The research papers titled, “Efficient autotrophic denitrification performance through integrating the bio-oxidation of Fe(II) and Mn(II)”, “Comparison of denitrification performance by bacterium Achromobacter sp. A 14 under different electron donor conditions” and “Effect of mixed electron donors on autotrophic denitrification by Pseudomonas sp. SZF15” is written by Junfeng Su. The three papers derive its inspiration from an issue that is at an alarming stage. Yes, it is environmental pollution, a serious problem on a global scale.
All three papers deal with nitrate removal from groundwater. Groundwater is widely used for drinking water. In most cases, groundwater from anoxic acquifiers contains excessive levels of iron, manganese and/or nitrogen. Nitrate-nitrogen contamination has become an environmental and a public health issue is most developed and developing countries. It is often seen that nitrate contamination causes a rare disease called methemoglobinemia when ingested by infants. It may also cause carcinoma, malformation and mutation when transformed into nitrosamines. A large amount of nitrogen is also discharged into the aquatic ecosystems thus leading to severe deterioration of water quality.
A study showed that approximately 10-25% of the groundwater in the US was contaminated with nitrate. It was seen that the condition was worse in some developing nations. Drinking contaminated groundwater or its use in irrigation can lead to serious health issues. Junfeng and the team of researchers analysed such data and decided to develop a novel, facile and an efficient approach to remove nitrate from the water body.
According to Junfeng and the team, high concentrations of Fe(II) and Mn(II) which co-existed in the natural groundwater body, could be easily oxidized as the electron donor. On the other hand, the team observed that transformation from nitrate/nitrite to N2 (i.e., denitrification process) usually consumed the electrons and this according to them could be regarded as an electron acceptor. Therefore, Junfeng and others concluded that coupling denitrification process with oxidation of Fe(II) and Mn(II) might develop a new type of autotrophic denitrification which could aid in simultaneous removal of nitrate, nitrite, ferrous and manganese.
In the paper titled, “Efficient autotrophic denitrification performance through Integrating the bio-oxidation of Fe(II) and Mn(II)”, according to Junfeng and the team, high concentrations of Fe(II) and Mn(II) which co-existed in the natural groundwater body, could be easily oxidized as the electron donor. Junfeng and the team proposed a novel and efficient strain Pseudomonas. sp. H117-based bioremediation process. Furthermore, the kinetics and parameters about substrate (nitrate) and substrate self- inhibition (nitrite) were obtained. The results showed that the Edwards model used by the team suited their experimental data. It was also assessed that Fe(II) and Mn(II) could be formed to biogenic Fe-Mn oxides (FeOOH and MnO2) via microbial oxidation.
In the paper titled, “Comparison of denitrification performance by bacterium Achromobacter sp. A 14 under different electron donor conditions” Junfeng Su mentions the use of heterotrophic, mixotrophic and autotrophic denitrification in the treatment of nitrate-contaminated water. While conducting the study a newly anaerobic denitrifying bacterium, A14, with high denitrification and Mn(II) oxidation ability was isolated from sediments. This process made his study easier. It exhibited efficient denitrification ability in all the three mediums viz., autotrophic, mixotrophic and heterotrophic. Furthermore, the meteorological chromatography findings suggested that N2 and N2O were detected in the gas produced by strain A14. It was also concluded that the characteristic of gas composition varied in different mediums.
In the paper titled, “Effect of mixed electron donors on autotrophic denitrification by Pseudomonas sp. SZF15” a mixed electron donors of Mn(II) and Fe(II) were tested for their effects on autotrophic denitrification. Complete nitrate removal was found at high Mn(II)/Fe(II) molar ratios, 30 °C, pH 7.0, and an electron donor/electron acceptor molar ratio of 3.00.Furthermore, In addition to the above, the findings showed that nitrate could be converted to nitrite and further be degraded to N2 by nitrite reductase (nirS).
This research is pivotal as it deals with one of the most important natural resource, groundwater. Groundwater is what humans rely on in some way or the other. Hence, it should not be exploited and any contamination must not be overlooked. The study conducted by Junfeng Su can encourage environmental researchers and the government of the various countries to save this vital resource. The three research papers by Junfeng Su play a pivotal role in saving the environment.
About the Author:
Professor Junfeng Su is a doctoral tutor and fellow of the International Water Association (IWA). He is at School of Environmental and Municipal Engineering, Xi’an University of Architecture and Technology of China. He is a key member of the innovation team “Northwestern Town Water Resources Recycling and Water Quality Safety Guarantee” of the Ministry of Education. The current research interests of his group include (1) Wastewaters and groundwater bio treatment by biofilm (2) Genomics, transcriptomics and proteomics of autotrophic denitrifying bacteria and metal oxidizing bacteria (3) New theory and technology of biological nitrogen and phosphorus removal.
Prof. Su is the principal investigator of 8 national or provincial programs including National Natural Science Foundation of China, Excellent Youth Foundation of Shaanxi Province, EY Research and Development Project of Shaanxi Province of China, and Doctoral Fund of Ministry of Education of China. Prof. Su has published more than 40 SCI papers and authorized 11 invention patents. He has won several awards in the recent years including First Prize of Shaanxi Science and Technology Progress Award, Third Prize of Shaanxi Science and Technology Progress Award, First Prize of Science and Technology Award of Shaanxi Provincial Higher Education, and Second Prize of Science and Technology Award of Shaanxi Provincial Higher Education.
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