Analysis of submerged membrane for a sludge-bed anaerobic membrane bioreactor treating prehydrolysis liquor.

An analysis of foulants and the performance of membranes in innovative sludge-bed anaerobic membrane bioreactors (SB-AnMBRs) were evaluated at mesophilic (35°C for approx. 400 days) followed by thermophilic (55°C for approx. 400 days) temperatures while treating the prehydrolysis liquor (PHL) waste stream from a dissolving pulp production plant. The membrane fouling of SB-AnMBR was analyzed for 0.1, 0.15 and 0.2 m(3)/m(2)/d flux conditions. Physico-chemical analyses of the membrane showed that the combination of 5% citric acid, 0.5% NaOCl and 2% NaOH solutions was effective in achieving more than 80% recovery of membrane flux. Chemical characterization of foulants showed that proteins were more predominant in membrane fouling than carbohydrates. Sugars and lignin contribution were negligible as compared to proteins in the total organic carbon content of the foulant. Membrane fouling occurred through a biofilm-dominated process and organic fouling. Combination of cleaning chemicals which included 0.5% NaClO and 2% NaOH solutions was most effective in the removal of the organic foulants. SEM analysis showed the pictorial evolution of the impact of fouling on the pore openings and the effect of cleaning on the membrane surface.