Optimization Of Two Sludge Process For Domestic Wastewater Treament

The A₂N process, based on denitrifying phosphorus removal, is efficient in treatingthe domestic wastewater with low C/N ratio, and is suitable for upgrading of theexisting wastewater treatment plants. The A₂N/BAF process had been researched fromlab-scale and pilot-scale to demonstration project. It was proved to be suitable for theconstruction of new wastewater treatment plant. In this dissertation, the optimization ofreflux of the backwashing sludge of the primary BAF and online control of BAFaeration were studied. The fiber filler was selected to substitute the BAF as thenitrification unit of A₂N aiming at the shortages of BAF, which was not fit for theupgrade of the built sewage plant, and the operation parameters were optimized. Finally,the treatment efficiency of A₂N/fiber process and A²O process were compared.The reflux program of the backwashing sludge of the primary BAF in A₂N/BAFprocess was opimizated. Results showed that: the backwashing sludge was morefavorable to recycle to the anoxic tank. The backwashing sludge had strong absorptioncapacity. The amount of phosphorus uptake was18mg/L after2h. Online control ofBAF aeration experiment showed that: in the primary BAF，the DO probe should beinstalled at the height of1.0-1.5m of the filter media, and when NH₄⁺-N concentrationof raw water was below40mg/L （influent NH4+-N concentration of the primary BAFwas below29mg/L） and the value of the DO probe device was above5.2mg/L, theeffluent NH4+-N less than5mg/L could be ensured. In the secondery BAF, the DOprobe should be installed at the height above1.2m of the filter media, the value of theDO probe device was above6.0mg/L, the effluent NH4+-N could be ensured.A₂N/fiber process optimization showed that biofilm formation of the fiber fillercould be achieved within5d and appropriate recycle ratio of sludge in secondarysettling chamber and ratio of surpass sludge were both0.25.The treatment performance of A₂N process and A²O process were compared.Results showed that COD and ammonia of the A²O process, could be removedeffectively, while, TN and TP removals were poor. It was due to the deficiency ofcarbon source. As for the A₂N process, the removals of COD, ammonia, TN and TPwere82%,97%,70%and98%, respectively, and the first-A standard could be achieved.The uptakes of phosphorus in the anoxic and aerobic tank were significant. The averageamounts of phosphorus uptake were9.5mg/L and6.04mg/L each. Moreover, thesecondary phosphorus uptake could ensure the quality of effluent. On another aspect,nitrification was efficient, indicated by7.15mg/L ammonia removal in the aerobic tank.