Liquid purification or separation – Processes – Treatment by living organism
Patent
1999-01-26
2000-11-14
Upton, Christopher
Liquid purification or separation
Processes
Treatment by living organism
210630, 210631, 210638, 210903, 210906, C02F 330
Patent
active
061465321
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the field of wastewater treatment, more precisely in particular the treatment of municipal and industrial wastewaters.
From the aspect that every form of biomass, including organic waste, is carbon-bound solar energy, and that economic handling of energy is the supreme directive for action for the future, current sewage treatment technology must be considered from a different perspective.
The current position in the sewage treatment plant field is open wastewater basins. Because aerosol formation cannot be prevented during the aeration of open basins, and volatile wastewater constituents can also be emitted, sewage treatment plants, on account of odor nuisances resulting therefrom, are frequently built far away from settlements. This causes high costs (material and energy costs) for laying sewers. At the same time, a long sewer is nothing else than a tubular bioreactor in which organic substance is converted in a highly uncontrolled manner. Since in the sewer grid oxygen input cannot be prevented, aerobic mineralization takes place, i.e. 50% of the organic substance converted there is lost in the form of industrially unutilizable heat. Facultative anaerobes predominate in this conversion, since sufficient supply with oxygen is not always ensured. Even if they are removed in the primary sedimentation, they are not digestible in the digestion tower and are thus not available for energy recovery. They arrive unutilized on the landfill and there possibly cause secondary problems.
In the case of the activation tanks, the oxygen input does not proceed in a similar manner to the COD input, and in flat basins, the utilization of atmospheric oxygen is frequently very low, based on the input power. In comparison with the state of the art, energy is destroyed on a massive scale. Furthermore, the concentration of the biocatalysts, specifically the active organisms, is very low, so that the reaction rate in the activation plants is very low. However, since solids other than active biocatalysts also pass into the activation plants, specific increase of the biocatalyst concentration is not possible.
The upstream denitrification and the recycling of a wastewater partial stream downstream of nitrification in the activation to the anaerobic denitrification promotes the development of facultative anaerobes in the secondary sludge. It has been proposed to increase the sludge age by downstream connection of a filter. The purpose of this mode of operation is increased sludge consumption, since energy is converted into unutilizable heat because of a decrease of organic substance caused by repeated catabolism of dead biomass.
The facultative anaerobes preferably formed again withstand digestion (see above). They are thus no longer available for material/energy recycling. In addition, the volume of the bioreactors is considerably increased by the high hydraulic recirculation.
Digestion towers serve to stabilize sewage sludges prior to the deposition in agriculture or the refuse tip. They are not designed as a net energy production plant with respect to their residence time and their integration into energy grids. The spatial separation of the sewage treatment plant from heat consumers does not permit efficient heat and power cogeneration via block combined heat and power stations. Thus in the most favorable case, digester gas is converted into electricity and serves alone to reduce the electrical energy consumption in the sewage treatment plant. Not infrequently, digester gas is flared off. The high residence times in digestion towers not only starve the bacteria catalyzing the digestion process, but occasionally lead, because of the unfavorable ratio of volumetric energy production and thermal radiation in winter, to additional energy consumption during thermostating of the digester material.
The industrial purification of wastewater has found better approaches to solution of the problem, for economic reasons--though the industrial implementation has not taken place until the course of the last 10
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Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung
Upton Christopher
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