An aerobic nitrifier WY-01, isolated from coking wastewater, was identified as Alcaligenes faecalis by its 16S rRNA gene sequence analysis. It exhibited unusual capability for ammonium removal at initial NH₄⁺–N 400 mg L⁻¹ with low accumulated intermediates, and converted ammonium to N₂ under aerobic conditions. Based on nitrogen removal and enzyme assay, two distinct nitrogen removal pathways were proposed in strain WY-01. Additionally, the effect of different factors on ammonium removal by strain WY-01 was investigated. The results show that efficient removal of ammonium occurred at temperatures as low as 10 °C, 60 g L⁻¹ salinity, 8 mmol L⁻¹ Cu²⁺ or 0.5 mmol L⁻¹ Zn²⁺ or 1 mmol L⁻¹ of equivalent Cu²⁺–Zn²⁺, initial NH₄⁺–N concentration from 50 to 1200 mg L⁻¹ and pH from 5 to 10. The strong adaptability of strain WY-01 makes it a promising candidate for future application in actual wastewater treatment.