effects of nickel(II) and chromium(VI) on oxygen demand, nitrogen and metal removal in a sequencing batch reactor

• Published in: Environmental technology Vol. 32; no. 16; pp. 1903 - 1914
• Main Authors: Khor, S. M, Ng, S. L, Lim, P. E, Seng, C. E
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 01.12.2011; Taylor & Francis Ltd
• Subjects: ammonium nitrogen; Applied sciences; Biological and medical sciences; Biological Oxygen Demand Analysis; Bioreactors; Biotechnology; Chemical engineering; chemical oxygen demand; chromium; Chromium - chemistry; chromium(VI); environmental technology; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Metals - isolation & purification; Methods. Procedures. Technologies; nickel; Nickel - chemistry; nickel(II); nitrogen; Nitrogen - isolation & purification; Others; oxygen; oxygen demand; Pollution; Reactors; sequencing batch reactor; Sewage - chemistry; Various methods and equipments; British Isles; chromium(VI); oxygen demand; Nickel II; nickel(II); Laboratory scale; Nitrogen; Steady state; Synergism; Biological purification; Ammonia; Bioreactor; Sequencing batch reactor; Chemical oxygen demand; Water quality
• ISSN: 1479-487X; 0959-3330; 1479-487X
• DOI: 10.1080/09593330.2011.568008

The objective of this study was to evaluate the effects of Ni(II) and Cr(VI) individually and in combination on the simultaneous removal of chemical oxygen demand (COD), nitrogen and metals under a sequencing batch reactor (SBR) operation. Three identical laboratory-scale SBRs were operated with FILL, REACT, SETTLE, DRAW and IDLE periods in a ratio of 1:12:1:2:8 for a cycle time of 24 h until the steady state was achieved. Nickel(II) at increasing concentrations up to 35 mg/L was added to one of the reactors; Cr(VI) at increasing concentrations up to 25 mg/L was added to a second reactor; while a combination of Ni(II) and Cr(VI) in equal concentrations up to 10 mg/L was added to a third reactor. The results demonstrate that both Ni(II) and Cr(VI) exerted a more pronounced inhibitory effect on the removal of ammonia nitrogen (AN) than on COD removal. Synergistic and antagonistic inhibitory effects on the rates of COD and AN removal, respectively, were observed for the 50% Ni(II) and 50% Cr(VI) (w/w) mixture in the concentration range between 10 and 20 mg/L. The simultaneous presence of 50% Ni(II) and 50% Cr(VI) at a concentration of 20 mg/L resulted in system failure.