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

Krom, MD, Ben David, A, Ingall, ED, Benning, LG, Clerici, S, Bottrell, S, Davies, Ceri ORCID: 0000-0003-3484-2866, Potts, NJ, Mortimer, RJG and van Rijn, J (2014) Bacterially mediated removal of phosphorus and cycling of nitrate and sulfate in the waste stream of a "zero-discharge" recirculating mariculture system. Water Research, 56. pp. 109-121. doi:10.1016/j.watres.2014.02.049

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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 3Â 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.

Item Type: Article
Article Type: Article
Uncontrolled Keywords: Aquaculture; Anaerobic sludge; Phosphorus removal; Denitrification; Apatite formation; Sulfur cycling
Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences
S Agriculture > SH Aquaculture. Fisheries. Angling
Divisions: Schools and Research Institutes > School of Education and Science
Research Priority Areas: Place, Environment and Community
Depositing User: Ceri Davies
Date Deposited: 13 Nov 2023 10:45
Last Modified: 13 Nov 2023 10:45

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