Nutrient Retention in a Northern Prairie Marsh (Frank Lake,Alberta) Receiving Municipal and Agro-Industrial Wastewater

Agro-industrial wastewater and municipal sewage wereused to restore Frank Lake, a 1246 ha northernprairie marsh in southern Alberta, Canada, to providewaterfowl habitat and improve water quality. Meanannual inflow wastewater nutrient concentrations were17 mg L^-1 NH₃-N, 30 mg L^-1 NO₃-Nand 11 mg L^-1 SRP. Mean flows greater than 5000 m³ day^-1 loaded the marsh with 23 000 kg of P annually. Summer NH₃-N, NO₃-N andtotal phosphorus (TP) surface water concentrationswere decreased by 76, 87 and 64%, respectively, aswaters flowed through the first basin of the marsh.Winter treatment was less successful, with surfacewater NH₃-N, NO₃-N and TP reductions of46, –26 (export) and 26%, respectively.Short-circuiting of water flow through the marsh andcold seasonal conditions with ice cover caused spatialand temporal variation in marsh treatment. Continuedhigh loadings to the marsh may lead to sediment saturation, eutrophication or phosphorus export from the marsh.