Evaluation of solid polymeric organic materials for use in bioreactive sediment capping to stimulate the degradation of chlorinated aliphatic hydrocarbons

Abstract

In situ bioreactive capping is a promising technology for mitigation of surface water contamination by discharging polluted groundwater. Organohalide respiration (OHR) of chlorinated ethenes in bioreactive caps can be stimulated through incorporation of solid polymeric organic materials (SPOMs) that provide a sustainable electron source for organohalide respiring bacteria. In this study, wood chips, hay, straw, tree bark and shrimp waste, were assessed for their long term applicability as an electron donor for OHR of cis-dichloroethene (cDCE) and vinyl chloride (VC) in sediment microcosms. The initial release of fermentation products, such as acetate, propionate and butyrate led to the onset of extensive methane production especially in microcosms amended with shrimp waste, straw and hay, while no considerable stimulation of VC dechlorination was obtained in any of the SPOM amended microcosms. However, in the longer term, short chain fatty acids accumulation decreased as well as methanogenesis, whereas high dechlorination rates of VC and cDCE were established with concomitant increase of Dehalococcoides mccartyi and vcrA and bvcA gene numbers both in the sediment and on the SPOMs. A numeric simulation indicated that a capping layer of 40 cm with hay, straw, tree bark or shrimp waste is suffice to reduce the groundwater VC concentration below the threshold level of 5 μg/l before discharging into the Zenne River, Belgium. Of all SPOMs, the persistent colonization of tree bark by D. mccartyi combined with the lowest stimulation of methanogenesis singled out tree bark as a long-term electron donor for OHR of cDCE/VC in bioreactive caps.

An analytical model for chemical diffusion in layered contaminated sediment systems with bioreactive caps

“…72 Following the systematized procedure of the CITT, an auxiliary homogeneous problem for the space variable function ψ m (ω) in the same layers of the original problem needs to be defined. An auxiliary problem can be obtained by applying separation of variables to Equations (14) to (21):…”

“…The active caps incorporating reactive or sorptive constituents are designed to reduce contaminant flux . For instance, the coke and other “active” materials (eg, activated carbon and kraft lignin) are used as capping to enhance sorption in order to reduce the availability of the contaminant and improve the effectiveness of in situ capping . The isolation times provided by the sorbent layers increased with the increase of sorption strength and capacity (activated carbon >> coke ≈ soil >> sand) .…”

“…[8][9][10] For instance, the coke and other "active" materials (eg, activated carbon and kraft lignin) are used as capping to enhance sorption in order to reduce the availability of the contaminant and improve the effectiveness of in situ capping. 5,[11][12][13][14][15] The isolation times provided by the sorbent layers increased with the increase of sorption strength and capacity (activated carbon >> coke ≈ soil >> sand). 5 Eek et al 1 developed the laboratory microcosm test to measure the diffusion of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) from sediment with different capping layers.…”

Ecophysiology and environmental distribution of organohalide-respiring bacteria

“…Similar presence of Dehalobacter [225] and D. mccartyi [225,226] was noticed in a number of follow up studies using microcosms prepared with material from the same site, whereas no Desulfitobacterium was detected. In both microcosm studies, VC RDase encoding vcrA, and bvcA genes were the most abundant rdhA genes [225,226].…”

“…However, in spite of repeated detection of biomarkers associated with OHRB in the field, microcosm studies with Zenne riverbed sediments [224][225][226] and high OHR performance in microcosm studies with material from different locations at the Zenne river site [222,226], high spatial variability of OHR potential was observed in field measurements from the 39 2…”