Abstract
The applicability of the model derived by Ramanathan and Gaudy (Biotechnol. Bioeng., 11, 207, (1969)) for completely mixed activated sludge treatment holding the recycle solids concentration as a system constant was investigated using an actual industrial organic wastewater. Shortβterm experiments were conducted at various dilution rates (1/8, 1/6, 1/4, 1/2, 1/1.5 hr^β1^) for two recycle solids concentration values (5000 and 7000 mg/liter). The influent substrate concentration was maintained at 1000 mg/liter COD and the hydraulic recycle ratio, Ξ±, was kept at 0.3. It was found that for bottling plant (Pepsi Cola) wasteβwaters, a steady state with respect to reactor biological solids and effluent COD, at different dilution rates, could be attained, lending experimental evidence to the assumption that a steady state could be reached in developing the model and also affecting the applicability of the model in industrial organic wastewater. The reactor biological solids and effluent COD calculated from the model closely agreed with the observed values at dilution rates lower than 0.5 hr^β1^. Operation at dilution rates higher than 0.5 hr^β1^ will washout the biological solids from the reactor and the recycle substrate concentration will be apparent if the concentration of X~R~ were not increased.