Conference on Environmental Science and Technology

The pulp and paper (P&P) industry consumes significant amounts of fresh water and produces wastewater that should be treated effectively to minimize environmental impact. Conventional treatment methods based on aeration and sedimentation tanks are energy-intensive and pose a serious environmental problem. Membrane bioreactors (MBR) are a promising and efficient treatment technology. Therefore, this study focuses on the treatment of wastewater streams from the pulp and paper industry using a laboratory pilot unit with an integrated anaerobic and anaerobic membrane bioreactor (an/ae MBR) unit. Experimental tests were conducted to determine the optimal operating conditions and evaluate process efficiency by determining the physicochemical properties of feed and permeate streams and estimating the biogas production rate and its composition. The results of a six-month demonstration phase of the an/aeMBR pilot unit showed an overall promising system performance. Despite the significant differences in feed stream characteristics, the an/ae MBR unit showed high organic load removal (>94% in the anMBR and ~99% overall of the integrated an/aeMBR unit), resulting in water suitable for safe disposal or reuse. In addition, complete removal of suspended solids was achieved thanks to the ultrafiltration membranes (turbidity removal efficiency >99%). The biogas production rate was continuously increased up to 480 ml/day, keeping the methane content high and approaching about 70% v/v, while the methane production capacity was in the range of 0.02–0.16 Nm³/Kg COD. Finally, a chemical cleaning of the UF membranes was performed during the laboratory tests for both membrane bioreactors to restore their original permeability.