Treatment of a mixed wood preservative leachate by a hybrid constructed wetland and a willow planted filter

• Published in: Water science and technology Vol. 76; no. 1-2; pp. 164 - 171
• Main Authors: Lévesque, S, Demers, E, Brisson, J, Comeau, Y
• Format: Journal Article
• Language: English
• Published: England IWA Publishing 01-07-2017
• Subjects: Adsorption; Arsenates; Arsenates - chemistry; Arsenic; Artificial wetlands; Benzofurans - chemistry; Chlorination; Chromated copper arsenate; Chromates; Chromium; Chromium - chemistry; Contamination; Copper; Copper - chemistry; Copper arsenate; Dechlorination; Dioxins; Discharge; Evapotranspiration; Iron; Leachates; Mammals; Manganese; Metabolism; Pentachlorophenol; Pentachlorophenol - chemistry; Polychlorinated dibenzodioxins; Polychlorinated dibenzofurans; Polymers - chemistry; Precipitation; Preservatives; Rain; Salix - chemistry; Settling basins; Storm sewers; Wetlands; Willow; Wood - chemistry; Wood poles; Wood preservatives
• ISSN: 0273-1223; 1996-9732
• DOI: 10.2166/wst.2017.197

The performance and removal mechanisms of a hybrid constructed wetland (HCW) followed by a willow planted filter (WPF) were evaluated for the treatment of a leachate contaminated by wood pole preservatives (pentachlorophenol (PCP) and chromated copper arsenate) to reach the storm sewer discharge limits. The HCW aimed to dechlorinate the PCP and polychlorodibenzo-p-dioxins/polychlorodibenzofuran (PCDD/F) and to remove metals by adsorption and precipitation. The HCW was efficient in removing PCP (>98.6%), oil, arsenic (99.4%), chromium (>99.2%), copper (>99.6%%) and iron (29%) to under their discharge limits, but it was unable to reach those of Mn and PCDD/F, with residual concentrations of 0.11 mg Mn/L and 0.32 pg TEQ/L. Iron and manganese could be removed but were subsequently released by the HCW due to low redox conditions. No dechlorination of PCDD/F was observed since its chlorination profile remained the same in the different sections of the HCW. Adsorption was the most probable removal mechanism of PCDD/F. The WPF was able to remove some residual contamination, but it released Mn at a gradually decreasing rate. Total evapotranspiration of the leachate by a larger fertilized WPF and the construction of an underground retention basin are proposed to prevent any discharge of PCDD/F traces in the environment.