Adsorption of biologically inhibitory compounds as a process control mechanism in biological reactors

An innovative reactor design that decouples biological removal mechanisms from physical removal mechanisms has demonstrated promise for the treatment of wastewaters containing high concentrations of inhibitory compounds. Inhibition and toxicity prevent treatment of such wastewaters in conventional biological reactors. The reactor design consists of a high-rate biological reactor with a granular activated carbon (GAC) adsorber inserted into the recycle line of the biological reactor. Partial replacement of GAC from the GAC adsorber provides a mechanism for controlling the concentration of inhibitory compounds in the biological reactor. As a process control parameter, GAC replacement can be used to maintain the concentration of inhibitory compounds in a range optimal for growth and acclimation. GAC replacement is also varied in response to changes in the influent loading and can be used to provide rapid recovery from shock loadings. Agreement between isotherm studies and experimental data from pilot-scale systems was observed when the average GAC particle residence was greater than 3.75 days. Isotherm studies may be used to design the GAC adsorber and predict optimal operating conditions. The concept of using an adsorption process to optimize biological removal provides an environmentally sound treatment alternative for many high-strength wastewaters.