Microbial communities biostimulated by ethanol during uranium （VI） bioremediation in contaminated sediment as shown by stable isotope probing

Stable isotope probing （SIP） was used to identify microbes stimulated by ethanol addition in microcosms containing two sediments collected from the bioremediation test zone at the US Department of Energy Oak Ridge site, TN, USA. One sample was highly bioreduced with ethanol while another was less reduced. Microcosms with the respective sediments were amended with ^13C labeled ethanol and incubated for 7 days for SIP. Ethanol was rapidly converted to acetate within 24h accompanied with the reduction of nitrate and sulfate. The accumulation of acetate persisted beyond the 7 d period. Aqueous U did not decline in the microcosm with the reduced sediment due to desorption of U but continuously declined in the less reduced sample. Microbial growth and concomitant 13C-DNA production was detected when ethanol was exhausted and abundant acetate had accumulated in both microcosms. This coincided with U（VI） reduction in the less reduced sample. I3C originating from ethanol was ultimately utilized for growth, either directly or indirectly, by the dominant microbial community members within 7 days of incubation. The microbial community was comprised predominantly of known denitrifiers, sulfate-reducing bacteria and iron （Ⅲ） reducing bacteria including Desulfovibrio, Sphingomonas, Ferribacterium, Rhodanobacter, Geothrix, Thiobacillus and others, including the known U（VI）-redueing bacteria Acidovorax, Anaeromyxobacter, Desulfovibrio, Geobac- ter and Desulfosporosinus. The findings suggest that ethanol biostimulates the U（VI）-reducing microbial com- munity by first serving as an electron donor for nitrate, sulfate, iron （IH） and U（VI） reduction, and acetate which then functions as electron donor for U（VI） reduction and carbon source for microbial growth.

Vegetated treatment area (VTAs) efficiencies for E. coli and nutrient removal on small-scale swine operations

As small-scale animal feeding operations work to manage their byproducts and avoid regulation, they need practical, cost-effective methods to reduce environmental impact. One such option is using vege-tative treatment areas (VTAs) with perennial grasses to treat runoff;however, research is limited on VTA effectiveness as a waste management alternative for smaller operations. This study evaluated the effi-ciencies of VTAs in reducing bacteria and nutrient runoff from small-scale swine operations in three counties in Central Texas. Based on 4 yr of runoff data, the Bell and Brazos VTAs significantly reduced loads and concentrations of E. coli and nutrients (except NO3-N) and had treatment efficiencies of 73–94%. Most notably, the Bell VTA reduced loads of E. coli, NH4-N, PO4-P, total N, and total P similar to that of the background (control). In spite of significant reductions, runoff from the Brazos VTA had higher concentrations and loads than the control site, especially following installation of concrete pens and increased pen washing, which produced standing water and increased E. coli and nutrient influx. The Robertson VTA produced fewer significant reductions and had lower treatment efficiencies (29–69%);however, E. coli and nutrient concentrations and loads leaving this VTA were much lower than observed at the Bell and Brazos County sites due to alternative solids management and enclosed pens. Based on these results and previous research, VTAs can be practical, effective waste management alternatives for reducing nutrient and bacteria losses from small-scale animal operations, but only if properly designed and managed.