ANAEROBIC TREATMENT IN PULP AND PAPER-MILL WASTE MANAGEMENT - A REVIEW

The pulp- and paper-industry generates large volumes of highly heterog enous wastewaters containing compounds from wood or other raw material , process chemicals and compounds formed during processing. The wastew aters from mechanical pulping and secondary fiber pulping as well as t he condensates from chemical and semi-chemical pulping are typically n on-toxic to methanogenic degradation and contain easily degradable org anic compounds. Consequently, anaerobic digestion is an attractive tre atment alternative for these effluents. In addition, both primary and secondary sludges from pulp- and paper-industry wastewater treatment-p lants are amenable to anaerobic digestion. In contrast, the bleaching effluents from chemical pulping, the debarking effluents as well as th e CTMP effluents are likely to be inhibitory to methanogenic degradati on; also their biodegrability is relatively low. Dilution with other w astewater streams or detoxification by various pretreatments have been used to facilitate anaerobic treatment of these inhibitory wastewater s. The potential of the anaerobic systems for reductive dechlorination and sulfur recovery is unique and of great interest. In almost all pu lp- and paper-industry full-scale applications, anaerobic treatment is followed by aerobic post-treatment. The suitability and the cost of t he anaerobic-aerobic and aerobic treatment-systems are largely affecte d by a variety of mill-specific factors.