title: Dynamics of Fe(II), sulphur and phosphate in pilot-scale constructed wetlands treating a sulphate-rich chlorinated hydrocarbon contaminated groundwater.
abstract: Long-term investigations were carried out in two pilot-scale horizontal subsurface flow constructed wetlands (planted and unplanted) with an iron-rich soil matrix for treating sulphate-rich groundwater which was contaminated with low concentrations of chlorinated hydrocarbons. The temporal and spatial dynamics of pore-water sulphide, Fe(II) and phosphate concentrations in the wetland beds were characterized and the seasonal effects on sulphide production and nitrification inhibition were evaluated. The results demonstrated that the pore-water sulphide concentrations gradually increased from less than 0.2 mg/L in 2005 to annual average concentrations of 15 mg/L in 2010, while the pore-water Fe(II) concentrations decreased from 35.4 mg/L to 0.3 mg/L. From 2005 to 2010, the phosphate removal efficiency declined from 91% to 10% under a relatively constant inflow concentration of 5 mg/L. The pronounced effect of plants was accompanied by a higher sulphate reduction and ammonium oxidation in the planted bed, as compared to the unplanted control. A high tolerance of plants towards sulphide toxicity was observed, which might be due to the detoxification of sulphide by oxygen released by the roots. However, during the period of 2009-2010, the nitrification was negatively impacted by the sulphide production as the reduction in the removal of ammonium from 75% to 42% (with inflow concentration of 55 mg/L) correlated with the increasing mean annual sulphide concentrations. The effect of the detoxification of sulphide and the immobilization of phosphate by the application of the iron-rich soil matrix in the initial years was proven; however, the life-span of this effect should not only be taken into consideration in further design but also in scientific studies.
authors.affiliation: Key Laboratory of Agricultural Engineering in Structure and Environment of Ministry of Agricultural, College of Water Conservancy & Civil Engineering, China Agricultural University, 100083 Beijing, PR China.
authors.forename: Shubiao
authors.initials: S
authors.lastname: Wu
authors.forename: Zhongbing
authors.initials: Z
authors.lastname: Chen
authors.forename: Mareike
authors.initials: M
authors.lastname: Braeckevelt
authors.forename: Eva M
authors.initials: EM
authors.lastname: Seeger
authors.forename: Renjie
authors.initials: R
authors.lastname: Dong
authors.forename: Matthias
authors.initials: M
authors.lastname: Kästner
authors.forename: Heidrun
authors.initials: H
authors.lastname: Paschke
authors.forename: Anja
authors.initials: A
authors.lastname: Hahn
authors.forename: Gernot
authors.initials: G
authors.lastname: Kayser
authors.forename: Peter
authors.initials: P
authors.lastname: Kuschk
mesh_terms: D060587:Groundwater / Q000737:chemistry*; D006843:Hydrocarbons, Chlorinated / Q000302:isolation & purification; D007501:Iron / Q000032:analysis*; D010710:Phosphates / Q000032:analysis*; D010865:Pilot Projects; D016062:Porosity; D000644:Quaternary Ammonium Compounds / Q000302:isolation & purification; D012621:Seasons; D013431:Sulfates / Q000032:analysis*; D013440:Sulfides / Q000032:analysis; D013455:Sulfur / Q000032:analysis*; D013696:Temperature; D014865:Waste Disposal, Fluid; D014874:Water Pollutants, Chemical / Q000302:isolation & purification; D014876:Water Pollution / Q000032:analysis; D018508:Water Purification / Q000379:methods*; D060753:Water Quality; D053833:Wetlands
chemical_list: D006843:Hydrocarbons, Chlorinated; D010710:Phosphates; D000644:Quaternary Ammonium Compounds; D013431:Sulfates; D013440:Sulfides; D014874:Water Pollutants, Chemical; D013455:Sulfur; D007501:Iron