餐厨垃圾与剩余污泥协同发酵提升低C/N污水脱氮效能的中试研究

我国城镇污水处理厂进水碳源普遍偏低，严重影响生物脱氮效能。外加碳源会造成大量化学品消耗及碳排放，与双碳战略背道而驰。考察了餐厨垃圾和剩余污泥联合发酵中试装备 (规模10 t·d⁻¹) 制备挥发性脂肪酸 (VFA) 效能，并将生产的VFA发酵液投加至昆山市某城镇污水处理厂，以减少外源乙酸钠碳源投加量，以期探索城市污水与有机固废的协同、高效、低碳处理技术。结果表明：餐厨垃圾与剩余污泥体积比为7∶3时，VFA质量浓度最高，达到54.3 g·L⁻¹ (以COD计) ，乙酸和丙酸质量分数分别为36.5%和22.8%；在批次发酵中试实验中，VFA最高质量浓度达67.5 g·L⁻¹ (以COD计) ，最低质量浓度为42.4 g·L⁻¹ (以COD计) ，平均质量浓度为55.0 g·L⁻¹ (以COD计) ；对比3类碳源的反硝化实验结果，投加乙酸钠组1.5 h脱氮率为86.5%，投加发酵液组4.5 h脱氮率为81.0%，投加餐厨垃圾组仅为69.8%；根据出水总氮预警阈值 (>8 mg·L⁻¹) 补加发酵液，替代部分乙酸钠，通过实际污水厂运行数据，拟合得到发酵液投量X (m³) 与乙酸钠吨水节约量Y (g·m⁻³) 的线性关系式Y=4.9X+3.5，其中R²=0.91。该研究结果可为联合发酵制备优质碳源提升污水厂脱氮工程应用提供参考。

Pilot study on co-digestion of food waste and waste activated sludge to improve nitrogen removal efficiency of low c/n sewage

The low content of carbon sources in the influent of municipal wastewater treatment plants (WWTP) in China generally affects the effectiveness of biological denitrification. At present, sodium acetate and other additional carbon sources are mostly supplemented to meet the effluent total nitrogen standard, resulting in a large number of chemical consumption and carbon emissions, which is not in line with the goal of “Carbon peak carbon neutral” in China. In this study, the efficacy of volatile fatty acid (VFA) concentration from co-fermentation of food waste and waste activated sludge in pilot equipment (10 t·d−1) was evaluated. Fermentation broth with high content of VFA was fed as carbon sources into a municipal WWTP in Kunshan, China to reduce the addition of exogenous acetate. The experimental results showed that the concentration of VFA was the highest when the volume ratio of food waste to residual sludge was 7∶3, which reached 54.3 g·L−1 (in terms of COD). The main content of VFA was acetate and propionate, which accounted for 36.5% and 22.8%, respectively. In pilot experiments, the maximum, minimum, and average concentration of VFA was 67.5 g·L−1(in terms of COD), 42.4 g·L−1(in terms of COD), and 55.0 g·L−1(in terms of COD), respectively. In denitrification experiments, the nitrogen removal was 86.5% in 1.5 h with the addition of acetate, 81.0% in 4.5 h with the addition of fermentation broth with high content of VFA, and only 69.8% with the addition of food waste. The fermentation broth was added to replace part of the acetate according to the warning threshold of TN in the effluent (>8 mg·L−1). Based on the data of the municipal WWTP, the linear relationship between the dosage of fermentation broth X (m3) and the saving of acetate per ton of wastewater Y (g·m−3) was obtained as “Y=4.9X+3.5 (R2=0.91)”. This study can provide a technical case for the application of high-efficiency carbon sources from the co-fermentation of food waste and waste activated sludge to enhance nitrogen removal in municipal WWTP.