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Title: Kinetic models for nitrogen inhibition in ANAMMOX and nitrification process on deammonification system at room temperature

item DE PRA, MARINA CELANT - Universidade Federal De Santa Catarina (UFSC)
item KUNZ, AIRTON - Embrapa-Pigs And Poultry
item BORTOLI, MARCELO - Federal University Of Parana Polytechnic Center
item SCUSSIATO, LUCAS ANTUNES - University Of Paranaense
item COLDEBELLA, ARLEI - Embrapa-Pigs And Poultry
item Vanotti, Matias
item SOARES, HUGO MOREIRA - Universidade Federal De Santa Catarina (UFSC)

Submitted to: Bioresource Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/17/2015
Publication Date: 12/2/2015
Citation: De Pra, M., Kunz, A., Bortoli, M., Scussiato, L., Coldebella, A., Vanotti, M.B., Soares, H. 2015. Kinetic models for nitrogen inhibition in ANAMMOX and nitrification process on deammonification system at room temperature. Water Research. 202: 33-41.

Interpretive Summary: Since the discovery of anaerobic ammonium oxidation (anammox) several processes using anammox bacteria have been implemented to improve the biological nitrogen removal in wastewater. Among these processes, the deammonification process was recently proposed seeking more effectiveness for the treatment of concentrated effluents with low carbon/nitrogen ratio, such as municipal side-stream wastewater or digestate effluents from livestock farms. The deammonification process combines nitrification bacteria with anammox bacteria, both working together, without the need for carbon addition, as well as having reduced energy requirements and lower biomass production compared to traditional nitrification/denitrification. When the process is done in a single tank, it could be very economical. In this research, we used several kinetic models to better understand the inhibition of nitrification and anammox bacteria to high strength wastewaters when grown separately, or mixed together in the single-tank deammonification system. Our results indicated that the deammonification system had a large capacity to withstand high removal loads without bacteria inhibition at wastewater concentrations of more than 600 milligrams of ammonia per liter. Knowing and controlling the conditions that favor the activity of the bacteria involved are a first step for development of economical nutrient removal systems based on deammonification in the near future. In this regard, the results obtained in this study provide critical information towards achieving this goal.

Technical Abstract: The performance of the deammonification process depends on the microbial activity of ammonia oxidizing bacteria (AOB) and ANAMMOX bacteria. These autotrophic organisms have different preferences for substrate, operating conditions and some external factors that may cause inhibition or imbalance of the process. Kinetic studies are very important to characterize these problems and to be able to predict future adverse inhibitions in the system. In this study we fitted the best kinetic model for nitrogen inhibition by ammonium and nitrite in three different nitrogen removal systems operated at 25 degrees Celsius: a nitrifying system (NF) containing only AOB bacteria, an ANAMMOX system (AMX) containing only ANAMMOX bacteria, and a deammonification system (DMX) containing both AOB and ANAMMOX bacteria. The statistical analysis proved that the Andrews model was the best kinetic model to describe ammonium inhibition of the nitrification process in the NF system. It showed that the nitrifying biomass studied presented little inhibition when subjected to high substrate concentration, above 1000 milligrams ammonia nitrogen per liter. For the AMX system, the Edwards model was the best to describe both ammonium and nitrite inhibition, and showed that the inhibitory effect of substrate concentrations were more evident and rapid for nitrite (above 100 milligrams nitrite nitrogen per liter), than ammonia (above 400 milligrams ammonia nitrogen per liter). For the DMX system, the Monod model was the best model to describe the performance of the deammonification process, showing that increased substrate concentration in the range of 80 to 1060 milligrams ammonia nitrogen per liter tested was not limiting for the ammonia consumption rate, represented by a saturation constant (KS) value of 175.48 milligrams ammonia nitrogen per liter, and the absence of the inhibition constant (KI). The AOB and ANAMMOX sludges combined in the DMX system displayed a very good activity at 25 degree Celsius, possessed great substrate affinity and excellent substrate tolerance, with actual specific nitrogen conversion rate of 6.24 milligrams per gram of volatile suspended solids (VSS) per hour (380 mg of nitrogen removed per liter of reactor per day) obtained at more than 600 milligrams of ammonia per liter substrate concentration and room temperature.