Inhibition of anaerobic ammonium oxidation by heavy metals

Abstract

BACKGROUND Anaerobic ammonium oxidation (anammox) is a promising approach for removing nitrogen from landfill leachates and other nitrogen‐laden wastewater. Although heavy metals, which are known for their microbial toxicity, are commonly present in those wastewater streams information on their inhibitory impact on anammox activity is still limited. The main aim of this study is to investigate the inhibitory effects of six common metal ions (Cu2+, Cd2+, Ni2+, Zn2+, Pb2+, and molybdate) on anammox activity. RESULTS The soluble concentrations of cationic metals decreased due to precipitation reactions. Cu, Zn, Cd, and Ni were the most toxic metals with 50% inhibiting soluble concentrations of 4.2, 7.6, 11.2, and 48.6 mg L‐1, respectively. Molybdate and Pb2+ were not or only moderately inhibitory at the highest soluble concentrations tested (22.7 mg Mo L‐1 and 6.0 mg Pb L‐1, respectively). A noncompetitive inhibition model successfully described the relationship between microbial inhibition and metal concentrations for all tested metals except for Pb. CONCLUSION Cu, Zn and Cd were the most toxic heavy metals for anammox bacteria. The soluble concentration of these heavy metals needs to be monitored carefully before applying anammox processes. © 2014 Society of Chemical Industry

A novel strategy for accelerating the recovery of an anammox reactor inhibited by copper(II): EDTA washing combined with biostimulation via low-intensity ultrasound

“…To date, we are aware of few publications concerning the inhibitory impact of Cu(II) on anammox activity [8,[10][11][12][13]. These publications indicate that AnAOB are highly sensitive to Cu(II).…”

“…Thus, EDTA continues to be intensively explored for soil remediation due to its ability to efficiently mobilize metal cations with only a minor effect on the physical and chemical properties of the soil matrix. General consensus holds that inhibition is not a function of the total analytical metal concentration but, instead, is strongly correlated with free cation concentration [8,17]. Furthermore, free Ni(II) or Cd(II) concentrations may be modulated by the addition of EDTA, resulting in reduced deleterious effects on nitrification [17].…”

“…Certain heavy metals, such as Cu(II), Zn(II), Cd(II), Pb (II) and Ni(II), are found in municipal landfill leachates, centrates from anaerobic digestion sludge, anaerobic digestion piggery/dairy slurries, effluents from the production of nitrogenous fertilizers and semiconductor manufacturing wastewater streams [8]. At low concentrations, heavy metals are indispensable micronutrients and components of many enzymes or co-enzymes.…”

Short-Term and Long-Term Inhibitory Effects of Copper on Anammox Process

“…Consequently, many studies have been focused on a great variety of inhibitory factors over the Anammox process in wastewater streams including organic matter [20], substrates [11,21,22], salts [23] etc. So far, however, little attention has been paid to inhibitory effects of heavy metals [24][25][26][27][28] and little is known about the short and long-term effect of copper on Anammox activity.…”

“…Although some of the heavy metals are fundamental for microbial cell production, they are also common inhibitors for biological processes in high concentrations. Although some specific heavy metals have been studied Cd(II), Cu(II), Ni(II), Zn(II), Hg, Pb, Ag on Anammox activity [24][25][26][27][28][30][31][32][33][34], there has been little agreement on inhibition doses of these heavy metals. However, the experimental data are rather controversial, and there is no general agreement about inhibitory concentrations.…”