title: Sequential in situ hydrotalcite precipitation and biological denitrification for the treatment of high-nitrate industrial effluent.
abstract: A sequential process using hydrotalcite precipitation and biological denitrification was evaluated for the treatment of a magnesium nitrate (Mg(NO3)2)-rich effluent (17,000mgNO3(-)-N/L, 13,100mgMg/L) generated from an industrial nickel-mining process. The hydrotalcite precipitation removed 41% of the nitrate (7000mgNO3(-)-N/L) as an interlayer anion with an approximate formula of Mg5Al2(OH)14(NO3)2·6H2O. The resultant solute chemistry was a Na-NO3-Cl type with low trace element concentrations. The partially treated effluent was continuously fed (hydraulic retention time of 24h) into a biological fluidised bed reactor (FBR) with sodium acetate as a carbon source for 33days (1:1 v/v dilution). The FBR enabled >70% nitrate removal and a maximal NOx (nitrate+nitrite) removal rate of 97mg NOx-N/Lh under alkaline conditions (pH 9.3). Overall, this sequential process reduced the nitrate concentration of the industrial effluent by >90% and thus represents an efficient method to treat Mg(NO3)2-rich effluents on an industrial scale.
authors.affiliation: CSIRO Land and Water, 147 Underwood Avenue, Floreat, WA 6014, Australia.
authors.forename: Ka Yu
authors.initials: KY
authors.lastname: Cheng
authors.affiliation: CSIRO Land and Water, 147 Underwood Avenue, Floreat, WA 6014, Australia.
authors.forename: Anna H
authors.initials: AH
authors.lastname: Kaksonen
authors.affiliation: CSIRO Land and Water, 147 Underwood Avenue, Floreat, WA 6014, Australia. Electronic address: grant.douglas@csiro.au.
authors.forename: Grant B
authors.initials: GB
authors.lastname: Douglas
mesh_terms: D000536:Aluminum Hydroxide / Q000737:chemistry*; D058440:Denitrification / Q000502:physiology; D005590:Fractional Precipitation / Q000379:methods*; D007220:Industrial Waste / Q000517:prevention & control*; D008276:Magnesium Hydroxide / Q000737:chemistry*; D008906:Mining; D009566:Nitrates / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism*; D010084:Oxidation-Reduction; D012722:Sewage / Q000737:chemistry* / Q000382:microbiology*; D018511:Systems Integration
chemical_list: D007220:Industrial Waste; D009566:Nitrates; D012722:Sewage; C010467:hydrotalcite; D000536:Aluminum Hydroxide; D008276:Magnesium Hydroxide
keywords: Bioreactor; Denitrification; Effluent; Fluidised bed reactor; Hydrotalcite