Aerobic possible processes

The primary advantage of aerobic digestion is that it produces a biologically stable end product suitable for subsequent treatment in a variety of processes. Volatile solids reductions similar to anaerobic digestion are possible. Some parameters affecting the aerobic digestion process are ... 

The flow in sanitary sewers may be controlled by gravity (gravity sewers) or pressure (pressure sewers). In a partially filled gravity sewer, transfer of oxygen across the air-water interface (reaeration) is possible, and aerobic heterotrophic processes may proceed. On the contrary, pressurized systems are full flowing and do not allow for reaeration. In these sewer types, anaerobic processes will, therefore, generally dominate. 

This volume was conceived with the goal of complementing the growing number of widely available academic review articles that describe research advances in the field of aerobic oxidation catalysis. Our goal was to bring together as many experts as possible, who could provide a perspective on either (i) existing liquid phase aerobic oxidation processes that are practiced in industry... 

Principle The test method determines the ultimate biodegradability and degree of disintegration of test material under conditions simulating an intensive aerobic composting process. The inoculum used consists of stabilized, mature compost derived, if possible, from composting the organic fraction of solid municipal waste. 

Though the direct production of l-AA from D-glucose seems to be an ideal process, L-AA could be easily degraded in both water solutions [54] and ethanol solutions [55] under aerobic conditions. The aerobic culture processes for direct l-AA production have to face the oxidation of l-AA during the production processes. A possible process to avoid the oxidation of l-AA in water solution is to further convert it into its more stable derivatives, such as 2-O-D-glucopyranosyl-L-ascorbic acid (AA2G) [56]. 

Maturation is conducted in closed, full containers to prevent oxidation and aerobic growth of microorganisms. Etee air contact with low alcohol wine soon leads to vinegar. Except for those sherry types already mentioned, wines ate exposed to air minimally and temporarily. During transfers incident to bulk storage and processing, some air exposure is almost inevitable, mote in total the longer the wine is held. In the cases of white and pink table wines, it is ordinarily as neat zero as possible, and stainless steel or other impermeable containers, inert gas headspace, etc ate employed. Red wines withstand and even benefit from small but repeated exposures to air. 

On the other hand. Type II process competes efficiently with the electron-transfer pathway in aerobic environments where the concentration of ground triplet state molecular oxygen is relatively high ( 0.27 mM), and singlet molecular oxygen (1O2) is the most abimdant ROS generated under these conditions, with a quantum yield 0.48 (Valle et al., 2011), eqn. 8. It is also possible an electron-transfer reaction from 3RF to 02 to form anion superoxide, but this reaction occurs with very low efficiency <0.1% (Lu et al., 2000). 

To facilitate biodegradation, the leachate may require modification through pH adjustment, removal or addition of oxygen, amendment with nutrients, or dilution or removal of toxic species. Microbial nutrition is complex and is better understood for aerobes than for anaerobes.34 Biological processes typically favor a pH near 7. Pretreatment processes to remove inhibitory components include coagulation and precipitation, carbon adsorption, and possibly ozonation. 

Spore formation is limited almost entirely to two genera of rodshaped bacteria Bacillus (aerobic or facultatively anaerobic), and Clostridium (anaerobic or aerotolerant). With one possible exception, the common spherical bacteria do not sporulate. Some spore-bearing species can be made to lose their ability to produce spores. When the ability to produce spores is once lost, it is seldom regained. SporMation is not a process to increase bacterial numbers because a cell rarely produces more than one spore. 

Although the investigations of both Raunkjaer et al. (1995) and Almeida (1999) showed that removal of COD — measured as a dissolved fraction — took place in aerobic sewers, a total COD removal was more difficult to identify. From a process point of view, it is clear that total COD is a parameter with fundamental limitations, because it does not reflect the transformation of dissolved organic fractions of substrates into particulate biomass. The dissolved organic fractions (i.e., VFAs and part of the carbohydrates and proteins) are, from an analytical point of view and under aerobic conditions, considered to be useful indicators of microbial activity and substrate removal in a sewer. The kinetics of the removal or transformations of these components can, however, not clearly be expressed. Removal of dissolved carbohydrates can be empirically described in terms of 1 -order kinetics, but a conceptual formulation of a theory of the microbial activity in a sewer in this way is not possible. The conclusion is that theoretical limitations and methodological problems are major obstacles for characterization of microbial processes in sewers based on bulk parameters like COD, even when these parameters are determined as specific chemical or physical fractions. 

Basically, a concept for microbial transformations in sewer networks should cover soluble and particulate components and relevant processes in the water phase, in the biofilm and in the sewer sediments. In addition, mass transfer between these phases and an air-water transfer of oxygen should be taken into account (Figures 1.3 and 5.2). Although only the aerobic microbial activity will be focused on in the concept presented in this chapter, anoxic and anaerobic processes should be considered possible extensions (cf. Chapter 6). 

Handling of a sample in terms of investigations and studies is exemplified in Section 7.1.1. Handling by transport from the sampling site to a laboratory must ideally be done without changing the sample, i.e., without changes in the parameters that will be analyzed. The potential process rates and the time needed for transport must be considered. Process rates are typically lower under anaerobic conditions than under aerobic conditions. If possible, a wastewater sample is, therefore, often transported under anaerobic conditions. 

The integrated aerobic-anaerobic WATS model has changed this situation. As an example, it is possible to use the model in a gravity sewer with changing aerobic and anaerobic conditions. As previously stressed, a number of in-sewer processes still need to be dealt with. Examples are the anoxic transformations and the processes related to the extended sulfur cycle, particularly, the oxidation of sulfide and the emission of hydrogen sulfide into the sewer atmosphere, including its further oxidation at the sewer walls. Combined use of empirical and conceptual models is still needed. 

Each type of technique can be applied in several modifications. Microbiological degradation processes offer the possibility to purify wastewater streams which contain a wide range of organic pollutants. In contrast, physical/chemical techniques are much more specific. The quality of the purified water regarding residual amounts of soluble organic pollutants, and colloidal and suspended particle pollutants, strongly depends on the type of treatment process and the applied treatment conditions. Very often a combination of different types of treatment techniques is necessary to satisfy the effluent quality required (for example a combination of anaerobic and aerobic treatment). 

Many wastewater flows in industry can not be treated by standard aerobic or anaerobic treatment methods due to the presence of relatively low concentration of toxic pollutants. Ozone can be used as a pretreatment step for the selective oxidation of these toxic pollutants. Due to the high costs of ozone it is important to minimise the loss of ozone due to reaction of ozone with non-toxic easily biodegradable compounds, ozone decay and discharge of ozone with the effluent from the ozone reactor. By means of a mathematical model, set up for a plug flow reactor and a continuos flow stirred tank reactor, it is possible to calculate more quantitatively the efficiency of the ozone use, independent of reaction kinetics, mass transfer rates of ozone and reactor type. The model predicts that the oxidation process is most efficiently realised by application of a plug flow reactor instead of a continuous flow stirred tank reactor. 

Water Reclamation Works by their very nature can, at times be the source of unpleasant odorous emission. The odour-intensive compounds (osmogenes) which make up these emissions are believed to arise mainly as the decomposition products of carbohydrates and proteins. The breakdown of this waste material proceeds by aerobic and anaerobic processes at various stages of the treatment plant. Atmospheric pollution of this nature frequently results in complaints from members of the public either resident, or perhaps employed in the vicinity of such works. In order to confirm or deny that a reclamation works is responsible for a particular nuisance and, if possible to identify the causal agents it was decided that the Authority should have the capability of analysing for odorous and other polluting constituents of the atmosphere. This paper describes the progress made towards this objective and summarises the experience gained with a procedure in use. There are two principle approaches available for the analytical classification of odorous emissions -... 

The significance of this approach is that not only were the wastes treated at a very concentrated level using anaerobic and aerobic treatment, but the removals were extremely good. The implications for enhanced bioremediation suggest that some combination of aerobic and/anaerobic processes where nutrients are applied to the waste site and collected beneath the waste site could turn the entire waste site into an efficient bioreactor. These are interesting possibilities and the possibility of using a flooded system or other top down distribution system which recycles wastes from beneath the contaminated sites and returns it to the surface is an... 

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