Nitrogen reduction in stormwater from livestock lots by vertical subsurface flow wetlands packed with woodchips

Abstract

A B S T R A C TThis study was done to investigate the performance of vertical subsurface flow (VSF) wetlands with additional carbon sources in reducing the nitrogen in stormwater from livestock lots. Three experimental lab-scale VSF wetlands packed with woodchips were constructed. The wetlands were operated with number of dry days (NDD) of 2, 4, and 8, respectively, for a duration of 136 d. The average removal efficiencies of total nitrogen (TN) were 26.2, 34.1, and 50.0% at NDD as 2, 4, and 8, respectively. The average nitrogen removal rate based on woodchips volume was 3.6 g N m −3 d −1 for NDD of 2, 2.1 g N m −3 d −1 for NDD of 4, and 1.7 g N m −3 d −1 for NDD of 8. Nitrification and denitrification were the major mechanisms of nitrogen reduction in the studied wetlands. The contribution of other pathways to nitrogen removal was small. The removal of total Kjeldahl nitrogen (TKN) and TN was not affected by the influent pH, whereas the removal of TKN was enhanced by the increase in influent alkalinity. Nitrification was promoted by the abundant oxygen supplied during the course of recirculation, whereas denitrification might be suppressed to some degree by the oxygen.

Integrated wetlands for food production

“…It is regarded as a low cost, and a low carbon method for wastewater treatment and has been applied in food production processes. For instances: CTWs have been used to treat the wastewater from animal husbandry (Hammer et al, 1993;Lee et al, 2014;Niu et al, 2015) and aquaculture (Lin et al, 2002a;Schwartz and Boyd, 1995), and non-point source pollution from agriculture (O'Geen et al, 2010). It has also been applied to lower heavy metal bioaccumulation (Cheng et al, 2002;Guittonny-Philippe et al, 2014;Yadav et al, 2012), and mitigate the use of hazardous pesticides (Kohler et al, 2004;Krone-Davis et al, 2013;Vymazal and Březinová, 2015).…”