EP3 Case Studies

Electroplating

Textiles

Battery Manufacture

Printing

Tanning

Electroplating

Summary

This assessment evaluated an electroplating facility. The objective of the assessment was to propose a program of pollution prevention that would:

1. reduce the quantity of toxics, raw materials, and energy used in the manufacturing process, thereby reducing pollution and worker exposure,
   
2. demonstrate the environmental and economic value of pollution prevention methods to the electroplating industry, and improve operating efficiency and product quality.

Overall, the assessment identified 18 pollution prevention opportunities at this facility. Recommendations for pollution prevention include replacing the solvent degreaser with an alkaline cleaner, improving process solution monitoring, and capturing and returning 100 percent of chromium dragout to the process solution.

Facility Background

This facility is an electroplater that performs zinc, nickel, brass, and chrome plating. Seventy percent of production is comprised of brass articles. The facility operates with 23 workers who work in a single 8-hour shift, 300 days a year. Approximately 15 m2 of metal surface is finished per day.

Manufacturing Process

Facility operations can be divided into five main steps:

1. polishing,
   
2. cleaning,
   
3. racking,
   
4. electroplating, and
   
5. gilding as shown in Figure 1.

Prior to electroplating, many parts are cleaned in a vapor degreaser that uses trichloroethylene (TCE) to remove grease and other impurities. Parts removed from the degreaser are dried with paper towels.

The facility electroplates many different kinds of parts. Several parts are hung on special racks that are constructed specifically to handle the part. Other pieces are plated inbaskets that are placed directly in the solutions. The electroplating line consists of washing tanks, rinsing tanks, and nickel and chrome plating and recuperation baths. A copper cyanide bath is located across from the line and is used to plate zamak before it is plated to nickel and chrome. All plating is manual. Times are not exact, and there is considerable variation in soaking times among different parts and different workers. Before gilding, parts are rinsed in special rinse baths. They are then immersed in gilding solution for less than a minute.

Existing Pollution Problems

At the time of the assessment, there were a number of pollution problems including

1. polishing debris,
   
2. the use of organic solvents for degreasing,
   
3. acid dip contamination,
   
4. inefficient cyanide electroplating,
   
5. unnecessary chrome and nickel waste, and
   
6. excessive water use.

Pollution Prevention Opportunities

The assessment identified 18 pollution prevention opportunities that could address the problems identified above, with significant environmental and economic benefits to the facility. Table 1 [see source document] lists the recommended opportunities for the facility, and presents the environmental benefits and implementation costs for each.

• Polishing Debris. As currently performed, the polishing process leaves considerable debris (consisting of a mixture of polishing compound and solids from the polishing wheel) inside the pieces. These deposits cannot be removed by scraping or wiping.

  To alleviate this problem, the facility can take several steps. Reducing the amount of polishing compounds used will reduce the amount of debris. Removing visible residue will allow less debris to harden on the pieces. Reducing the time between buffing and cleaning will also allow less debris to harden on the pieces. Lastly, employing a polishing compound that is compatible with alkaline cleansers will improve the efficiency of the cleaning process (along with recommendations outlined in the next section).

• Degreasing. The facility currently employs the chlorinated solvent TCE to degrease parts. TCE is highly toxic and chemically reactive, and has been inked to liver cancer and ozone depletion. Parts can be cleaned equally well, or better, through the use of aqueous alkaline cleaners. Thus, the facility can greatly reduce its environmental impact and improve product quality by implementing an alkaline cleaning system. Further, the alkaline system is more cost effective than the TCE system. A $5,000 investment will yield savings (from eliminated solvent purchases) of $12,000 per year.

• Acid Dips. In this facility s plating process, an acid dip (usually 10 percent sulfuric acid) is used to remove any oxides that may have developed on the brass or steel surface. With time, copper and organic contamination accumulates in the acid bath. If more than 300 mg/l of copper is present in the acid dip, the bath can cause adhesion problems for the steel substrate. Further, copper contamination also impacts the nickel electroplating solution. While the facility utilizes nickel depassivation to remove the copper contamination, it is not efficient, wasting nickel, brightener, and energy.

  Separate acid dips for steel and brass substrates will improve the quality of both the steel substrate cleaning, and the nickel electroplating solution, and hence reduce the number of rejects the facility produces. Additionally, by employing tighter process control over the acid dips, the facility will save $816 a year in reduced solution cost.

• Inefficient Cyanide Electroplating. Cyanide electroplating cannot be eliminated at this facility because the known non-cyanide alkaline alternatives do not function well in this application. However, improved process control and solution monitoring could enhance product quality, and hence reduce the number of rejects the facility produces.

• Unnecessary Nickel and Chrome Waste. Currently, the facility purifies the nickel bath six times per year. By improving process control and purifying the nickel bath only once per year, the facility should save between $4,100 and $5,900 a year from recovered nickel solution.

  The lost chrome solution is only valued at $180 per year. However, if 100 percent of this chrome could be captured, the facility would not have to install expensive chrome waste treatment required by the facility's government. A porous pot purification system (priced between $500 and $1,000) is capable of removing the chromium from the waste water. While the expected costs of meeting chromium discharge limits have not been determined, they are sure to be greater than the cost of the purification system.

• Excessive Water Use. Waste water is generated in significant volumes from the facility s rinse steps. Some fairly simple changes can be made that will reduce water use by 25 percent. The use of air or solution agitation would increase the efficiency of the rinses, and reduce the frequency of changes. Spray rinses would also be more efficient than the current practice. Lastly, water inputs should be installed with switches that turn off the inputs after a set period of inactivity. For an investment of less than $100, the facility should save $1,728 a year from reduced water usage.

Textiles

Summary

This assessment evaluated a dye house serving a variety of fabric manufacturers. The objective of the assessment was to identify actions that would:

1. reduce the quantity of toxics, raw materials, and energy used in the dying process, thereby reducing pollution and worker exposure,
   
2. demonstrate the environmental and economic value of pollution prevention methods to the dyeing industry, and
   
3. improve operating efficiency and product quality.

Facility Background

This facility is a dye house serving fabric manufacturers. The facility operates two eight-hour shifts, six days per week, employing seventy shift workers and twenty technical and administrative employees. In 1992, the facility processed 350,000 kg of cotton and 360,000 kg of wool fabric.

Manufacturing Process

In general, cotton dyeing involves two procedures, desizing and bleaching, and dyeing. Each procedure involves a number of steps that must be carried out in proper sequence and under optimal conditions.

Wool dyeing also involves several procedures:

1. washing,
   
2. podding (heating thin wool fabrics in boiling water to improve appearance and brightness), and
   
3. dyeing.

Existing Pollution Problems

At the time of the assessment, there were a number of pollution problems at the facility, including

1. excessive loss of water, chemicals, and heat energy from the becks,
   
2. excessive use of water in the rinsing process due to residual solution left at bottom of the beck,
   
3. excessive suspended solids, primarily lint washed off fabric,
   
4. leakage of detergent-laden water from the wool washing machines,
   
5. excessive pH of effluent from the decarbonizing acid bath,
   
6. excessively hot effluent,
   
7. excessive oil and grease and sulfate concentrations in effluent,
   
8. leakage from steam coils,
   
9. hydrogen sulfide generation at the wool laundry sump,
   
10. disposal of dry wool, cotton combings and shavings, and sodium sulfate bags (materials that could be recycled),
    
11. excessive air emissions of particulates, and
    
12. lint and sulfuric acid mist in the wool laundry room.

Pollution Prevention Opportunities

The assessment identified almost 40 pollution prevention opportunities that could address the problems identified, with significant environmental and economic benefits to the facility. The assessment team prioritized these opportunities based on pollution prevented and implementation cost (a complete list of recommendations is available from the EP3 Clearinghouse). Many of the recommendations can be implemented with no capital investment. Further, many can be implemented almost immediately, and most are not dependent upon other projects for their initiation.

Of the 19 high priority opportunities recommended, the savings possible from implementing six have been quantified. These six recommendations will reduce operating costs by almost $106,000 per year for an initial investment of $1,900. The simple payback period for these changes is one week. Another $2,600 in investments is required to implement other changes whose savings potential cannot be quantified without further research.

Effect on the Environment

Implementation of the recommended actions will produce positive environmental impacts in three areas: reduced air emissions, lower water and chemical use, and reduced generation of solid waste.

1. Air Emissions. Many of the proposed changes will reduce steam consumption and lower fuel use, thereby reducing air emissions. Repairing all traps should reduce fuel consumption by 36 percent, or 454 metric tons of number 6 residual oil per year. The expected reductions in air emissions from this change total over 14 metric tons per year. In addition, this change will result in reduced carbon dioxide and heavy metal emissions.

2. Water and Chemical Use. When all rinsing changes have been implemented, the facility should consume half the water it currently does. The yearly reduction in water use will be about 125,000 cubic meters. Chemical use will decline due to a number of changes. Sulfate in the effluent will be reduced by more than 70,000 kg/year by changing to sodium chloride and filtering the decarbonizing acid bath.

   Releases to the sewer of other chemicals such as dye, dye stabilizers, de-foamers, detergents, sodium hydrosulfite, bleach, optical brighteners, acetic acid, equalizers, and boiler treatment chemicals will be reduced as a result of the recommended changes.

   Among the changes that will affect chemical releases are:

   1. better process controls,
      
   2. screening drains and cleaning sumps regularly to prevent sulfide generation,
      
   3. preventing beck boil-over,
      
   4. repairing coil steam leaks that contaminate boiler feed water and process baths,
      
   5. using a lower-foaming jet-dye detergent,
      
   6. calibrating and shimming becks,
      
   7. repairing and modifying becks and wool laundries, and
      
   8. determining sizing formulae.

   Until these changes are made, it is not possible to calculate the degree to which releases will be reduced.

3. Solid Waste. Solid waste discarded by the facility consists mainly of sulfate chemical bags and shavings and combings from fabric finishing. Assuming that the eight sulfate bags generated per day fill one large (0.1 cubic meter) garbage bag and that the combings fill ten bags per day, the yearly un-compressed volume of these solid wastes is 330 cubic meters. If both wastes are recycled, this volume of waste can be reused at least once before being discarded.

Battery Manufacture

Overall, the assessment identified nineteen pollution prevention opportunities that could save over $1,531,206 in the first 12 months for an investment of $522,500. If implemented, these changes could reduce employee exposure to lead dust, reduce energy and water use per unit output, reduce the amount of lead purchased, reduce lead-contaminated waste water, and improve product quality.

Facility Background

This facility manufactures starting, lighting, and ignition (SLI) batteries. Most of the facility's output is sold domestically, although about 20% is exported. The facility operates one, two, or three 8-hour shifts (depending upon the equipment, process, and season) and employs 220 people. In 1993, they sold 231,000 batteries.

Manufacturing Process

Facility operations can be divided into six main steps:

1. conversion of scrap lead into cast panels,
   
2. conversion of virgin lead into lead oxide powder and paste,
   
3. pasting and curing of panels,
   
4. container formation of batteries,
   
5. tank formation of batteries, and
   
6. laboratory analysis and process controls.

To make the lead oxide paste, lead oxide powder is mixed with de-ionized water, sulfuric acid, and organic expanders. One recipe makes a positive plate, while a slightly different recipe makes a negative plate. The pasted plates then move on a conveyor belt through a drying oven. After pasting and drying, the plates move into a curing chamber for about 48 hours to convert the remaining lead into lead oxide. In tank formation, the positive and negative plates are immersed in tanks of low specific gravity sulfuric acid, where electrodes pass a current through the plates. In the positive plates, the current converts lead sulfate from the paste into lead oxide. In the negative plates, the reaction converts the paste into sponge lead, a very porous, high surface area form of elemental lead. Container formation employs the same electrochemical process, but occurs in the plastic battery case instead of the tank. Cured plates that are not tank formed must be cut in half and assembled into battery elements, which are then placed into batteries for container formation.

After tank formation, the plates go through a washing and drying process to remove any remaining sulfuric acid. Overall, the plate washing process accounts for over 60 percent of the factory's water contaminated with lead and sulfuric acid.

Existing Pollution Problems

At the time of the assessment, there were a number of pollution problems at the facility, including:

1. waste acid from the used batteries that are cracked to recover lead is disposed of on site,
   
2. uncovered lead slag and dust piles,
   
3. excessive energy use in smelting ovens, curing rooms, and the tank formation process, and
   
4. excessive wastewater generation in the grid pasting and washing processes.

Pollution Prevention Opportunities

Overall, this assessment identified nineteen pollution prevention opportunities that could address the problems identified and produce significant economic benefits for the facility. If implemented, these opportunities could save over $1,531,206 in the first 12 months for an investment of $522,500. The pollution prevention strategy is premised on the belief that addressing sources of waste and pollutants also improves the company's economic health by reducing operating costs and improving product quality. In this case, product quality is increased by

1. increasing the lead oxide particle size by buying a liquid atomization mill,
   
2. increasing the moisture content of the paste recipes,
   
3. increasing the curing temperature, humidity, and air circulation,
   
4. analyzing the moisture content of the pasted plates on-site, at the oven,
   
5. monitoring the smelting oven temperature and adjusting to the optimal level,
   
6. curing larger batches of pasted plates, and
   
7. utilizing cadmium sticks in the laboratory to measure cell voltage.

Additional Recommendation

There is an additional opportunity to prevent pollution and conserve raw materials in the battery recycling process. Before cracking the battery case, workers could pour the acid into a large plastic plating tank. The acid could be recycled (possibly through ion exchange) and returned to the production process, replacing purchases of high concentration acid.

Evaluating Performance

EP3 is developing a methodology for measuring and tracking pollution prevention performance. The approach uses simple but critical ratios to compare data among facilities in the same industrial sector. This assessment identified four critical ratios. The Assessment Team developed best industrial performance (BIP) values for these ratios, and found that each of this facility's current values were significantly above the BIP values.

Implementation Status

The facility has already implemented many of the low/no cost recommendations, including covering recycled lead piles, recycling dropped virgin lead into the lead oxide mill rather than into the smelter, recycling waste paste into the hopper rather than sending it to the smelter, and maintaining optimal temperature and humidity in the curing room. In addition, the facility has begun to implement several capital intensive changes. For example, it has placed an order for boost charging equipment ($100,000) and requested price quotes for a liquid lead atomization mill ($240,000).

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Printing

Pollution Prevention Opportunities

The assessment identified several pollution prevention opportunities. The environmental benefits, implementation costs, financial benefits, and payback periods are given where the data were available. The total financial benefit for those opportunities that were quantifable total $54,600 per year plus paper scrap reduction savings.

• Press cleaning solvents: There are three significant opportunities for the facility to address solvent use and disposal. When presses are cleaned, liquid solvent wastes are discarded into the sewer system. The used solvent waste can be combined with solvent recovered from the centrifuge and sold to a solvent recycler. This would reduce the amount of solvent going to the sewer by 10,000 liters/year and save $1,000/year.

  The presses are cleaned with cotton wipers which are discarded along with other solid wastes to un-lined municipal landfills when they become contaminated with ink and cleaning solvent. These rags can be laundered and reused, reducing the amount of solvent going to landfills by 20,000 liters/year. However, to prevent the solvents from being discharged into the sewer during the laundering process, it is recommended that a centrifuge be used to recover the solvents from the rags.

  This requires a large up front cost of US$22,000 to install the equipment. The financial benefits are estimated at $25,000/year in savings from purchasing new rags. The captured solvents can also be reused for less demanding cleaning uses or sold to local solven re-distillers.

  The rags used to clean the blankets can also be reused. Because the rags are not very dirty, a hand-powered wringer can be used to wring out the rags so they can be reused prior to laundering. Using this method, the blanket wash can also be recovered and reused, reducing solvent use by 6,700 liters per year. It will cost the facility $4,900 to install the wringer; annual savings will be $7,500.

• Paper: This facility is recycling some paper scrap, but additional opportuntities were identified. About 80% of the facility s solid waste is scrap paper. The facility believed that their current paper recycler would not accept varnished paper; however, upon further examination, it was discovered that they did accept varnished paper except for two types of plastic-containing paper. By recycling the accepted varnished paper, the facility could reduce the landfilling of paper by 500 tons of paper per year, yielding a financial benefit of $13,500.

  The facility currently generates 8 tons of scrap paper. There are significant opportunities to reduce overall paper scrap. Currently, scrap generation rates are about 42% but could be brought down to about 10% if all avoidable scrap generation causes were identified and eliminated. The facility would create 2,300 tons less scrap paper. The net value of paper recovered by reducing paper scrap could reach as much as US$1,656,000/year.

Other pollution prevention opportunties:

• Rotary press inking: The ink colors are delivered to the rotary press by drum presses. When emptied, one-half to one and one-half inches of ink remains in the drums when they are changed. A four position drain rack can be installed to allow the remaining ink to drain, be collected, and reused. The recovered ink is worth $4,400 per year.

• Image-processing: To reduce chrome discharges to the sewer, the facility can recycle the spent image processing or find alternate silver removal solutions which do not contain chrome. This would eliminate the discharge of 9.9 kg/year of hexavalent chrome to the sewer.

• Ink mixing room enlargement: The ink mixing room can be enlarged to allow for more space for triple countercurrent rinsing of mixing vessels, blades, and spatulas. This would reduce ethyl acetate purchases by 3,700 liters per year at a cost savings of $3,200 per year. In addition, the additional space will allow for the installation of fume hood to protect ink room employees from solvent vapors.

• Fountain solution: The fountain solution currently used contains isopropyl alcohol. Isopropyl alcohol losses to the air amount to 34,700 liters per year (about 27,000 kg). Switching to a solution with less volatile components could reduce VOC emissions by as much as 24,000 kg per year. Worker exposure to solvent vapors would also be reduced.

• Lubricating oil: One of the presses will generate about 200 liters per year of used lubricating oil. This is currently disposed of in the sewers but can be recycled.

Tanning

Summary

This assessment evaluated a facility that manufactures lead-acid batteries used in automobiles and trucks. The objective of the assessment was to identify actions that would:

1. reduce the quantity of toxics, raw materials, and energy used in the manufacturing process, thereby reducing pollution and worker exposure,
   
2. demonstrate the environmental and economic value of a pollution prevention assessment, and
   
3. improve manufacturing efficiency and product quality.

Overall, the assessment identified eight pollution prevention opportunities at this facility. Recommendations for pollution prevention include recycling of the spent chrome tanning wastes, oxidation of the sulfide containing wastes, decreasing the volatile organic discharge by changing finishing materials, decrease of water use by batch washing, and use of solid wastes from the waste stream as fertilizer.

Facility Background

This facility is a goatskin tannery producing chrome tanned suede and grain shoe, garment, and fancy leathers. Dy and green salted skins, as well as wet blue goatskins are used. The tannery produces leather from approximately 1,000 kg of dried goatskins per day.

The wastes generated by the tannery come from the hides and the chemicals used in the production process. Tannery wastes are discharged in a number of batches during the production day.

Manufacturing Process

In the production of leather from dry goatskins, the dry skins must be thoroughly re-wet and the dirt, salt and undesirable hide substances removed. Soaking and washing the skins is done in three steps. The first step removes dirt, salt, and some organic matter, while the other two are rinses. The waste water is nearly neutral, and contains salt and some suspended solids.

Next, the skins are unhaired by treatment with lime and sulfides. The waste water is very alkaline, contains toxic sulfides, and is the main cause of the high BOD and suspended solids in the total waste stream.

The next step is de-liming and bating to remove the lime in the skins and soften them by enzymatic action. The first dump of this process contains ammonium sulfate, enzymes, and some protein. The subsequent washes are very dilute, nearly neutral pH solutions.

The skins are then tanned. The chrome tanning process is standard for the industry: the solutions contain chromium as chromium sulfate salt and some free acid. About 75 percent of the chromium present combines with the hide.

Finally, the retan, color, and fatliquor steps are employed to color and oil the leather to make it as soft or firm as desired. A number of chemicals are used in these steps, and about 90 percent of the load is fixed to the leather. The spent solutions are mildly acidic, with a pH of between 4 and 6. BOD and suspended solids are relatively low.

Existing Pollution Problems

At the time of the assessment, there were a number of pollution problems at the facility, including

1. excessive chromium discharge,
   
2. excessive VOC discharge,
   
3. excessive water usage,
   
4. excessive leather waste,
   
5. excessive sulfide waste,
   
6. excessive suspended solids in effluent,
   
7. excessive oil and grease in the effluent, and
   
8. excessive BOD of effluent.

Pollution Prevention Opportunities

The assessment identified eight pollution prevention opportunities that could address the problems identified, with significant environmental and economic benefits to the facility. Two of the recommendations can be implemented with no capital investment.

Effect on the Environment

The recommended actions are based on cost effective methods that have been proven in commercial applications. These actions will have a number of positive environmental impacts.

1. Chromium recycling will decrease the chromium in the discharge by 80-90 percent. The spent chromium solutions contain about 25 percent of the total chromium used in the tannage. The loss of this valuable material can be decreased and the chromium concentration lowered by recycling. Some of the spent chromium solution can be directly used to make the pickle solution without affecting the quality of the leather. The remainder can be saved, and the chromium precipitated with the addition of an alkali. The recovered chromium can be dissolved in acid for use in the tannage.

2. The suppliers of finishing products have developed water-based lacquers with significantly lower volatile solvent contents. The reduction of volatile solvents will decrease VOC releases to the atmosphere by 60-75 percent.

3. In some hide wetting processes there is an opportunity to recycle the final rinses. In the goatskin process, extensive washing of the bated skin is common. The water from this wash could be used for rinse water in the original soaking, as the final rinse wastewater is compatible with fluids used for the first wetting of hides. The judicious recycling of rinse waters and automated systems in a tannery could result in savings of up to 50 percent of water consumed.

4. Elimination of solid leather waste discharges by using trimmings to make reconstituted leather will ease the burden on landfills.

5. Eliminating sulfide discharges is very important as sulfides can corrode pipes, cause objectionable odors, and cause fatal accidents. The sulfide-lime solution, and washes from this process can be easily collected, placed in a tank, and the sulfides oxidized by air with a manganese sulfate catalyst. This method is effective and can destroy the sulfide in 4-8 hours. The oxidized wastes are kept for use in controlling the pH of the effluent stream.

6. Decreasing by 80 percent the suspended solids discharged, and instituting secondary treatment will serve to decrease BOD. With primary and secondary treatment, the BOD can be reduced by 75 percent. In addition, the reduction of suspended solids creates a useable by-product in the form of an organic fertilizer, thus eliminating possible high disposal costs.

Implementation Plan

The schedule and timing of implementation of the recommendations will depend on the relative costs and benefits and the availability of personnel and capital. The recycling of the chrome tanning solutions is the most cost effective rcommendation in that the company will have a large saving in material costs in addition to significant pollution prevention.

• Chrome Recycling. The value of chrome recycling to the tannery and its low capital costs should make it an attractive option. Implementation may be accomplished in 2-6 months.

• Solvents. The shift to low VOC finishes should occur between 6-12 months as the system is accepted by the company for each of the leathers it makes.

• Process Water. The decrease in the volume of process water used can be accomplished without a capital investment. The batch washing of coloring and fatliqouring batches could result in savings of about 50 percent in these operations. With the recommended pretreatment system, a decrease in flow would decrease the capital and operating costs of the treatment system. The shift to lower water use should come gradually over the next 12 months.

• Solid Wastes. At present, the tannery has useful disposal of most of its solid wastes in the form of fleshings, trimmings, and leather shavings. With the introduction of the pretreatment system, a new source of solid waste -- about 1000 kg of solid sludge containing 120-150 kg of nitrogen -- will be generated. This organic nitrogen and the other materials in the sludge have been proven to be very valuable as fertilizers and soil conditioners. The implementation of the primary treatment system over the next 6-18 months will not only clean the liquid tannery's wastes, but result in an environmental benefit to the community.

• Pretreatment. The implementation of the pretreatment system will require design data and engineering and construction of the system. Total time to completion should be 12-15 months.

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Reposting permission requested from Andrew Martin, RCG/Hagler Bailly Inc., on 11/17/99.  Betsy Marcotte 703-312-8684 - project contact.