接种物浓度和负荷对餐厨垃圾消化性能及产气动力学的影响

为探析接种物浓度(Biomass concentration,BC)和负荷(Organic loading rate,OLR)对餐厨垃圾厌氧消化性能及产气动力学的影响,在中温批次厌氧消化反应器中进行BC和OLR梯度试验,采用理化分析探析各反应器的性能参数,并采用一阶模型和modified Gompertze模型评价各反应器的产气动力学特征.试验结果表明,超负荷会降低反应器运行效率,影响过程稳定性,而提高BC可以减少单位细胞承受的有机负荷,有利于优化厌氧消化过程.产甲烷阶段是餐厨垃圾厌氧消化的限速步骤,各实验条件下水解速率常数(k)始终大于产甲烷速率常数(R_m').OLR和BC对k和R_m'的影响是波动的,从两个参数的数值上无法判断反应器的稳定性.相比之下,高效运行的反应器k/R_m'保持在(2.54±0.62),k/R_m'随OLR的增加及BC的下降单调递增,而随着k/R_m'增加,反应器运行效率下降.这从反应动力学上证实了增加OLR会加剧产酸和耗酸过程的不匹配,引起反应器失稳;而提高的BC浓度有利于缓解这种失衡,对保证反应器的过程稳定具有重要意义.

Influence of biomass concentration and organic loading rate on performance and kinetics of anaerobic digestion of food waste

To investigate the influence of biomass concentration (BC) and organic loading rate (OLR) on the performance and kinetics of anaerobic digestion (AD) of food waste (FW), BC and OLR grading experiments were carried out in batch mesophilic digesters. Physical-chemical analysis was performed to monitor state parameters and the digestion kinetics were evaluated by the application of first-order and modified Gompertz models. Results revealed that the overloading can reduce the process efficiency and stability while increased BC can otherwise minimize the organic loading of unit cell so as to optimize the AD process. Methanogenesis is the rate-limiting step in the digestion of FW. Under all experimental conditions, the hydrolysis rate constant (k) is always greater than the methanogenesis rate constant (R_m''). The influence of OLR and BC, on k and R_m'' respectively, is fluctuant, so the value of these two parameters are unable to determine the stability of the digesters. In contrast, the ratio of k/R_m'' in highly efficient digesters maintained at a level of (2.54 ±0.62) and increased monotonously with the increase of OLR as well as the decrease of BC. Moreover, along with the increase of k/R_m'', the efficiency of the AD process dropped as well. From the perspective of reaction kinetics, this study confirms that the increase in OLR exacerbates the mismatch between acid production and consumption, eventually resulting in process acidification and instability. However, the increased BC concentration tends to alleviate this imbalance, which is of significance for the efficiency and stability of the AD process.