Comparison of agricultural wastes and synthetic macromolecules as solid carbon source in treating low carbon nitrogen wastewater

Abstract

This paper investigated the feasibility of using agricultural wastes and synthetic macromolecules as solid carbon sources and studied the effects of improvement of denitrification by the selected agricultural wastes. The carbon release capacity and denitrification performance of corncob (CC), peanut shell (PS), obsolescent rice (OR) and polycaprolactone (PCL), poly butylene succinate (PBS), polyvinyl alcohol sodium alginate (PVA-SA) were systematically analyzed. The results showed that for each carbon source, the first-order kinetic equation was basically followed during the carbon release process. PVA-SA, CC and PS had higher carbon release capacity with accumulative dissolved organic carbon (DOC) of 16.22–20.63 mg·g−1 and chemical oxygen demand (COD) of 100.86–134.10 mg·g−1. Correspondingly, they showed excellent denitrification performance with almost no residual NO3−-N, and the denitrification process well followed the Monod equation. PCL, PBS and OR had lower carbon release capacity with accumulative DOC of 2.06–3.14 mg·g−1 and COD of 13.29–24.13 mg·g−1, respectively. Nevertheless, these materials can also improve the denitrification performance, with the residual NO3−-N in the range of 6.02–6.36 mg·L−1, and the effluent DOC was in the range of 10–15 mg·L−1. Synthetic polymers are more suitable for nitrogen removal in groundwater treatment, while agricultural wastes are ideal carbon sources for secondary effluent treatment.