Biological denitrification for water detoxification: A review

Abstract

Biological denitrification is an established process for nitrate (NO3-) removal that is typically applied in wastewater treatment plants (WWTPs) and sometimes for drinking water treatment. In WWPTs, conventional denitrification is driven by the oxidation of the organic matter existing in the influents of municipal and/or industrial origin. Alternatively, some inorganic compounds, including sulfur, hydrogen, and iron, can act as electron acceptors for denitrification purposes. In industrial wastewater and in water from contaminated water bodies, toxic compounds including heavy metals such as chromium, arsenic, uranium, and manganese as well as other pollutants such as sulfide, thiocyanate, perchlorate, and aromatic compounds can be present. Interestingly, these compounds can also act as energy sources for denitrifying bacteria and/or be co-reduced with NO3 - and other denitrification intermediates. In this way, their toxicity can be partially or totally removed, which demonstrates the potential of biological denitrification for the detoxification of both water and wastewater. This work reviews the toxicity, degradation pathways, and impacts on denitrification steps, microorganisms, and bioreactor operation of eight types of toxic compounds that can be detoxified via biological denitrification. The role of the different compounds on nitrous oxide (N2O) emissions during denitrification is also discussed to provide useful information for the minimization of greenhouse gas emissions.