ABSTRACT
This chapter examines if pulp and paper wastewaters could be treated to a level of quality acceptable for recycle and reuse. Metal ion coagulants such as aluminum and iron salts are efficient for the removal of color from pulp and paper wastewaters, especially when pH conditions of coagulation are optimized. The chapter investigates methods of wastewater treatment which could potentially be used to help produce water for recycle in pulping and bleaching systems. Major sources of color from a pulp mill include the caustic extraction stage in bleaching, the unbleached screenings, and the decker filtrates. Compounds with molecular weight of 5000 mass units and greater are efficiently removed; compounds less than 5000 mass units in weight are only marginally removed by chemical coagulation. The pH utilized during carbon treatment had a significant impact on color removal efficiency noted; lower pH conditions resulted in much more efficient carbon utilization.
