Combination of coagulation and catalytic wet oxidation for the treatment of pulp and paper mill effluents

Wet oxidation (WO) is a well established process for purification of concen trated municipal and industrial wastewaters. Many attempts have been made t o modify the WO process or to create a suitable combination of processes. T his work was undertaken to investigate wet oxidation integrated with coagul ation, i.e. to treat the sludge remaining after coagulation with a WO proce ss. The possibility of regeneration of the used coagulant was also consider ed. Two waters from paper mills were used: TMP (thermomechanical pulp) circ ulation water and membrane concentrate. About 50% of the COD in the origina l water can be removed by coagulation using Fe-2(SO4)(3). The results from the wet oxidation experiments show the positive effect of iron in the chemi cal sludge as a catalyst. The efficiency of the WO process was enhanced alm ost by 100%. The remaining dissolved organic matter can be easily removed b iologically.