Electricity generation and acid and alkaline recovery from pickled waters/wastewaters through anaerobic digestion, bipolar membrane electrodialysis and solid oxide fuel cell hybrid system

Pickled industrial wastewater (PIWW) containing concentrated organics, ammonia, phosphorus and NaCl is a bioenergy and renewable resource. This study developed a hybrid system of anaerobic digestion (AD), bipolar membrane electrodialysis (BMED) and solid oxide fuel cells (SOFC) to recover biogas and ammonia as renewable fuels, and generate acid and alkaline from four pickle waters/wastewaters. The results demonstrated that anaerobic sludge particles were granulated in hypersaline circumstances and halophilic Bacteroidetes and Firmicutes were two dominant phyla. AD converted 70% of chemical oxygen demand (COD) to biogas and methane yield was 0.051 L-CH₄ g-COD⁻¹ on average. The maximum desalination, acid and alkaline generation rates achieved by BMED were 0.304 mol h⁻¹, 0.114 mol h⁻¹, and 0.136 mol h⁻¹, respectively. SOFC used recovered biogas and NH₃/H₂ and output 500 mW cm⁻² and 530 mW cm⁻² of peak power densities, respectively. AD-BMED-SOFC hybrid system finally gained 55% of maximum net energy efficiency for the 3rd pickled water. These results signify that AD-BMED-SOFC hybrid system is more feasible and potential when pickled waters are independently treated from pickled wastewaters.