Liquid purification or separation – Processes – Treatment by living organism
Patent
1985-10-11
1988-05-24
Wyse, Tom
Liquid purification or separation
Processes
Treatment by living organism
210605, 210617, C02F 328
Patent
active
047464330
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a process for the anaerobic treatment of organic substrates, in solid or dissolved form, wherein the reaction products (for instance, CH.sub.4, CO.sub.2, biomass) are gathered and then discharged. In addition, it is an object of the invention to create an apparatus for carrying out such a process.
Equipment for the anaerobic treatment of organic substrates are known in the prior art. Here, basically two different purposes may be pursued, namely the origination of energy--in the form of methane gas--from organic substrates or the removal of organic substances in the sense of a purification of the added substrate. Although chemical and biological reactions are very similar, ultimately several standards of economy need be set as concerns supply and discharge which, in turn, affect the design and operation of the apparatus. An important feature in the anaerobic purification of waste water is the fact that here the major portion of the dissolved organic impurities is not removed by merely providing new cellular material as in aerobic waste water treatment, but that only a small portion is used for the installation of new cellular material, while the remaining carbonic compositions are converted into enriched gas--methane gas--and carbonic dioxide. Thus, in the anaerobic process no energy is needed to introduce the oxygen, as is required in the aerobic process for maintaining flow conditions. In addition, the amount of sludge collecting in the anaerobic process is substantially reduced and already fully stabilized. Another big advantage, especially where seasonal operations are involved, is the fact that the anaerobic sludge can be kept active for many months--even with no addition of substrate--and that it can be caused to become highly active in no time at all as soon as new amounts of substrate are added. However, the low biomass production also results in some disadvantages, exhibiting themselves in some problems in starting operation of the apparatus and in disturbances in the biological activity of the sludge. This, however, can in part be remedied not only by certain steps taken during construction, but also by the way of directing the process.
As already mentioned, anaerobic fermentation, for the major part, entails methane fermentation. By-products, such as hydrogen sulfide and ammonia, etc., are almost always formed--in different amounts--but will not be especially considered here. They are only important in some substrates where their accumulation exercizes a negative effect on the process or where their pollution of the gas detract from their usefulness. In the present state of science, methane fermentation is best carried out in the three-phase model of Bryant (1977), wherein in the first phase, the so-called hydrolysis fermentation, carbohydrates, fats and albumina are decomposed into volatile fatty acids and alcohols. The next phase entails the hydrogen and aceton-forming phase as well as fermentation into acetic acid, whereby the methane bacteria are activated. However, a level of acetic acid that is too high will result in the destruction of the bacteria so that it will be absolutely necessary to exercize precise control over the formation of acid. In the third phase, the splitting of the acetic acid, which results in reductive methane formation, concludes the process.
In methane fermentation commonly occuring in nature (in marshes, moors, the bellies of ruminants, etc.), such processes unfold closely one after the other. In order to utilize this process in an economical way, it was necessary to accelerate the methane fermentation process which under natural conditions unfolds but slowly. To create favorable marginal conditions, there were created a large number of different devices, the so-called anaerobic reactors, viewing optimum efficiency in the unfolding of the process.
Originally, observing the most favorable temperature as well as leading the new substrate to the bacteria were the most important parameters, but it was soon recognized that the velocity of flow co
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Nobl Astrid
Nobl Ernst
Nobl Ernst
Wyse Tom
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