Investigation Of G3 Strain Performance For Heterotrophic Nitrification-aerobic Denitrification

The work contained in the current thesis explains the mitigation strategy for nitrogen removal using a bacteria specie G3 strain.We explored the ability and performance of the strain G3 under the laboratory experimentation as a potential heterotrophic nitrifier and aerobically denitrifier to reduce nitrogen content in a typical synthetic wastewater.Heterotrophic nitrification-aerobic denitrification process has interested the scientific community to search deep in its potentiality for the wastewater treatment applications because of its non-negligible contribution in the nitrogen reduction.Nitrogen-based emissions by N2O or NO from wastewater system account for about 10%of the global greenhouse gas and are originated globally from about 94%of wastes,and therefore,a development of strategies capable to eliminate their emissions or accelerate their recovery would be solicited in the advancement of biological technologies.Significant progress has been made in the biological research for wastewater treatment and yet more trials are being experimented to find out more efficient system that could promote the feasibility and cost-effective applications.The existing challenges in the applications of the biological technologies in the wastewater treatment consist of utilization of the bacterial species capable to resist under harsh conditions of oxygen(absence or available oxygen),temperature,pH,presence of organic matters,etc.Some bacteria species have high ability to withstand either one or many environmental fluctuations(presence or absence of oxygen,low or high temperature,and pH changes),and therefore,investigating the potential of microorganisms that could respond to the challenges is of paramount in the research.In the current work,we aim at exploring the possibility of using the strain G3 in the mitigation of nitrogen removal more specifically in the wastewater treatment.We investigated the heterotrophic nitrification and aerobic denitrification ability of the strain to understand its performance for future applications under various nitrogen sourcing including Ammonium Chloride(NH4CI),Na15NO3,Na15NO2,and hydroxylamine(NH2OH.HCl).The experimental results disclosed that the strain G3 has the ability to remove nitrogen in the experimental formulations adopted in our study.Under the NH4Cl selection as the sole source of nitrogen,Ammonium oxidation to Nitrate was efficiently carried out by the strain at 92.35%efficiency.Small amount of Nitrite was detected in the incubation experiments indicating that most of the nitrite was aerobically converted to nitrate by G3.Following the nitrification of ammonium,aerobic denitrification also took place by reduction of nitrate/nitrite sources to produce N2O which could be a prospective pathway towards the N2O recovery for further energy production.The denitrification results showed that the strain can sustain the availability of oxygen and can use O2 for cells growth and also for enhancing the denitrification process through electron transfer mechanism.The efficiency of nitrate removal was found at 98.58%suggesting aerobic denitrification ability of the strain G3.The interesting features of G3 strain in the SND applications as observed in our work are attributed to:(?)a short experimental time within 24 hours of incubation the ammonium oxidation was complete,and thus no longer duration would be needed in the wastewater treatment application;(?)the ability of the strain to perform as heterotrophic nitrifier and aerobic denitrifier within a single process would guarantee a reasonable batch reactor application in the wastewater treatment units;(?)the strain capability to perform at relatively ambient temperature about 30?assuring low-energy cost for future applications.Therefore,along with this thesis we provided a comprehensive review on heterotrophic nitrification and aerobic denitrification and their implications in the wastewater treatment applications.We also discussed the experimental part of our investigations and explain the outcomes in correlation with the observed facts and literature findings.Finally,we proposed future directions and orientations of the research investigations to explore in deep the performance and applications of the strain G3 in technological wastewater treatment plants.