Novel hybrid system for organic matter removal and energy production from dairy and textile wastewaters: anaerobic digestion and electrocoagulation approach

Novel and hybrid treatment approaches are recommended for the effective remediation of heavily polluted industrial effluents, concurrently enabling the recuperation of energy resources. This study employed a dual-stage treatment system comprising anaerobic digestion (AD) and electrocoagulation (EC) for dairy and textile industry effluents with high chemical oxygen demand (COD) levels. The co-digestion process was carried out at mesophilic temperature (37 °C) in an anaerobic sequencing batch reactor (ASBR) functioning as a pre-treatment step. Biochemical methane potential (BMP) tests involving co-digestion blends of dairy wastewater (DWW) and raw textile wastewater (RTW) were conducted, spanning a range of 0 to 100%, with a consistent amount of food waste added to each mixture to achieve equilibrium in the C/N ratio. AD of these mixtures showed promising results, with around 69.8% COD removal efficiency and 384 ml/gVS of methane generation rate reported for co-digestion mix with 80% DWW. Modified Gompertz model results revealed that the mixtures with a higher proportion of DWW exhibited complete anaerobic digestibility when contrasted with the fraction of RTW. Subsequently, EC was applied as a post-treatment method, utilising various current densities (2.97, 5.95, and 8.93 mA/cm²) and treatment durations (0, 15, 30, 45, and 60 min) for all combinations of the AD digestate. At an optimal treatment time of 45 min, a maximum COD removal efficiency of 89% was attained through EC at a current density of 8.93 mA/cm². Moreover, adopting an integrated approach that incorporates both AD and EC has proven effective in achieving an overall COD removal rate of 97%. This approach stands out as an economically viable and sustainable technique for the treatment of diverse industrial effluents such as RTW and DWW.