Nitrification inhibition by Cadmium and its mitigation in a novel membrane bioreactor system

Abstract

The inhibitory effect of heavy metals in nitrification has not been extensively investigated although it is expected that some form of inhibition would show up in the presence of these. Since Cadmium is a common heavy metal present in industrial effluents, its effect on nitrification has yet to be evaluated in qualitative and quantitative terms. In this investigation, a novel approach to studying heavy metal inhibition and mitigation in a full nitrification regime has been adopted. This approach consisted of employing a twocompartment membrane bioreactor and conducting a series of nitrification experiments in the absence and presence of a natural adsorbent placed in either compartment. The results obtained thus far clearly indicated an inhibitory effect when both heavy metal and biomass were placed in the same compartment. Diffusive transport across the membrane of produced nitrite and heavy metal showed different characteristics: whilst nitrite evolved to the other compartment according to the concentration driving force, the heavy metal concentration in either compartment change little.