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

Abstract

In operation of the full-scale upflow anaerobic sludge bed (UASB) system at the Stellenbosch Farmers' Winery (SFW) Wellington distillery, a problem encountered in the treatment of grain distillation wastewater was the accumulation of a floating scum layer. On occasion this was so severe that it forced shutdown of the UASB system to facilitate the physical removal of the scum. A preliminary investigation indicated that the scum-layer behaviour could be replicated at laboratory-scale. Thereafter, two laboratory-scale UASB systems were run in parallel: one (control) receiving wine distillation wastewater as influent, and the other (experimental) grain distillation wastewater at both high and low total suspended solids (TSS) concentrations. Scum-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 to be linked to the TSS content of the grain wastewater. Reducing the TSS by drum filtration, settling or blending with wine wastewater could reduce, but not eliminate, the scum-layer accumulation. With wine distillation wastewater as influent, concentration profiles exhibited the typical three distinct zones of sludge bed behaviour. However, with grain distillation wastewater as influent, the concentration profiles were markedly different; the three zones of behaviour did not develop. This raises the question of the long-term viability of a UASB system treating grain distillation wastewaters.



WaterSA Vol.27(4) 2001: 433-444