Acute and chronic toxicity of nickel to nitrifiers at different temperatures

This study investigated the acute nickel toxicity on nitrification of low ammonia synthetic wastewater at 10, 23, and 35 degrees C. The nickel inhibition half-velocity constants (K-I,K-Ni) for ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) based on Ni/MLSS ratio at 10, 23, and 35 degrees C were 5.4 and 5.6 mg Ni/g MLSS, 4.6 and 3.5 mg Ni/g MLSS, and 9.1 and 2.7 mg Ni/g MLSS, respectively. In addition, chronic toxicity of nickel to nitrification of low ammonia synthetic wastewater was investigated at 10 degrees C in two sequencing batch reactors (SBRs). Long-term SBRs operation and short-term batch tests were comparable with respect to the extent of inhibition and corresponding Ni/MLSS ratio. The mu(max), b, and K-o of AOB were 0.16 day(-1), 0.098 day(-1) and 2.08 mg O-2/L after long-term acclimatization to nickel of 1 mg/L at 10 degrees C, high dissolved oxygen (DO) (7 mg/L) and long solids retention time (SRT) of 63-70 days. Acute nickel toxicity of nitrifying bacteria was completely reversible. (c) 2019 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.