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).…”

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.…”

Inhibitory Effects of Copper on Nitrifying Bacteria in Suspended and Attached Growth Reactors

“…In comparison to the different heavy metals (example, Zn, Cd, Ni) that inhibit nitrification, biological wastewater systems inhibited by copper seemed to have the longest recovery time after the metal load is removed (Nelson et al 1981;Hu et al 2003). There are many studies on the inhibitory effects of copper on nitrifying bacteria in wastewater systems (Braam and Klapwijk 1981;Sato et al 1988;Lee et al 1997;Cabrero et al 1998;Hu et al 2004;Kim et al 2006) and the mechanism of inhibition is generally thought to be the binding of copper to enzymes and/or membranes of cells via extracellular sorption or intracellular internalization which in turn may cause disruption of enzyme structure in the cell (Sterritt and Lester 1980;Wood et al 1981;Sato et al 1986aSato et al , b, 1988.…”

“…Several researchers have shown that adsorbed copper concentration has no direct correlation with nitrification inhibition even though the biomass has a higher sorption affinity for copper than other heavy metals (Zn, Cd, Ni;Chua et al 1999;Hu et al 2003). On the other hand, some studies have shown that inhibition to the growth of Nitrosomonas europaea was correlated to Cu(II)-amine species, regardless of the total copper activity present in the medium (Sato et al 1986a(Sato et al , b, 1988Lee et al 1997).…”