Optimization and system energy balance analysis of anaerobic co-digestion process of pretreated textile dyeing sludge and food waste

Anaerobic digestion treatment can transform textile dyeing sludge (TDS) to resources, but direct anaerobic digestion of TDS products only little biogas. In order to improve the effect of anaerobic digestion, pre-treatment and co-anaerobic digestion were performed in this study. Two pre-treatment methods, which are thermal pretreatment and free nitrous acid (FNA) pre-treatment, were selected for comparison. Then, food waste (FW), as the co-digestion substance, co-digested with thermally pre-treated TDS to explored the optimized ratio of pre-treated TDS and FW. Results indicated that both the two pre-treatment methods have a certain solubilization effect on TDS, but the effect of thermal pre-treatment is better than that of FNA. The optimal mixing ratio of thermally pre-treated TD and FW is 1:1. The removal rates of soluble chemical oxygen demand and aromatic amines were the highest (75% and 64%, respectively). The cumulative methane yield reached 479.9 mL CH4/g VS, which was increased by 20-40% compared to others ratios and 66.6% to the TDS. Furthermore, system energy balance analysis was evaluated. Based on the dyeing wastewater treatment plant with a daily treatment capacity of 15000 t, electricity produced by biogas can completely satisfy the electric consumption of the wastewater treatment plant and the anaerobic co-digestion system with 57.69% and 41.78% for the respective. It was found that TDS can be reused resourcefully by the AcoD and costs can be significantly reduced.