Abstract
The results of this study show that, using an organic loading rate of 4kg COD m‐3d‐1, the UASB process can treat a simulated, soluble coffee waste in the thermophilic range. However, to achieve the highest COD removals (>75%) there was a need to add additional calcium ions to compensate for the inhibitory effects produced by potassium ions which originate from the coffee. When the hydraulic retention times were reduced, sequentially, from 24 hours to 6 hours, a deterioration in performance was found when the retention time was less than 12 hours.