Anaerobic digestion of pulping wastewater using up-flow anaerobic sludge blanket (UASB) reactor at mesophilic condition

Abstract

The waste considered for this study was the effluent of the pulping process produced during the manufacture of pulp and paper in the Rakta integrated pulp and paper mill in Alexandria. The pulping process in Rakta mill is conducted under pressure of 7-8 bar, 165°C using 10% NaOH based on straw weight for 2 h. The spent liquor after alkali cooking contains any where 8 to 15% solids in solution and primarily these dissolved solids are lignin and dissolved carbohydrates. The effect of some operating parameters on the performance of the Using Up-flow Anaerobic Sludge Blanket was studied; these include mainly the organic loading rate and hydraulic retention time. The gas production rate increased to 3.43 m3 biogas/(m3 reactor volume. day), by increasing the Biochemical Oxygen Demand (BOD) loading rate to 16 kg BOD feed/(m3 reactor volume. day), with a gas yield of 0.66 m3 biogas/(kg reduced organic matter). The efficiency was reduced by increasing the loading rate. Thus by increasing the BOD loading rate from 0.4 to 16 kg BOD feed/(m3 reactor volume. day), the reduction in BOD decreased from 79% to 42%.