Aerobic process

The major biological treatment processes can be divided into aerobic processes, which require the presence of oxygen, and anaerobic processes, which require the complete absence of oxygen. 

Aerobic treatment process works by introducing organic waste into a reactor where an aerobic bacterial culture is maintained in suspension. Here the bacteria carry out the conversion of organic compounds in accordance with the following equations. 

COHNS represents organic matter present in wastewater. 

Under aerobic conditions, ammonia is removed by a two-step biological oxidation process see reaction (10.6). Ammonia is first oxidized to nitrite 

The oxidation of nitrite to nitrate is carried out by Nitrobacter, according to  

The floodwater and uppermost part of the soil are oxygenated by photosynthetic organisms, and the rhizosphere is oxygenated by leakage of O2 from plant roots. 

The penetration of the O2 into the soil depends on its rate of consumption in aerobic processes and its rate of transport by mass flow and diffusion, and in the floodwater-soil interface, mixing by burrowing invertebrates. Various aerobic processes take place in these oxygenated zones. 

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In aerobic processes, the mean sludge residence time is typically 5 to 10 days. The hydraulic residence time is typically 0.2 to 0.3 days. Suspended growth aerobic processes are capable of removing up to 95 percent of BOD. 

In all types of biological processes, excess sludge is produced which must be disposed of. The treatment and disposal of sludge are major problems which can be costly to deal with. Anaerobic processes have the advantage here, since they produce considerably less sludge than aerobic processes (on the order of 5 percent of aerobic processes for the same throughput). 

A suitable means of scale-up for aerobic processes is to measure the dissolved oxygen level that is adequate in small equipment and to adjust conditions in the plant until this level of dissolved oxygen is reached. However, some antibiotic fermentations and the production of fodder yeast from hydrocarbon substrates have very severe requirements, and designers are hard-pressed to supply enough oxygen. 

We can see that for type 1 processes, high growth rate is obligately linked to a high rate of product formation. Indeed, this is the case for all products produced by a fermentative mode of metabolism, eg ethanol, lactic add, acetone. Chemostat studies have shown that for most aerobic processes when growth is limited by some nutrient other than the carbon source, the yield of product decreases with increase in spedfic growth rate (p or D p = dilution rate (D) in chemostat culture). Conversely, both the biomass yield and the spedfic rate of substrate utilisation (qs g substrate g biomass-1 h-1) increase with spedfic growth rate. 

In fermentation for the production of acetic acid, ethyl alcohol is used in an aerobic process. In an ethanol oxidation process, the biocatalyst Acetobacter aceti was used to convert ethanol to acetic acid under aerobic conditions. A continuous fermentation for vinegar production was proposed for utilisation of non-viable A. aceti immobilised on the surface of alginate beads. 

As the majority of technically important bioprocesses for the obtainment of useful materials and active substances are aerobic processes, the oxygen supply and CO2 removal play an important part in the design and operation of bioreactors. 

Although fatty acids are both oxidized to acetyl-CoA and synthesized from acetyl-CoA, fatty acid oxidation is not the simple reverse of fatty acid biosynthesis but an entirely different process taking place in a separate compartment of the cell. The separation of fatty acid oxidation in mitochondria from biosynthesis in the cytosol allows each process to be individually controlled and integrated with tissue requirements. Each step in fatty acid oxidation involves acyl-CoA derivatives catalyzed by separate enzymes, utihzes NAD and FAD as coenzymes, and generates ATP. It is an aerobic process, requiring the presence of oxygen. 

Recently, anaerobic filter process has been widely used for the treatment of various waste-waters because of several advantages over aerobic process such as lower nutrient requirement, less surplus sludge production, and energy recovery via methane production [1]. Although many types of anaerobic filter process have already been successfully commercialized, the details of their complicated process dynamics are still challenging issues to be clarified for their stable operations. 

Wright R.M., Repine T. Repine J.E. (1993) Reversible pseudohyphal growth in haploid Saccharomyces cerevisiae is an aerobic process. CurrGenet, 23, 388-391. 

Ronen Z, A Abeliovich (2000) Anaerobic-aerobic process for microbial degradation of tetrabromobisphenol-A. Appl Environ Microbiol 66 2372-2377. 

The milk production stage is the largest source of GHG emissions over the entire life cycle of fluid milk production. CH4 is generafed primarily through enteric fermentation of dairy cows and also through the microbial, anaerobic decomposition of manure. Manure deposifed on soil or handled as a solid, an aerobic process, emits little CH4. However, manure generates CH4 when stored under the aerobic conditions of a lagoon. 

In this study, anaerobic and aerobic processes using sequential two-step UASB/CSTR reactors were found to form a feasible process for treating the leachate from food solid waste. COD removal efficiencies for the first and second anaerobic, aerobic and total system processes were 79%, 42%, 89%, and 98%, respectively. The COD loading rate used ranged from 4.3 to 16kg/m3/d. 

So far, only aerobic processes have proved to be effective for in situ removal of organic waste in groundwater and soil. 

In the aerobic process, organic contaminants such as gasoline releases are broken down by bacteria to produce new biomass (bacteria) and other byproducts ... 

U.S. EPA has shown that 90% of process water can be recycled to the front end of the system for slurry preparation, and the rest must be treated on site or transported to an off-site facility.80 During the aerobic process, some contaminated air may be formed and emitted from the reactor. Depending on the air characteristics, a compatible air pollution control device may be used, such as activated carbon. Slurry biodegradation has been shown to be successful in treating soils contaminated with soluble organics, PAHs, and petroleum waste. The process has been most effective with contaminant concentrations ranging from 2500 mg/kg to 250,000 mg/kg. 

The treatment of sludge contaminated with NPl,2EO and NP by mesophilic and thermophilic aerobic processes has also been studied. Experiments carried out in batch cultures (60°C) and in continuous reactors (55°C) showed that, respectively, only 66% and 40% of the initial NP and NPl,2EO amounts were removed [58, 59]. In contrast, experiments done in continuous reactors under mesophilic temperatures (35°C) showed that these compounds were completely removed [56]. These results are in accordance with previous observations showing that NPEO are more easily transformed in aerobic environments [38]. 

Combalbert S, Capdeville MC, Motte JC, Bellet V, Balaguer P, Dabert P, Beline F, Budzinski H, Bemet N, Hemandez-Raquet G (2012) Estrogens and antibiotics elimination during swine manure treatment by anaerobic digestion coupled to aerobic process. Bioresour Technol (submitted)... 

Kojic acid, 5-hydroxy-2-(hydroxymethyl)-4//-pyran-4-one1 (II), is produced from carbohydrate sources in an aerobic process by a variety of microorganisms. The acid was discovered in 1907, its structure was established in 1924, and its chemical synthesis from D-glucose was achieved in 1930. Since then, a considerable amount of study has been devoted to the biosynthesis of kojic acid, and numerous publications have dealt with its chemical and biological properties. After nearly half a century, kojic acid remains a scientists curiosity, without industrial importance. It con-... 

Elisangela F, Andrea Z, Fabio DG et al (2009) Biodegradation of textile azo dyes by a facultative Staphylococcus arlettae strain VN-11 using a sequential microaerophilic/aerobic process. Int Biodeter Biodegr 63 280-288... 

Panswad T, Anan C (1999) Impact of high chloride wastewater on an anaerobic/anoxic/ aerobic process with and without inoculation of chloride acclimated seeds. Wat Res 33 1165-1172... 

Luangdilok W, Paswad T (2000) Effect of chemical structures of reactive dyes on color removal by an anaerobic-aerobic process. Water Sci Technol 42(34) 377-382... 

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