Fact Sheet: Waste Reduction for Metal Finishers

The Virginia Waste Minimization Program
Vol. 1 Issue 4

A Fact Sheet from the Virginia Waste Minimization Program on waste reduction for metal finishers.

Waste Reduction for Metal Finishers

Background

There are over 3 1,000 metal finishing facilities in the United States. They vary in size. age and type of operation. They all have one thing in common: the generation of hazardous waste from their production processes. Reducing the generation of hazardous waste can save you money while at the same time decrease your future liabilities

Typical wastes generated are:

• Industrial wastewater and treatment residues
  
• Spent plating baths
  
• Spent process baths
  
• Spent cleaners
  
• Waste solvents and oils.

Waste Reduction

Both state (Virginia Department of Waste Management Regulations. Section 6.5.B.1) and federal (40 CFR, Part 262, Subpart D) regulations require that generators of hazardous waste file a biennial generator's report. Among other things, this report must include a description of the efforts undertaken and achievements accomplished during the reporting period to reduce the volume and toxicity of waste generated.

The Uniform Hazardous Waste Manifest requires large generators to certify that they have a program in place to reduce the volume and toxicity of waste generated... [as] determined to be economically practicable' and have selected the most 'practicable method of treatment, storage, or disposal currently available.. . [that] minimizes the present and future threat to human health and the environment."

Since waste reduction methods reduce the amount of waste generated as well as the amount subject to regulation, these practices can help a shop to comply with the requirements and to save money. The following list details some common waste reduction methods used by metal finishing shops.

Begin at the Top

• The shop's owner or manager must be committed to waste reduction and pass that commitment on to the employees.
  
• Training should be established for employees involved in waste reduction, hazardous material handling and emergency response.
  
• Incentive programs should be formed to encourage employees to design and employ new waste reduction ideas.

Assess Hazardous Waste

Waste assessments are used to list the sources. types and amounts of hazardous waste generated to make it easier to pinpoint where wastes may be reduced.

Source Reduction

Source reduction is usually the least expensive approach to minimize waste. Many of these techniques involve housekeeping changes or minor in-plant process modifications.

Improve Procedures and Segregate Wastes

• Keep work areas clean. Good housekeeping is the easiest and often the cheapest way to reduce waste.
  
• improve inventory procedures to reduce the amount of off-specification materials generated.
  
• Reduce quantities of raw materials to levels at which materials will be used up just as new materials are
  
• Designate protected raw material and hazardous waste storage areas with spill containment. Keep the areas clean and organized, and give one person the responsibility for maintaining the areas.
  
• Label containers as required, and cover them to prevent contact with rainfall and to avoid spills.
  
• Employ a "first-in. first-out' policy for raw materials to keep them from becoming too old for use. Give one person the responsibility for maintaining and distributing raw materials.
  
• Use bench-scale testing for samples rather than in process baths.
  
• Designate one person to accept chemical samples and to return unused samples to suppliers.
• Limit bath to trained personnel.
  
• Segregate waste streams for recycling and treatment and keep non-hazardous material from becoming contaminated.
  
• Prevent and contain spills and leaks by installing drip trays and splash guards around processing equipment.
  
• Conduct periodic inspections of tanks, tank liners. and other equipment to avoid failures. Repair malfunctions when they are discovered. Use inspections logs to follow up on repairs.
  
• Inspect plating racks for loose insulation that would cause increased drag-out.
  
• Use dry cleanup wherever possible to reduce the volume of wastewater.

Material Substitution

• Use process chemistries that are treatable or recyclable on-site.
  
• Use Qeionized water instead of tap water in process baths and/or rinsing operations to reduce sludge generated.
  
• Use non-chelated rather than chelated process chemistries to reduce sludge volume.
  
• Replace cyanide process baths with non-cyanide process baths to simplify treatment required.
  
• Use alkaline cleaners instead of solvents in degreasing operations. These cleaners may be treated on-site and may usually be discharged to the sewer with permit authorization.

Extending Process Bath Life

• Treatment (e.g., filtration, electrolytic dummying. etc.) of process baths can extend their useful life.
  
• Bath replenishment extends the useful life of the bath.
  
• Monitoring (using pH meters or conductivity meters) the process baths can determine the need for bath replenishment.

Drag-Out Reduction

• Bath concentrations to the lower end of their operating range.
  
• Maximize bath operating temperatures to lower solution viscosity.
  
• Use wetting agents (which reduce the surface tension of the solution) in process baths to decrease the amount of drag-out.
  
• Withdraw work pieces from tanks slowly to allow maximum drainage back into the process tank.
  
• Use air knives or spray rinses above process tanks to rinse excess solution off of work pieces and into the process bath.
  
• Install drainage boards between process tanks and rinse tanks to route drag-out back into the process tank.
  
• Use dedicated drag-out tanks after using process baths to capture drag-out.
  
• Install rails above process tanks to hang work piece racks for drainage prior to rinsing.

Rinse Systems

• Use spray rinses as the initial rinse after tank processing and before using the dip tank. Use air or work piece agitation to improve rinse efficiency.

• Install multiple rinse tanks (including counterflow rinse tanks) after process baths to improve rinse efficiency and to reduce waste consumption.

Recycling and Resource Recovery

• Reuse acid rinse effluent as influent for the alkaline rinse tank, thus allowing the fresh water to feed to the alkaline rinse tank to be turned off (reactive rinsing). This process may also be applied to process tank rinses.
  
• Treat rinse water effluent to recover process bath chemicals. This procedure allows for the reuse of effluent for riming or neutralization prior to discharge.
  
• Reuse spent reagents from the process baths in the wastewater treatment process.
  
• Recycle spent solvents on-site or off-site.
  
• Use treatment technologies to recycle rinse waters in a closed-loop or open-loop system. (Some recycling and most treatment processes require a permit.)

Treatment Alternatives

• Pre-treat process water to reduce the natural contaminants that contribute to sludge volume.
  
• Use treatment chemicals that reduce sludge generation (e.g., caustic soda instead of lime).
  
• Use sludge de-watering equipment to reduce sludge volume.
  
• Use treatment technologies (such as ion exchange, evaporation, and electrolytic metal recovery) that do not use standard precipitation/clarification methods, which generate heavy metal sludges.

For more information on opportunities to reduce waste contact:

Virginia Waste Minimization Program
11th Floor Monroe Building, 101 North 14th Street
Richmond, Virginia 23219
804-371-8716 or 1-800-552-2075
TDD 804-371-8737