In this work, a loofah sponge was used as the solid carbon source and the carrier in a biofilm reactor. Simultaneous nitrification and denitrification (SND) technology was used to achieve nitrogen removal in low-carbon municipal wastewater in a sequencing batch biofilm reactor (SBBR). At room temperature, the effects of filling ratio, dissolved oxygen (DO), pH, C/N(COD Cr /TN), and aeration time on the removal of nitrogen were systematically studied. In addition, the removal efficiency of total nitrogen (TN) was used as the evaluation index in response surface models (RSM) for optimization of nitrogen removal. The results showed that DO, pH, and aeration time affected nitrogen removal significantly. Therefore, DO, pH, and aeration time were used as the independent variables in RSM. The optimum conditions for nitrogen removal were found to be as follows in RSM: DO = 4.09 mg/L, pH = 7.58, aeration time = 10.47 h. Under the optimum conditions, the maximum TN removal efficiency reached 86.27%. The results also demonstrated that the deviation between the experimental and predicted TN removal efficiency was only 0.58%, the predicted model was reliable for future application.

Based on low carbon wastewater as the research object and using corncob as an external solid carbon source, the performance of corncob organic matter was assessed for its release potential, quantity of release, and safety of use. The effects of varying quantities of the solid carbon source on simultaneous nitrification and denitrification were investigated in a sequencing biofilm batch reactor (SBBR). Results show that the regularity of corncob as solid carbon source material was linear, with released concentrations of heavy metals being below the Chinese national standard limit values for heavy metals according to the surface water environment quality standards (I and II) (GB3838-2002). When temperatures were within 28~31°C, the dissolved oxygen level was 4.0 ± 0.2 mg/L and the pH conditions were within 7.5~8.0. The optimal quantity for corncob dosing was 5 g per 1.5 L of low carbon wastewater. Following treatment, the average effluent concentrations of NH4+-N and TN were 2.85 mg/L and 4.51 mg/L, respectively. The effluent concentration of NH4+-N, TN had reached the A level national standard of sewage treatment plant pollutant discharge standard (GB18918-2002).