Nitrogen Removal in Column Wetlands Packed with Synthetic Fiber Treating Piggery Stormwater

Abstract

prevention of piggery stormwater is of vital difficulty due to the dispersibility and uncertainty of the occurrence and the pollution source. Piggery stormwater has attracted more and more attention, since it contains high concentration of nutrients (e.g. nitrogen, phosphorus and organic matters), toxic substances (e.g. ammonia, nitrate and toxic organics) and risky pathogens and bacterial. It pollutes rivers and seas (Al-Hafedh et al., 2003;Mearns et al., 2013) AbstractA set of lab-scale polymer synthetic fiber packed column wetlands composing three columns (CW1, CW2 and CW3) with different hydraulic regimes, recirculation frequencies and pollutant loading rates, were operated in 2012. Synthetic fiber tested as an alternative wetland medium for soil mixture or gravel which has been widely used, has very high pore size and volume, so that clogging opportunity can be greatly avoided. The inflow to the wetland was artificial stormwater. All the wetlands achieved effective removal of TSS (94%~96%), TCOD (68%~73%), TN (35%~58%), TKN (62%~73%) and NH 4 -N (85%~ 99%). Particularly, it was observed that COD was released from the fiber during one distinct period in all wetlands. This was probably due to the degradation of polymer fiber, and the released organic matters were found to serve as carbon source for denitrification. In addition, with longer retention time and frequent recirculation, lower effluent concentration was observed. With higher pollutant loading rate, higher nitrification and denitrification rates were achieved. However, although organic matters were released from the fiber, the lack of carbon source was still the limiting factor for the system since the release persisted only for 40 days.