Benzene, Toluene, Ethylbenzene, Xylene (BTEX) Removal in Experimental Vertical-Flow Constructed Wetlands

BTEX Removal in Experimental Vertical-Flow Constructed Wetlands

Abstract

Increase in the use of petroleum hydrocarbon as a source of energy has resulted in a tremendous increment in discharge of a wide diversity of hydrocarbon pollutants to the water and soil bodies. These pollutants are usually harmful and carcinogenic. Wetlands are a sustainable and cost-efficient technology to treat large quantities of these pollutants. The aim of this study is to explore the efficacy of different laboratory-scale vertical-flow constructed wetlands (VFCWs) filled with gravel and planted with common reed in degrading and removing BTEX (Benzene, Toluene, Ethylbenzene, Xylene) organic compounds as a function of different organic loading rates, media size, and contact and rest time. The wetlands were operated between September, 2013 and April, 2014 in a greenhouse located on top of Newton building, University of Salford, Manchester, UK. To evaluate the hydrocarbon pollution, approximately 130 grams of diesel fuel was poured into each of four wetland filters which is equivalent of a one-off inflow concentration of 20,000 mg/l. A range of hydraulic loading rates was applied across the systems using real urban wastewater. Analysis of BTEX hydrocarbon concentrations of effluent waters along with other water quality parameters were carried out to monitor both removal efficiency and treatment performance variations. The results indicated that all the BTEX hydrocarbon components treated in the wetland filters were highly degraded with high removal efficiency (above 90%) in all contaminated filters with some even attenuated below detection limit. However, with regards to water quality parameters, filters contaminated by hydrocarbon performed worse in terms of COD and BOD, but considerably better regarding nitrate-nitrogen, ortho-phosphate phosphorus and ammonia-nitrate removal.  This result has shown the robustness of VFCWs in eliminating BTEX organic compounds in urban waste-water. The successful removal of the hydrocarbon compounds and other pollutants will make constructed treatment wetlands very attractive and sustainable technology in environmental pollution control.