| dc.description.abstract | The attached biofilm systems on simultaneously removing organic carbons, total nitrogen, total phosphates are based on activated sludge process, with investigation in progress of decades, that are available to apply in pilot-plant scale. This study of setting up a three-stage submerged biofilter is investigated the feature of removing nutrients.
Because of residual COD in the initial zone of the biofilter, aerobic heterotrophs tend to overgrow in the zone. With the height of the biofilter being higher, the COD loading lower, PAOs and denitrifying bacteria would bring into the better activity.
This study involves five cycle duration (CD) runs — 1,3,6,12,18 hours. The run of CD = 1 hr alternative aeration is frequent, then resulting in poor activity of phosphorus release. CD = 12,18 hrs, COD loading lasts accumulating in all zones of the biofilter and causes inactive PAOs. CD = 3,6 hrs, sufficient anaerobic time and lower COD loading would result in increasing phosphorus release and accumulation of PHAs. Hence, TP removal efficiency is dependent on anaerobic phosphorus release. In TN removal, nitritation is specific reaction in the biofilter, but complete nitrification isn’t predominant. Denitritation is then forced to play an important role on TN removal. In general, TN removal efficiency is poorer in this study. The run of CD = 3 hrs has more complete nitrification than other ones, and that would be more practicable on simultaneous TN & TP removal.
With CD increasing, nitrification rate has a tendency to decrease. Nitrifying bacteria distributed in the middle to upper zones that are lower COD loading, these microorganisms would have better performance. Denitrification rate is also higher in the zones.
TP removal efficiency depends on activity of phosphorus release. The better activity of phosphorus release is in anaerobic phase, the more excess uptake of phosphorus is in aerobic phase. Hence, TP removal efficiency is increasing. The runs of CD = 3,6 hrs are better performing examples of this study. SPRR, SPRM, SPUR have the similar trend accompanied with time. Batch experiment revealed that the better are SPRR and SPRM, the better is SPUR. | en_US |