title: Effects of sorption, sulphate reduction, and Phragmites australis on the removal of heavy metals in subsurface flow constructed wetland microcosms.
abstract: The removal of Co, Ni, Cu and Zn from synthetic industrial wastewater was studied in subsurface flow constructed wetland microcosms filled with gravel or a gravel/straw mixture. Half of the microcosms were planted with Phragmites australis and half were left unplanted. All microcosms received low-strength wastewater (1 mg L(-1) of Co, Ni, and Zn, 0.5 mg L(-1) Cu, 2,000mg L(-1) SO4) during seven 14-day incubation batches. The pore water was regularly monitored at two depths for heavy metals, sulphate, organic carbon and redox potential. Sorption properties of gravel and straw were assessed in a separate experiment. A second series of seven incubation batches with high-strength wastewater (10 mg L(-1) of each metal, 2,000 mg L(-1) SO4) was then applied to saturate the substrate. Glucose was added to the gravel microcosms together with the high-strength wastewater. Sorption processes were responsible for metal removal during start-up, with the highest removal efficiencies in the gravel microcosms. The lower initial efficiencies in the gravel/straw microcosms were presumably caused by the decomposition of straw. However, after establishment of anaerobic conditions (Eh approximately -200 mV), precipitation as metal sulphides provided an additional removal pathway in the gravel/straw microcosms. The addition of glucose to gravel microcosms enhanced sulphate reduction and metal removal, although Phragmites australis negatively affected these processes in the top-layer of all microcosms.
authors.affiliation: Laboratory of Analytical Chemistry and Applied Ecochemistry, Ghent University, Coupure Links 653, 9000 Ghent, Belgium. els.lesage@ugent.be
authors.forename: E
authors.initials: E
authors.lastname: Lesage
authors.forename: D P L
authors.initials: DP
authors.lastname: Rousseau
authors.forename: A
authors.initials: A
authors.lastname: Van de Moortel
authors.forename: F M G
authors.initials: FM
authors.lastname: Tack
authors.forename: N
authors.initials: N
authors.lastname: De Pauw
authors.forename: M G
authors.initials: MG
authors.lastname: Verloo
mesh_terms: D000327:Adsorption; D001673:Biodegradation, Environmental; D019216:Metals, Heavy / Q000302:isolation & purification*; D013431:Sulfates / Q000737:chemistry*; D014865:Waste Disposal, Fluid; D014872:Water Movements; D018508:Water Purification / Q000379:methods*; D053833:Wetlands