Remediation of PCE-contaminated groundwater from an industrial site in southern Italy: A laboratory-scale study Angela Volpe a, * , Guido Del Moro a , Simona Rossetti b , Valter Tandoi b , Antonio Lopez a a Consiglio Nazionale delle Ricerche, Istituto di Ricerca Sulle Acque, Sezione di Bari, Via Francesco De Blasio, 5, 70123 Bari, Italy b Consiglio Nazionale delle Ricerche, Istituto di Ricerca Sulle Acque, via Reno 1, 00198 Roma, Italy Received 31 January 2007; received in revised form 22 June 2007; accepted 24 July 2007 Abstract Batch reactors and microcosms were used to evaluate groundwater bioremediation potential of tetrachloroethene (PCE) in the presence of additional pollutants present at a site located in the Apulia Region (SE Italy). Reductive dechlorination of PCE was studied under anaerobic conditions by comparing the effectiveness of three inocula: (a) soil sampled at the contaminated site, (b) anaerobic sludge from a municipal wastewater plant, and (c) an enriched dehalogenating culture containing Dehalococcoides species. In order to enhance dehalogenation, reactors inoculated with sludge were also amended with selected electron donors. Aerobic reactors were also established to study oxidative degradation of vinyl chloride (VC), that may accumulate after incomplete dechlorination of PCE. Results showed that consortia derived from anaerobic sludge and amended with electron donors quantitatively and incompletely degraded PCE to cis-dichloroethylene, whereas in reactors augmented with a dehalogenating culture complete dechlorination of PCE occurred even in the presence of additional toxic contaminants. The presence of Dehalococcoides spp. in the dehalogenating culture and its absence in reactors inoculated with anaerobic sludge was confirmed using FISH community analyses. In all cases, prolonged incubation periods were necessary for dechlorination. On the other hand, oxidative degradation of VC in aerobic reactors occurred after short lag times. # 2007 Elsevier Ltd. All rights reserved. Keywords: Bioremediation; Bioaugmentation; Tetrachloroethylene (PCE); Dechlorination; Microcosms; Fluorescence in situ hybridization (FISH) 1. Introduction Remediation of groundwater is a high priority task, as emphasized by EU and national regulations concerning clean- up of contaminated sites [1–3]. Hence bioremediation technologies are receiving growing attention as cost-effective and in situ applicable strategies for environmental pollution control. Chlorinated ethenes are among the most common pollutants at industrial sites due to their extensive application in chemicals production, metal degreasing and dry cleaning. These compounds are environmentally persistent and many pose serious health threats due to their toxic and sometimes carcinogenic effects [4,5]. Studies carried out in the last 15 years have shown that chlorinated ethenes are subject to microbial degradation [6]. Due to their high oxidation state, chloroethenes are resistant to aerobic degradation but susceptible to reductive dechlorination under anaerobic conditions. Dechlorination of highly chlori- nated compounds such as tetrachloroethylene (PCE) and trichloroethylene (TCE) usually occurs by a stepwise hydro- genolysis mechanism [7], leading to formation of less chlorinated by-products and, eventually, to harmless ethylene [8]. Several bacterial strains can use chloroethenes as electron acceptors in a growth-supporting process known as halor- espiration [9]. Of these Dehalococcoides is the only bacterial genus known so far to completely dechlorinate PCE to ethylene. [10]. More commonly seen are bacteria capable of reducing PCE and TCE to the more toxic by-products cis- dichloroethylene (DCE) [11–13] and vinyl chloride (VC) [14]. Degradation of chloroethenes has also been shown to occur through anaerobic cometabolic pathways by methanogenic and acetogenic bacteria [6]. On the other hand, less chlorinated compounds such as DCE and VC are more easily oxidized than reduced [15]. Several examples of the aerobic biodegradation of DCE and VC either by growth-supporting or cometabolic pathways have also been reported [16–19]. www.elsevier.com/locate/procbio Process Biochemistry 42 (2007) 1498–1505 * Corresponding author. Fax: +39 080 5313365. E-mail address: angela.volpe@ba.irsa.cnr.it (A. Volpe). 1359-5113/$ – see front matter # 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.procbio.2007.07.017