Treatment of grain distillation wastewaters in an upflow anaerobic sludge bed (UASB) system

In operation of the full-scale upflow anaerobic sludge bed (UASB) system at the Stellenbosch Farmers' Winery (SFW) Wellington: distillery, a problem e ncountered in the treatment of grain distillation wastewater was the accumu lation of a floating scum layer. On occasion this was so severe that it for ced shutdown of the UASB system to facilitate the physical removal of the s cum. A preliminary investigation indicated that the scum-layer behaviour co uld be replicated at laboratory-scale. Thereafter, two laboratory-scale UAS B systems were run in parallel: one (control) receiving wine distillation w astewater as influent, and the other (experimental) grain distillation wast ewater at bot high and low total suspended solids (TSS) concentrations. Scu m-layer accumulation, COD removal and concentration profiles along the axis of flow through the reactors were compared. The scum layer developed only with grain distillation wastewater as influent, and its severity appeared t o be linked to the TSS content of the grain wastewater. Reducing the TSS by drum filtration, settling or blending with wine wastewater could reduce, b ut not eliminate, the scum-layer accumulation. With wine distillation waste water as influent, concentration profiles exhibited the typical three disti nct zones of sludge bed behaviour. However, with grain distillation wastewa ter as influent, the concentration profiles were markedly different; the th ree zones of behaviour did not develop. This raises the question of the lon g-term viability of a UASB system treating grain distillation wastewaters.