Liquid purification or separation – Processes – Chemical treatment
Patent
1994-01-21
1996-04-02
McCarthy, Neil
Liquid purification or separation
Processes
Chemical treatment
210777, 210778, C02F 152
Patent
active
055037518
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the treatment of photographic effluent.
In photographic processing, the performance of processing solutions need to be constantly maintained. This is achieved by replenishing the processing solutions in accordance with their use and also with their deterioration due to their inherent instability. During replenshment, used processing solution is discarded for disposal.
It is well known to treat used processing solution to recover useful components, for example, silver from fixing solutions prior to disposal. It is also known to treat such solutions to make them less harmful to the environment.
U.S. Pat. No. 3,978,506 discloses apparatus and method for neutralizing processing solutions. Used processing solution from at least one processing tank is discharged into a container. Neutralizing solution is added to the container in proportion to the processing solution to be neutralized, and the two solutions are mixed to achieve neutralization, the resulting neutralized fluid being discharged for disposal.
EP-A-0 315 373 discloses apparatus for the treatment of liquid waste from photographic processes. The liquid waste is heated to produce a solid portion in precipitate form and a concentrated liquid portion. The precipitate is separated from the liquid portion for disposal, and the concentrated liquid portion is recirculated for further heating and concentration prior to its disposal.
However, U.S. Pat. No. 3,978,506 has the disadvantage that there is no provision for dealing with toxic particles which may be suspended in the used processing solution. Furthermore, the precipitate produced in EP-A-0 315 373 may still present a problem for disposal.
U.S. Pat. No. 4,332,687 discloses apparatus and method for the removal of heavy metals from photographic processing waste solutions. This is achieved by first treating the solution using ozone and a peroxy compound which exhibits strong oxidizing properties to destroy the complexing agents, and then precipitating the heavy metals as insoluble hydroxides or oxides by raising the pH of the solution using a suitable caustic material, for example sodium hydroxide. Additional precipitation of the heavy metals is achieved by adding a sulphide to the alkaline solution to form insoluble heavy metal sulphides.
It is therefore an object of the present invention to provide apparatus which overcomes the problems and disadvantages of known apparatus for the treatment of photographic effluent. In particular, apparatus according to the invention is used to convert toxic photographic-waste into a harmless liquid phase which can be put down the drain, and a solid phase which can be put into a land fill.
According to one aspect of the present invention, there is provided a method of treating photographic effluent comprising the steps of:
delivering untreated photographic effluent to a mixing unit;
dispensing treatment chemicals for treating the untreated effluent into the mixing unit;
mixing the untreated effluent with the dispensed treatment chemicals in the mixing unit; and
separating the mixed and treated effluent into a liquid phase and a solid phase for disposal;
characterized in that the method comprises the further step of establishing a filter bed by passing the treated effluent into a filter unit which includes a filter member, the filter bed being formed on the filter member as the treated effluent is passed therethrough.
In accordance with a second aspect of the present invention, there is provided apparatus for the treatment of photographic effluent using the method described above, the apparatus comprising:
a mixing unit for mixing photographic effluent with treatment chemicals;
delivery means for delivering untreated photographic effluent to the mixing unit;
dispensing means for dispensing treatment chemicals into the mixing unit;
a separation unit for separating the mixed and treated effluent into a liquid phase and a solid phase; and
control means for controlling the delivery means, the dispensing means and the mixing unit to ensure that the tre
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patent: 4465593 (1984-08-01), Weinhoff
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patent: 5211843 (1993-05-01), Wester et al.
Glover Edward C. T. S.
Glover Martyn S.
Eastman Kodak Company
McCarthy Neil
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