Pretreatment Program

​Silver Best Management Practices (BMPs)

Category Determination

Participation in the BMP program is simple. First, determine the total volume of process effluent or the volume of silver-rich solution generated by your developing operations on a typical day. Process effluent is the total volume of all water and liquid waste that is generated by film processing operations--including developer and rinse water. Silver-rich solution is defined as "a solution containing sufficient silver that cost-effective recovery can be conducted on-site or off-site." Silver-rich solutions include fixers, bleach-fixers, stabilizers from low-flow washes, and all functionally similar solutions. For radiographic processes, silver-rich solutions are limited to the fixer solution. Developer solution and wash waters are not considered silver-rich solutions.

Maintain a written record of your calculations demonstrating how the volume of total process effluent or silver rich solution was determined. There are BMP guidebooks that may help you calculate the total processing effluent volume. Review this calculation annually to determine if the total volume of silver-rich or total process effluent has changed. These volumes will determine the category--or size--of the facility (Small, or Large) and the percentage of silver that must be recovered from the silver-rich solution prior to discharge.

The categories are (volumes are in gallons per day or gpd):

  • Small: Less than or equal to 10,000 gpd of total process effluent OR less than or equal to 20 gpd of silver-rich solution.
  • Large: More than 10,000 gpd but less than 25,000 gpd of total process effluent OR more than 20 gpd of silver-rich solution.

Facilities discharging more than or equal to 25,000 gpd of process wastewater are defined as Significant Industrial Users (SIUs) by the United States Environmental Protection Agency. Significant Industrial Users are permitted and monitored under the Pretreatment program and therefore are required to obtain permits and meet other specific requirements in addition to the BMP program requirements.

To determine the size of the facility using a water bill, subtract from the total gallons per day (gpd) any water not used in the photo processing operations; including domestic sewage (usually 20 gpd/per employee), landscape irrigation, and non-contact cooling water. Specific information about how to determine facility size can be obtained from the Pretreatment program.