Integrated thermophilic submerged aerobic membrane bioreactor and electrochemical oxidation for pulp and paper effluent treatment – towards system closure

A novel integrated thermophilic submerged aerobic membrane bioreactor (TSAMBR) and electrochemical oxidation (EO) technology was developed for thermomechanical pulping pressate treatment with the aim of system closure. The TSAMBR was able to achieve a chemical oxygen demand (COD) removal efficiency of 88.6 ± 1.9–92.3 ± 0.7% under the organic loading rate of 2.76 ± 0.13–3.98 ± 0.23 kgCOD/(m3 d). An optimal hydraulic retention time (HRT) of 1.1 ± 0.1 d was identified for COD removal. Cake formation was identified as the dominant mechanism of membrane fouling. The EO of the TSAMBR permeate was performed using a Ti/SnO2–Sb2O5–IrO2 electrode. After 6-h EO, a complete decolourization was achieved and the COD removal efficiency was increased to 96.2 ± 1.2–98.2 ± 0.3%. The high-quality effluent produced by the TSAMBR-EO system can be reused as process water for system closure in pulp and paper mill.