Effect of nitrilotriacetic acid on bioavailability of nickel during methane fermentation

In the case of anaerobic reactors for the treatment of wastewaters, the ubiquitous presence of sulfide and carbonate leads to extensive precipitation of metals like nickel, which are essential for the metabolism of the anaerobic microorganisms that carry out the mineralization of the pollutants present in the wastewater. This study is concerned with the complexation of nickel with nitrilotriacetic acid (NTA) and its effect on the biogas production by methanogenic archaea in the presence of sulfide. Methane production was enhanced 10, 30 and 48%, at sulfide concentration of 0.25, 0.5 and 1 mM, respectively, by the addition of 10 μM NTA. Accompanying with that, substrate degradation and methane production were accelerated and the carbonate and sulfide fraction of nickel in the biomass decreased 28.8 and 58.0%. NTA boosted the internalization of Ni, consequently enhancing the bioavailability of Ni for methanogenic archaea and promoting the methane production.