Impact of Heavy Metals on Denitrification of Simulated Mining Wastewaters

Abstract

Thespreading of nitrogenous compounds into the environment is a common challenge duringmining industries. Typical explosives used in mining are N-based compoundswhich lead to nitrogen contamination of groundwater and water bodies. In goldextraction, cyanide used as lixiviant is also another source of nitrogen pollution.The present work aims to investigate the effect of heavy metals ondenitrification using batch bioassays. Cu, Ni, Co and Fe influence ondenitrification process was studied at pH 7.0. Below the soluble concentrationof 62 mg/L, Ni did not inhibit denitrification, whereas denitrification wasrepressed at soluble Ni concentration above 62 mg/L. At 122 mg/L of soluble Ni,50% inhibition of denitrification was observed. Below soluble concentration of86 mg/L, Co exerted no inhibitory effect on nitrate removal but moderatelydecreased the denitrification rate. Cu slowed denitrification down resulting in40% of nitrate removal averagely at the soluble concentration below 1 mg/L. Onthe contrary, Fe supplementationresulted in iron oxidation and soluble Fe concentrations ranging from 0.4-1.6mg/L that stimulated denitrification. Thepresent work indicates that denitrification can tolerate heavy metals and canbe suitable for acid mine drainage remediation.