Evaluation of internal thermophilic biotreatment as a strategy in TMP millclosure

Closure of the water circuit during thermomechanical pulping (TMP) was stud ied on the laboratory scale. Internal treatment of white waters was carried out using a thermophilic (55 degrees C) anaerobic hybrid reactor or an aer obic moving-bed reactor. Dissolution of wood organic material in the water circuit was simulated by hot disintegration of TMP pulp in the anaerobicall y/aerobically treated white water. The anaerobic treatment removed all of t he material dissolved during hot disintegration during the first 10 recircu lations, after which there was a slight buildup in concentration. With inte rnal aerobic treatment, organic material accumulated from the beginning of the study. It appears that the anaerobic thermophilic process, possibly in combination with other treatment such as nanofiltration, is a feasible stra tegy for closing the water circuit of the TMP process.