Influence of sand layer depth on partial nitritation as pretreatment of anaerobically digested swine wastewater prior to anammox

This work aimed to investigate the influence of sand layer depth on partial nitritation performance as a preparative step for anaerobic ammonium oxidation (anammox) process in treating anaerobically digested effluent of swine wastewater. A lab-scale biological sand filter system was constructed and partial nitritation was successfully maintained with nitrogen loading rate (NLR) of approximately 50 g NH 4 + -N m - 3 d - 1 . An average NH 4 + -N removal efficiency of 61.34% and conversion efficiency of NH 4 + -N to NO 2 - -N of 79.77% were achieved with a sand layer depth of 32 cm. An effluent with a NH 4 + -N concentration of 242.52 mg L−1 and a NO 2 - -N concentration of 306.39 mg L−1 was achieved when the sand layer depth was 32 cm, giving a NO 2 - -N / NH 4 + -N ratio close to 1.32, as required by anammox. Overall, using a biological sand filter system to treat anaerobically digested effluent of swine wastewater by partial nitritation pretreatment prior to anammox is feasible.