Liquid purification or separation – Processes – Treatment by living organism
Patent
1995-09-15
1998-08-25
Wyse, Thomas G.
Liquid purification or separation
Processes
Treatment by living organism
210615, 210903, 210906, C02F 330, C02F 306
Patent
active
057980446
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method for sewage treatment, in particular for municipal sewage, with a mechanical purification stage and a first and second biological purification stage, in which the second biological purification stage is a biological filter system, which has a filter stage for nitrification and a filter stage for denitrification connected behind it in the flow direction, and with the filter stages having at least one biological filter.
BACKGROUND OF THE INVENTION
One such method is known from German Patent Disclosure DE 39 33 513. The first biological purification stage contemplated there involves two series-connected light load activation basins, which are followed--as a second biological purification stage--by a biologically intensified filter system for nitrification and denitrification. This addition of the filters that form a second biological purification stage for nitrification and denitrification is intended to reduce both the space and area requirement of the preceding light load activation stage and at the same time to reduce microscopic contaminants in the discharge (see DE 39 33 513 A1, column 2, lines 18-24 and column 3, lines 49-53). DE 39 33 513 A1 refers expressly to a patent application, filed shortly before it, of the same applicant and inventor, namely DE 39 16 679 A1 (see DE 39 33 513 A1, column 2, line 6). In it, it is also stated that the first biological purification stage is a light load activation stage; in DE 39 16 679 A1, it is then also stated in conjunction with an example (column 4, lines 57) that the nitrogen load is reduced down to a content of 10 mg/l.
The term light load activation stage is understood to mean a plant having a sludge burden of less than 0.1 kg of BSB/kg of sludge per day. This is a conventional term in this profession (see Degredmont Handbuch Purification and Sewage Treatment!, Bauverlag Wiesbaden and Berlin, page 344).
If this understanding of the term "light load activation stage", as used in DE 39 16 679 A1 and DE 39 33 513 A1 and a reduction of the nitrogen load to a maximum of 10 mg/l (as indicated in DE 39 16 679, see column 4, line 57) is the point of departure, then, from calculations familiar to one skilled in the art, it can be found that the first biological purification stage is still relatively large, being designed namely for an impact factor of f.sub.N >1. These calculations are written down in the wastewater/refuse regulations of the Abwassertechnische Vereinigung e.V. cooperation with the Verband kommunaler Stadtereinigungsbetriebe (VKS) A 131, February 1991. The result f.sub.N >1 means that in the first stage, more than the 24-hour mean value of the load has been reduced. Peak loads in the discharge of 10 mg/l of NH.sub.4 -N, as indicated in the above publication, represent mean values of at most 3 mg per liter. Because of the fact that this value is so low, it follows that the light load activation stage is already designed for adequate nitrification. Such a size is necessary if one wants to keep the BSB load correspondingly low. However, if one were to dispense with designing the light load activation stage such that it reduces the peak loads, then this would have to be done at the cost of having a higher residual nitrogen load in the discharge.
Hence a disadvantage of this design is that the first biological purification stage requires a very great deal of space and surface area. In particular, it must be relatively large because currently the goal is very low maximum values in the discharge even at peak loads or in other words loads that are above the daily average value (24-hour average).
Another disadvantage of the known arrangement of DE 39 16 679 A1 is that within the first filter stage, nitrification must be converted into denitrification. The various biocenoses inside the filter can mix. A filter of this kind is hard to operate for process technical reasons, since no oxygen can be present in the denitrification stage.
SUMMARY OF THE INVENTION
The object of the present inv
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Rovel Jean-Marie
Schroeter Ingulf
Strohmeier Andreas
Philipp Muller GmbH
Wyse Thomas G.
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