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United Photos and Graphic Services Pty Ltd
Cleaner Production - Recovery of Bleach Solution

United Photo and Graphics Services Pty Ltd has installed a regeneration system on its film processing line. The system is used to regenerate the bleach solution. The savings from reduced purchases of new bleach solution and reduced waste disposal costs amount to between $30,150 and $37,680 per annum, depending on the total number of films processed.

Background

United Photo and Graphic Services Pty Ltd (UPGS) are specialist developers and printers of aerial photography film. The negatives are a special large format, measuring 23cm by 23cm, with each roll containing between 60 and 120 metres of film.

The Process

The film is developed in a continuous film processor. The Kodak process involves running the film through a number of different baths, or solutions, within the developing machine. These solutions include pre-hardener, neutraliser, developer, bleacher, fixer, stop bath and rinse.

In the pre-excisting process, the various solutions had to be discarded when they became depleted.

The bleach solution used in the development process is a proprietary chemical, Kodak EA5. The bleach consists of a solution of potassium ferricyanide. In the developing process, the bleach converts the exposed silver back to unexposed silver halide, which enables it to be dissolved by the fixing process. During this process the ferricyanide is converted to ferrocyanide and the bleach solution is gradually depleted.

Cleaner Production Initiative

UPGS installed a bleach regeneration system that converts the used ferrocyanide back to a ferricyanide, thus allowing the bleach solution to be reused. The regeneration unit utilises electrolysis to oxidise the ferrocyanide to ferricyanide. The unit contains an electrolytic cell, in which the oxidation reaction takes place at the anode. The anode is separated from the cathode by a membrane. Water is converted to hydrogen and hydroxide ions at the cathode. The reactions that take place are shown below:

Anode Reactions:

Fe(CN)6-4 ------> Fe(CN)6-3 + e-

4OH- ------> O2 + 2H2O + 2e-

 

Cathode Reactions:

2H2O + 2e- ------> H2 + 2OH-

Fe(CN)6-3 + e- ------> Fe(CN)6-4

Hydrobromic acid is added to the regeneration unit to control pH and to add bromide back into the process (bromide is consumed in the bleaching stage). The installation of the bleach regeneration unit has allowed total reuse of depleted bleach solutions and has eliminated the need for disposal of used solutions.

The bleach regeneration unit

The bleach regeneration unit

Advantages of the Process

The annual generation of waste bleach solution was dependent on the number of films developed, and varied between 6,000 and 12,000 litres per annum. Installation of the recovery system has totally eliminated the need to discard the used solution, with subsequent savings in chemical and waste disposal costs. The cost savings are outlined below.

ECONOMIC BENEFITS

Costs

 

Capital Cost of Recovery Unit

$40,000

Annual Savings

 

Raw Material Costs

$28,800-$36,000*

Disposal Costs

$ 1,350-$ 1,680*

Total Annual Savings

$30,150-37,680

Payback Period

1.3 - 1.1 years

*directly related to the number of films processed

An additional advantage that has flowed from installation of the regeneration unit is that it has initiated continued interest in cleaner production and an overall increased awareness about environmental responsibility. For example, UPGS has optimised the rate of chemical additions to the print processor, with rates of one sixth the chemical manufacturer’s recommended rate being achieved and implemented. Office cardboard and paper wastes are also recycled.

Cleaner Production Incentive

The most significant incentive for the recovery of bleach solution was concern about the cost of using bleach on a once-through basis.

Barriers

The single barrier to implementation of the project was access to technical knowledge. A chance meeting between UPGS and a visiting Kodak representative from the United States resulted in regeneration being considered as a viable option for reducing chemical costs.

Further Developments

The bleach regeneration system continues to add value to the company (2001).

Following the installation of the bleach regeneration system in 1996, UPGS also considered a regeneration unit for the fixer solution. This step was previously complicated by contamination of the fixer solution from carryover bleach solution, but a modification to the developing process, developed by Kodak, eliminates the pre-hardening and neutralisation stages. The modification frees up a tank for use as a rinse tank between the bleach and fixer solutions, which in turn allows an electrolytic regeneration unit to be installed for recovery of the fixer solution. Whilst embodying the principles of cleaner production, this technology was not adopted as a result of changed processing requirements at UPGS which reduced the use of this process and only would have lead to a very long payback period. 

In 2001, however, Kodak 2445 aerial film was replaced with newly developed Kodak 2444 aerial film, thereby achieving the same objective of eliminating the prehardener and neutraliser stages (and the incumbent use of formaldehyde) in its processing.

Contact

Clive Freegard
Managing Director
United Photo & Graphic Services
4/2 Apollo Court
Blackburn VIC 3130
Ph: (03) 9877 3922
Fax: (03) 9894 2971
Email: info@unitedphoto.com.au

Implementation: 1996
Casestudy initially prepared: February 1997 by the Australian Centre for Cleaner Production

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Last modified: June 2001