Diatoms in wastewater treatment: Potentials, applications, and values of biomass

Diatoms have unique silica cellular and metabolic characteristics and can grow in various environments, including wastewater, facilitating pollutant removal. Diatoms provide a sustainable solution to municipal wastewater treatment, particularly in the tertiary and quaternary stages, contributing to carbon neutrality. Diatom-based materials (such as diatom biomass) have wide applications and can be processed into value-added bioproducts such as lipids, polysaccharides, and pigments. Despite their potentials, the applications of diatoms in wastewater treatment are limited. Existing reviews fail to address how diatom growth kinetics affects wastewater treatment. Here, we for the first time summarize diatom growth kinetics and propose promising species for municipal wastewater treatment. Given the scarcity of reviews on diatom performance in wastewater treatment, we also discuss the efficacy of diatoms in removing contaminants from municipal wastewater. Moreover, we elucidate the removal mechanisms of nutrients, heavy metals, and emerging contaminants by diatoms that are missing in existing reviews. Considering the complexity of wastewater, we emphasize selecting diatom species with high growth rates, tolerance to contaminants, efficient nutrient removal/uptake, and COD removal, and bioproduct yields. This will ensure both effective treatment and economic viability. In addition, we discuss the value of diatom frustules and bioproducts generated from wastewater. Lastly, we highlight future directions including promoting diatom growth, exploring diatom-dominated consortia in wastewater treatment, and evaluating the values of diatom biomass cultivated in wastewater. This review examines the potential and applications of diatoms in municipal wastewater treatment, especially effluent polishing.