Simultaneous ANAMMOX and denitrification (SAD) process in batch tests

The occurrence of simultaneous anaerobic ammonia oxidation and nitrate reduction (SAD) processes by enrichment culture in the presence of glucose were clarified in batch tests. Nitrate conversion and the formation of interim by-products were investigated under autotrophic and mixotrophic conditions. Eventually, the nitrite was fully consumed and co-occurred with ammonia oxidation. The effect of penicillin G and methanol on the SAD process was also investigated. Methanol addition led to complete loss of ANAMMOX activity at concentrations as low as 1 mM. Penicillin G has little effect on the SAD process. Scanning electron microscopy (SEM) observation and denaturing gradient gel electrophoresis (DGGE) analysis revealed that ANAMMOX bacteria and co-existing bacteria are responsible for the SAD process. In conclusion, this study indicates that the ratio of nitrogen to organic carbon, and the cooperation and competition between microbes can affect the dynamics of this process. It has a potential application to remove ammonia and nitrate in the presence of organic matter by the SAD process.