Bacterially mediated removal of phosphorus and cycling of nitrate and sulfate in the waste stream of a "zero-discharge" recirculating mariculture system

M D Krom, A Ben David, E D Ingall, L G Benning, S Clerici, S Bottrell, C Davies, N J Potts, R J G Mortimer, J van Rijn

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

Simultaneous removal of nitrogen and phosphorus by microbial biofilters has been used in a variety of water treatment systems including treatment systems in aquaculture. In this study, phosphorus, nitrate and sulfate cycling in the anaerobic loop of a zero-discharge, recirculating mariculture system was investigated using detailed geochemical measurements in the sludge layer of the digestion basin. High concentrations of nitrate and sulfate, circulating in the overlying water (∼15 mM), were removed by microbial respiration in the sludge resulting in a sulfide accumulation of up to 3 mM. Modelling of the observed S and O isotopic ratios in the surface sludge suggested that, with time, major respiration processes shifted from heterotrophic nitrate and sulfate reduction to autotrophic nitrate reduction. The much higher inorganic P content of the sludge relative to the fish feces is attributed to conversion of organic P to authigenic apatite. This conclusion is supported by: (a) X-ray diffraction analyses, which pointed to an accumulation of a calcium phosphate mineral phase that was different from P phases found in the feces, (b) the calculation that the pore waters of the sludge were highly oversaturated with respect to hydroxyapatite (saturation index = 4.87) and (c) there was a decrease in phosphate (and in the Ca/Na molar ratio) in the pore waters simultaneous with an increase in ammonia showing there had to be an additional P removal process at the same time as the heterotrophic breakdown of organic matter.

Original languageEnglish
Pages (from-to)109-21
Number of pages13
JournalWater Research
Volume56
DOIs
Publication statusPublished - 1 Jun 2014

Keywords / Materials (for Non-textual outputs)

  • Aquaculture
  • Bacteria
  • Bioreactors
  • Nitrates
  • Phosphorus
  • Sulfates
  • Waste Water
  • Water Pollutants, Chemical
  • Water Purification

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