Silver Recovery Systems For Darkrooms and Photo-Processors
Environment | Systems | Set up | Maintenance | Disposal | Decommissioning
If you use fixer or similar solutions in a photo-processor or in a darkroom, then you are discharging silver that must be recovered before it reaches the environment. This web page takes you through the steps of setting up and maintaining a silver recovery system. The Environmental Health and Safety Department (617-495-2060) is available for assistance with these steps.
1. Silver in the Environment
Silver attaches readily to surfaces and is toxic to aquatic wildlife. This property of silver has driven regulations which limit the concentration of silver that can be discharged into the environment. Silver is also a valuable element that can be re-used; this has created an interest in industry for the development of collection and recycling technology.
Silver bearing wastes found in fixer, bleach-fix, stabilizers and similar solutions are discharged after the developing process.Due to a silver content in fixer of between 3,000 to 4,000 Parts per Million (PPM), these wastes typically exceed the Massachusetts Water Resource Authority's (MWRA) 2 PPM limit for the discharge of silver. A pre-treatment (silver recovery) system can treat these substances so that silver levels are below MWRA limitations.
2. Silver Recovery Systems
All of Harvard’s silver recovery systems use metallic replacement secondary terminal units. Metallic replacement occurs when a metal, commonly iron, contacts a solution containing dissolved ions of a less active metal, such as silver. The iron goes into solution as an ion, and the silver is now a solid metal. As the cartridge nears depletion the silver concentration in the exiting fixer rises rapidly.
Film Developing Systems
There are two general types of development systems: “tray” and “machine.”
Tray developing
Tray developing also referred to as “hand” developing, is done independently of machines. In rooms that contain hand-developing operations, silver recovery is accomplished by pumping the waste fixer into a bucket that holds a cartridge system. The systems can have electric pumps that pump the waste solution from the trays into the buckets. This eliminates the need for lifting and pouring used material and reduces the risk of a spill. The vendor replaces these cartridges every six months at most systems. The set up cost of a silver recovery system for a hand developing dark room is about $200, which includes a pump to move spent fixer into the filtration system. Maintenance is approximately $150 per year, which covers the cost of replacement of the filter buckets.
Machine developing
Machine developing at Harvard is often done by Kodak X-Omat machines, and machine print processors. These types of machines use silver recovery systems that have two or three silver recovery filters in clear cartridges. Cartridges should be used in a series to increase efficient silver recovery. When the first filter saturates with silver, the second filter is moved to the first position, and a new cartridge is put on in the second position. This process allows for a more effective silver recovery and for optimal use of the filters. Some benefits of the metallic replacement method are the low cost, simple non-electrical installation, and potentially high efficiency. Some of the systems have a secondary, “EPAN” system that further lowers the silver content. The decision on how many cartridges to obtain is made based on an estimate of the amount of usage and silver waste that will be flowing through the system. The installation cost of a machine processing silver recovery system is around $300 and the maintenance cost is about $300 per year, which covers the cost of replacing filter cartridges.
3. How to set up a Silver Recovery System
The facility should refer to the manufacturer's specifications for its silver recovery equipment along with the darkroom equipment. In addition, it is recommended that the facility maintain a silver recovery management log, which records all maintenance and silver recovery activity. At Harvard, the requirement for silver recovery logs is fulfilled by the vendor’s system of mounting logs on the wall of each room with a silver recovery system. A sink label is available from building managers alerting users not to dispose of silver and other pollutants down the sink.
EH&S maintains a list of vendors who collect, recycle, and dispose of silver cartridges. Evolve Environmental Services will help you set up a silver recovery system that is appropriate for each location. There are silver recovery cartridges and silver recovery systems for every type of operation. Your vendor will help you to select the size of the silver recovery system and determine the frequency of cartridge exchanges.
Design Recommendations
To quantify and report the amount of fixer and developer used during the year, a counter can be installed that will calculate these measures. This counter measures machine usage and is a good tool to use when setting up cartridge replacement schedules. If the photo processor is not used frequently, a timer and solenoid shut off valve should be installed to save water.
Additional Requirements
- Notify EH&S as soon as silver recovery system is installed
- EH&S will incorporate the system into its MWRA permit
- Fixer, developer and catalogue number will be listed.
- System specifications will be entered in an inventory system
4. Maintenance of Silver Recovery Systems
The vendor who services silver cartridges may also clean critical components of the photo processor and check machine functioning. Too frequent a service increases maintenance costs without improving performance, while too infrequent a service will allow silver to penetrate through the cartridges resulting in silver discharge violation and compliance problems.
The vendors will check the filtration equipment on a monthly basis and will rotate and change the filter cartridges when necessary. They will test the wastewater at each darkroom that has a silver recovery system for silver content. If a water test comes back higher than 2 PPM, they will contact the research operations manager or department contact to discuss strengthening the silver recovery system. The EH&S will also receive a copy of the test results and will be available for guidance. The cost of periodic maintenance will be the responsibility of the Department or Principal Investigator that is responsible for the dark room.
Recordkeeping
An annual silver sample from the photo processor discharge is required if silver sampling is not already being taken at the building discharge level. This sample should be taken before the end of each year and is reported by March 31st of the following year when there is an MWRA Group Permit for Photo Processing. An inventory sheet is posted near the photo processor which documents maintenance visits, replacement of cartridges and silver sample results. Regulatory officials look for this inventory sheet during their audits. All records must be kept for three years.
5. Hazardous Waste Disposal of Silver
If you do not have a silver recovery system installed, the spent silver must be hauled away as hazardous waste. The silver bearing waste must be collected in containers and placed in established Satellite Accumulation Areas for removal by vendors under the supervision of EH&S. Harvard is working to convert all photo processing facilities from hazardous waste areas to silver recovery units. This is partly due to MWRA permit requirements, pollution minimization efforts, EPA concerns, and overall potential for reduction of improper discharge.
6. How to decommission a darkroom or a photo processor
EH&S and your Silver Recovery vendor should be notified when decommissioning or moving a photo process from a facility. Cambridge Facility Managers should report all new or relocated darkrooms and photo-processors to EH&S at (617-495-2060). Longwood staff should contact EH&S at (617-432-1720).
Vendor process in decommissioning a darkroom If relocation is intended, the new site will need to be audited for site readiness and accessibility. Both relocation and disposal decommissions will require a vendor quote. Typical vendor provided decommissioning protocol:
- Pull an effluent grab sample from processor for its final sample documentation.
- Proper drainage of photo processor through silver recovery system.
- De-install silver recovery system.
- Log the system being decommissioned. Serial numbered recovery units logged out and recycled.
- New location site audit (If applicable)
- Preparation of processor hardware for removal/transport.
- Re-Install system and new silver recovery cartridges.
- Assign new location ID #’s, and maintenance logs.
- System start up and calibration
- Effluent grab sample within 10 days post re-installation
