Welz, Pamela J.Ramond, Jean-BaptisteBraun, LorenzVikram, SurendraLe Roes-Hill, Marilize2019-01-112018-02Welz P.J., Ramond J.-B., Braun L. et al. 2018, 'Bacterial nitrogen fixation in sand bioreactors treating winery wastewater with a high carbon to nitrogen ratio', Journal of Environmental Management, vol. 207, pp. 192-202.0301-4797 (print)1095-8630 (online)10.1016/j.jenvman.2017.11.015http://hdl.handle.net/2263/68129Heterotrophic bacteria proliferate in organic-rich environments and systems containing sufficient essential nutrients. Nitrogen, phosphorus and potassium are the nutrients required in the highest concentrations. The ratio of carbon to nitrogen is an important consideration for wastewater bioremediation because insufficient nitrogen may result in decreased treatment efficiency. It has been shown that during the treatment of effluent from the pulp and paper industry, bacterial nitrogen fixation can supplement the nitrogen requirements of suspended growth systems. This study was conducted using physicochemical analyses and culture-dependent and -independent techniques to ascertain whether nitrogen-fixing bacteria were selected in biological sand filters used to treat synthetic winery wastewater with a high carbon to nitrogen ratio (193:1). The systems performed well, with the influent COD of 1351 mg/L being reduced by 84–89%. It was shown that the nitrogen fixing bacterial population was influenced by the presence of synthetic winery effluent in the surface layers of the biological sand filters, but not in the deeper layers. It was hypothesised that this was due to the greater availability of atmospheric nitrogen at the surface. The numbers of culture-able nitrogen-fixing bacteria, including presumptive Azotobacter spp. exhibited 1–2 log increases at the surface. The results of this study confirm that nitrogen fixation is an important mechanism to be considered during treatment of high carbon to nitrogen wastewater. If biological treatment systems can be operated to stimulate this phenomenon, it may obviate the need for nitrogen addition.en© 2017 Elsevier Ltd. All rights reserved. Notice : this is the author’s version of a work that was accepted for publication in Journal of Environmental Management. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. A definitive version was subsequently published in Journal of Environmental Management, vol. 207, pp. 192-202. 2018. doi : 10.1016/j.jenvman.2017.11.015.Bacterial nitrogen fixationBiological sand filtersHigh C:N wastewaterWinery wastewaterBacteria (microorganisms)AzotobacterWater samplingWaste water managementSurface propertySpecies differentiationSandRhizobialesRestriction fragment length polymorphismPlanktonPhysical chemistryNitrogen-fixing bacteriumNitrogen fixationnifH geneNext generation sequencingMicrobial communityMetagenomicsGram stainingGeobacterGammaproteobacteriaEffluentDNA extractionDiazotrophDeltaproteobacteriaConcentration (parameters)Community structureChemical oxygen demandBioremediationBiofilmBacterium cultureBacterial geneBacterial colonizationAzotobacterAmpliconAlphaproteobacteriaPostprint Article