Anaerobic ammonium-N removal from modified greenhouse turtle breeding wastewater with different chemical oxygen demand (COD) strengths (194.0-577.8 mg L-1) at relatively fixed C/N ratios (similar to 2) was investigated using a lab-scale up-flow anaerobic sludge blanket (UASB) anammox reactor. During the entire experiment, the total nitrogen (TN) removal efficiency was about 85% or higher, while the average COD removal efficiency was around 56.5 +/- 7.9%. Based on the nitrogen and carbon balance, the nitrogen removal contribution was 79.6 +/- 4.2% for anammox, 12.7 +/- 3.0% for denitrification + denitritation and 7.7 +/- 4.9% for other mechanisms. Denaturing gradient gel electrophoresis (DGGE) analyses revealed that Planctomycete, Proteobacteria and Chloroflexi bacteria were coexisted in the reactor. Anammox was always dominant when the reactor was fed with different COD concentrations, which indicated the stability of the anammox process with the coexistence of the denitrification process in treating greenhouse turtle breeding wastewater. (C) 2013 Elsevier Ltd. All rights reserved.