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Published in Maria Csuros, Csaba Csuros, Klara Ver, Microbiological Examination of Water and Wastewater, 2018
Maria Csuros, Csaba Csuros, Klara Ver
The effluent from secondary treatment contains only 5 to 20 percent of the original quantity of organic matter and can be discharged into flowing rivers without causing serious problems. However, this effluent can contain large quantities of phosphates and nitrates, which can increase the growth rate of plants in the river. Tertiary treatment is an extremely costly process that involves physical and chemical methods. Fine charcoal and sand is used for filtration. Various flocculating chemicals precipitate phosphates and particular matter. Denitrifying bacteria convert nitrates to nitrogen gas. Finally, chlorine is used to destroy any remaining organisms. Water that has received tertiary treatment can be released into any body of water without danger to cause eutrophication. Such water is pure enough to be recycled into the domestic water supply. However, the chlorine-containing effluent, when released into streams and lakes, can react and produce cancer causing compounds that may enter the food chain or be ingested directly by humans in their drinking water. It would be safer to remove the chlorine before releasing the effluents, but this is rarely done today, although the cost is not great. Ultraviolet lights are now replacing chlorination as the final treatment of effluent. They destroy microbes without adding carcinogens to our streams and drinking waters.
Design Criteria — Domestic Wastewater Treatment
Published in Ronald L. Antonie, Fixed Biological Surfaces — Wastewater Treatment, 1976
In some areas of the U.S., removal of all forms of nitrogen from the wastewater is required. In areas such as Long Island, New York, where wastewaters are discharged to ground aquifers to become part of the water supply, it is necessary to limit the nitrogen content of the effluent to prevent an accumulation of nitrates and exceed public health standards for drinking water. In other areas, such as Florida and some mid-Atlantic states, the total nitrogen content of wastewater discharges is being limited as a means of controlling eutrophication and avoiding undesired development of algae in receiving waters. To meet total nitrogen requirements for all of these cases, it is first necessary to nitrify or aerobically oxidize ammonia nitrogen to nitrate and then anaerobically denitrify or convert the nitrates to nitrogen gas. Denitrification is an anaerobic process and usually requires the addition of organic carbon to the wastewater to provide a source of energy for the denitrifying bacteria. They utilize the oxygen contained in the nitrate ion in their metabolic processes. Methanol is most often considered as the source of carbon, because it is relatively inexpensive, easy to handle, and most important, results in relatively little biological sludge generation.
Water quality systems
Published in A. W. Jayawardena, Environmental and Hydrological Systems Modelling, 2013
Denitrification is the process by which nitrates are converted into molecular nitrogen in the presence of denitrifying bacteria (Paracoccus denitrificans). It is an anaerobic process with the intermediate stages of converting nitrates (NO3) to nitrites (NO2), nitric oxide (NO), and nitrous oxide (N2O). NO3−→NO2−→NO→N2O→N2
Relationship between denitrification and anammox rates and N2 production with substrate consumption and pH in a riparian zone
Published in Environmental Technology, 2023
Shuangjian Li, Xuefei Xie, Hu Li, Dongmei Xue
Denitrification and anaerobic ammonium oxidation (anammox) are two important NO3− removal processes in the environment. Denitrification generally refers to the process in which denitrifying bacteria convert inorganic N into N2O or N2 by oxidizing organic matter as the energy source and NO3− or NO2− as electron acceptors in anaerobic or anoxic environments [4]. Anammox is a process in which ammonia oxidation bacteria directly oxidize NH4+ to N2 with NO2− as the electron acceptor under anaerobic or anoxic conditions [5]. Anammox could contribute to N2 production from 0 to 77% in sediments, from 18 to 90% in the water [6–9] and from 0 to 37% in soils [10–12]. Denitrification could contribute to N2 production from 61 to 83% in sediments [6], from 10.4% to 80% in the water and from 65 to 99.5% in soils [12,13].
Investigation into the nitrate removal efficiency and microbial communities in a sequencing batch reactor treating reverse osmosis concentrate produced by a coking wastewater treatment plant
Published in Environmental Technology, 2018
Enchao Li, Rongchang Wang, Xuewen Jin, Shuguang Lu, Zhaofu Qiu, Xiang Zhang
Denitrifying bacteria are generally spread across a number of genera of Proteobacteria and Bacteroidetes, including Hyphomicrobium, Thauera, and Methyloversatilis. Due to their high taxonomic diversity, previous studies [39,41] have targeted the gene clusters that encode key enzymes involved in the denitrification pathway, including nitrate reductase (Nar), nitrite reductase (Nir), and nitrous oxide reductase (Nos). In the denitrification process of coking RO concentrate using sodium acetate as the sole carbon source, qPCR was adopted to study the changes in 16S rRNA genes, narG, nirS, nirK, and nosZ in activated sludge samples.
Principles for quorum sensing-based exogeneous denitrifier enhancement of nitrogen removal in biofilm: a review
Published in Critical Reviews in Environmental Science and Technology, 2023
Ying-nan Zhu, Jinfeng Wang, Qiuju Liu, Ying Jin, Lili Ding, Hongqiang Ren
Traditional denitrification involves two pathways: one is the dissimilatory process, in which denitrifying bacteria gradually reduce nitrate (NO3−) to nitrogen (N2) through a series of intermediate products (NO2−, NO, and N2O), and the other is the assimilation process, in which denitrifying bacteria use nitrate (NO3-) as a nitrogen source, absorb and convert it into biomass after ammonification. Table 1 lists the enzymes and genes related to the metabolic steps in denitrification (revised from Cui et al., 2019).