Hazardous or toxic waste destruction or containment – Containment – Solidification – vitrification – or cementation
Patent
1991-11-12
1993-09-14
Niebling, John
Hazardous or toxic waste destruction or containment
Containment
Solidification, vitrification, or cementation
204109, 204151, 204152, 204252, C25C 120
Patent
active
052451119
DESCRIPTION:
BRIEF SUMMARY
The invention refers to a method and an apparatus for the treatment of liquid wastes from photographic processes, which wastes, bound by law, cannot be discharged into waters or into the sewage disposal system without a treatment which is accomplished to remove harmful substances contained in the wastes.
The liquid wastes, which are produced in photographic processes are especially developer, fixing, bleach, bleach-fixing, stop and reducer baths as well as optionally rinsing baths.
As damaging components, which have to be removed, the wastes especially contain metals, as for example silver and iron, sulfur containing compounds, as for example sulfites, and thiosulfates, further ammonium, complexing agents and reducing aromatic organic compounds, as for example hydroquinone, aminophenols as well as phenylene diamine.
The COD values of the liquid wastes to be treated may be above 100,000 g/m.sup.3 and the BOD values may be at up to 50 000 g/m.sup.3.
The methods for the treatment of liquid wastes from photographic processes, which may be produced in medical centers, studios, film studios, at the radar control and air traffic control, in printing offices, photolabs, hospitals, public imaging centers, reprolabs, printed circuit board producers and so on, which methods are known until now, generally comprise the following steps: electrolytically removing silver, to precipitate residual amounts of silver and other heavy metals by using precipitating agents like H.sub.2 S or Na.sub.2 S, oxidizing sulfite and thiosulfate to sulfate, precipitating the produced sulfate as calcium sulfate and stripping off the ammonium nitrogen as ammonia.
A survey of wet chemical methods, which can be used for the treatment of liquid wastes from photographic processes can be found in a Working Paper of the Ministerium fur Ernahrung, Landwirtschaft, Umwelt und Forsten, Baden-Wurttemberger, May 1986.
This Working Paper mentions as oxidizing agents for the oxidation of sulfite and thiosulfate to sulfate as well as for the oxidation of organic damaging substances, as for example hydroquinone in desilverized wastes, air oxygen and hydrogen peroxide.
As a further oxidizing agent ozone became known, for example from a publication of the Society of Photographic Scientists and Engineers, Volume 14, No. 4, June-July 1972 and Volume 14, No. 5, August-September 1972 as well as from a publication of T. W. Bober and T. J. Dagon, published in the Journal WPCF, Volume 47, No. 8, 1975, pages 2114-219.
Although by using the methods which became known until now and which have been used until now, an extensive reduction of damaging substances is possible, the requirements with regard to the reduction of damaging substances will be raised more and more as a consequence of the increasing environment consciousness of the people. This means that the maximum values, permissible by law of the individual damaging substances in the liquid wastes will be more and more reduced.
Accordingly, there exists a want for a method, which makes it possible to treat wastes from photographic processes, that means photo-chemical waste waters, with an efficiency as high as possible
In the DE-OS 39 21 436, a method is already proposed, which method comprises the following process steps:
1. Introducing wastewater, which is continuously or discontinuously obtained, into a storage container;
2. as an auxiliary means: a biological treatment to decompose reactive substances;
3. Oxygen aeration by using air or an other oxygen containing gas for the treatment of those components of the waste water which are more easily to oxidize;
4. the addition of ozone for a sufficient oxidation of those substances which are more difficult to degrade with a simultaneous pH control in two or more reactor steps and
5. catalytic aftertreatment by a chemical and/or catalyzed photo-chemical OH radical reaction.
The kernel of said older method is the combination of a biological treatment with two oxidizing steps. The catalytic aftertreatment by chemical and/or catalyzed photochemical OH radical reaction
REFERENCES:
patent: 4217188 (1980-08-01), Ono
Mizusawa, "Disposal of Photographic Processing Wastes", Chem. Abs., vol. 81, No. 26, 175657u (1974).
Cody Peter C.
Delacroix-Muirheid C.
Eastman Kodak Company
Niebling John
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