Biogas production from recycled paper mill wastewater by UASB digester: Optimal and mesophilic conditions

Highlights • UASB was proposed for RPMW anaerobic treatement under mesophilic conditions. • Start-up up of the UASB reactor was completed in the 24 days. • 80,76 % COD and 90 % TS were removed at an OLR of 7,27 g COD/L d. • At optimal OLR of 8.31 g COD/L d was required to produce 62.51 L/d biogas. • For HRT 15.14 h, after reactor start-up 80.63 % of COD was removed. • The average biogas composition was 72.98 % CH4, 19.76 % CO2, 0.9 % O2.
The anaerobic digestion (AD) has become an alternative source and an attractive treatment method. Up-flow Anaerobic Sludge Blanket (UASB) digester has been designed to treat the Recycled paper mill wastewater (RPMW) in Morocco. This paper provides a research on anaerobic digestion of RPMW using UASB technology. The UASB digester was designed following the characterization of wastewater and the feed rate, with the volume of 70 liters. The UASB reactor treating the RPMW was operated for 130 days with minimal overload problems. The experiments were carried out in the mesophilic temperature (37 °C) at different organic loading rates (OLR). A daily analysis was performed to ensure the efficiency of the digester. In this study, the AD experiment was performed in continuous mode with an effluent inlet flow rate equal to 1 L/h. Using the optimal OLR value 5.18 g COD/Ld and with an effluent 5,7 g COD/L, a biogas yield of 92 N mL/g COD removed (at normal temperature and pressure) was obtained during the RPMW anaerobic treatment. The reactor was operated at an optimal hydraulic retention time (HRT) of 15.14 h with a biogas production volume of the optimal value 62.5 L/d. These results indicate that RPMW can be effectively treated in a UASB reactor with the advantage of producing biogas. We tested our system with RPMW, to see the production capacity of the UASB system, which the objective is to develop the system for the industrial scale.