Dynamic behavior of the adsorption, activated sludge and combined activated sludge-adsorption process for treatment of cheese whey wastewater

Treatment of cheese whey wastewater (CWW) in terms of chemical oxygen demand (COD) removal by adsorption, activated sludge (AS), and combination of these two processes was investigated. The equilibrium and kinetic data for adsorption of organics available in CWW onto three types of powdered activated carbons (PACs) were successfully described by hybrid Langmuir-Freundlich and pseudo-second-order models, respectively. The results indicated that AS-PAC combined system outperformed individual AS process in different COD concentrations. The most significant result was observed at the 7,500 mg/L COD concentration with the broom sorghum PAC (BSPAC) with a PAC dose of 4 g/L which could improve COD removal efficiency from 52.3% for AS to 63.8% for AS-PAC system. The most substantial result in this study was demonstration of the PAC bioregeneration mechanism in AS-PAC process. Dynamic behavior of the AS, PAC adsorption, and AS-PAC process was modeled in terms of a set of coupled differential equations. An optimization procedure was followed to obtain the model adjustable parameters that showed the desorption index (K-des) for AS-PAC process was more than the value that was obtained for adsorption process. Also, in AS-PAC process, the maximum specific adsorption capacity of PAC decreased.