Free water surface wetlands for wastewater treatment in Sweden: nitrogen and phosphorus removal

Abstract

In South Sweden, free water surface wetlands have been built to treat wastewater from municipal wastewater treatment plants. Commonly, nitrogen removal has been the prime aim, though a significant removal of tot-P and BOD7 has been observed. In this study, performance data for 3-8 years from four large (20-28 ha) FWS wetlands have been evaluated. Two of them receive effluent from WWTP with only mechanical and chemical treatment. At the other two, the wastewater has also been treated biologically resulting in lower concentrations of BOD7 and NH4+-N. The wetlands performed satisfactorily and removed 0.7-1.5 ton N ha(-1) yr(-1) as an average for the time period investigated, with loads between 1.7 and 6.3 ton N ha(-1)yr(-1). Treatment capacity depended on the pre-treatment of the water, as reflected in the k20-values for N removal (first order area based model). In the wetlands with no biological pre-treatment, the k20-values were 0.61 and 1.1 m month(-1), whereas for the other two they were 1.7 and 2.5 m month(-1). P removal varied between 10 and 41 kg ha(-1) yr(-1), and was related to differences in loads, P speciation and to the internal cycling of P in the wetlands.

Nitrogen removal from nitrate-laden wastewater by integrated vertical-flow constructed wetland systems

“…Wastewater and nonpoint runoff are the main sources of nitrate supply for natural water bodies. Treated wastewater from conventional activated sludge wastewater treatment plants with nitrification generally contains relatively high concentrations of nitrate but low levels of organic matter (Spieles and Mitsch, 2000;Andersson et al, 2005;Leverenz et al, 2010). Nitrate is also the predominant nitrogen form in nonpoint sources; especially from agricultural runoff due to increasing application of nitrogen fertilizer, which accounts for two-thirds of nitrogen loading to surface waters (Howarth et al, 1996;Beutel et al, 2009;Tanner and Sukias, 2011).…”

Treatment Wetlands as Ecotechnological Tools for Regenerative Reclamation of Wastewater: Experiences from Working with Kalyani Model

“…A lower nitrogen removal has been observed in wetlands receiving large concentrations of ammonium nitrogen, i.e. municipal wastewater, than in those receiving nitrogen in the form of nitrate [3].…”

“…High sedimentation rate of organic matter in AP (1381.5-2409.6 g day -1 m -3 ) implied that Cd was precipitated rapidly in AP. Presence of profuse DO (7.46-17.0 mg L -1 ) in facultative pond created conducive condition for the formation of Fe(OH) 3 and its subsequent removal from FP water was attained the highest level.…”

“…Removal of pollutants relies on a combination of physical, chemical and biological processes naturally occurring in wetlands and are associated with vegetation, sediments and their microbial communities. As biologically active ecosystems bolstered with many active bio-filters wetlands transform many pollutants at a high rate and have increasingly been used for wastewater treatment [3].…”

Assessing the Integration of Wetlands along Small European Waterways to Address Diffuse Nitrate Pollution

“…In this case, the surface water flow, the NO 3 -N concentrations of the waterway, air temperature fluctuations due to seasonality, and nitrate removal rates were the parameters of focus for the development of this conceptual model. Andersson et al [26], Carleton et al [49], and Tonderski et al [11] took into account the same parameters to estimate the reduction of nitrogen and phosphorus in potential wetlands. The outcome of the developed dynamic mass balance model showed a positive contribution of the air temperature on the water balance to simulate the nutrient dynamics and to determine the impact of CWs on their reduction.…”