Although photochemical concentrates may have clear hazard warnings on packaging and in MSDSs, once diluted and exhausted their toxicity to the environment is also diluted and exhausted. They should still not be carelessly released into your local environment. Since we love this analog world that we live in, we should be sure that photo-processing waste is disposed of through responsible channels.
Knowing your local restrictions, where your chemicals go and how they are treated if they are put down a drain is paramount. Most municipalities in the U.S. allow certain amounts of photo chemicals to be discharged into the municipal sewer system, i.e., hobbyist amounts. Larger users, such as photo finishers are subject to other regulations. Since replenished photo lab chemicals are not quickly exhausted they will maintain a high potency up until they are discarded, and retain much higher concentrations of silver waste from processing large volumes of film. Users in other countries need to investigate their own national and local arrangements for dealing with domestic chemical wastes.
If you have chemicals that cannot be disposed of locally through conventional methods, most communities have local household hazardous waste collection facilities. These facilities are available to the public to collect items from domestic use that should not be disposed of through municipal trash, septic, or sewer systems. In the U.S. this option should be available if you generate less than 220 pounds (100 kilograms) of hazardous waste per calendar month. Most home hobbyist photographers fall well below this limit. You can also discharge your photographic wastes to a local municipal sewer authority for treatment, often referred to as a Publicly Owned Treatment Works (POTW). Contact the POTW directly to see if they will accept your waste.
Most photographic processing effluents and washwaters contain chemicals that are biodegradable. They are, therefore, compatible with aerobic (with oxygen) biological treatment systems and may be effectively treated when discharged to municipal sewer systems such as Publicly Owned Treatment Works (POTWs). POTWs that have secondary (biological) wastewater treatment can effectively treat the waste stream through the use of biological action, such as bacteria nutrients and aeration, to break down the waste it receives so that it may be safely discharged. Check with your local municipality to be sure. Septic systems operate with anaerobic (without oxygen) biological treatment. Therefore, septic systems do not have the ability to properly treat photographic processing effluents.
Your local municipality establishes sewer codes or sewer discharge limits for commonly discharged materials. Limits are generally placed on parameters such as pH, Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Ammonia as Nitrogen, Total Suspended Solids (TSS), and Total Dissolved Solids (TDS). If you are discharging to the local sewer system, you should obtain and review the discharge requirements for your area and determine whether your photographic processing effluent can meet those limits established by your local municipality.
Photographic processing effluent includes developer, fixer, bleach, and wash water involved in processing films and papers. Two key characteristics of photo-processing effluent are pH and the concentration of silver. Developer has a high pH and is therefore alkaline or caustic. Fixer has a low pH and is therefore acidic. Film processing chemicals contain an alkaline developer, with a pH about 10.0, and an acidic fixer, with a pH about 4.3. These are discharged roughly in a 2 to 1 relationship along with considerable wash water (1/2 to 3 gallons per minute). When exhausted fixer and developer are combined with the total process effluent, the effluent is neutralized, resulting in a better compatibility with drain pipes and treatment at the POTW.
Business owners are responsible for disposing of used or unwanted processing chemicals and scrap film and paper through a licensed waste disposal operator. The amount and type of chemical wastes that can be disposed down the drain can be very limited, as international, national and local regulations often apply and strict limitations are imposed on businesses regarding which chemicals can be disposed of and in what quantities. In some countries waste disposal is the only option for any chemical wastes from commercial operations.
Photographers should investigate the arrangements applicable to their local area. Local authorities should also have arrangements for receiving small quantities of used or unwanted chemical wastes (such as paint, cleaning agents, bleach, weed killer, etc.). We do not recommend that you dispose of used or unused photographic processing solution in your regular trash. This is to ensure the safety of the trash collectors who would not know that this material is in the trash and could possibly come into contact with it.
Another key characteristic of photo-processing effluent is the silver concentration found in photographic fixer or bleach-fix effluent. Black and white films contain high concentrations of silver and color film less so. Once processed, silver can be retained in the photographic material or transferred to solutions used to process the photographic materials. Although the form of silver (silver thiosulfate) found in photographic processing effluent is not harmful and is removed during secondary treatment at the POTW, it is a good practice to recover silver before discharging the effluent.
Just as one-shot chemistry will only retain trace amounts of silver, replenished solutions retain much higher concentrations of silver waste than chemistry reused until exhaustion. Commercial business must recover silver from photo-processing effluent to meet sewer discharge limits established by POTWs. Amateur photographers may not be required to recover silver. But whether you are a professional or amateur photographer, silver recovery provides environmental benefits, conserves a natural resource, and may provide a source to recover revenue.
The amount of silver found in photo-processing effluent will depend upon the amount of film or paper you’ve processed. For small volume users like amateur photographers, metallic replacement is usually a good method for recovering silver from photographic processing effluent. In this method, iron metal (steel wool) reacts with the silver in the fixer solution. The iron replaces the silver in solution, while the less active metal (silver) settles out as a solid sludge. To bring the silver in contact with the iron, the used fixer passes through the container filled with steel wool. The steel wool provides the source of iron to replace the silver. If you do not want to recover silver from used photographic fixer or bleach-fix, you may choose to utilize other disposal options, such as household hazardous waste collection.
As a photographer, you have a unique sensitivity to the environment around you. The best way to conserve the environment, and your pocketbook, is to use photographic processing solutions efficiently. As an amateur photographer, you may not have to worry about the environmental and safety regulations that apply to commercial businesses, but you still need to know how to safely handle and dispose of photographic processing chemicals. Be sure to be aware of all warnings and read all instructions. And as always, be safe.