U

Flowing rinse tank

Rinsewater out to sewer, Q1

Work

FIGURE 9.3 Modified method of double drag-out for partial reuse. (Adapted from U.S. EPA, Meeting Hazardous Waste Requirements for Metal Finishers, Report EPA/625/4-87/018, U.S. Environmental Protection Agency, Cincinnati, OH, 1987.)

TABLE 9.13

Chemical Costs of Treatment and Disposal in 2007 USD

Chemical Cost (2007 USD/kg)a

Pollutant Treatmentb Disposalc

Nickel 2.73 6.70

Copper 2.73 6.70

Cyanide 17.63 NA

Source: U.S. EPA, Meeting Hazardous Waste Requirements for Metal Finishers, Report

EPA/625/4-87/018, U.S. Environmental Protection Agency, Cincinnati, OH, 1987. a Costs were converted from 1979 USD to 2007 USD using U.S. ACE Yearly Average Cost

Index for Utilities.10 b Cost of NaOH @ USD1.00/kg and NaOCL @ USD2.35/kg. c Cost of disposal @ USD1.84 /kg of sludge (USD400/drum) @ 30% solids content.

generation of cyanide and copper waste by about 50% by eliminating cyanide cleaners and utilizing pour-back of copper cyanide solution; generation of nickel waste can be reduced 90% by pour-back of the nickel solution. Reducing wasted salts also allows a reduced rinsewater flow rate, thus saving water and sewer use fees. The chemical costs of treatment are given in Table 9.13 and the annual replacement costs of chemicals are given in Figure 9.4. Calculations of the annual dollar savings are shown in Table 9.14. All costs have been converted into 2007 USD using U.S. ACE Yearly Average Cost Index for Utilities.10

9.4 POLLUTANT REMOVABILTY

This section reviews the technologies currently available and used to remove or recover pollutants from the wastewater generated in the metal finishing industry.5-711 Treatment options are presented

Nickel

Copper

Nickel

Copper

Cyanide

8000

6000

la 4000

l 2000

Pollutants discharged (kg/d)

FIGURE 9.4 Annual replacement cost of chemicals in 2007 USD. (Adapted from U.S. EPA, Meeting Hazardous Waste Requirements for Metal Finishers, Report EPA/625/4-87/018, U.S. Environmental Protection Agency, Cincinnati, OH, 1987.)

Cyanide u n n

8000

6000

la 4000

l 2000

Pollutants discharged (kg/d)

FIGURE 9.4 Annual replacement cost of chemicals in 2007 USD. (Adapted from U.S. EPA, Meeting Hazardous Waste Requirements for Metal Finishers, Report EPA/625/4-87/018, U.S. Environmental Protection Agency, Cincinnati, OH, 1987.)

TABLE 9.14

Illustration of Annual Cost Savings for Waste Reduction

Item Cost Savinga (2007 USD)

Process chemical savings'5

Copper 2425

Cyanide 485

Nickel 7760 Treatment chemical savingc

Copper 310

Cyanide 2000

Nickel 700 Reduced treatment sludge disposalc

Copper 760

Cyanide 0

Nickel 1700

Water and sewer use fee reductiond 4360

Total annual savings 20,500

Source: U.S. EPA, Meeting Hazardous Waste Requirements for Metal Finishers, Report

EPA/625/4-87/018, U.S. Environmental Protection Agency, Cincinnati, OH, 1987. a Costs were converted from 1979 USD to 2007 USD using U.S. ACE Yearly average Cost

Index for Utilities.10 b From Figure 9.4. c From Table 9.12 and Figure 9.4. d USD 0.77/m3.

for each subcategory within the metal finishing industry. Table 9.15 lists the treatment techniques available for treating wastes from each subcategory.

9.4.1 Common Metals

The treatment methods used to treat wastes within the common metals subcategory fall into two groupings:

1. Recovery techniques

2. Solids removal techniques.

Recovery techniques are treatment methods used for the purpose of recovering or regenerating process constituents, which would otherwise be discarded. Included in this group are5-7

1. Evaporation

2. Ion exchange

3. Electrolytic recovery

4. Electrodialysis

5. Reverse osmosis.

Solids removal techniques are employed to remove metals and other pollutants from process wastewaters to make these waters suitable for reuse or discharge. These methods include5-7

1. Hydroxide and sulfide precipitation

2. Sedimentation

TABLE 9.15

Treatment Methods in Current Use or Available for Use in the Metal Finishing Industry

Common metals

Hydroxide followed by sedimentation 103

Hydroxide followed by sedimentation and filtration 30

Evaporation (metal recovery, bath concentrates, rinse waters) 41

Ion exchange 63

Electrolytic recovery 11

Electrodialysis 3

Reverse osmosis 8

Post-adsorption 0

Insoluble starch xanthate 2

Sulfide precipitation 3

Flotation 29

Membrane flotation 7

Precious metals

Evaporation 1

Ion exchange NR

Electrolytic recovery NR

Complexed metals

High-pH precipitation with sedimentation NR

High-pH precipitation with sedimentation NR

Hexavalent chromium

Chemical chrome reduction 343

Electrochemical chromium reduction 2

Electrochemical chromium regeneration 0

Advanced electrodialysis NR

Evaporation 1

Ion exchange 1

Cyanide

Oxidation by chlorine 201

Oxidation by ozone 2

Oxidation by ozone with UV radiation NR

Oxidation by hydrogen peroxide 3

Electrochemical cyanide oxidation 4

Chemical precipitation 3

Reverse osmosis NR

Evaporation NR

Oils (segregated)

Emulsion breaking 28

Skimming 94

Emulsion breaking and skimming NR

Ultrafiltration 20

Reverse osmosis 3

Carbon adsorption 10

Coalescing 3

Flotation 29

TABLE 9.15 (continued)

Subcategory/Technology

Centrifugation Integrated adsorption Resin adsorption Ozonation Chemical oxidation Aerobic decomposition Thermal emulsion breaking Solvent waste Segregation Contract handling

Sludges

Gravity thickening Pressure filtration Vacuum filtration Centrifugation Sludge bed drying

In-process control Flow reduction

Number of Plants

NR NR

78 66 68 55 77

Source: U.S. EPA, Treatability Manual, Volume II, Industrial Descriptions, Report EPA-600/2-82-001b, U.S. Environmental Protection Agency, Washington, DC, September 1981. Note: NR, not reported.

3. Diatomaceous earth filtration

4. Membrane filtration

5. Granular bed filtration

6. Peat adsorption

7. Insoluble starch xanthate treatment

8. Flotation.

Three treatment options are used in treating common metals wastes:

• Option 1 system consists of hydroxide precipitation12 followed by sedimentation.13 This system accomplishes the end-of-pipe metals removal from all common metals-bearing wastewater streams that are present at a facility. The recovery of precious metals, the reduction of hexavalent chromium, the removal of oily wastes, and the destruction of cyanide must be accomplished prior to common metals removal.

• Option 2 system is identical to the Option 1 treatment system with the addition of filtration devices14 after the primary solids removal devices. The purpose of these filtration units is to remove suspended solids such as metal hydroxides that do not settle out in the clarifiers. The filters also act as a safeguard against pollutant discharge should an upset occur in the sedimentation device. Filtration techniques applicable to Option 2 systems are diatomaceous earth and granular bed filtration.1516

• Option 3 treatment system for common metal wastes consists of the Option 2 end-of-pipe treatment system plus the addition of in-plant controls for lead and cadmium. In-plant controls would include evaporative recovery, ion exchange, and recovery rinses.16

In addition to these three treatments, there are several alternative treatment technologies applicable to the treatment of common metals wastes. These technologies include electrolytic recovery, electrodialysis, reverse osmosis, peat adsorption, insoluble starch xanthate treatment, sulfide precipitation, flotation, and membrane filtration.1516

9.4.2 Precious Metals

Precious metal wastes can be treated using the same treatment alternatives as those described for treatment of common metal wastes. However, due to the intrinsic value of precious metals, every effort should be made to recover them. The treatment alternatives recommended for precious metal wastes are the recovery techniques—evaporation, ion exchange, and electrolytic recovery.

9.4.3 Complexed Metal Wastes

Complexed metal wastes within the metal finishing industry are a product of electroless plating, immersion plating, etching, and printed circuit board manufacture. The metals in these waste streams are tied up or complexed by particular complexing agents whose function is to prevent metals from coming out of solution. This counteracts the technique employed by most conventional solids removal methods. Therefore, segregated treatment of these wastes is necessary. The treatment method well suited to treating complexed metal wastes is high-pH precipitation. An alternative method is membrane filtration17 that is primarily used in place of sedimentation for solids removal.

9.4.4 Hexavalent Chromium

Hexavalent chromium-bearing wastewaters are produced in the metal finishing industry in chromium electroplating, in chromate conversion coatings, in etching with chromic acid, and in metal finishing operations carried out on chromium as a basis material.

The selected treatment option involves the reduction of hexavalent chromium to trivalent chromium either chemically or electrochemically. The reduced chromium can then be removed using a conventional precipitation-solids removal system. Alternative hexavalent chromium treatment techniques include chromium regeneration, electrodialysis, evaporation, and ion exchange.16

9.4.5 Cyanide

Cyanides are introduced as metal salts for plating and conversion coating or as active components in plating and cleaning baths. Cyanide is generally destroyed by oxidation. Chlorine, in either elemental or hypochlorate form, is the primary oxidation agent used in industrial waste treatment to destroy cyanide. Alternative treatment techniques for the destruction of cyanide include oxidation by ozone, ozone with ultraviolet (UV) radiation (oxyphotolysis), hydrogen peroxide, and electrolytic oxidation.18 Treatment techniques, which remove cyanide but do not destroy it, include chemical precipitation, reverse osmosis, and evaporation.16,18

9.4.6 Oils

Oily wastes and toxic organics that combine with the oils during manufacturing include process coolants and lubricants, wastes from cleaning operations, wastes from painting processes, and machinery lubricants. Oily wastes are generally of three types: free oils, emulsified or water-soluble oils, and greases. Oil removal techniques commonly employed in the metal finishing industry include skimming, coalescing, emulsion breaking, flotation, centrifugation, ultrafiltration, reverse osmosis, carbon adsorption, and aerobic decomposition.18-20

Because emulsified oils and processes that emulsify oils are used extensively in the metal finishing industry, the exclusive occurrence of free oils is nearly nonexistent.

Treatment of oily wastes can be carried out most efficiently if oils are segregated from other wastes and treated separately. Segregated oily wastes originate in the manufacturing areas and are collected in holding tanks and sumps. Systems for treating segregated oily wastes consist of separation of oily wastes from the water. If oily wastes are emulsified, techniques such as emulsion breaking or dissolved air flotation (DAF)21 with the addition of chemicals are necessary to remove oil. Once the oil-water emulsion is broken, the oily waste is physically separated from the water by decantation or skimming. After the oil-water separation has been carried out, the water is sent to the precipitation/ sedimentation unit used for metals removal. There are three options for oily waste removal:

• Option 1 system incorporates the emulsion breaking process followed by surface skimming (gravity separation is adequate if only free oils are present).

• Option 2 system consists of the Option 1 system followed by ultrafiltration.

• Option 3 treatment system consists of the Option 2 system with the addition of either carbon adsorption or reverse osmosis.

In addition to these three treatment options, several alternative technologies are applicable to the treatment of oily wastewater. These include coalescing, flotation, centrifugation, integrated adsorption, resin adsorption, ozonation, chemical oxidation, aerobic decomposition, and thermal emulsion breaking.18-20

9.4.7 Solvents

Spent degreasing solvents should be segregated from other process fluids to maximize the value of the solvents, to preclude contamination of other segregated wastes, and to prevent the discharge of priority pollutants to any wastewaters. This segregation may be accomplished by providing and identifying the necessary storage containers, establishing clear disposal procedures, training personnel in the use of these techniques, and checking periodically to ensure that proper segregation is occurring. Segregated waste solvents are appropriate for on-site solvent recovery or may be contract hauled for disposal or reclamation.

Alkaline cleaning is the most feasible substitute for solvent degreasing. The major advantage of alkaline cleaning over solvent degreasing is the elimination or reduction in the quantity of priority pollutants being discharged. Major disadvantages include high energy consumption and the tendency to dilute oils removed and to discharge these oils as well as the cleaning additive.

9.5 TREATMENT TECHNOLOGIES

9.5.1 Neutralization

One technique used in a number of facilities that utilize molten salt for metal surface treatment prior to pickling is to take advantage of the alkaline values generated in the molten salt bath in treating other wastes generated in the plant. When the bath is determined to be spent, it is in many instances manifested, hauled off-site, and land disposed. One technique is to take the solidified spent molten salt (molten salt is sold at ambient temperatures) and circulate acidic wastes generated in the facility over the material prior to entry into the waste treatment system. This in effect neutralizes the acid wastes and eliminates the requirements of manifesting and land disposal.

9.5.2 Cyanide-Containing Wastes

There are eight methods applicable to the treatment of cyanide wastes for metal finishing5,22:

1. Alkaline chlorination

2. Electrolytic decomposition

3. Ozonation

4. UV/Ozonation

5. Hydrogen peroxide

6. Thermal oxidation

7. Acidification and acid hydrolysis

8. Ferrous sulfate precipitation.

Alkaline chlorination is the method most widely applied in the metal finishing industry. A schematic for cyanide reduction via alkaline chlorination is provided in Figure 9.5. This technology is generally applicable to wastes containing less than 1% cyanide, generally present as free cyanide. It is conducted in two stages; the first stage is operated at a pH greater than 10 and the second stage is operated with a pH in the range of 7.5-8. Alkaline chlorination is performed using sodium hypochlo-rite and chlorine.

Electrolytic decomposition technology was applied to cyanide-containing wastes in the early part of this century. It fell from favor as alkaline chlorination came into use at large-scale facilities. However, as wastes become more concentrated, this technology may find more widespread application in the future. The reason is that it is applicable to wastes containing cyanide in excess of 1%. The basis of this technology is electrolytic decomposition of the cyanide compounds at an elevated temperature (200°F) to yield nitrogen, CO2, ammonia, and amines (Figure 9.6).

Ozonation treatment can be used to oxidize cyanide, thereby reducing the concentration of cyanide in wastewater. Ozone, with an electrode potential of +1.24 V in alkaline solutions, is one of the most powerful oxidizing agents known. Cyanide oxidation with ozone is a two-step reaction similar to alkaline chlorination.22 Cyanide is oxidized to cyanate, with ozone reduced to oxygen as per the following equation:

NaCN + Cl2 CNCl + NaCl CNCl + 2NaOH ->■ NaCNO +

NaCN

Cyanide bearing waste

NaOCl or

NaOCl or

NaCNO

NaCl

FIGURE 9.5 Cyanide reduction via alkaline chlorination. (Adapted from U.S. EPA, Meeting Hazardous Waste Requirements for Metal Finishers, Report EPA/625/4-87/018, U.S. Environmental Protection Agency, Cincinnati, OH, 1987.)

2NaCNO + 3Cl2 + 4NaOH

FIGURE 9.6 Cyanide reduction via electrolytic decomposition. (Adapted from U.S. EPA, Meeting Hazardous Waste Requirements for Metal Finishers, Report EPA/625/4-87/018, U.S. Environmental Protection Agency, Cincinnati, OH, 1987.)

Then cyanate is hydrolyzed, in the presence of excess ozone, to bicarbonate and nitrogen and oxidized as per the following reaction:

The reaction time for complete cyanide oxidation is rapid in a reactor system with 10-30 min retention times being typical. The second-stage reaction is much slower than the first-stage reaction. The reaction is typically carried out in the pH range of 10-12 where the reaction rate is relatively constant. Temperature does not influence the reaction rate significantly.

One interesting variation on ozonation technology is augmentation with UV radiation. This is a technology that has been applied to wastes in the coke by-product manufacturing industry. A significant development has been made that has resulted in significantly less ozone consumption through the use of UV radiation. UV absorption has the following effects:

• Ozone and cyanide are raised to higher energy status

• Free radicals are formed

• More rapid reaction

• Less ozone is required.

Cyanide reduction with hydrogen peroxide is effective in reducing cyanide. It has been applied on a less frequent basis within this industry, due to the fact that there are high operating costs associated with hydrogen peroxide generation. The reduction of cyanide with peroxide occurs in two steps and yields CO2 and ammonia:

Thermal oxidation is another alternative for destroying cyanide. Thermal destruction of cyanide can be accomplished through either high-temperature hydrolysis or combustion. At temperatures between 140°C and 200°C and a pH of 8, cyanide hydrolyzes quite rapidly to produce formate and ammonia.23 Pressures up to 100 bar are required, but the process can effectively treat waste streams over a wide concentration range and is applicable to both rinsewater and concentrated solutions22:

In the presence of nitrates, formate and ammonia can be destroyed in another reactor at 150°C, according to the following equations:

Direct acidification of cyanide waste streams was once a relatively common treatment. Cyanide is acidified in a sealed reactor that is vented to the atmosphere through an air emission control system. Cyanide is converted to gaseous hydrogen cyanide, treated, vented, and dispersed.

Acid hydrolysis of cyanates is still commonly used, following a first-stage cyanide oxidation process. At pH 2 the reaction proceeds rapidly, while at pH 7 cyanate may remain stable for weeks.24 This treatment process requires specially designed reactors to assure that HCN is properly vented and controlled. The hydrolysis mechanisms are as follows22:

In acid medium

In strongly alkaline medium

Each of the technologies described above is effective in treating wastes containing free cyanides, that is, cyanides present as CN in solution. There are instances in metal finishing facilities where complex cyanides are present in wastes. The most common are complexes of iron, nickel, and zinc. A technology that has been applied to remove complex cyanides from aqueous wastes is ferrous sulfate precipitation. The technology involves a two-stage operation in which ferrous sulfate is first added at a pH of 9 to complex any trace amounts of free cyanide. In the second stage, the complex cyanides are precipitated through the addition of ferrous sulfate or ferric chloride at a pH in the range of 2-4.5

9.5.3 Chromium-Containing Wastes

There are three treatment methods applicable to wastes containing hexavalent chromium. Wastes containing trivalent chromium can be treated using chemical precipitation and sedimentation, which is discussed below. The three methods applicable to treatment of hexavalent chromium are

1. Sulfur dioxide

2. Sodium metabisulfite

3. Ferrous sulfate.

Hexavalent chromium reduction through the use of sulfur dioxide and sodium metabisulfite has found the widest application in the metal finishing industry. It is not truly a treatment step, but a conversion process in which the hexavalent chromium is converted to trivalent chromium. The hexavalent chromium is reduced through the addition of the reductant at a pH in the range of 2.5-3 with a retention time of approximately 30-40 min (Figure 9.7).

Ferrous sulfate has not been as widely applied. However, it is particularly applicable in facilities where ferrous sulfate is produced as part of the process, or is readily available. The basis for this

pH 2.5-3.0 30 min retention

pH 2.5-3.0 30 min retention

FIGURE 9.7 Hexavalent chromium reduction. (Adapted from U.S. EPA, Meeting Hazardous Waste Requirements for Metal Finishers, Report EPA/625/4-87/018, U.S. Environmental Protection Agency, Cincinnati, OH, 1987.)

technology is that the hexavalent chromium is reduced to trivalent chromium and the ferrous iron is oxidized to ferric iron.

9.5.4 Arsenic- and Selenium-Containing Wastes

It may be necessary to segregate waste streams containing elevated concentrations of arsenic and selenium, especially waste streams with concentrations in excess of 1mg/L for these pollutants. Arsenic and selenium form anionic acids in solution (most other metals act as cations) and require special preliminary treatment prior to conventional metals treatment. Lime, a source of calcium ions, is effective in reducing arsenic and selenium concentrations when the initial concentration is below 1mg/L. However, preliminary treatment with sodium sulfide at a low pH (i.e., 1-3) may be required for waste streams with concentrations in excess of 1mg/L.22 The sulfide reacts with the anionic acids to form insoluble sulfides that are readily separated by means of filtration.

9.5.4.1 Chemical Precipitation and Sedimentation

The most important technology in metals treatment is chemical precipitation and sedimentation. It is accomplished through the addition of a chemical reagent to form metal precipitants, which are then removed as solids in a sedimentation step. The options available to a facility as precipitation reagents are lime Ca(OH)2, caustic NaOH, carbonate CaCO3 and Na2CO3, sulfide NaHS and FeS, and sodium borohydride NaBH4. The advantages and disadvantages of these reagents are summarized below22:

1. Lime

• Least expensive precipitation reagent

• Generates highest sludge volume

• Sludges generally cannot be sold to smelter/refiners.

2. Caustic

• More expensive than lime

• Generates smaller volume of sludge

• Sludges can be sold to smelter/refiners.

3. Carbonates

• Applicable for metals where solubility within a pH range is not sufficient to meet treatment standards.

Lime is the least expensive reagent; however, it generates the highest volume of residue. It also generates a residue which cannot be resold to smelters and refiners for reclaiming because of the presence of the calcium ion. Caustic is more expensive than lime; however, it generates a smaller volume of residue. One key advantage of caustic is that the resulting residues can be readily reclaimed. Carbonates are particularly appropriate for metals where solubility within a pH range is not sufficient to meet a given set of treatment standards. The sulfides offer the benefit of achieving effective treatment at lower concentrations due to lower solubilities of the metal sulfides. Sodium borohydride has application where small volumes of sludge that are suitable for reclamation are desired.

It is appropriate to look at reagent use in the context of the current regulatory framework under HSWA. Historically, lime has been the reagent of choice. It was relatively inexpensive and simple to handle. The phrase "lime and settle" refers to the application of lime precipitation and sedimentation technology. In the 1970s, new designs made use of caustic as the precipitation reagent because of the reduction in residue volume realized and the ability for reclamation. In the 1980s, a return to lime and the use of combined reagent techniques have come into use.

One obvious question is why return to lime as a treatment reagent, given that caustic results in a smaller residue volume and a waste that can undergo reclamation? The answer lies in the three points that result from the implementation of the HSWA hierarchy. As source reduction and material reuse and recovery techniques are applied, facilities will be generating

• More concentrated wastes

• Wastes with a varied array of constituents

• Wastes with a greater degree of complexation.

9.5.4.2 Complexation

Complexation is a phenomenon that involves a coordinate bond between a central atom (the metal) and a ligand (the anions). In a coordinate bond, the electron pair is shared between the metal and the ligand. A complex containing one coordinate bond is referred to as a monodentate complex. Multiple coordinate bonds are characteristic of polydentate complexes. Polydentate complexes are also referred to as chelates. An example of a monodentate-forming ligand is ammonia. Examples of chelates are oxylates (bidentates) and EDTA (hexadentates).

The reason for the return to lime is due to the calcium ion present in lime. The calcium ion present in solution through the addition of lime is very effective in competing with the ligand for the metal ion. The sodium ion contributed by caustic is not effective. As such, lime dramatically reduces complexation and is more effective in treating complexed wastes. The term "high-lime treatment" has been applied in cases where excess calcium ions are introduced into solution. This is accomplished through the addition of lime to raise the pH to approximately 11.5 or through the addition of calcium chloride (which has a greater solubility than lime).

The use of combinations of precipitation reagents has been most effective in taking advantage of the attributes of caustic as well as the advantages of lime. As an example, a system may use caustic in a first stage to make a coarse pH adjustment followed by the addition of lime to make a fine adjustment. This achieves an overall reduction in the sludge volume through the use of the caustic and more effective metal removal through the use of lime. Sulfide reagents are used in a similar fashion in combination with caustic or lime to provide additional metal removal, due to the lower solubility of the metal sulfides. Sulfides are also applicable to wastes containing elevated concentrations (i.e., in excess of 2mg/L) of selenium and arsenic compounds.22

9.5.5 Other Metals Wastes

There are three techniques applicable to managing solids generated in metal finishing. These are

1. Dewatering

2. Stabilization

3. Incineration.

There are four dewatering techniques that have been applied in metal processing. The most widely applied techniques are vacuum and belt filtration.25 They have a higher relative capital cost but generally have a lower relative operating cost. Plate and frame filter presses have experienced less widespread application. Belt filters generally have a lower relative capital cost and have higher relative operating costs. The higher operating costs are due to the fact that the units are more labor intensive. Centrifuges25 have been applied in specific instances, but are more difficult to operate when a widely varying mix of wastes is treated.

Experience has shown that companies are most successful in applying a dewatering technique that they have successfully designed and operated in similar applications within the company. As an example, many companies operate plate and frame filter presses as a part of metal manufacturing operations. The knowledge gained in metal processing had been successfully transferred to treatment of metal finishing wastes.

There are six stabilization techniques currently available; however, only two of them have found widespread application. These are cementation and stabilization through the addition of lime and fly ash.25,26 There is currently developmental work being undertaken to make use of bitumen, paraffin, and polymeric materials to reduce the degree to which metals can be taken into solution. Encapsulation with inert materials is also under development.

9.6 COSTS

The investment, operation and maintenance,2728 and energy costs for the application of control technologies to the wastewaters of the metal finishing industry have been analyzed. These costs were developed to reflect the conventional use of technologies in this industry. The detailed presentation of the cost methodology and cost data is available in a U.S. EPA publication.6 The available industry-specific cost information is characterized below.

9.6.1 Typical Treatment Options

Many waste treatment options are available.28-32 Only several unit operation/unit process configurations have been analyzed for the cost of application to the wastewater of this industry. The components included in these configurations are

• Option 1: Emulsion breaking and oil separation by skimming, cyanide oxidation, chromium reduction, chemical precipitation and sedimentation, and sludge drying beds.

• Option 2: All of Option 1 plus multimedia filtration.

• Option 3: All of Option 2 plus ultrafiltration and carbon adsorption for oily waste, zero discharge of any processes using either cadmium or lead by using an evaporative system.

The flow diagram for suggested Option 1 is shown in Figure 9.8. The flow diagram for the other options would be similar.

9.6.2 Costs

The cost estimates prepared for the treatment technologies commonly used in this industry are described below in a brief fashion. More details of the factors considered in the cost analysis are available in the source.6

Oily raw waste

Raw waste

Raw waste

Raw waste

Raw waste

Emulsion breaking

Skimmed oil

Cyanide oxidation

Chromium reduction

Common metals t

Hydroxide precipitation

Clarifier y

Treated effluent

Complexed metals

Hydroxide precipitation

Sludge

Sludge

Clarifier

Sludge drying beds

Treated effluent

Contractor removal

FIGURE 9.8 Metal finishing wastewater treatment flow diagram. (Adapted from U.S. EPA, Treatability Manual, Volume II Industrial Descriptions, Report EPA-600/2-82-001b, U.S. Environmental Protection Agency, Washington, DC, September 1981.)

9.6.2.1 Emulsion Breaking and Oil Separation

Method: Emulsion broken by mixing oily waste with alum and a chemical emulsion breaker, followed by gravity oil separation in a tank.

System component: A small mixing tank, two chemical feed tanks, a mixer, and a large tank equipped with an oil skimmer and a sludge pump. The mixing tank has a retention time of 15min and the oil skimming tank has a retention time of 2.5 h.

9.6.2.2 Cyanide Oxidation

Method: Cyanide is destroyed by reaction with sodium hypochlorite under alkaline conditions. System component: Reaction tanks, a reagent storage and feed system, mixers, sensors, and controls: two identical reaction tanks sized as the above-ground cylindrical tank with a retention time of 4 h. Chemical storage consists of covered concrete tanks to store 60 d supply of sodium hypochlorite and 90 d supply of sodium hydroxide.

9.6.2.3 Chromium Reduction

Method: Chemical reduction of hexavalent chromium by sulfur dioxide under acid conditions for the continuous operating system and by sodium bisulfite under acid conditions for the batch operating system. The reduced trivalent form of chromium is subsequently removed by precipitation as the hydroxide.

System component: Reaction tanks, a reagent storage and feed system, mixers, sensors, and controls for continuous chromium reduction. A single above-ground concrete tank with retention time of 45 min is provided. For batch operation, dual above-ground concrete tanks with 4 h retention time are provided.

9.6.2.4 Lime Precipitation and Sedimentation

Method: Chemical precipitation of dissolved and complexed metals by reaction with lime and subsequent removal of the precipitated solids by gravity settling in a clarifier. Alum and polyelectrolyte are added for coagulation and flocculation.

System component: The continuous treatment system includes reagent storage and feed equipment, a mix tank for reagent feed addition, sensors and controls, and clarification basin with associated sludge rakes and pumps. Lime is fed as 30% lime slurry prepared by using hydrated lime. The mix tank is sized for a retention time of 45 min and the clarifier is sized for hydraulic loading of 1360 L/m2 and a retention time of 4h. Batch treatment includes dual reaction-settling tanks sized for 8h retention time and sludge pumps.

9.6.2.5 Sludge Drying Beds

Method: Sludge dewatered by means of gravity drainage and natural evaporation. System component: Beds of highly permeable gravel and sand underlain by drain pipes.29

9.6.2.6 Multimedia Filter

Method: Polishing treatment after chemical precipitation and sedimentation by filtration through a bed of particles of several distinct size ranges.

System component: Filter beds, media, backwash mechanism, pumps, and controls. The filter beds were sized for hydraulic loading of 81 L/min/m2 (2gpm/ft2).

9.6.2.7 Ultrafiltration

Method: The process used for oily waste stream after emulsion breaking-gravity oil separation. System component: Filter modules sized on the basis of hydraulic loading of 1 L/min/m2.

9.6.2.8 Carbon Adsorption

Method: A packed-bed throwaway system to remove organic pollutants from oily waste stream. System component: A contactor system, and a pump station designed for a contact time of 30 min and hydraulic loading of 162 L/min/m2 (4gpm/ft2).

Unit costs shown in Table 9.16 are for the complete treatment options described previously. Unit costs are computed for a model plant where flows are contributed by several waste streams as follows:

• 4% cyanide waste stream

• 9% chromium waste stream

TABLE 9.16

Total Annual Unit Cost (USD/m3 in 2007 Dollars)3

Option 1 Continuous

2.10

Batch

14.28 5.04

2.10

Option 2 Continuous

Batch

3.78

Option 3

Continuous

Batch

28.35 10.29

4.41

Source: U.S. EPA, Treatability Manual, Volume IIIndustrial Descriptions, Report EPA-600/2-82-001b, U.S. Environmental Protection Agency, Washington, DC, September 1981. a Costs were converted from 1979 USD to 2007 USD using U.S. ACE Yearly Average Cost Index for Utilities.9

• 52.5% common metals stream

9.7 U.S. CODE OF FEDERAL REGULATIONS FOR METAL FINISHING EFFLUENT DISCHARGE MANAGEMENT

This section introduces the U.S. Code of Federal Regulations (CFR) Title 40, Part 433 (40 CFR part 433) for effluent discharge management of metal finishing point source category.

The topics introduced in this section include (a) the applicability, description of the metal finishing point source category; (b) the monitoring requirements of metal finishing effluent discharges; (c) the effluent limitations representing the degree of effluent reduction attainable by applying the best practicable control technology currently available (BPT); (d) the effluent limitations representing the degree of effluent reduction attainable by applying the best available technology economically achievable (BAT); (e) the pretreatment standards for existing sources (PSES); (f) the new source performance standards (NSPS); and (g) the pretreatment standards for new sources (PSNS).

9.7.1 Applicability, Description of the Metal Finishing Point Source Category

Except as noted in the next two paragraphs of this section, the provisions of this subpart apply to plants that perform any of the following six metal finishing operations on any basis material: electroplating, electroless plating, anodizing, coating (chromating, phosphating, and coloring), chemical etching and milling, and printed circuit board manufacture. If any of those six operations are present, then this part applies to discharges from those operations and also to discharges from any of the following 40 process operations: cleaning, machining, grinding, polishing, tumbling, burnishing, impact deformation, pressure deformation, shearing, heat treating, thermal cutting, welding, brazing, soldering, flame spraying, sand blasting, other abrasive jet machining, electric discharge machining, electrochemical machining, electron beam machining, laser beam machining, plasma arc machining, ultrasonic machining, sintering, laminating, hot dip coating, sputtering, vapor plating, thermal infusion, salt bath descaling, solvent degreasing, paint stripping, painting, electrostatic painting, electropainting, vacuum metalizing, assembly, calibration, testing, and mechanical plating.

In some cases, effluent limitations and standards for the following industrial categories may be effective and applicable to wastewater discharges from the metal finishing operations listed above. In such cases, the 40 CFR part 433 limits shall not apply and the following regulations shall apply:

• Nonferrous metal smelting and refining (40 CFR part 421)

• Porcelain enameling (40 CFR part 466)

• Battery manufacturing (40 CFR part 461)

• Metal casting foundries (40 CFR part 464)

• Aluminum forming (40 CFR part 467)

• Plastic molding and forming (40 CFR part 463)

• Nonferrous forming (40 CFR part 471)

• Electrical and electronic components (40 CFR part 469).

The 40 CFR part 433 does not apply to (a) metallic platemaking and gravure cylinder preparation conducted within or for printing and publishing facilities and (b) existing indirect discharging job shops and independent printed circuit board manufacturers which are covered by 40 CFR part 413.

9.7.2 Monitoring Requirements of Metal Finishing Effluent Discharges

In lieu of requiring monitoring for total toxic organics (TTO), the permitting authority (or, in the case of indirect dischargers, the control authority) may allow dischargers to make the following certification statement:

Based on my inquiry of the person or persons directly responsible for managing compliance with the permit limitation [or pretreatment standard] for total toxic organics (TTO), I certify that, to the best of my knowledge and belief, no dumping of concentrated toxic organics into the wastewaters has occurred since filing of the last discharge monitoring report. I further certify that this facility is implementing the toxic organic management plan submitted to the permitting [or control] authority.

For direct dischargers, this statement is to be included as a "comment" on the Discharge Monitoring Report required by 40 CFR 122.44(i), formerly 40 CFR 122.62(i).

For indirect dischargers, the statement is to be included as a comment to the periodic reports required by 40 CFR 403.12(e). If monitoring is necessary to measure compliance with the TTO standard, the industrial discharger need analyze for only those pollutants that would reasonably be expected to be present.

In requesting the certification alternative, a discharger shall submit a solvent management plan that specifies to the satisfaction of the permitting authority (or, in the case of indirect dischargers, the control authority) the toxic organic compounds used; the method of disposal used instead of dumping, such as reclamation, contract hauling, or incineration; and procedures for ensuring that toxic organics do not routinely spill or leak into the wastewater. For direct dischargers, the permitting authority shall incorporate the plan as a provision of the permit.

Self-monitoring for cyanide must be conducted after cyanide treatment and before dilution with other streams. Alternatively, samples may be taken of the final effluent, if the plant limitations are adjusted based on the dilution ratio of the cyanide waste stream flow to the effluent flow.

9.7.3 Effluent Limitations Based on the BPT

Except as specifically provided in the U.S. CFR, any existing point source subject to the 40 CFR part 433 must achieve the effluent limitations shown in Table 9.17, which represents the degree of

TABLE 9.17

U.S. BPT Effluent Limitations for the Metal Finishing Point Source Category

Pollutant or Maximum for Any 1 Day Monthly Average shall not Exceed

Pollutant Property (mg/L Except for pH) (mg/L Except for pH)

TABLE 9.17

U.S. BPT Effluent Limitations for the Metal Finishing Point Source Category

Pollutant or Maximum for Any 1 Day Monthly Average shall not Exceed

Pollutant Property (mg/L Except for pH) (mg/L Except for pH)

Cadmium (T)

0.69

0.26

Chromium (T)

2.77

1.71

Copper (T)

3.38

2.07

Lead (T)

0.69

0.43

Nickel (T)

3.98

2.38

Silver (T)

0.43

0.24

Zinc (T)

2.61

1.48

Cyanide (T)

1.20

0.65

TTO

2.13

Oil and grease

52

26

TSS

60

31

PH

6-9

6-9

Source: U.S. EPA, Code of Federal Regulations, Metal Finishing Point Source Category, Title 40, Volume 27, Part 433, U.S. Environmental Protection Agency, Washington, DC, Revised as of July 1, 2003.

Source: U.S. EPA, Code of Federal Regulations, Metal Finishing Point Source Category, Title 40, Volume 27, Part 433, U.S. Environmental Protection Agency, Washington, DC, Revised as of July 1, 2003.

TABLE 9.18

Alternative U.S. BPT Effluent Limitations on Cyanide (A) for the Metal Finishing Point Source Category

Pollutant or Pollutant Property Maximum for Any 1 Day (mg/L) Monthly Average shall not Exceed (mg/L)

Source: U.S. EPA, Code of Federal Regulations, Metal Finishing Point Source Category, Title 40, Volume 27, Part 433, U.S. Environmental Protection Agency, Washington, DC, Revised as of July 1, 2003.

effluent reduction attainable by applying the BPT. Alternatively, for metal finishing industrial facilities with cyanide treatment, and upon agreement between a source subject to those limits and the pollution control authority, the amenable cyanide limit shown in Table 9.18 may apply in place of the total cyanide limit specified in Table 9.17. No user subject to the provisions of these regulations shall augment the use of process wastewater or otherwise dilute the wastewater as a partial or total substitute for adequate treatment to achieve compliance with this limitation.

9.7.4 Effluent Limitations Based on the BAT

Except as specifically provided in the U.S. CFR, any existing point source subject to this subpart must achieve the effluent limitations shown in Table 9.19 which represents the degree of effluent reduction attainable by applying the BAT. Alternatively, for the metal finishing industrial facilities with cyanide treatment, and upon agreement between a source subject to those limits and the pollution control authority, the amenable cyanide limit shown in Table 9.20 may apply in place of the total cyanide limit specified in Table 9.19. No user subject to the provisions of these regulations shall augment the use of process wastewater or otherwise dilute the wastewater as a partial or total substitute for adequate treatment to achieve compliance with this limitation.

9.7.5 Pretreatment Standards for Existing Sources

Except as specifically provided in the U.S. CFR, any existing source subject to this 40 CFR part 433 that introduces pollutants into a publicly owned treatment works must also comply with 40 CFR

TABLE 9.19

U.S. BAT Effluent Limitations for the Metal Finishing Point Source Category

Pollutant or Maximum for Any 1 Day Monthly Average shall not Exceed

Pollutant Property (mg/L Except for pH) (mg/L Except for pH)

TABLE 9.19

U.S. BAT Effluent Limitations for the Metal Finishing Point Source Category

Pollutant or Maximum for Any 1 Day Monthly Average shall not Exceed

Pollutant Property (mg/L Except for pH) (mg/L Except for pH)

Cadmium (T)

G.69

G.26

Chromium (T)

2.77

1.71

Copper (T)

3.38

2.G7

Lead (T)

G.69

G.43

Nickel (T)

3.98

2.38

Silver (T)

G.43

G.24

Zinc (T)

2.61

1.48

Cyanide (T)

1.2G

G.65

TTO

2.13

Source: U.S. EPA, Code of Federal Regulations, Metal Finishing Point Source Category, Title 40, Volume 27, Part 433, U.S. Environmental Protection Agency, Washington, DC, Revised as of July 1, 2003.

Source: U.S. EPA, Code of Federal Regulations, Metal Finishing Point Source Category, Title 40, Volume 27, Part 433, U.S. Environmental Protection Agency, Washington, DC, Revised as of July 1, 2003.

TABLE 9.20

Alternative U.S. BAT Effluent Limitations on Cyanide (A) for the Metal Finishing Point Source Category

Pollutant or Maximum for Any Monthly Average shall not

Pollutant Property 1 Day (mg/L) Exceed (mg/L)

Source: U.S. EPA, Code of Federal Regulations, Metal Finishing Point Source Category, Title 40, Volume 27, Part 433, U.S. Environmental Protection Agency, Washington, DC, Revised as of July 1, 2003.

part 403 and achieve the PSES. Table 9.21 indicates the PSES for all metal finishing plants except job shops and independent printed circuit board manufacturers. Alternatively, for industrial facilities with cyanide treatment, upon agreement between a source subject to those limits and the pollution control authority, the amenable cyanide limit shown in Table 9.22 may apply in place of the total cyanide limit specified in Table 9.21. No user introducing wastewater pollutants into a publicly owned treatment works under the provisions of this subpart shall augment the use of process wastewater as a partial or total substitute for adequate treatment to achieve compliance with this standard. An existing source submitting a certification in lieu of monitoring pursuant to this regulation must implement the toxic organic management plan approved by the control authority. An existing source subject to this subpart shall comply with a daily maximum pretreatment standard for TTO of 4.57 mg/L.

9.7.6 New Source Performance Standards

Any new metal finishing point source subject to the 40 CFR part 433 regulations must achieve the NSPS shown in Table 9.23. Alternatively, for the metal finishing industrial facilities with cyanide treatment, and upon agreement between a source subject to those limits and the pollution control authority, the amenable cyanide limit shown in Table 9.24 may apply in place of the total cyanide limit specified in Table 9.23. No user subject to the provisions of this subpart shall augment the use

TABLE 9.21

U.S. PSES for All Metal Finishing Plants Except Job Shops and Independent Printed Circuit Board Manufacturers

Pollutant or Maximum for Any 1 Day Monthly Average shall not Exceed

Pollutant Property (mg/L Except for pH) (mg/L Except for pH)

TABLE 9.21

U.S. PSES for All Metal Finishing Plants Except Job Shops and Independent Printed Circuit Board Manufacturers

Pollutant or Maximum for Any 1 Day Monthly Average shall not Exceed

Pollutant Property (mg/L Except for pH) (mg/L Except for pH)

Cadmium (T)

G.69

G.26

Chromium (T)

2.77

1.71

Copper (T)

3.38

2.G7

Lead (T)

G.69

G.43

Nickel (T)

3.98

2.38

Silver (T)

G.43

G.24

Zinc (T)

2.61

1.48

Cyanide (T)

1.2G

G.65

TTO

2.13

Source: U.S. EPA, Code of Federal Regulations, Metal Finishing Point Source Category, Title 40, Volume 27, Part 433, U.S. Environmental Protection Agency, Washington, DC, Revised as of July 1, 2003.

Source: U.S. EPA, Code of Federal Regulations, Metal Finishing Point Source Category, Title 40, Volume 27, Part 433, U.S. Environmental Protection Agency, Washington, DC, Revised as of July 1, 2003.

TABLE 9.22

Alternative U.S. PSES on Cyanide (A) for All Metal Finishing Plants Except Job Shops and Independent Printed Circuit Board Manufacturers

Pollutant or Maximum for Any Monthly Average shall

Pollutant Property 1 Day (mg/L) not Exceed (mg/L)

Source: U.S. EPA, Code of Federal Regulations, Metal Finishing Point Source Category, Title 40, Volume 27, Part 433, U.S. Environmental Protection Agency, Washington, DC, Revised as of July 1, 2003.

TABLE 9.23

U.S. NSPS for the Metal Finishing Point Source Category

Pollutant or Maximum for Any 1 Day Monthly Average shall not Exceed

Pollutant Property (mg/L Except for pH) (mg/L Except for pH)

TABLE 9.23

U.S. NSPS for the Metal Finishing Point Source Category

Cadmium (T)

0.11

0.07

Chromium (T)

2.77

1.71

Copper (T)

3.38

2.07

Lead (T)

0.69

0.43

Nickel (T)

3.98

2.38

Silver (T)

0.43

0.24

Zinc (T)

2.61

1.48

Cyanide (T)

1.20

0.65

TTO

2.13

Oil and grease

52

26

TSS

60

31

pH

6-9

6-9

Source: U.S. EPA, Code of Federal Regulations, Metal Finishing Point Source Category, Title 40, Volume 27, Part 433, U.S. Environmental Protection Agency, Washington, DC, Revised as of July 1, 2003.

TABLE 9.24

Alternative U.S. NSPS on Cyanide (A) for the Metal Finishing Point Source Category

Pollutant or Maximum for Any Monthly Average

Pollutant Property 1 Day (mg/L) shall not Exceed (mg/L)

Source: U.S. EPA, Code of Federal Regulations, Metal Finishing Point Source Category, Title 40, Volume 27, Part 433, U.S. Environmental Protection Agency, Washington, DC, Revised as of July 1, 2003.

of process wastewater or otherwise dilute the wastewater as a partial or total substitute for adequate treatment to achieve compliance with this limitation.

9.7.7 Pretreatment Standards for New sources

Except as provided in the U.S. CFR, any new source subject to this subpart that introduces pollutants into a publicly owned treatment works must comply with 40 CFR part 403 and achieve the

TABLE 9.25

U.S. PSNS for the Metal Finishing Point Source Category

Pollutant or Maximum for Any Monthly Average shall not Exceed

Pollutant Property 1 Day (mg/L Except for pH) (mg/L Except for pH)

TABLE 9.25

U.S. PSNS for the Metal Finishing Point Source Category

Pollutant or Maximum for Any Monthly Average shall not Exceed

Pollutant Property 1 Day (mg/L Except for pH) (mg/L Except for pH)

Cadmium (T)

0.11

0.07

Chromium (T)

2.77

1.71

Copper (T)

3.38

2.07

Lead (T)

0.69

0.43

Nickel (T)

3.98

2.38

Silver (T)

0.43

0.24

Zinc (T)

2.61

1.48

Cyanide (T)

1.20

0.65

TTO

2.13

Source: U.S. EPA, Code of Federal Regulations, Metal Finishing Point Source Category, Title 40, Volume 27, Part 433, U.S. Environmental Protection Agency, Washington, DC, Revised as of July 1, 2003.

Source: U.S. EPA, Code of Federal Regulations, Metal Finishing Point Source Category, Title 40, Volume 27, Part 433, U.S. Environmental Protection Agency, Washington, DC, Revised as of July 1, 2003.

PSNS, shown in Table 9.25. Alternatively, for industrial facilities with cyanide treatment, and upon agreement between a source subject to these limits and the pollution control authority, the amenable cyanide limit shown in Table 9.26 may apply in place of the total cyanide limit specified in Table 9.25.

No user subject to the provisions of this subpart shall augment the use of process wastewater or otherwise dilute the wastewater as a partial or total substitute for adequate treatment to achieve compliance with this limitation. An existing source submitting a certification in lieu of monitoring pursuant to Section 433.12 (a) and (b) of this regulation must implement the toxic organic management plan approved by the control authority.

9.8 SPECIALIZED DEFINITIONS

The definitions set forth in the U.S. CFR for the metal finishing point source category are incorporated in this section for reference.

1. The term "T," as in "Cyanide, T," shall mean total.

2. The term "A," as in "Cyanide A," shall mean amenable to alkaline chlorination.

3. The term "job shop" shall mean a facility that owns not more than 50% (annual area basis) of the materials undergoing metal finishing.

TABLE 9.26

Alternative U.S. PSNS on Cyanide (A) for the Metal Finishing Point Source Category

Pollutant or Maximum for Any Monthly Average

Pollutant Property 1 Day (mg/L) shall not Exceed (mg/L)

Source: U.S. EPA, Code of Federal Regulations, Metal Finishing Point Source Category, Title 40, Volume 27, Part 433, U.S. Environmental Protection Agency, Washington, DC, Revised as of July 1, 2003.

4. The term "independent" printed circuit board manufacturer shall mean a facility that manufactures printed circuit boards principally for sale to other companies.

5. The term "TTO" shall mean total toxic organics, which is the summation of all quantifiable values greater than 0.01 mg/L for the following toxic organics:

Acenaphthene

Acrolein

Acrylonitrile

Benzene

Benzidine

Carbon tetrachloride (tetrachloromethane)

Chlorobenzene

1,2,4-Trichlorobenzene

Hexachlorobenzene

1,2-Dichloroethane

1.1.1-Trichloroethane Hexachloroethane

1.1-Dichloroethane

1.1.2-Trichloroethane 1,1,2,2-Tetrachloroethane Chloroethane Bis(2-chloroethyl)ether 2-Chloroethyl vinyl ether (mixed) 2-Chloronaphthalene 2,4,6-Trichlorophenol Parachlorometa cresol Chloroform (trichloromethane) 2-Chlorophenol

1.2-Dichlorobenzene 1,3 -Dichlorobenzene 1,4-Dichlorobenzene 3,3 -Dichlorobenzidine

1.1-Dichloroethylene

1.2-trans-Dichloroethylene 2,4-Dichlorophenol 1,2-Dichloropropane

1, 3 -Dichloropropylene (1,3 -Dichloropropene)

2,4-Dimethylphenol

2,4-Dinitrotoluene

2,6-Dinitrotoluene

1,2-Diphenylhydrazine

Ethylbenzene

Fluoranthene

4-Chlorophenyl phenyl ether 4-Bromophenyl phenyl ether Bis(2-chloroisopropyl)ether Bis(2-chloroethoxy)methane Methylene chloride (dichloromethane) Methyl chloride (chloromethane) Methyl bromide (bromomethane) Bromoform (tribromomethane)

Dichlorobromomethane

Chlorodibromomethane

Hexachlorobutadiene

Hexachlorocyclopentadiene

Isophorone

Naphthalene

Nitrobenzene

2-Nitrophenol

4-Nitrophenol

2,4-Dinitrophenol

4,6 -Dinitro-o -cresol

N-Nitrosodimethylamine

N-Nitrosodiphenylamine

N-Nitrosodi-n-propylamine

Pentachlorophenol

Phenol

Bis(2-ethylhexyl)phthalate Butyl benzyl phthalate Di-n-butyl phthalate Di-n-octyl phthalate Diethyl phthalate Dimethyl phthalate

I,2-Benzanthracene (benzo(a)anthracene) Benzo(a)pyrene (3,4-benzopyrene)

3,4-B enzofluoranthene (benzo (fc)fluoranthene)

II,12-Benzofluoranthene (benzo(£)fluoranthene) Chrysene

Acenaphthylene Anthracene

1,12-Benzoperylene (benzo(ghi)perylene)

Fluorene

Phenanthrene

1,2,5,6-Dibenzanthracene (dibenzo(aft)anthracene) Indeno(1,2,3-cd) pyrene (2,3-o-phenlene pyrene) Pyrene

Tetrachloroethylene Toluene

Trichloroe

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