Using 2,6-dichlorobenzamide (BAM) degrading Aminobacter sp. MSH1 in flow through biofilters—initial adhesion and BAM degradation potentials

Abstract

Micropollutants in groundwater are given significant attention by water companies and authorities due to an increasing awareness that they might be present even above the legal threshold values. As part of our investigations of the possibility to remove the common groundwater pollutant 2,6-dichlorobenzamide (BAM) by introducing the efficient BAM degrader Aminobacter sp. MSH1 into biologically active sand filters, we investigated if the strain adheres to filters containing various filter materials and if the initial adherence and subsequent degradation of BAM could be optimized. We found that most of the inoculated MSH1 cells adhered fast and that parameters like pH and ionic strength had only a minor influence on the adhesion despite huge influence on cell surface hydrophobicity. At the given growth protocol, the MSH1 strain apparently developed a subpopulation that had lost its ability to adhere to the filter materials, which was supported by attempted reinoculation of non-adhered cells. Analysis by quantitative PCR showed that most cells adhered in the top of the filters and that some of these were lost from the filters during initial operation, while insignificant losses occurred after 1 day of operation. The inoculated filters were found to degrade 2.7 μg/L BAM to below 0.1 μg/L at a 1.1-h residence time with insignificant formation of known degradation products. In conclusion, most filter materials and water types should be feasible for inoculation with the MSH1 strain, while more research into degradation at low concentrations and temperatures is needed before this technology is ready for use at actual waterworks.

Establishment of Bacterial Herbicide Degraders in a Rapid Sand Filter for Bioremediation of Phenoxypropionate-Polluted Groundwater

“…Coprecipitation of the herbicides with iron oxide precipitation was investigated by adding 14 C-labeled DCPP and MCPP to an iron(III) chloride-quartz sand slurry and then raising the pH to 7 to allow precipitation of iron oxides on the sand grains, as previously described (37).…”

Degradation of trace concentrations of the persistent groundwater pollutant 2,6-dichlorobenzamide (BAM) in bioaugmented rapid sand filters

“…Inoculation with MSH1 was carried out as follows: MSH1 was grown from a freeze-culture in 5 L sterile conical bottles as previously described (Albers et al, 2014). A ten liter culture containing 2 Â 10 12 bacteria/L was produced for each inoculation, corresponding to 10 13 MSH1-bacteria per filter.…”

“…The water level was then lowered quickly to the top of the filters and the top of the filter material was stirred with a shovel to ensure equal bacterial distribution in the top 20 cm. The bacteria were allowed to adhere for two hours before the filters were set into operation (Albers et al, 2014). Outlet water was sampled regularly during the first two hours of operation to determine loss of bacteria by turbidity (spectrophotometric absorbance at 600 nm) and quantitative real-time polymerase chain reaction (qPCR) analysis (section 2.4).…”

“…Water samples were collected in acid-washed and heated (300 C) glass bottles containing 1.5 mL preserving agent (3.5 M H 2 SO 4 ) and stored at 5 C until analysis of BAM and potential degradation products as described previously (Albers et al, 2014). Briefly, 500 mL samples were preconcentrated to 0.5 mL and analyzed on an Acquity UPLC with a BEH C18 1.7-mm column and a PDA UV detector (Waters Corp., Milford, MA).…”

“…MSH1, was isolated and shown to grow on BAM provided as carbon source (Sørensen et al, 2007;Simonsen et al, 2012). The bacterium adheres well to sand and was found to degrade an inlet BAM concentration of 3 mg/L to below the 0.1 mg/L threshold limit in a laboratory sand filter with a water residence time of one hour (Albers et al, 2014). The aim of the present study was to investigate the potential for remediation of BAM-polluted drinking water by introduction of Aminobacter sp.…”