title: Combination of aquifer thermal energy storage and enhanced bioremediation: resilience of reductive dechlorination to redox changes.
abstract: To meet the demand for sustainable energy, aquifer thermal energy storage (ATES) is widely used in the subsurface in urban areas. However, contamination of groundwater, especially with chlorinated volatile organic compounds (CVOCs), is often being encountered. This is commonly seen as an impediment to ATES implementation, although more recently, combining ATES and enhanced bioremediation of CVOCs has been proposed. Issues to be addressed are the high water flow velocities and potential periodic redox fluctuation that accompany ATES. A column study was performed, at a high water flow velocity of 2 m/h, simulating possible changes in subsurface redox conditions due to ATES operation by serial additions of lactate and nitrate. The impacts of redox changes on reductive dechlorination as well as the microbial response of Dehalococcoides (DHC) were evaluated. The results showed that, upon lactate addition, reductive dechlorination proceeded well and complete dechlorination from cis-DCE to ethene was achieved. Upon subsequent nitrate addition, reductive dechlorination immediately ceased. Disruption of microorganisms' retention was also immediate and possibly detached DHC which preferred attaching to the soil matrix under biostimulation conditions. Initially, recovery of dechlorination was possible but required bioaugmentation and nutrient amendment in addition to lactate dosing. Repeated interruption of dechlorination and DHC activity by nitrate dosing appeared to be less easily reversible requiring more efforts for regenerating dechlorination. Overall, our results indicate that the microbial resilience of DHC in biosimulated ATES conditions is sensitive to redox fluctuations. Hence, combining ATES with bioremediation requires dedicated operation and monitoring on the aquifer geochemical conditions.
authors.affiliation: Sub-Department of Environmental Technology, Wageningen University, P.O. Box 17, 6700 AA, Wageningen, the Netherlands. nizhuobiao@hotmail.com.|Wetsus, European Centre of Excellence for Sustainable Water Technology, P.O. Box 1113, 8900 CC, Leeuwarden, the Netherlands. nizhuobiao@hotmail.com.
authors.forename: Zhuobiao
authors.initials: Z
authors.lastname: Ni
authors.affiliation: Soil and Groundwater Systems, Deltares, P.O. Box 85467, 3508 AL, Utrecht, the Netherlands.
authors.forename: Pauline
authors.initials: P
authors.lastname: van Gaans
authors.affiliation: Sub-Department of Environmental Technology, Wageningen University, P.O. Box 17, 6700 AA, Wageningen, the Netherlands.|Eurofins Analytico, P.O. Box 459, 3770 AL, Barneveld, the Netherlands.
authors.forename: Martijn
authors.initials: M
authors.lastname: Smit
authors.affiliation: Sub-Department of Environmental Technology, Wageningen University, P.O. Box 17, 6700 AA, Wageningen, the Netherlands.
authors.forename: Huub
authors.initials: H
authors.lastname: Rijnaarts
authors.affiliation: Sub-Department of Environmental Technology, Wageningen University, P.O. Box 17, 6700 AA, Wageningen, the Netherlands.
authors.forename: Tim
authors.initials: T
authors.lastname: Grotenhuis
mesh_terms: D001673:Biodegradation, Environmental; D041862:Chloroflexi / Q000378:metabolism*; D060587:Groundwater / Q000737:chemistry* / Q000382:microbiology; D054879:Halogenation; D010084:Oxidation-Reduction; D055549:Volatile Organic Compounds / Q000737:chemistry* / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000378:metabolism
chemical_list: D055549:Volatile Organic Compounds; D014874:Water Pollutants, Chemical
keywords: Aquifer thermal energy storage (ATES); Dehalococcoides; Microbial resilience; Redox potential (E Ag/AgCl); Reductive dechlorination; cis-dichloroethene (cis-DCE)