Riboflavin enhanced denitrification of artificial wastewater under low C/N condition in cold season

Abstract

Nitrogen removal under low C/N ratio in cold season is an arduous task. In this study, riboflavin was used as an eco-friendly electron mediator to improve the denitrification process in an SBR reactor under conditions of low temperature (10 °C to 15 °C) and limited carbon source (C/N ratio = 4.0). The results indicated that riboflavin created a suitable pH in the system for denitrification. Under water temperature of 10 °C to 15 °C, riboflavin (10 mg/L) stimulated the NO3–N and TN removal rate by 16.5%, and 51%, respectively. Riboflavin promoted the utilization efficiency of limited carbon source, driving the denitrification process with low residual acetate as electron donor. The rising cost of riboflavin supplement (10 mg/L) was 0.025 USD per m3 of wastewater. To satisfy the efficient nitrogen removal from municipal wastewater, the optimum C/N ratio and the selection of solid/immobilized redox mediators should be developed in future work.

Environmental applications of immobilized and bio-resourced redox mediators: A Review

“…In these processes, RMs could speed up the electron transferring from the electron donors -carbohydrate, protein, volatile fatty acids, alcohol, hydrogen, (biogenic)sulfide, zero valent iron and ferrous iron, nicotinamide adenine dinucleotide phosphate hydrate, and electrical power -to the acceptors of oxidized contaminants, increasing the reduction rates by several folds or even dozens. Mixed cultures of microorganisms (such as activated sludge) as well as pure strains have been reported to contribute to the above mediated processes (Borch et al 2005;dos Santos et al 2005;Bhushan et al 2006;Finneran 2006, 2008;Bibi et al 2019;Liu et al 2021;Ren et al 2022). Moreover, TEMPO-mediated decolorization, cellulose oxidation, photocatalysis and electroreduction have also been reported in the literature, implying the electron shuttling role of TEMPO/TEMPOH couple (Gharehkhani et al 2019;Wen et al 2019;Lukyanov et al 2022).…”