Wastewater coming from cheese-producing industries in Greece is high in org
anic matter (about 40-60 g/l Chemical Oxygen Demand, GOD) since it generall
y contains discarded cheese-whey as well. This wastewater is rich in easily
biodegradable carbohydrates and has a relatively low content in suspended
solids (1-5 g/l). Because of the high organic content of dairy wastewater,
anaerobic digestion is essentially the only viable treatment method.
An Upflow Anaerobic Sludge Blanket (UASB) reactor is a high rate treatment
system, especially feasible for treating soluble (containing low solids) wa
stewaters. A well-performing UASB reactor is characterized by highly floccu
lated, well-settling, compact methanogenic sludge granules, resulting in a
very high biomass content.
The aim of this work is the study of a UASB reactor treating dairy wastewat
er. A UASB reactor of 101 useful volume was constructed and inoculated with
anaerobic mixed liquor from dairy wastewater and glucose fed digesters. Th
e digester efficiency of treating dairy wastewater at various organic loadi
ng rates was studied and its performance was assessed by monitoring pH, dis
solved chemical oxygen demand (COD), biogas production and composition. Ope
ration at an organic loading rate of 6.2 g COD/ld was found to be safe and
could be increased to a maximum of 7.5 g COD/ld. A draw and fill digester f
ed with non-diluted wastewater was also studied in parallel for comparison
purposes. The advantages of using a UASB reactor versus a conventional dige
ster become questionable for the high COD (>42 g/l), non-diluted dairy wast
ewater case. (C) 1999 Silsoe Research Institute.