Evaluation of COD, color and lignin removal from pulp and paper effluent by anaerobic sludge biosorption

The biosorption of COD, color and lignin from synthetic and industrial pulp and paper effluent was investigated. The biomass of the treatment plant applied in anaerobic conditions as biosorption media. The biomass was obtained from aeration tank return sludge line of the Mazandaran pulp and paper industry. A bench-scale reactor was used for this study. The effects of initial COD, color and lignin concentration, organic loading rate and hydraulic residence time were assessed by the response surface methodology. Biomass gradient along the height of reactor and biogas production rate were also examined, and regression equations for system performance were reported. The results indicated a direct relation between efficiency and hydraulic residence time and the inverse with organic loading rate, upflow velocity and initial COD, color and lignin concentration. Although this system has low capability for color and lignin removal (< 30%), it was able to solve the COD and color problem in effluent to the discharge standard limit for surface waters. The combination of reactors with species that have favorable ability for lignin removal or activated carbon as efficient adsorbent can be used as amplifier system efficiency too. [GRAPHICS]