5 THANKS! Linda Flyckt Ragn-Sells Avfallsbehandling AB Telefon: 8-5Mobil: 9-2 E-post: 5