Partial nitrification and anaerobic ammonium oxidation of ammonium-rich domestic wastewater in biofilm reactor system

In this study, the single reactor high-activity ammonium removal over nitrite (SHARON) and anaerobic ammonium oxidation (Anammox) process were incorporated in a biofilm reactor system. This study aims to serve as a guide for the design of a pilot plant for wastewater treatment which employs SHARON-Anammox process in biofilm reactor system. Batch and continuous runs were performed to study the performance of combined SHARON-Anammox process versus SHARON and Anammox operating separately, and to establish a kinetic model that best describes the SHARON-Anammox process. The data from batch and continuous runs were used to determine the kinetic model of the process. Monod kinetics was used to model substrate utilization. For nitrogen reduction, elementary chemical kinetics and Monod kinetics were applied. Kinetic parameters were determined by performing non-linear regression analysis to fit the experimental response to the model. The model was then simulated via MATLAB② ODE45, which follows Runge-Kutta method of integration. Based on the results, Monod model has a good fit to the actual COD profile and nitrogen profile, while elementary chemical kinetics does not take into account the effect of concentration of microorganisms in the bioreactor. The combined SHARON-Anammox process is much effective compared to individual SHARON and Anammox. When the two processes are combined the COD removal is increased by about 25.6%, and the TN removal is enhanced from 48.4% to 80.89%. Equivalent TN removal rate in combined SHARON- Anammox is 815 g N/m³-day. Nitrate-to-ammonium removal ratio for Anammox is 1.24. Also, it is remarkable that NO₂⻠removal in Anammox reached as high as 100%. The SHARON-Anammox process was found to prefer a low C/N ratio - the nitrogen removal is increased to as high as 97.43%. It was also observed that the process favors a low COD wastewater, which therefore suggests that there is no need to put additional COD for the process to occur. On the other hand, the flow rate was found to have no significant effect on COD and TN removal percentage