title: Bacterially mediated removal of phosphorus and cycling of nitrate and sulfate in the waste stream of a "zero-discharge" recirculating mariculture system.
abstract: 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.
authors.affiliation: School of Earth and Environment, Leeds University, UK; Charney School of Marine Sciences, Haifa University, Israel.
authors.forename: M D
authors.initials: MD
authors.lastname: Krom
authors.affiliation: The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel.
authors.forename: A
authors.initials: A
authors.lastname: Ben David
authors.affiliation: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, USA.
authors.forename: E D
authors.initials: ED
authors.lastname: Ingall
authors.affiliation: School of Earth and Environment, Leeds University, UK.
authors.forename: L G
authors.initials: LG
authors.lastname: Benning
authors.affiliation: School of Earth and Environment, Leeds University, UK.
authors.forename: S
authors.initials: S
authors.lastname: Clerici
authors.affiliation: School of Earth and Environment, Leeds University, UK.
authors.forename: S
authors.initials: S
authors.lastname: Bottrell
authors.affiliation: School of Earth and Environment, Leeds University, UK.
authors.forename: C
authors.initials: C
authors.lastname: Davies
authors.affiliation: School of Earth and Environment, Leeds University, UK.
authors.forename: N J
authors.initials: NJ
authors.lastname: Potts
authors.affiliation: School of Earth and Environment, Leeds University, UK.
authors.forename: R J G
authors.initials: RJ
authors.lastname: Mortimer
authors.affiliation: The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel. Electronic address: jaap.vanrijn@mail.huji.ac.il.
authors.forename: J
authors.initials: J
authors.lastname: van Rijn
mesh_terms: D017756:Aquaculture; D001419:Bacteria / Q000737:chemistry / Q000378:metabolism; D019149:Bioreactors; D009566:Nitrates / Q000737:chemistry*; D010758:Phosphorus / Q000737:chemistry / Q000378:metabolism*; D013431:Sulfates / Q000737:chemistry*; D062065:Wastewater / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000378:metabolism; D018508:Water Purification / Q000379:methods
chemical_list: D009566:Nitrates; D010758:Phosphorus; D013431:Sulfates; D062065:Wastewater; D014874:Water Pollutants, Chemical
keywords: Anaerobic sludge; Apatite formation; Aquaculture; Denitrification; Phosphorus removal; Sulfur cycling