The application of anaerobic wastewater treatment system in paper industry

Since the beginning of the eighties, anaerobic effluent treatment plants have been applied in the paper industry. The UASB reactor has become the most popular reactor. It is operating on almost all types of paper industry effluents, but the largest numbers can be found in the paper recycling industry. When acid paper sizing was abandoned, circumstances for fresh water reduction improved considerably, so that process waters and resulting effluents became more concentrated in COD. Besides this, anaerobic plants have also become popular for the treatment of condensates from sulphite (SP) and sulphate (Kraft) mills as well as for TMP and CTMP effluents and even for black liquor from soda pulping and NSSC. Improvements to the conventional UASB reactor have further increased loading rates and reduced hydraulic retention times. The IC (Internal Circulation) UASB reactor can treat twice the COD loading of conventional UASB at hydraulic retention times of 2 hours or more and is replacing the role of UASB in the paper industry effluents.