Insights into Interactions between Vanadium (V) Bio-reduction and Pentachlorophenol Dechlorination in Synthetic Groundwater

Aquifer co-contamination by vanadium (V) and pentachlorophenol (PCP) involves complicated biogeochemical processes that remain poorly understood, particularly from the perspective of microbial metabolism. Batch experiment results demonstrated that V(V) and PCP could be competitively bio-reduced, with 96.0 ± 1.8% of V(V) and 43.4 ± 4.6% of PCP removed during 7 d operation. V(V) was bio-transformed to vanadium (IV), which could precipitate naturally under circumneutral conditions, facilitating the removal of up to 78.2 ± 3.1% dissolved total V. The PCP reductive dechlorination products were mainly 2,4,6-trichlorophenol and 4-monochlorophenol with lower toxicity. High-throughput 16S rRNA gene sequencing indicated that Pseudomonas, Soehngenia, and Anaerolinea might be responsible for the two bio-transformations, with detected functional genes of nirS and cprA. Extracellular reduction by cytochrome c and intracellular conversion by nicotinamide adenine dinucleotide (NADH) occurred for both V(V) and PCP. Extracellular proteins in microbial-secreted extracellular polymeric substances (EPS) might also be involved in these enzymatic bioprocesses. EPS could protect microbial cells through V(V) binding by the chemically reactive carboxyl (COO−), and hydroxyl (–OH) groups. These findings elucidate the metabolic processes during anaerobic V(V) and PCP biotransformation, advance understanding of their biogeochemical fates, and provide a foundation on which to develop novel strategies for remediation of co-contaminated aquifers

Utilization of single-chamber microbial fuel cells as renewable power sources for electrochemical degradation of nitrogen-containing organic compounds

By employing promising single-chamber microbial fuel cells (MFCs) as renewable power sources, an aerated electrochemical system is proposed and for nitrogen-containing organic compounds (pyridine and methyl orange) removals. Carbon felt performed the best as electrode material while lower initial contaminant concentration and lower initial pH value could improve the performance. A degradation efficiency of 82.9% for pyridine was achieved after 360 min electrolysis with its initial concentration of 200 mg/L, initial pH of 3.0 and applied voltage of 700 mV. Mechanisms study implied that indirect electrochemical oxidation by generated hydrogen peroxide was responsible for their degradation. This study provides an alternative utilization form of low bioelectricity from MFCs and reveals that applying it to electrochemical process is highly-efficient as well as cost-effective for degradation of nitrogen-containing organic compounds. (C) 2015 Elsevier B.V. All rights reserved.National Natural Science Foundation of China (NSFC) [21307117, 41440025]; Research Fund for the Doctoral Program of Higher Education of China [20120022120005]; Beijing Excellent Talent Training Project [2013D009015000003]; Beijing Higher Education Young Elite Teacher Project [YETP0657]; Fundamental Research Funds for the Central Universities [2652015226, 2652015131]SCI(E)[email protected]