Kraft mill anaerobic effluent color enhancement by a fixed-bed adsorption system

An anaerobic reactor and a fixed-bed adsorption sequential system (FBAS) were applied to remove color from kraft mill effluent. Under anaerobic conditions, Biological Oxygen Demand (BOD(5)) removal was between 84 to 90% w/w, while Chemical Oxygen Demand (COD) removal ranged between 46 to 55% w/w. Total phenolic compounds were poorly removed (8 to 15% w/w) whereas the color was not removed by anaerobic digestion. For the FBAS system, three different columns were packed with natural and activated (calcinated and acidified) allophanic soil and fed with kraft mill anaerobic effluent. In activated soil columns, color and total phenolic compounds removal were around 95% w/w, whereas in the natural soil column the values were 87% w/w and 81% w/w, respectively.