Water treatment aeration

Oxygen is used to treat municipal wastewater and wastewater from the pulp and paper industry (see Aeration, water treatment Wastes, industrial Water). Many of these water appHcations can use VSA-produced oxygen (advantage /). Demonstration and development programs are in place that use oxygen to oxidize sludge from municipal waste and bum hazardous wastes and used tires (advantages 1—4). 

Oxygen solubility, in aeration water treatment, 26 153-154 Oxygen sources, for fermentation, 44 25 Oxygen steelmaking, quicklime requirements for, 45 68 Oxygen steelmaking processes, 23 255-260 Oxygen transfer, 26 153... 

Water treatment, 26 102-152. See also Aeration water treatment, Industrial water treatment ABS manufacture, 7 421-422 activated carbon application, 4 752 aerators, 26 158-170 alkanolamines from nitro alcohols, 2 120 coagulation and flocculation in,... 

Parking areas Primary water treatment—filtration, coagulation, aeration... 

For some applications, notably feed-water treatment for high-pressure boilers, removal of oxygen is essential. For most industrial purposes, however, de-aeration is not applicable, since the water used is in continuous contact with air, from which it would rapidly take up more oxygen. Attention must therefore be given to creating conditions under which oxygen will stifle rather than stimulate corrosion. 

KL-a and v for the 10 litres/min airflow rate for the 15 litre aeration system was 0.0509 h-1 and 1.3 ms 1. From the experimental results, the microbial growth was not at the optimum stage for the reasons mentioned earlier. Nevertheless, a reduction of around 95% can be achieved for carbohydrate reduction. However, further studies should be earned out for optimisation of the treatment and to improve COD reduction for pharmaceutical waste-water treatment. 

Posttreatment of the permeate for potable water use can include dissolved CO2 removal to prevent corrosion (by aeration, lime treatment), chlorination for microbial control, and oxygenation to improve taste. 

Moura A, Tacao M, Henriques I et al (2009) Characterization of bacterial diversity in two aerated lagoons of a waste water treatment plant using PCR-DGGE analysis. Microbiol Res 164(5) 560-569... 

Historically, the alpha factor, a, was developed from oxygen mass transfer studies in the aerated basins of municipal waste water treatment plants. It thus denotes the ratio of the mass transfer coefficient for oxygen measured in the waste water (WW) to that measured in tap water (TP). 

Organic radicals formed in these reactions may further react with oxygen (in an aerated medium as in water treatment) to yield organic peroxyl radicals that can eventually react with compounds present in the medium to release the superoxide ion radical (see route through 5 in Fig. 6 see also the work of von Sonntag and Schuchmann [122] for more details about peroxyl radical reactions). In these cases, compounds that react with the hydroxyl radical are known to be promoters of ozone decomposition because the superoxide ion radical consumes ozone at a fast rate [see reaction (63) above]. On the contrary, if the reaction between hydroxyl radical and compound M does yield inactive radicals, M is known as a scavenger or inhibitor of ozone decomposition (see route to 4 in Fig. 6). Many natural substances such as humic substances and carbonates are known to possess such a role [121]. However, the case of carbonate ion is rather special because it reacts with hydroxyl radicals to yield the carbonate ion radical ... 

Zlokamik, M., Adv. Biochem. Eng. 11 (1979), 158—180 Scale-up of Surface Aerators for Waste Water Treatment... 

Surface aeration is usually employed for slow reactions or for batch processes. It can be used in semicontinuous systems when it is desirable to recirculate the gas from the headspace. This is frequently the case in hydrogenation and is referred to as dead-end hydrogenation. In this system, gas is fed continuously to the reactor at the rate at which hydrogen is being consumed no compression costs to overcome the static head of liquid or external recirculation is needed. Feeding gas from the headspace may be preferred when there is a possibility of plugging sparger holes with reaction products. Surface aerators are also extensively used for waste-water treatment. There are two types of surface aerators the brush aerator, and the most commonly used turbine aerator. 

The surface aerator has been used for decades in biological waste-water treatment with H < 4 m. For various sizes of turbine stirrers whose disks were positioned exactly in the surface of the liquid, the mass-transfer coefficient can also be related as... 

In waste-water treatment, the energy-efficient transfer of oxygen in the aqueous phase is very critical. Since reactions are slow, a long contact time is required. Both of these can be achieved by a conventional surface aerator or novel UNOX surface aeration system. The minimum impeller speed needed for surface aeration in the absence of gas sparging can be obtained from Eq. (6.30). Similar calculations in the presence of gas sparging can be carried out using either Eq. (6.31) for a turbine stirrer or Eq. (6.36) for other stirrers. The gas entrainment and the power consumption in the presence of gas entrainment can be obtained using Eqs. (6.37) and (6.38), respectively. 

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