Simultaneous adsorption and biodegradation of synthetic melanoidin

Abstract

Molasses spent wash contains melanoidin, a dark brown recalcitrant compound. It is not easily biodegraded and causes a number of problems such as reduction in photosynthetic activities and dissolved oxygen when discharged to aqueous environment. Being an antioxidant, melanoidin removal through purely biodegradation has been inadequate. Consequently, in the current study, simultaneous adsorption and biodegradation (SAB) was employed in a stirred tank system to remove melanoidin from synthetic wastewater. Mixed microbial consortium was immobilized onto 200 g of activated carbon and used to degrade 3.5 L of melanoidin solutions with varying chemical oxygen demand (COD) concentrations. The effects of the initial COD level, pH and temperature on COD removal were then studied. Ultimately, the SAB performance was compared to that of batch adsorption or biodegradation carried out independently. After 48 h of operation, the SAB process yielded the best COD removal efficiency of 75% as compared to 49.3 and 51.9% for adsorption and biodegradation, respectively, for the initial COD value of 10800 mg/ L at a temperature of 296 K and pH 6.97. This therefore showed that the SAB process can successfully be applied to enhance the removal of melanoidin from wastewater.

Key words: Adsorption, biodegradation, melanoidin, SAB, wastewater.