Comparative investigations on COD-removal in sequencing batch reactors andcontinuous flow plants

Investigations on enhanced COD removal from municipal wastewater were perfo rmed over a period of 2.5 years, comparing three different types of reactor . The main idea was to determine the influence of the mixing characteristic s of the reactor on the treatment processes and the effluent quality. There fore three pilot plants (a completely mixed reactor, a cascade of three rea ctors and a SBR) were operated under equal conditions (wastewater, hydrauli c load, temperature, sludge age) in parallel to each other. Investigations were carried out at different sludge ages. It could be shown that within one sludge age the CODf removal efficiency increased, when mix ing characteristics came closer to the plug flow and it also increased with higher temperatures. A significant correlation was observed between the CO D removal efficiency and the sludge load. The higher the sludge load was th e greater the CODf concentration in the effluent. Especially the SBR reacto r showed an excellent performance under the given operating conditions. Dyn amic simulation calculations were carried out, to investigate whether the i nfluence of the type of reactor on the COD-elimination could be described t heoretically by combining growth kinetics and the mixing characteristics of the individual reactors. The results showed that performance was better wh en mixing characteristics came closer to plug flow.