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Waste Management and Pollution Control

1) PCBs are regulated under which law? List PCB classifications with concentrations.
2) Describe the disposal requirements for transformers, capacitors, containers, and liquids. Is manifesting required for PCB disposal?
3) Detail the spill reporting requirements for PCB spills.
4) Which law studied this term is the most burdensome to environmental managers and why?
Use the following scenario to answer questions 5, 6, and 7. Give detailed answers.
Fabricating printed wiring boards (PWB) involves a variety of different processes that are
divided into two categories: dry and wet fabrication. Dry fabrication is composed of drilling,
routing, and imaging; whereas wet fabrication is composed of scrubbing, developing, plating,
and etching. This study focuses only on the wet processes and the associated problems relative to
environmental stewardship. This shop had much to learn about environmental responsibility and natural resource conservation. The past processes of the shop were not a deliberate "nose-thumbing" attitude toward the environment and natural resources; but rather it was brought about by lack of knowledge and awareness. All of the chemicals involved in wet processing are hazardous to some degree. These hazards revolve around the properties of the chemicals. For example, strong mineral acids are extremely corrosive and the vapors readily degrade most metals on contact. Inhalation of these vapors can cause a range of problems such as slight respiratory irritation, pulmonary edema, and death. All these hazards can be reduced or even eliminated from the work place by engineering and administrative controls. Engineering controls include proper ventilation and material substitution. Administrative controls include Standard Operating Procedures (SOP) and training. Personal protective equipment (PPE) is used when the hazard hasn't been eliminated from the workplace.

Past Operation Practices
The processes of environmental concern were electroless copper deposition, electrolytic copper
plating, and electrolytic tin/lead or solder plating. All of the plating shop rinses consisted of tap
water overflow that were discharged directly into an Industrial Sewer System (ISS). The initial
processing flow rates were approximately 2,000 gallons/hour. Contained within this substantial
rinse discharge were regulated materials (i.e., copper, tin, lead, and formaldehyde).
Scrubbing and deburring equipment used to process PWB panels was plumbed to discharge
directly into the ISS. This discharge was approximately 12 gallons/minute and contained copper
particles along with fibrous material from the scrubber wheels.

The photoresist developer and stripper used in the imaging process were also plumbed to
discharge directly into the ISS with approximately 6 gallons/minute of outflow. Alkaline effluent
in the imaging process contained residual organic material in solution and suspended particles.
Temperature control was a critical parameter in many of the steps involved in fabricating PWBs.
Maintaining predetermined temperature parameters was accomplished with tap water circulation.
All of the cooling water was discharged into the ISS. There were no recycling steps practiced.
The etchers, developer, lamination press, and vapor degreasers required tap water cooling to
control the temperature. During normal operations, approximately 8,000 gallons of noncontact
cooling water was used weekly. (Water usage fluctuated depending on the temperature of the
ground water.)

Hazardous Materials
Materials used in the wet fabrication processes are hazardous. The chemicals employed can be
categorized into three groups: oxidizers, corrosives, and toxins.

1. Oxidizers are materials that readily oxidize substances with which they come into contact. An example is chlorine gas, which was used to regenerate an etching system. The etchant was chemically reduced as copper was removed from the PWB panel. Chlorine gas was used to reoxidize the etchant and restore etching ability.

2. Corrosive materials include acids, bases, and halogens. Each of these materials could cause corrosion on substances with which they come into contact. (An example of this is the effect that strong mineral acid vapors have on metals and respiratory systems.)

3. Toxins include toxic materials, irritants, carcinogens, and asphyxiants. These materials are known to have an adverse effect on humans. Most of the chemicals used in the fabrication of PWBs possessed one or more of these undesirable properties. Since there was a great concern for protecting the personnel exposed to these substances, it was extremely important that the PPE be properly used. The solution employed to etch copper without destroying the tin/lead plated pattern was chrome trioxide and sulfuric acid. The etching solution was heated to 120oF in a conveyorized spray module and was used until spent. Waste products were then transferred into drums, labeled, manifested, and sent to waste disposal. (The main component, chrome trioxide, is a known carcinogen and exposure to this compound has been documented to cause lung cancer.)

The solvent used to remove dryfilm photoresist was methylene chloride, a suspected carcinogen.
Removal was accomplished by placing a large solvent-resistant tray in an open sink and adding
solvent. A number of panels were then placed in the solution and allowed to soak for several
minutes. During this dwell time, the photoresist blistered and floated free of the panel surface.
The panels were then withdrawn from the tray and held under running water to rinse the residual
solvent into the Domestic Sewer System (DSS). A liquid photoimagable resist was used to fabricate fine line circuitry. This resist was a xylenebased material formulated with hotosensitive compounds. The resist was applied by pumping the compound onto a set of rollers which, in turn, was deposited onto the panels being processed. After each use, the equipment had to be cleaned by wiping the soiled areas with xylene. (Xylene is a chemical suspected of damaging bone marrow, thus causing anemia.).

As California was experiencing a 7-year drought a hard look was taken into operation practices.

5) Describe how you would manage this waste stream. Be specific in approaches and include personnel aspects. What law regulates this material?
6) Describe some waste minimization techniques that could be used for this waste stream. Keep in mind that water is scarce.
7) What HW characteristics do the materials used in this process have?


Solution Preview

In accordance with BrainMass standards this is not a hand in ready assignment but only background help.

Step 1
PCBs are regulated under the Toxic Substances Control Act (1976). There are three classifications for PCBs. The first is more than 50 ppm or the equivalent of less than 10 ug/100 cm, The second is more than 50 ppm and less than 500 ppm or equivalent which is 10-100 ug/100 cm2, and the third is more than 500 ppm or the equivalent more than 100 ug/100 com. PCBs under 50 ppm are not regulated by the Toxic Substances Control Act.

Step 2
The disposal requirement for PCB liquids is disposal by combustion. Incidental PCB contaminated liquids may be disposed through landfill. PCB transformers must be disposed through incineration, or if the requirements of 40 CFR 761.75 are fulfilled, through chemical waste landfill approved under the law. The disposal requirement for small PCB Capacitators is disposal as municipal solid waste provided they have not been manufactured or acquired during manufacturing. Otherwise they must be destroyed through an incinerator, or chemical waste landfill approved for the purpose. Large capacitators with 500 ppm of PCB should be disposed in an incinerator or chemical waste landfill. PCB containers should be disposed through decontamination according to 40CFR 761.79, after which it should be disposed through incineration or chemical waste landfill approved under 40 CFR 761.75.
Manifesting is required in case of PCB capacitaors which is $50 ppm is intact/non-leaking/ or is damaged/leaking. If the PCB capacitator is leaking, whether it is less than 50 ppm or equal to 50 ppm, it must be manifested. In general PCB waste that is subject to EPA regulation must be manifested.

Step 3
All spills involving 1 pound or more by weight of PCBs must be reported to the National Response Center. The phone is ...

Solution Summary

This solution explains waste management and pollution control response. The sources used are also included in the solution.