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Water Microbiology
Published in Frank R. Spellman, Handbook of Water and Wastewater Treatment Plant Operations, 2020
In the anoxic treatment process (anoxic means without oxygen), microorganisms use the fixed oxygen in nitrate compounds as a source of energy. The process produces more organisms and removes nitrogen from the wastewater by converting it to nitrogen gas that is released into the air (see Figure 10.13). Nitrate oxygenMore bacteriaBacteriaStable solidsOrganic matter⇒Settleable solidsNutrientsNitrogen
Biological stabilisation of sludge
Published in Bhola R. Gurjar, Vinay Kumar Tyagi, Sludge Management, 2017
Bhola R. Gurjar, Vinay Kumar Tyagi
The removal of nitrogen in the form of nitrate by conversion to nitrogen gas can be accomplished biologically under anoxic (without oxygen) conditions. The process is known as denitrification. In this process, the facultative anaerobic bacteria obtain energy for growth. from the conversion of nitrate to nitrogen gas, but require an external source of carbon for cell synthesis. Nitrified effluents are usually low in carbonaceous matter and so methanol is commonly used as carbon source, but industrial wastes that are poor in nutrients have also been used. Overall energy reaction of this process may be given as: () 6NO3−+5CH3OH(methanol)→5CO2+3N2+7H2O+6OH−(alkalinity)
Anaerobic and Anoxic Biotreatment of Waste
Published in Volodymyr Ivanov, Environmental Microbiology for Engineers, 2020
An important application of anaerobic Gram-positive fermenting bacteria in environmental engineering is the production of biofuel.the anoxic treatment of wastewater.methanogenic fermentation.anaerobic nitrogen fixation.
Removal of ethanethiol using a biotrickling filter with nitrate as an electron acceptor
Published in Environmental Technology, 2020
Mohammed Salim Shihab, Kadir Alp, Mustafa Türker, Ilker Akmirza, Rasha Khalid Mhemid
Anoxic biodegradation offers an environmentally friendly alternative which results in the bio-conversion of sulphurous compounds into elemental sulphur and /or sulphate using as an electron acceptor under specific ET/ ratios (ET/ yield ratio 0.74 and 0.34 mole/mole). A few researchers have recently studied the exploitation of nitrate (as oxidant) in biogas desulphurization [33–37] but there is a need to develop bio treatment alternatives to achieve proper stoichiometric relations between sulphide and nitrate, i.e. the S/NO3 molar ratio by which elemental sulphur can produced [38]. Anoxic biodegradation of ET offers another advantage in that it combines sulphide removal with nitrate removal in a single process, something required by industrial wastewater treatment systems. An example is the treatment of biogas emissions, mainly H2S, using nitrate (as oxidant) from anoxic wastewater treatment tanks in the yeast industry [33].
Floating treatment wetlands as biological buoyant filters for wastewater reclamation
Published in International Journal of Phytoremediation, 2019
Khadeeja Rehman, Amna Ijaz, Muhammad Arslan, Muhammad Afzal
The removal of two types of nutrients (total nitrogen and total phosphorus) from wastewater has been the main focus of FTWs. The removal of total nitrogen mainly depends on microbial processes, such as nitrification and denitrification, for aerobic and anaerobic conditions, respectively, whereas phosphorus removal take place mainly due to physical processes, such as sorption, fixation, complexation, and precipitation (Stottmeister et al.2003; Maine et al.2007; Chen et al.2015; Zhang, Zhao, et al.2016). Stewart and colleagues hypothesized microbial contribution to be the dominant factor in nutrient removal; they studied this hypothesis by using floating mats that were commercially available as BioHaven® floating islands (Stewart et al.2008). The material for this island was composed of intertwined polymer strands, where each strand was capable of being colonized by microbial biofilms while supporting macrophyte growth. The successful removal of nitrate, ammonium, and phosphate was observed in municipal wastewater. The study concluded that plants use nitrate as a nutrient source; since it is also an electron acceptor for anaerobic denitrifying bacteria, part of the denitrification process occurs in the anaerobic zones of the mat leading to successful removal of nutrients. Nitrifying bacteria in the plant rhizosphere would have converted all ammonium to nitrite aerobically and then to nitrate. This nitrate is finally transformed to nitrogen gas by anaerobic bacteria due to the development of anoxic interfaces after continuous submergence of the filtration bed. Finally, the authors establish that 10,600 mg per day nitrate, 273 mg per day ammonium, and 428 mg per day of phosphate can be removed by microbes living in a unit volume of BioHaven® floating island (1 ft2 = surface area and 0.6 ft = thickness). In the same context, Sun and colleagues performed experiments based on immobilized nitrifying bacteria in FTWs planted with Canna (Sun et al.2009). The addition of bacteria to the system enhanced nitrogen removal up to 72.1% in 5 days; while without bacterial enhancements, the removal rate was only 39.9–50.4% in the same time frame. Another study reported that microbial activity in the wetland environment is limited by the surface area of the floating mat and the nutrient availability (Stewart et al.2008). An expansive internal surface area allows effective colonization of bacteria owing to improved nutrient transport to the bacteria; such a design can make relatively small floating platforms function with an efficiency equal to much larger traditional wetlands (Stewart et al.2008). This signifies the importance of plant-bacterial synergism for nitrogen removal by FTWs.