Effects of heavy metals on nitrifying bacteria

Abstract

Laboratory evaluations were conducted to study the toxic responses of heavy metals such as copper and nickel of an autotrophic culture of strict nitrifiers (Nitrosomonas sp. and Nitrobacter sp.) in continuous flow stirred tank reactors (CSTR). One of the CSTRs was operated as a suspended growth (SG) system while the other was operated as an attached & suspended growth (A&SG) system. Nitrification inhibition in a SG and A&SG systems was investigated with the emphasis on the effect of shock loading of copper and nickel. As a result of the copper and nickel test, Nitrosomonas sp. was found to be equally or more sensitive than Nitrobacter sp. However, a higher influent nickel concentration of 50 mg/L was needed to cause a similar percent inhibition of ammonium oxidation than the copper concentration of 5 mg/L. A geochemical equilibrium speciation model, MINTEQA2/PRODEFA2, was used to compute the concentrations of various chemical species present in the wastewater for both systems. The high correlations of Cu(NH3)4+2 and Ni(NH3)4+2 with percent inhibition were found and it was thought that they were probably the species responsible for the inhibition of ammonia oxidation.

Detection of nitrifiers and evaluation of partial nitrification for wastewater treatment: A review

“…than Nitrobacter sp. (Lee et al, 1997). In addition, copper was more inhibitory for ammonia oxidation while nickel for nitrite oxidation (1998).…”

Electrochemical treatment of ammonia in wastewater by RuO2–IrO2–TiO2/Ti electrodes

“…Well-developed methods such as biological processes, air stripping, and breakpoint chlorination have been applied to remove ammonia from some domestic and industrial wastewaters [1]. Unfortunately, nitrification is not only easily inhibited by the toxicity of industrial wastewater [2][3][4], but it is also very sensitive to temperature variation [5]. The synergic effect of low temperature and the presence of inhibitory substances prevent the nitrification of industrial wastewaters even at 15-16°C, a temperature at which nitrification of domestic wastewater still proceeds well.…”

Effect of Ni2+ and Pb2+ on the efficiency of packed cage rotating biological contactor system

“…Theoretically, the nitrogenous compounds of the wastewater were biologically removed by assimilation and oxidation-reduction mechanisms [4,5,19,20,[22][23][24]. According to the results above, HM might have a strong effect to both aerobic heterotrophic and nitrogen removal bacteria due to the decrease of TKN and TN removal efficiencies and the increase of effluents NH 4 + and NO 3 À [5,19,20,22,25]. However, their activities and growths would not be repressed by low HM loadings of less than 0.204 g/m 2 d. Then, to increase the efficiency of the system, HRT was investigated.…”