Resiliency of Anammox against External Stress Factors – Effects of Temperature and Wastewater Constituents

Nitrogen removal based on anaerobic ammonium oxidation (anammox) has gained tremendous popularity as it is energy efficient and environmentally friendly. In this case, anammox is coupled with partial nitrification (collectively called partial nitritation-anammox or PN/A systems) to accomplish nearly 80–90% total inorganic nitrogen removal. Despite significant knowledge gained about the process engineering and microbiology related to PN/A systems, very little is known about the effect of external perturbations on PN/A systems especially in a system biology framework. In this research we first evaluated the effects of metal and toxic loading on an enriched anammox community. Thereafter, we operated a single-stage PN/A lab-scale reactor to evaluate the effect of temperature on the process efficiency and system microbiology. Mercury led to a 50% reduction and lead caused a 20% reduction in specific anammox activity at 0.8 mg/L concentrations. Cyanide, used as a toxic chemical, caused significant anammox activity inhibition at 50 ppb concentration. The results related to temperature changes showed that ammonium oxidizing bacteria (Nitrosomonas sp.) can maintain a relatively stable activity at lower temperatures (13~21°C), while anammox bacteria (Candidatus Brocadia) are more sensitive to temperature reductions.