A review of nitrate reduction using inorganic materials

Abstract

In a biological denitrification system for water and wastewater treatment, an external carbon source (electron donor) is usually needed to generate dedicated microbial communities if intrinsic organic substances are insufficient. Alternative sources of electron donors, especially inorganic donors, are becoming more and more attractive in order to replace or reduce carbon use. In this article, inorganic electron donors, i.e. zero-valent iron, ferrous ion, sulphur and hydrogen are reviewed. While carbon dioxide (greenhouse gas) is produced when organic electron donors are used, inorganic electron donors have the potential advantages to reduce a plant's carbon footprint, and prevent carbon eluting out of the system, as occurs with heterotrophic processes. While sulphur and hydrogen are promising for nitrate removal in terms of reaction kinetics and economical feasibility, zero-valent iron and ferrous ion show potential to be utilized as a supplement to heterotrophic denitrification, where it is anticipated that synergistic effects would occur with autotrophic and heterotrophic denitrification, and thus external carbon consumption can be reduced.