Nutrient retention in a northern prairie marsh (Frank Lake, Alberta) receiving municipal and agro-industrial wastewater

Agro-industrial wastewater and municipal sewage were used to restore Frank Lake, a 1246 ha northern prairie marsh in southern Alberta, Canada, to prov ide waterfowl habitat and improve water quality. Mean annual inflow wastewa ter nutrient concentrations were 17 mg L-1 NH3-N, 30 mg L-1 NO3-N and 11 mg L-1 SRP. Mean flows greater than 5000 m(3) day(-1) loaded the marsh with 2 3 000 kg of P annually. Summer NH3-N, NO3-N and total phosphorus (TP) surfa ce water concentrations were decreased by 76, 87 and 64%, respectively, as waters flowed through the first basin of the marsh. Winter treatment was le ss successful, with surface water NH3-N, NO3-N and TP reductions of 46, -26 (export) and 26%, respectively. Short-circuiting of water flow through the marsh and cold seasonal conditions with ice cover caused spatial and tempo ral variation in marsh treatment. Continued high loadings to the marsh may lead to sediment saturation, eutrophication or phosphorus export from the m arsh.