| An anaerobic hybrid reactor (AHR), comprising an anaerobic filter (AF) upper section and an up-flow anaerobic sludge blanket (UASB) lower section, was used to treat synthetic wastewater under different loading conditions. The AF was then separately investigated for its role in contributing to the performance and process stability of the AHR. The immobilized biomass and population distribution of the different microbial species in the AF were also studied under steady operating and different shock loading conditions.; With the incorporation of the AF section in the upper portion of the system, the AHR presented a better capability against the environments of the shock loadings. The AF section of the AHR played a significant role in the removal of COD; particularly when the AHR system was operated under adverse conditions, such as shock loadings. The AF section of the AHR performed as a biofilter to maintain the temporarily inhibited microorganisms on the surfaces of the packing medium and thus prevented a wash out of the inhibited microorganisms under shock loadings. This rendered the AHR more tolerant to shock loadings. During shock loadings at different HRTs, the average COD removed by the AF section was about 36%, ranging from 49 to 21%, whereas the UASB section only accounted for about 10% of the COD removal, ranging from 10.4 to 8.2%. Even under critical shock loading at an HRT 0.5 day, the average COD removed by the AF section was maintained at about 21%; whereas the COD removed by the UASB section declined to about 9%. In response to the shock loadings, the AHR showed a temporary drop in the efficiency of COD removal, but resumed to steady state operations after the adverse situation ceased. As a general trend, the COD removal rate decreased as the HRTs decreased from 5 to 0.5 days. The efficiency of removal of COD of the AF section was much higher than that of the UASB section during the transient state of shock loadings. The COD removal rate of the AHR was maintained at between 1.5 and 0.4 g COD/L-d at HRTs of 2.5 to 0.5 days before the failure of the AHR at an HRT of 0.25 day.; The AF section was then isolated to study its process stability and responses to hydraulic and organic shock loadings. For the hydraulic shock loading experiments, the AF was started-up with synthetic wastewater of 3000 mgCOD/L at 5.0 days of HRT, achieving 98.1% COD removal efficiency. Under 2, 4 and 5 times hydraulic shock loadings, the efficiency o£ COD removal was temporary reduced, ranging from 92.7 to 89.7%, the pH of the treated effluent and biogas production were also affected. (Abstract shortened by UMI.)... |
