Comparative analysis of brewing wastewater and lactate as carbon sources for microbial community treating acid mine drainage in anaerobic MBBR systems

Abstract

This study investigated the effect of carbon sources (n = 2) on the performance of a microbial community in an anaerobic moving-bed biofilm reactor (MBBR) treating acid mine drainage (AMD). The 1.5 L anaerobic MBBR was operated across a range of hydraulic retention times - HRT's (3-18 days), using different substrates, i.e. brewing wastewater and lactate as sole carbon sources and electron donors. Maximum sulphate reduction and chemical oxygen demand (COD) consumption rate was 21.94 and 24.28 mg ${\mathrm{SO}}_4^{2-}$ L^-1 h^-1, and 0.473 and 0.697 mg COD L^-1 d^-1 for brewing wastewater and lactate supplemented bioreactors, respectively, at an HRT of 3 days. The maximum COD/${\mathrm{SO}}_4^{2-}$ ratio was found to be 2.564 in the bioreactor supplemented with brewing wastewater at an HRT of 15 days. The metal removal above 70% in the system supplemented with brewing wastewater followed the order; Be²⁺ > Fe²⁺ > Sr²⁺ > Pb²⁺ > Mg²⁺ > Cu²⁺ > Zn²⁺ > Li¹⁺ > Ca²⁺ in comparison to the system supplemented with lactate, Be²⁺ > Fe²⁺ > Sr²⁺ > Mg²⁺ > Cu²⁺ > Li¹⁺ > Zn²⁺ > Pb²⁺ after an HRT of 18 days. Complete removal of beryllium (II) was observed irrespective of the carbon source used. The results clearly showed that brewing wastewater can be deployed as a nutritional supplement in environmental remediation of AMD.

Keywords: Acid mine drainage; brewing wastewater; lactate; moving-bed biofilm reactor.