Constructed Wetlands: Treatment of Concentrated Storm Water Runoff (Part A)

Abstract

The aim of this research was to assess the treatment efficiencies for gully pot liquor of experimental vertical-flow constructed wetland filters containing Phragmites australis (Cav.) Trin. ex Steud. (common reed) and filter media of different adsorption capacities. Six out of 12 filters received inflow water spiked with metals. For 2 years, hydrated nickel and copper nitrate were added to sieved gully pot liquor to simulate contaminated primary treated storm runoff. For those six constructed wetland filters receiving heavy metals, an obvious breakthrough of dissolved nickel was recorded after road salting during the first winter. However, a breakthrough of nickel was not observed, since the inflow pH was raised to eight after the first year of operation. High pH facilitated the formation of particulate metal compounds such as nickel hydroxide. During the second year, reduction efficiencies of heavy metal, 5-days at 20°C N-Allylthiourea biochemical oxygen demand (BOD) and suspended solids (SS) improved considerably. Concentrations of BOD were frequently Ͻ20 mg/L. However, concentrations for SS were frequently Ͼ30 mg/L. These are the two international thresholds for secondary wastewater treatment. The BOD removal increased over time due to biomass maturation, and the increase of pH. An analysis of the findings with case-based reasoning can be found in the corresponding follow-up paper (Part B).

Effect of artificial aeration on the performance of vertical-flow constructed wetland treating heavily polluted river water

“…Various CWs have been customized to treat polluted surface water (Lee et al, 2006;Mitsch et al, 2005), domestic, agricultural and industrial wastewaters (Ngo et al, 2010;Braskerud, 2002). Important factors affecting the treatment performance include the flow type, substrate characteristics, plant species, hydraulic loading rate (HLR) and temperature.…”

Policy implications of pollution swapping

“…mine waste (Demin et al, 2002) and urban storm water (Lee et al, 2006)) but there is an increased interest in the construction of wetlands for the management of diffuse pollution. There have been comparatively few studies investigating the use of constructed wetlands to treat diffuse pollution, the majority of information relates to semi-natural wetlands or those constructed for other purposes.…”

Constructed Wetlands: Prediction of Performance with Case-based Reasoning (Part B)

“…The processes within an experimental constructed treatment wetland are difficult to model due to the complexity of the relationships between most water quality variables (Gernaey et al, 2003;Nunez et al, 2004). However, it is necessary to monitor, control, and predict the treatment processes to meet environmental and sustainability policies, and regulatory requirements such as secondary wastewater treatment standards (Lee et al, 2005). CBR methodologies (Aamodt and Plaza, 1994) could be used to make water quality predictions and to optimize the operation of treatment wetlands.…”

“…A regulator such as the Scottish Environmental Protection Agency imposes thresholds for water quality variables. The corresponding secondary wastewater treatment thresholds for BOD and SS are 20 and 30 mg/L, respectively (Scholz et al, 2002;Lee et al, 2005).…”