Study On Influence Factors Of Biological Phosphorus Removal

With the increasing eutrophication, more and more attention was paid on control of phosphorus content of water body worldwide. How to remove phosphorus from the wastewater quickly and efficiently becomes the forefront issue of wastewater treatment. In this paper, the biological phosphorus removal sludge was cultivated in a SBR. The effects of temperature and C/P ratio on enhanced biological phosphorus removal were studied. And yellow water was tried initially as the carbon source to cultivate the sludge. The experimental results showed as follows:(1) Phosphorus removal sludge was cultivated in alternate anaerobic and aerobic condition with sodium acetate as carbon source. After running for 25 days, PAOs were enriched successfully. The system had a good and stable phosphorus removal performance with phosphorus removal efficiency above 90%, and the readily biodegradable COD was almost removed in the anaerobic stage.(2) when different temperature(respectively being controlled at 10℃,20℃and 30℃), the rates of COD consumption and phosphorus release increased with increasing temperature, but the ratio of COD consumption/phosphorus release was almost the same at different temperatures. The rates of phosphorus release and uptake would decrease when the system was run at high temperature for a long-term, and the performance of phosphorus removal deteriorated gradually even collapsed. The impact of low temperature(5℃) on biological phosphorus removal would lead to the increase of filamentous bacteria and the deterioration of the sludge settling characteristics.(3) When the initial COD concentration was in a range of 30-180mg/L, the amount of phosphorus release and the specific phosphorus release rate (SPRR) increased as C/P ratio in the anaerobic stage. In the experiment condition, it was found that the ratio of phosphorus releaseto COD uptake was 0.352mg-P/mg-COD. The maximum phosphorus release rate of 78.89mg/gVSS·h, and the maximum COD absorption rate of 224.81mg/gVSS·h was attained at high concentration of oaganic carbon, respectively. The interruption of anaerobic COD-uptake and phosphorus-release may be resulted from exhaustion of the glycogen in the PAOs. When the C/P ratio was more than 23.4, further increase on the COD concentration in the reactor seldom had any effect on phosphorus removal. The optimal C/P for phosphorus removal was about 23.4 in this study.(4) Yellow water contained high concentration of organic matter with C/N and C/P of 580～610 and 240～275, respectively. So it has some use value. In this experiment, it was difficult to achieve desired phosphorus removal performance with yellow water as carbon source, the average efficiency of phosphate removal was about 40%, which may be resulted from complicated organic components in the yellow water.(5) The structure of sludge which was cultivated with sodium acetate as carbon source was more compact than that with yellow water as carbon source. The result of SEM micrographs showed that coccus morphotype PAOs dominated in sodium acetate-fed sludge and a variety of forms (coccus, rod and so on) morphotype PAOs occurred in yellow-water-fed sludge. The activated sludge production ratio of the former is 0.65gVSS/gBOD, slightly higher than the latter which is 0.59gVSS/gBOD.