The effects of some inhibitory components on biological activated carbon processes

Some experimental results have already reported on a biological activated carbon (BAC) process to show its effectiveness of the treatment of a kind of wastewater collected from plating industries, in which refractory organic pollutants and small amounts of heavy metal ions existed after physical–chemical treatment. However, the removal behavior of the organic pollutants in the BAC treatment under the existence of inhibitors, such as heavy metal ions, was not made clear. Therefore, some laboratory-scale experiments were performed using some types of model wastewater. The organic substances chosen as the target pollutants were typical commercial reagents used in plating industries. The influence of some inhibitory factors, such as concentrations of heavy metal ions, pH and salt concentrations on the removal of organic substances in the BAC treatment was examined. As a result, it was found that the activated carbon adsorption decreased the inhibition of coexisting heavy metal ions, while the ratio of the inhibition was not reduced by use of activated carbon when salt concentrations or pH values were varied. In addition, different levels of inhibition ratio appeared as different organic substances were treated and it was found that less biodegradable organic substances tended to be affected by heavy metal ions acting as inhibitors. A proposed index, (BOD/COD)/(q/q0), could express some relationships with the magnitude of inhibition and with the removal efficiency of the organic pollutants under the conditions that the heavy metal ions coexist. Also, the possibility of this approach for examinations to evaluate various kinds of treatments was suggested.