Study on the carbon source stability of constructed wetland prepared from modified aged straw

The low cost of biomass has made it an important option for providing carbon sources in the treatment of low carbon to nitrogen ratio (C/N) wastewater constructed wetland (CW). However, the unstable release of biomass carbon source reduces utilization and operation efficiency of CW. In this study, aged corn straw was used as raw material, and modification treatments with acid, alkali and oxidant were to optimize the conditions for stable carbon source release. The results showed that the modified straw exhibited three trends (stable release, continuous release, and short-term release) under water immersion conditions. The electrical conductivity (EC) of straw modified by HCl, H₂SO₄ and low-concentration KMnO₄ (0.01 mol L^-1) was low, so the supply of carbon sources in CW was obviously insufficient. The straw modified by HNO₃ (1.5 or 2.5 mol L^-1), KMnO₄ (0.05 mol L^-1), KMnO₄ (0.05 mol L^-1) + HCl (0.004 mol L^-1) was continuously released chemical oxygen demand during the experiment, the increase in EC was significant, which could be used as an additional carbon source for CW. The research results will promote the improvement of biomass carbon source utilization in CW and improve the utilization value of straw.