Chemistry: fertilizers – Processes and products – Bacterial
Patent
1995-01-04
1997-08-12
Lander, Ferris
Chemistry: fertilizers
Processes and products
Bacterial
71 641, C05F 1108
Patent
active
056560591
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for processing a liquid nitrogen-rich organic waste product to an aqueous solution, in which method the waste product is subjected to a biological conversion process so as to obtain a biologically substantially stable aqueous solution, which conversion process includes at least a nitrification step wherein nitrifiable ammonium nitrogen from the waste product is converted into nitrate nitrogen in a nitrification reactor by means of nitrifying bacteria, in the event the nitrate content in the so-obtained nitrified fraction would exceed a predetermined nitrogen content, the nitrate content is limited to a content at which the nitrifying bacteria are active by subjecting at least a portion of a previously nitrified fraction to a denitrification step and subsequently to the nitrification step together with a further fraction which is to be nitrified.
The expression "liquid nitrogen rich organic waste product" used herein refers in particular to liquid manure products as obtained directly from farms, for example semi-liquid manure, liquid manure and the like, but possibly also further processing products of these manure products such as for example the aqueous fraction obtained after removal of the solid fraction out of semi-liquid manure or the resulting products obtained after a partial fermentation of the manure product, for example for the production of biogas. Of course, also manure products of human origin are included in this expression. Further the expression also embraces other liquid nitrogen rich organic waste products such as for example waste water from composting installations.
2. The Prior Art
EP-A-0 423 889 in the name of one of both applicants discloses already a method for processing semi-liquid manure or fermented semi-liquid manure of the hereabove indicated type. In this known method, use is made of a water purification installation wherein the manure product is subjected successively to a nitrification step and subsequently to a denitrification step so as to obtain a purified aqueous solution wherein the nitrogen and the organic matter are eliminated as much as possible since the denitrified fraction is subsequently discharged.
In order to eliminate the nitrogen from the manure as completely as possible, a portion of the denitrified fraction is recycled to the nitrification reactor in such a manner that the nitrate content in this reactor is preferably limited to between 1000 and 1400 mg NO.sub.3.sup.- -N/l. Within these limits, an optimal conversion of ammonium to nitrate nitrogen is obtained. For the same reason, use is further made of methanol as necessary carbon and energy source for the denitrifying bacteria. When use would be made herefor of said manure product, ammonium nitrogen is again produced during the denitrification which nitrogen would therefore end in the effluent of the purification installation. In the method according to this European patent application, purified waste water is obtained as effluent from the denitrification reactor.
Such a method has, however, the drawback that all of the plant nutrition elements are lost. Moreover, such a purification is never complete so that an amount of polluents will always arrive in the surface waters. In order to recuperate a portion of these nutrient elements, the solid fraction can be separated in advance out of the manure and can be dried, which requires however a lot of energy. In this case, the liquid fraction remains moreover to be purified and has still to be discharged.
An object of the present invention is therefore to provide a new method for processing liquid nitrogen rich organic waste products which obviates the hereabove indicated drawbacks and which permits in particular the nutrient elements present in this waste product to be used in a useful way.
The method according to the invention is characterized to this end in that said liquid nitrogen rich waste product is processed to an aqueous fertilizer solution which is separ
REFERENCES:
K. Mudrack et al., Biology of Sewage Treatment and Water Pollution Control, John Wiley & Sons, 1986, pp. 117-129 no month.
M. Boes, "Stickstoffentfernung mit intermittierender Denitrifikation" in Korrespondenz Abwasser, vol. 38, No. 2, 1991, pp. 228-234 no month.
H. Bode, "Mesophile und thermophile Hochlastdenitrifikation bei stark nitrathaltigem Abwasser" in Korrespondenz Abwasser, vol. 38, No. 2, 1991, pp. 228-234 no month.
Koster Willem Iman
Monster Anthonie Leendert
Ecotechniek B.V.
Epenhuysen Chemie N.V.
Lander Ferris
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