Determining the Optimized Hydraulic Retention Time in the USBF Reactor for Biological Phosphorus Removal

This research describes an experimental technique which has been used to determine the efficiency of the USBF process in organic matter reduction and phosphorus removal. Continuous feeding of synthetic wastewater was used in different hydraulic retention times to access the optimized HRT according to the phosphate removal capacity of the USBF pilot and the sludge quality. HRTs varied from 16, 14, 12, 10, 8, 6 and 4 hours for the settling compartment, with the COD/P ratio remaining around 50, while the PO₄^3–-P concentration was about 20 mg/l. The experiments were performed at pH between 6.5–7.8 and at room temperature (i.e. 20±2 °C). The results of the experiments showed that the test system was efficient in removing COD and P in more than 85 percent of the cases for all of the tests after 20 days. The best results for P removal were obtained at the HRTs less than 8 hours while the Sludge Volume Index (SVI) was more than 150ml in lower HRTs as 6 and 4 hour. In the statistical analysis done to explain the results, it is revealed that with the differing parameters of P removal efficiency, SVI and the Total Suspended Solid (TSS), the optimized HRT for the Settling compartment is 10 hours.