SECONDARY-TREATMENT OF A CTMP EFFLUENT

To assess aerobic biological processes for the treatment of chemitherm omechanical pulping effluents, the biodegradation of a chemithermomech anical pulp (CTMP) effluent by aeration and activated sludge treatment was studied on a laboratory scale. With the activated sludge treatmen t, a short hydraulic retention time (HRT) of 8 to 16 h resulted in hig h abatement (90-98%) of BOD5 and almost complete removal (94-98%) of r esin and fatty acids. A much longer HRT of at least 48 h, was required for the aeration treatment to achieve the same removal efficiencies. Good sludge settling prevailed for both treatments. Removals of indivi dual resin and fatty acids by each treatment were investigated. No sig nificant differences in the responses of individual acids to both trea tments were found for all the HRTs studied.