Activated sludge-loaded polyvinyl alcohol microparticles for starch wastewater treatment in an airlift bioreactor

Abstract

Emulsification followed by freezing and thawing cycles was applied to produce poly(vinyl alcohol) (PVA) microparticles and to simultaneously immobilize activated sludge. Activity of the obtained microparticles (similar to 400 mu m in diameter) was evaluated in glucose syrup solutions and heat-pretreated wastewater from a starch factory by measurements of permanganate index (COD (Mn) ) reduction. The reaction followed first-order kinetics, revealing slight mass transfer limitations in PVA microparticles as determined from the kinetic rate constant that was similar to 35% lower than that in the freely suspended activated sludge culture. Yet, efficiency of the microparticles increased almost five-fold in a laboratory airlift bioreactor operating either in batch or continuous regimes. Over 19 days of operation under high organic loadings in the industrial wastewater (similar to 100 kgCOD m(-3) d(-1)), PVA microparticles (12.4% volume fraction) remained active and induced a decrease of over 90% of biodegradable COD (Mn) at the hydraulic retention time of 8 h.