Study On Phosphorus And Nitrogen Removal In A Novel Two-Sludge Process By Combining SBR With BCO And The Dynamic Models For The Process

As known,phosphorus and nitrogen are the main contributors of water eutrophication,and a considerable part of them are from domestic sewage,so the standards of the phosphorus and nitrogen concentrations in the effluent of UWTP are more and more stricter.Denitrifying phosphorus removal processes has potential advantage in treating domestic sewage with low carbon source,for they have solved the problems which exist in the traditional phosphorus and nitrogen bio-removal processes.Denitrifying phosphorus removal processes have attracted a lot of interest,but most of them have complex structure.So a novel two-sludge was developed in this study by combing SBR with BCO.The SBR-BCO process has a simple structure and is easy to be controlled.In this study,some test apparatus for SBR-BCO process was constructed,then the cultivation of DPAOs as well as the stoichiometic relationship of different substance in the metabolism of this kinds of microorganism and the start of the BCO system were investigated.Meanwhile,the simplified dynamic models for SBR-BCO process were developed and fitted basing on a set of tests.Finally,the efficiency of SBR-BCO process on removing the pollutant including phosphorus and nitrogen were studied.This paper could provide reference to the further study of SBR-BCO process as well as other denitrifying phosphorus removal process,and the main results of this paper are as follow.The DPAOs sludge with SRT of 15d,25d,and 35d were cultivated through A/O and A/A/O processe simultaneously,taking the sludge of a running well oxidation ditch as seed sludge.The results shown that cultivating way could strengthen the phosphorus uptake under anoxic condition in all SRT,but the longer the SRT was the more phosphate were released or taken in by the DPAOs.Moreover,the stoichiometic parameters for phosphate releasing or uptake,COD reducing,PHB storage or degradation vary with SRT significantly,while the stoichiometic relationships between denitrification and PHB degradation of the sludge with different SRT was seemed to have no significant difference.Eventually,35d was taken as the best SRT.The efficiency of NH₃-N removal was increasing gradually during the start stage,and the start time was about 13 days.The efficiency of NH₃-N removal can reach96.89%-98.49%when the BCO system ran stably.The dynamic models for SBR-BCO process were simplified by reducing the model’s order,linearization or parameter combination basing on ASM2d,TUDP,and all the developed dynamic models consist of measurable component and parameters.Those models were used to fit the result of the experiments conducted with the rationality of those models were evaluated trough the fitting degree or the consistence of the parameters’value estimated with different data.The results shown that,those simplified models fit the data of the experiments well,and the parameters’value obtained by this study can provide a reference for the modeling of denitrifying phosphorus removal process.The running parameters of the SBR-BCO apparatus were decided according to the above study with the assistant of the models developed in this paper.The reaction time for anaerobic phase,anoxic phase,aerobic stage,settling,and draining water&feeding water of SBR are 3h,4h,2h,1.5h,and 1.5h,respectively.The HRT of BCO was 8h.In this operation condition,the SBR-BCO apparatus was run with artificial domestic sewage as feeding water.It was shown that,the SBR-BCO process had high efficiency at removing NH₃-N,TN,and TP,the average total removal of those pollutant are 92.7%,87.3%,72.7%,and 94.6%,respectively.The quality of the treated water met“A”level of“Discharge standard of pollutants for UWTP of china.In SBR-BCO process,most organic carbon were used effectively.The phosphate uptake process in anoxic phase of SBR plaid a major role in TP and TN removal,and the aerobic phase of SBR is necessary to guarantee NH₃-N and TP meeting the discharge standard.