进料浓度对鸡粪连续中温厌氧消化的影响

针对高固体鸡粪厌氧消化运行困难问题，利用完全混合式厌氧反应器(CSTR)，通过逐级提高进料总固体浓度(TS)的方法，研究不同进料TS((5.20±0.56)%、(7.24±0.36)%、(9.30±0.26)%和(6.22±0.26)%)的鸡粪连续中温厌氧消化效果。实验结果表明，进料TS由(5.20±0.56)%提高为(9.30±0.26)%，挥发性固体(VS)产气率由(0.64±0.05) L·g⁻¹下降为0.07 L·g⁻¹，有机物去除率明显减少，挥发性脂肪酸(VFAs)由(0.53±0.02) g·L⁻¹累积至(1.62±0.02) g·L⁻¹，总氨氮浓度(TAN)和游离氨浓度(FA)分别由(1.06±0.11) g·L⁻¹和(0.07±0.02) g·L^-1累积至3.40 g·L⁻¹和0.68 g·L⁻¹，消化过程受到氨抑制。采用Boltzmann模型对不同氨氮浓度下VS产甲烷率和VS去除率进行模拟，拟合结果表明，TAN升高所引发的FA持续累积导致高固体鸡粪厌氧消化氨抑制逐步形成，与VS产甲烷率相比，VS去除率对氨氮的抑制响应具有滞后性。降低进料TS至(6.22±0.26)%，氨抑制得到有效缓解，但反应器处于“抑制稳定状态”。因此，为保证反应器长期高效平稳运行，建议鸡粪连续中温厌氧消化的进料浓度不超过7.24%。研究为高固体鸡粪厌氧消化的工程化应用提供参考。

Effect of feeding concentration on continuous mesophilic anaerobic digestion of chicken manure

Difficult operation is a main problem for anaerobic digestion of high solid chicken manure. In this study, continuous mesophilic anaerobic digestion of chicken manure was carried out in a 6 L continuous stirring tank reactor (CSTR). The anaerobic digestion performance of this CSTR at different feeding concentrations ((5.20±0.56)%, (7.24±0.36)%, (9.30±0.26)% and (6.22±0.26)% based on total solid (TS)) was studied through the stepwise increase of feeding concentration. The obtained results indicated that anaerobic digestion suffered from ammonia inhibition when feeding concentration increased from (5.20±0.56)% to (9.30±0.26)%, the gas production of volatile solid (VS) dropped from (0.64±0.05) L·g−1 to 0.07 L·g−1 and the organic matter removal rate decreased significantly. Additionally, the volatile fatty acids (VFAs) accumulated from (0.53±0.02) g·L−1 to (1.62±0.02) g·L−1, the total ammonia nitrogen concentration (TAN) and free ammonia concentration (FA) accumulated from (1.06±0.11) g·L−1 and (0.07±0.02) g·L−1 to 3.40 g·L−1 and 0.68 g·L−1, respectively. The methane production and VS removal rate at different ammonia concentrations were simulated by Boltzmann model. The fitted results indicated that continuous FA accumulation induced by elevated TAN resulted in the gradual occurrence of ammonia inhibition in anaerobic digestion of high solid chicken manure. In comparison with methane production, the response of VS removal rate to ammonia inhibition had a lag period. However, ammonia inhibition was effectively alleviated when feeding concentration was adjusted to (6.22±0.26)%, and the reactor presented " inhibited steady state”. Therefore, to ensure efficient and stable operation of continuous reactor, it is suggested that feeding concentration of chicken manure continuous anaerobic digestion is not higher than 7.24%. This study provides a reference for the engineering application of anaerobic digestion of high solid chicken manure.