Abstract
The aim of this study was to investigate the effects of Ni(II) on the activity of activated sludge microorganisms in the sequencing batch reactor (SBR) treatment process. Two parallel lab-scale SBR systems were operated. One was used as a control unit, while the other received Ni(II) concentrations equal to 5 and 10 mg/l. The SBR systems were operated with FILL, REACT, SETTLE, DRAW and IDLE modes in the time ratio of 0.5 : 3.5 : 1.0 : 0.75 : 0.25 for a cycle time of 6 h. The presence of 5 mg/l Ni(II) in synthetic wastewater caused a slight reduction in TOC removal efficiency, whereas 10 mg/l Ni(II) addition significantly affected the SBR performance in terms of suspended solids and TOC removal efficiency. It was found that the addition of Ni(II) into SBR system caused drastic drop in TOC removal rate and specific oxygen uptake rate by activated sludge microorganisms due to the inhibitory effects of Ni(II) on the bioactivity of activated sludge microbes. Termination of Ni(II) addition led to almost full recovery of the bioactivity in microorganisms as shown in the increase of specific oxygen uptake rate and SBR treatment performance.
