Solid-phase denitrification for water remediation: processes, limitations, and new aspects

Nitrate pollution in water environments is a ubiquitous problem. Solid-phase denitrification (SPD) is a technology that has attracted in recent years increasing attention due to its significant advantage suitability over the aqueous-based denitrification for in situ water remediation. This paper provides a view of new aspects of the application of SPD for water remediation. The processes and mechanisms for nitrogen transformation in SPD, for example, direct denitrification, dissimilatory nitrate reduction to ammonium, and anammox are presented. The main processes of the transformation of the carbon substrate in SPD are also discussed. The major limitations of SPD, including low carbon availability, NO₂⁻ and N₂O accumulation, dissolved organic carbon release, and NH₄⁺ production, are summarized and the factors associated with such limitations are also discussed. In addition, some novel measures to mitigate these limitations, such as applying a biodegradable polymer substrate and heterotrophic-autotrophic denitrification (HAD) process, are described. Finally, simultaneous removal of nitrate and some typical concurrent contaminants for expanded application of SPD are discussed. This review attempts to advance our understanding of engineered denitrification processes for wastewater treatment or water remediation.