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Advanced Wastewater Treatment
Published in Subhash Verma, Varinder S. Kanwar, Siby John, Environmental Engineering, 2022
Subhash Verma, Varinder S. Kanwar, Siby John
The design of a suspended-growth denitrification system is similar to that of an activated sludge system. Complete mix and plug flow reactors can be used. The nitrogen released during this process can attach to biological solids, thus a nitrogen release step is required using aeration. Factors affecting the denitrification process include nitrate concentration, carbon, temperature and pH.
Emissions Control Measures
Published in Neil Petchers, Combined Heating, Cooling & Power Handbook: Technologies & Applications, 2020
Fuel denitrification of coal or heavy oils could, in principle, be used to control fuel NOX formation. The most likely application would be to supplement combustion modifications implemented for thermal NOX control. Currently, denitrification is used to remove other pollutants, such as in oil desulfurization and chemical cleaning or solvent refining of coal for ash and sulfur removal. The low denitrification efficiency and high cost of these processes currently render them unattractive as emissions control technologies.
Organics, Salts, Metals, and Nutrient Removal
Published in David H.F. Liu, Béla G. Lipták, Wastewater Treatment, 2020
R. David Holbrook, Sun-Nan Hong, Derk T.A. Huibers, Francis X. McGarvey, Chakra J. Santhanam
Biological denitrification reduces nitrate (NO3−) to nitrogen gas (N2), nitrous oxide (N2O) or nitric oxide (NO). This nitrogen removal process is the one most widely used in municipal wastewater treatment (Water Pollution Control Federation 1983). Denitrifying organisms are primarily facultative aerobic heterotrophs that can use nitrate in the absence of DO. Many genera of bacteria are capable of denitrification: Achromobacter, Bacilus, Brevi-bacterium, Enterobacter, Micrococcus, Pseudomonas, and Spirillum (Davies 1971; Prescott, Harley, and Klein 1990). Several conditions enhance the amount of biological denitrification: nitrate, a readily available carbon source, and a low DO concentration. Low DO is the most critical condition since denitrification is simply several modifications of the aerobic pathway used for BOD oxidation (U.S. EPA 1975).
Influence of the carbon source concentration on the nitrate removal rate in groundwater
Published in Environmental Technology, 2022
Ruinan Liu, Lu Xia, Manxi Liu, Zongjun Gao, Jianguo Feng, Haichi You, Wanlong Qu, Tongju Xing, Jing Wang, Yanli Zhao
In recent years, the biological denitrification technique has been widely applied to in situ remediation treatments of nitrate in groundwater. Denitrification is a biological reaction during which nitrate and nitrite are reduced to N2 by microorganisms. To maintain their own survival, microorganisms require carbon sources, electron donors, acceptors, water, mineral nutrients, etc. According to the type of electron donor, biological denitrification can be divided into autotrophic denitrification and heterotrophic denitrification, and autotrophic denitrification can be subdivided into hydrogen autotrophic denitrification and sulfur autotrophic denitrification [24,25]. Because most denitrifying bacteria are heterotrophic bacteria, there are more studies on heterotrophic denitrification than on autotrophic denitrification. Problems often occur, such as insufficient carbon sources in natural groundwater, and the effects of external carbon sources and immobilized denitrifying bacteria on denitrification under different conditions have been investigated. Research has indicated that under the same conditions, the denitrification rate of external carbon sources is much higher than that of noncarbon sources [26], so heterotrophic denitrification requires an additional organic carbon source, and organic carbon sources can be divided into soluble carbon sources and solid carbon sources. Soluble carbon sources include methanol, ethanol, sodium acetate, sucrose, glucose, and starch, while solid carbon sources include straw, sawdust, and cotton.
Effects of carbon source, C/N ratio, nitrate, temperature, and pH on N2O emission and functional denitrifying genes during heterotrophic denitrification
Published in Journal of Environmental Science and Health, Part A, 2018
Yun-Yeong Lee, Hyungjoo Choi, Kyung-Suk Cho
The effects of several parameters, including carbon source, nitrate concentration, C/N ratio, temperature, and pH, on denitrification were evaluated using the bacterial-denitrifying consortium. Overall, 6 mL of denitrifying consortium was mixed with 54 mL of culture medium in a 120 mL serum bottle. The serum bottle was purged with N2 gas, sealed with a rubber stopper, and incubated at 30 °C for 2 weeks. All experiments were conducted in triplicate.
Detection of multidrug-resistant Pseudomonas isolates and distribution of denitrifying functional genes
Published in International Journal of Environmental Health Research, 2021
Nur Önal, Cumhur Avşar, E. Sümer Aras
Pseudomonas species can be isolated from many natural sources such as water, soil, milk and dairy products, meat and meat products, sewage, intestines of mammals and various plants (Doudorof 1984). Today, there are 160 species in the genus Pseudomonas, of which only 12 species have clinical significance (Liu 2011). Pseudomonas is a group of bacteria that find habitat in soil, fresh water, sea water, plant roots, animals and even in the home and clinical environment. It is remarkable that these bacteria are versatile, present in various habitats and can even grow in distilled water. These ensure their continued existence and have a significant impact on ecology, agriculture, trade and health (Mena and Gerba 2009). Some strains of Pseudomonas flourecens that live on surfaces such as soil, plants and water are found in the plant rhizosphere and are capable of producing various secondary metabolites containing antibiotics against soil-borne plant pathogens. When the iron concentration is low, it produces soluble green fluorescent pigment. The use as a biocontrol against pathogens and the ability to degrade various contaminants have increased interest in these microorganisms (Palleroni 1984; Paulsen et al. 2005). Some species of Pseudomonas also use nitrate (NO2) as electron acceptor instead of O2. Denitrification is a process of bacterial respiration and the way nitrate is converted into gaseous nitrogen forms. There are four reaction steps in this process and the genes encoding nitrate reductase (napA or narG), nitrite reductase (nirK or nirS), nitric oxide reductase (qnorB or cnorB) and nitrous oxide reductase (nosZ) are involved. It has been particularly emphasized that nitrous oxide (N2O) has a greenhouse effect approximately 300 times greater than CO2 over a 100-year period (it is responsible for more than 7% of global warming) and causes direct damage to the ozone layer (Dandie et al. 2011; Wyman et al. 2013; Shcherbak et al. 2014).