Effects of Nitrogen-Rich Wastewater Reuse on Aerobic Fermentation Performance of Substrates with Different Carbon-Nitrogen Ratios
Reducing ammonia emissions and recovering lost nitrogen are critical for enhancing nitrogen content in compost. Biological trickling filters, as end-of-pipe odor control, retain ammonia nitrogen in effluent, offering a reuse pathway. However, the impact of nitrogen-rich wastewater reuse within the optimal C/N range (20.0:1–30.0:1) remains unclear. This study composted biogas residue, sawdust, food waste, and mushroom residue, setting initial C/N as the control variable. Four groups were established: low C/N with nitrogen-rich wastewater (LRN), low C/N with deionized water (LRW), high C/N with nitrogen-rich wastewater (HRN), and high C/N with deionized water (HRW). Simulated wastewater (2000 mg/L NH4+-N and 2000 mg/L NO2−-N) was recycled. Results showed no inhibition of final maturity; pH (8.17–8.48) and seed germination index (GI) (90.85%–122.96%) met organic fertilizer standards. HRN reduced cumulative total greenhouse gases, N2O, and NH3 by 20.32%–30.35%, 0.67%–53.38%, and 52.14%–62.15% compared to LRN and LRW. Although HRN emissions were slightly higher than HRW (total GHGs +4.56%, NH3 +4.99%), HRN final nitrogen content (4691.27 mg/kg) exceeded HRW (4514.96 mg/kg), attributed to sufficient carbon enhancing microbial assimilation. Conversely, low C/N with nitrogen-rich wastewater increased NH3 and N2O emissions (LRN vs LRW: +26.43% and +112.99%) due to carbon limitation. Thus, high initial C/N with nitrogen-rich wastewater reuse effectively reduces gaseous nitrogen loss and greenhouse gas emissions while maintaining compost maturity.