Simultaneous Nitrogen and Phosphorus Removal Using a Double Sludge Switching Sequencing Batch Reactor

A new process using a sequencing batch reactor (SBR) and two smaller sludge hoppers is proposed for the simultaneous removal of phosphorus and nitrogen from wastewater. In the double sludge switching sequencing batch reactor, denitrifying phosphate accumulating bacteria (DPB) sludge and nitrification sludge are transferred to the SBR at different phases instead of flowing wastewater through different reactors. The process was operated with a cycle time of $10.5\mathrm{h}$ , consisting of DPB sludge filling phase $\left(0.5\mathrm{h}\right)$ , anaerobic phase I $\left(2.0\mathrm{h}\right)$ , settling and changing DPB sludge phase $\left(0.5\mathrm{h}\right)$ , anaerobic phase II $\left(0.5\mathrm{h}\right)$ , aerobic phase $\left(4.0\mathrm{h}\right)$ , settling and changing nitrifying sludge phase $\left(0.5\mathrm{h}\right)$ , and anoxic phase $\left(3.0\mathrm{h}\right)$ . Results of stable operation showed that the process was very efficient over a range of temperatures varied from $10\text{to}28°\mathrm{C}$ . The average effluent concentrations and removal efficiencies were as follows: ${\mathrm{COD}}_{\mathrm{Cr}}$ $28.0\mathrm{mg}∕\mathrm{L}$ , 92.1%; ${\mathrm{BOD}}_5$ $7.0\mathrm{mg}∕\mathrm{L}$ , 95.1%; $\mathrm{N}{\mathrm{H}}_3–\mathrm{N}$ $0.8\mathrm{mg}∕\mathrm{L}$ , 98.0%; TN $9.8\mathrm{mg}∕\mathrm{L}$ , 76.7%; and TP $0.5\mathrm{mg}∕\mathrm{L}$ , 92.3%.