Acute and persistent toxicity of Cd(II) to the microbial community of Anammox process

In this study, the short- and long-term effects of Cd(II) on the bioactivity, nitrogen removal and microbial community of the anaerobic ammonia oxidation (Anammox) process were investigated by step-wise increasing Cd(II). The self-recovery ability of Anammox was also studied after long-term exposure in Cd(II). The bioactivity of anaerobic ammonia-oxidizing bacteria (AAOB) within short-term exposure of Cd(II) were detected by batch experiments. Results showed that Cd(II) had both acute and persistent toxicity to Anammox, the IC₅₀ in short-term exposure was calculated as 5.43 mg L^-1. Long-term exposure led to the microbial diversity increase, as well as the relative abundance decrease of AAOB in Anammox system. AAOB was continuously suppressed by Cd(II) in 1-20 mg L^-1, while it had self-adaption to Cd(II) in 1-10 mg L^-1. Anammox biofilm showed prominent adsorbing ability for cadmium, and the cadmium in biofilm was the key factor affecting Anammox.