Study on six agricultural wastes as additional carbon source of low C/N ratio sewage

The unstable carbon release rate and secondary pollutants of agricultural wastes lead to substandard effluent quality, and the mechanism of carbon and secondary pollutant release as well as denitrification efficiency of agricultural wastes can be clarified to facilitate their wide application. In this study, six common agricultural wastes (corn cob (CC), loofah sponge (LS), peanut shells (PS), corn stover (CS), rice straw, wheat straw) were selected, with high total cellulose contents of 61.59–70.68%, and the cumulative carbon releases of 11.333–41.547 mg (g L)⁻¹ in 168 h, which basically followed the second-order reaction kinetics and the Ritger–Peppas equation. The TN and TP contents released from several wastes were low and had little effect on denitrification, but the high-color substances released from straw wastes might affect the effluent in the denitrification process. The soluble organic matter of CC, LS, PS and CS are mainly protein-derived compounds, which are more favorable for microbial decomposition and utilization. In the denitrification experiment, denitrification efficiency was higher with CC and straw waste as carbon sources. The results of this study are expected to provide a theoretical basis and data support for the use of agricultural waste as a carbon source for denitrification.