High-rate aerobic treatment of winery wastewater using bioreactors with free and immobilized activated sludge

COD (chemical oxygen demand) removal rate and efficiency of winery wastewater (WW) aerobic treatments were evaluated in an air-bubble column bioreactor using self-adapted microbial populations either free or im mobilized on polyurethane particles and in a packed-bed bioreactor immobilized oh Raschig rings. The bioreactors were fed continuously for up to 12 months using WW of different origins and with different pollution loads (COD range, 0.8-11.0 kg.m(-3)): the maximum loading rate was approx. 8.8 kg-COD m(-3).d(-1). The highest COD removal rate (6.6 kg.m(-3).d(-1)) was obtained with free activated sludge in the bubble column bioreactor; treatment efficiency and hydraulic retention time were >90% and approx. 0.8 d, respectively. The microbial populations in the three reactors were characterized.