Further treatment of coking wastewater treated in A2O-MBR by the nanofiltration-powder activated carbon hybrid system

Anoxic–oxic membrane bioreactor (A2O-MBR), one of the biological systems requently used for the treatment of coking wastewater, increased under the influence of the growing iron and steel industry; however it cannot meet the discharge standards set by the Ministry of Environment, Urbanization and Climate Change of the Republic of Türkiye (CSB) due to recalcitrant pollutants in the wastewater. Advanced treatment of coking wastewater treated in A2O-MBR to meet the standards of the Ministry; nanofiltration (NF) (two different membranes and different pressures), powder activated carbon-microfiltration (PAC-MF), and PAC-NF (two different membranes and five different PAC concentrations) were investigated. In addition to the parameters determined by the Ministry, other parameters (ammonium, thiocyanate (SCN−), hydrogen cyanide (HCN), dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), color) were also investigated to evaluate the performance of flux and treatment efficiency of the hybrid process. According to the results, chemical oxygen demand (COD) in the NF process, COD, and total cyanide (T-CN) in the PAC-MF process could not meet the discharge standards. In the PAC-NF hybrid system, XN45 met the discharge standards in all parameters (COD = 96 ± 1.88 mg/L, T-CN = <0.02 mg/L, phenol = <0.05 mg/L), with a 78% recovery rate at 0.5 g/L PAC concentration.