title: The potential for bioaugmentation of sand filter materials from waterworks using bacterial cultures degrading 4-chloro-2-methylphenoxyacetic acid.
abstract: BACKGROUND
  The herbicide 4-chloro-2-methylphenoxyacetic acid (MCPA) is found frequently in Danish groundwater in concentrations exceeding the EU threshold limit of 0.1 µg L(-1) . Groundwater is used for drinking water, and one potential remediation strategy is bioaugmentation using inoculation of sand filters at affected waterworks with degrader bacteria. Numerous bacteria degrading phenoxyacetic acid herbicide have previously been isolated, and they may be candidates for bioaugmentation processes. Designing the optimum inoculum, however, requires knowledge of the capacity for degrading realistically low herbicide concentrations and the robustness of the bacteria when inoculated into sand filter materials.
  
  
  RESULTS
  Testing a range of different MCPA-mineralising bacterial combinations, using a high-throughput microplate radiorespirometric mineralisation assay, highlighted three efficient cocultures for mineralising low MCPA concentrations. Cocultures demonstrating a shorter time delay before initiation of (14) C-ring-labelled MCPA mineralisation to (14) CO2 , and a more extensive mineralisation of MCPA, compared with those of single strains, were found. When inoculated into different sand filter materials, the coculture effect was diminished, but several single strains enhanced MCPA mineralisation significantly at low MCPA concentrations.
  
  
  CONCLUSIONS
  This study shows that an increase in the potential for mineralisation of low herbicide concentrations in sand filter materials can be achieved by inoculating with bacterial degrader cultures. © 2014 Society of Chemical Industry.
authors.affiliation: Department of Geochemistry, Geological Survey of Denmark and Greenland, Copenhagen, Denmark.
authors.forename: Urse S
authors.initials: US
authors.lastname: Krüger
authors.forename: Anders R
authors.initials: AR
authors.lastname: Johnsen
authors.forename: Mette
authors.initials: M
authors.lastname: Burmølle
authors.forename: Jens
authors.initials: J
authors.lastname: Aamand
authors.forename: Sebastian R
authors.initials: SR
authors.lastname: Sørensen
mesh_terms: D008456:2-Methyl-4-chlorophenoxyacetic Acid / Q000378:metabolism*; D001419:Bacteria / Q000378:metabolism*; D003718:Denmark; D005374:Filtration; D060587:Groundwater / Q000032:analysis*; D006540:Herbicides / Q000378:metabolism*; D012822:Silicon Dioxide / Q000737:chemistry; D018508:Water Purification / Q000379:methods*
chemical_list: D006540:Herbicides; D012822:Silicon Dioxide; D008456:2-Methyl-4-chlorophenoxyacetic Acid
keywords: bacterial cocultures; bioaugmentation; biodegradation; sand filter