Biological treatment of pulp and paper mill process and wastewaters under thermophilic conditions - a review

The pulp and paper industry generates high-temperature process and wastewat ers, which are normally cooled dawn to about 40 degreesC or less before ext ernal biological treatment. So far, treatment at high temperature has rarel y been employed in the pulp and paper industry or other industrial wastewat er treatment. High temperature is generally considered to suppress the perf ormance of activated sludge and other processes. In this paper, we review s ome theories and recent findings from laboratory and pilot studies an biolo gical treatment at high temperature. Experimental studies clearly indicate that biological (anaerobic, aerobic, and anaerobic-aerobic) treatment at hi gh temperature (50-60 degreesC) is feasible. The thermophilic process has b een shown to be stable over long periods of operation, and the process remo val efficiency and loading rates are comparable to, if not higher than, tho se achieved in the mesophilic process. Furthermore, the thermophilic proces s can be readily scarred with sludge from a mesophilic process. Biological treatment at high temperature is thus workable and may well obviate the nee d to cool wastewater altogether. Further studies and full-scale implementat ion will disclose in derail the effects of high temperature on loading pote ntial and excess sludge production.