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Molecular Techniques to Study Microbial Ecology and Dynamics for Wastewater Treatment
Published in Maulin P. Shah, Wastewater Treatment, 2022
Tarun Gangar, Satyam, Risha Hazarika, Sanjukta Patra
Ammonia-oxidizing Archaea (AOA), ammonia-oxidizing bacteria (AOB), and nitrite-oxidizing bacteria (NOB) all constitute nitrifying bacteria. These organisms catalyze the complete oxidation of ammonia to nitrate with intermediate conversion to nitrite. This multistep reaction is accomplished by a consortia of microbes that work in conjunction. Nitrosomonas is the major class of nitrifying bacteria, which includes N. europaea, Nitrococcus mobilis, and N. marina. Other genera includes Nitrospira, Nitrosolobus, Nitrosovibrio, Nitrobacter, and Nitrospira.
Advanced Wastewater Treatment
Published in Subhash Verma, Varinder S. Kanwar, Siby John, Environmental Engineering, 2022
Subhash Verma, Varinder S. Kanwar, Siby John
In the suspended-growth process, nitrification is achieved in an activated sludge process along with the usual carbonaceous oxidation, with some modifications to the design. Nitrifying bacteria are very sensitive to pH (varying from 7.8 to 8.9 with an optimum value of 8.4) and have a very slow rate of growth compared to heterotrophic bacteria. Nitrification rate drops rapidly in temperatures below 10°C. Thus, nitrification is difficult to achieve in colder climates. It has been shown that to complete nitrification in a conventional process, a higher level of mixed liquor volatile suspended solids (MLVSS) and a longer solids retention time (SRT) should be maintained. In addition, the dissolved oxygen (DO) level should be maintained above 2.0 mg/L.
Biological Treatment Systems
Published in Paul N. Cheremisinoff, Handbook of Water and Wastewater Treatment Technology, 2019
Temperature affects bacterial metabolic activities, gas transfer rates (available DO), and settling characteristics of waste effluents. At temperatures above 40°C and below 5°C, nitrification rates are very slow. Studies have indicated that the optimum temperature for nitrifying bacteria is 22 and 30°C. Because the temperatures in summer and warm climates are within this optimum range, treatment plants can be operated at less favorable pHs and lower substrate levels that would be required during colder conditions to achieve the same degree of nitrification. In order to make up for the temperature difference, in winter up to five times the summer detention time (capacity) may be required. Temperature deficiencies also may be made up by increasing the mixed liquor suspended solids level of the system and or pH adjustment.
Rapid start-up of autotrophic shortcut nitrification system in SBR and microbial community analysis
Published in Environmental Technology, 2022
Nan Zhang, Yuecheng He, Xiang Yi, Yunan Yan, Wenlai Xu
A large amount of nitrogen enters the water environment, causing frequent occurrence of eutrophication in the water body, thereby destroying the balance of the ecosystem and people's normal life. Biological nitrogen removal is a process that uses the metabolic activities of microorganisms to completely remove nitrogen from water bodies through nitrification and denitrification. Voets [1] discovered the accumulation of nitrite during the nitrification process in 1975, and put forward the concept of biological nitrogen removal by shortcut nitrification-denitrification for the first time. The nitrification process mainly includes the participation of two types of nitrifying bacteria, ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB). Shortcut nitrification utilizes the difference in the physiological characteristics of AOB and NOB, through adjustment and control of dissolved oxygen (DO), pH, ammonium nitrogen concentration, temperature, sludge age and other conditions to inhibit NOB and enrich AOB. After the ammonium nitrogen is converted into nitrite under the action of AOB, it is not further oxidized to nitrate under the action of NOB [2–4].
Consumption of water contaminated by nitrate and its deleterious effects on the human thyroid gland: a review and update
Published in International Journal of Environmental Health Research, 2022
Edgar García Torres, Rebeca Pérez Morales, Alberto González Zamora, Efraín Ríos Sánchez, Edgar Héctor Olivas Calderón, José de Jesús Alba Romero, Esperanza Yasmín Calleros Rincón
Nitrogen, obtained through the nitrogen cycle, is the main component necessary for the survival of all organisms (Stevens 2019) thus, it is essential for the synthesis of biomolecules such as proteins, nucleic acids, and chlorophyll formation in plants (Holmes et al. 2019). The entire cycle has been divided into three essential processes which are fixation, nitrification, and denitrification (Stein and Klotz 2016) in which nitrogen can be found in different stable molecules, such as NH3 (ammonia) and NH4 (ammonium). The oxidation of nitrogen, in the nitrification stage of the nitrogen cycle, converts NH3 and NH4 to NO2− (nitrite) and NO3− (nitrate) by the action of nitrifying bacteria, which represents the most stable forms of nitrogen (Takai 2019). Inorganic nitrite and nitrate are ionic compounds present in nature, through soil and water but are also found in volcanic and igneous rocks (ATSDR 2017). These compounds are hydrophilic salts, and as a result of its physical properties, nitrate is colorless, odorless and insipid, making its identification in water difficult and imperceptible to the human being (Khanfar 2010; Almasi et al. 2016). Nitrate is the most stable metabolite and is a chemically nonreactive form of nitrogen, while the nitrogen in the nitrite ion is in an unstable oxidative state (WHO 2017). With this in mind, knowledge of the increase of these compounds in the environment takes relevance due to their relationship with some alterations in human health.
Biotreatment of petroleum refinery wastewater in vertical surface-flow constructed wetland vegetated with Eichhornia crassipes: lab-scale experimental and kinetic modelling
Published in Environmental Technology, 2020
Samuel E. Agarry, Kigho M. Oghenejoboh, Ganiyu K. Latinwo, Chiedu N. Owabor
The inlet wastewater has an average pH value of 7.96 which makes it alkaline. Trang et al. [62] obtained a similar alkaline pH value for inlet municipal wastewater. The pH of the outlet wastewater was found to range from 7.4 to 7.7. This is significantly (P < .05) lower than the pH of the inlet wastewater. The pH values of the inlet and outlet wastewaters were within the allowable range between 4 and 9.5, which is suitable for the survival of most bacteria. Most bacteria cannot survive outside this pH range [63]. Nitrifying bacteria prefer a pH greater than 7.2, while they are inhibited at pH less than 6. Denitrifying bacteria optimally operate in a pH range that is between 6.5 and 7.5 [1,63]. The results suggest that the pH in the constructed wetlands was conducive for both nitrification and denitrification. The reduction in pH during the course of wetland treatment favours microbial action to remove BOD5, COD and TPH in the wastewater [49].