Effect of Return Sludge Pre-concentration on Biological Phosphorus Removal in a Novel Oxidation Ditch

Abstract

A pilot-scale, pre-anoxic-anaerobic oxidation ditch was used in this study to treat municipal wastewater with limited carbon source. A novel return activated sludge (RAS) pre-concentration tank was adopted for improving the phosphorus removal efficiency and the effects of RAS pre-concentration ratio were studied. Under the optimal operational condition, the suspended total phosphorus (STP) and the total phosphorus (TP) removal efficiencies were around 58.9% and 63.9% respectively and the effluent 3 4 PO −-P was lower than 0.8 mg•L −1. The reason is that with the optimal RAS pre-concentration ratio, nitrate is completely removed with endogenous carbon source and the secondary phosphorus release is strictly restrained in the pre-anoxic tank. Therefore, the anaerobic phosphorus release and the carbon source uptake by phosphorus accumulation organisms (PAOs) in the sludge, which are extremely important to the phosphorus removal process, can be fully satisfied. Furthermore, the oxidation-reduction potential is proved to be suitable for controlling the RAS pre-concentration ratio due to influent fluctuation and varied conditions. The novel modified system is also beneficial for PAO accumulation.

Operation mode of a step-feed anoxic/oxic process with distribution of carbon source from anaerobic zone on nutrient removal and microbial properties

“…Aiming at lower nitrogen and phosphorus concentrations is essential not only in the design of new plants, but also for upgrading existing wastewater treatment plants. The nitrogen and phosphorus removal efficiencies of conventional active sludge technologies are relatively low and are limited by the carbon source 2 . Several technologies, such as external organic carbon for post-denitrification and recirculation approaches, can be used to solve this problem.…”

Study on Feasibility of Concentrated Activated Sludge Reflow of Biochemical Pool of Small-Sized Wastewater Plant

“…But the effluent quality still meets the standard for small and medium-sized wastewater plant. In addition, it is found through inspection that the total phosphorus concentration of effluent after transformation is reduced by about 0.1 mg/L, which is because the phosphorus release amount of concentrated sludge is higher than that of secondary settling tank sludge and thus the total phosphorus amount into aerobic pond is reduced so as to better remove phosphorus of the system [3,4] Based on experimental research and analysis above, the treatment efficiency of the system will be slightly decreased when concentrated sludge reflow instead of secondary settling tank reflow, but the effluent quality can still meet the standard of secondary emission standard of GB18918-2002. Thus it can be concluded that the technique is feasible.…”

Key factors governing alkaline pretreatment of waste activated sludge

“…It could also be a feedstock in the manufacture of high value products such as polyhydroxylalkanoates [2]. In order to warrant bioavailability of waste activated sludge, suitable pretreatments are needed to disintegrate the hard cell wall of microbes in waste activated sludge to improve substrate solubility and digestibility [3]. Among previously pretreatment methods, alkaline pretreatment has been proved to render relatively high disintegration efficiency [4].…”