Liquid purification or separation – Processes – Treatment by living organism
Patent
1995-02-08
1997-07-08
Silverman, Stanley S.
Liquid purification or separation
Processes
Treatment by living organism
210613, 210616, 210617, 210622, 210630, 210631, 210694, 210748, 210764, 210151, 210167, 210196, 210199, 210202, 210266, 210284, 210903, C02F 330, C02F 312, C02F 310
Patent
active
056457251
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a process and device for the biological treatment of organically polluted waste water and organic waste. It is the aim of such processes to decompose the organic material into low-molecular, low-energy compounds while reducing their volume as much as possible (mineralization), which can be discharged, for example into the ground or the sewer system, without placing a noticeable burden on the environment. The waste water from toilets, for example, essentially contains carbohydrates, C-polymers, proteins, amines, urea, ammonia and salts.
While the carbohydrate-containing components can be decomposed under aerobic conditions into carbon dioxide and water by microorganisms, the reduced nitrogen compounds are decomposed essentially into water and nitrates by nitrogen-fixing bacteria. Accordingly, the liquid obtained in the course of such aerobic decomposition processes contains considerable amounts of nitrate. Their introduction into rivers or lakes results in a nitrate over-fertilization having undesired consequences, such as increased growth of algae. Since nitrate ions are only lightly retained in the ground and accordingly can be easily washed out of the ground layers near the surface by rain water, their escape from, for example agricultural land, endangers the ground water.
Processes are known wherein an additional anaerobic decomposition stage is provided in order to convert at least a part of the nitrate into innocuous elementary nitrogen by means of nitrate-reducing microorganisms. A process is known from U.S. Pat. No. 4,210,528, wherein the waste water from toilets, together with the solids contained therein, is brought into a first anaerobic decomposition stage and is subsequently subjected to an aerobic treatment. In this process the liquid from the aerobic stage is filtered, passed over a bed of activated charcoal and used as the flushing water for the toilets. In this way the nitrate-containing water gets back into the anaerobic decomposition stage and is available there to the nitrate-reducing bacteria as a provider of oxygen for their respiratory metabolism.
A disadvantage of the known process or the known device lies in that the component of solids, which constitutes the main portion of the organic material to be decomposed, is subsequently decomposed under anoxic conditions. Biological communities of organisms are described by the term anoxic, in whose vicinity chemically fixed oxygen, for example in the form of nitrate, is present, but no dissolved oxygen. Decomposition under the mentioned conditions takes place by means of microorganisms which satisfy their oxygen requirements by reduction of the nitrate. This process is generally identified as nitrate reduction. Thus decomposition in the known processes depends on the presence of nitrate. To achieve complete decomposition, the portion of nitrogen compounds would have to attain values which are not present in conventional and particularly communal waste waters. The result is that, following the consumption of the nitrogen compounds, sulfate reduction and anaerobic decomposition processes begin. Besides the development of hydrogen sulfide, there is the main disadvantage that the anoxic decomposition processes proceed considerably more slowly. Accordingly, extended retention times or large reaction chambers are necessary to obtain a sufficient decomposition rate. A further disadvantage of the known process resides in that the return of nitrate-containing liquids from the anaerobic decomposition stage into the anoxic one is coupled to the use of the toilets. An extended non-use of the toilet leads, on the one hand, to a lack of nitrate in the anoxic stage and an increase in aerobic decomposition processes whose end products are gases such as methane, hydrogen sulfide and mercaptan. These gases enter the environment and contribute, among other things, to the destruction of the ozone layer, besides being strongly odiferous. A further disadvantage of the known device lies in that it is necessary to
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Ahne Gerd
Bleicher Karl
Winter Josef
Zitzelsberger Dorit
Green Theodore M.
Protec Partner Fuer Umwelttechnik GmbH
Silverman Stanley S.
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