Sequential in situ hydrotalcite precipitation and biological denitrification for the treatment of high-nitrate industrial effluent

• Published in: Bioresource technology 2014-11, Vol.172, p.373-381
• Main Authors: Cheng, Ka Yu, Kaksonen, Anna H., Douglas, Grant B.
• Format: Article
• Language: English
• Subjects: Aluminum Hydroxide - chemistry; Anions; Applied sciences; Biological; Biological and medical sciences; Bioreactor; Bioreactors; Biotechnology; Carbon; Denitrification; Denitrification - physiology; Effluent; Effluents; Exact sciences and technology; Fluidised bed reactor; Fractional Precipitation - methods; Fundamental and applied biological sciences. Psychology; Hydrotalcite; Industrial Waste - prevention & control; Magnesium; Magnesium Hydroxide - chemistry; Methods. Procedures. Technologies; Mining; Nickel; Nitrates; Nitrates - chemistry; Nitrates - isolation & purification; Nitrates - metabolism; Oxidation-Reduction; Pollution; Precipitation; Sewage - chemistry; Sewage - microbiology; Systems Integration; Various methods and equipments; Wastes
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2014.09.050

Flow sheet of the proposed two-step sequential hydrotalcite precipitation and biological denitrification treatment for Direct Nickel effluent. [Display omitted] •In situ formation of hydrotalcite (HT) capable of removing 41% of nitrate.•Biological denitrification removed >70% residual nitrate from HT-treated water.•Sodium acetate as electron donor allowed better denitrification than methanol.•Sewage sludge readily acclimatised to denitrify high-nitrate effluent. 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.