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

The up-flow Sludge Blanket Filtration (USBF) is a novel and efficient wastewatertreatment process which is a modification of conventational activated sludge system. The purpose of this study was to determine the efficiency of USBF process in biological phosphorus removal and to achieve the optimized hydraulic retention time according to the maximum phosphorus removal in the system. The experiments were carried out using a pilot scale USBF plant with a total volume of 60 liters by operating in different hydraulic retention times with flow rates of 0.57, 0.67, 0.8, 1.0, 1.33 and 2L per hour and the COD/P ratio around 50 at pH from 6.5 to 7.8 and room temperature (i.e. 20±2 °C). The experiments results according to the phosphorus removal showed that the system could commonly achieve steady state in a short time in flow rates of 0.8 and 0.67, and the phosphorus removal efficiency of more than 90 percent, but in the flow rates of 1.0, 1.33 and 2L per hour it would take a longer time to achieve the steady state and the desired phosphorus removal rate. At the end statistical analysis were carried out to determine an economical option for the hydraulic retention time for the biological phosphorus removal in this process, that it was 10 h for the hydraulic retention time in the clarifier.