New Horizons In Metal Removal And Recovery

Transcription

1 New Horizons In Metal Removal And Recovery BY W. DANIEL ERNT, P.E. ADVANCED RECOVERY SYSTEMS, INC. Presented at the American Insfitude of Chemical Engineers Annual Technical Meeting April 17,1990

2 Figure 1 shows a photograph of this system --called the METCON. Other systems provide adequate end-of-pipe treatment to meet effluent requirements and convert metals to non-hazardous metallic sheets; however, none provide the total holistic approach to sound at-source pollution control. Employing a LIX@/LX system, water conservation and waste minimization steps are employed to reduce the toxic metal problem, at the source - not at the end-of-the pipe. By solving the problem at the source of the problem, or as close to the source of the problem as possible, is where significant cost savings are realized. LIX@/LX systems take existing ion exchange technology one step further. LIX@/LX systems present a more efficient way to conserve water, the most efficient method to meet discharge requirements, and eliminate sludge formation, plus radically reduce waste treatment operating cost as well as overall plant operating cost. LIQUID ION EXCHANGEXIQUID-LIQUID EXTRACTION LIX*/LX was developed during World War 11, specifically during the Manhattan Project to purify and concentrate uranium for processing into the atom bomb. From the late 1940 s to the present, LIX*/LX was developed commercially by, first, the chemical division of General Mills and second the HENKEL Corp., to service the mining and nuclear industries. The major problem with LIX@/LX technology (and why it is not more widely used) is it requires large equipment and land areas to 1) blend the LIX@/LX with the aqueous stream containing the metal, and 2) separate, by gravity sedimentation, the LIX@/LX (which is an organic solvent) from the aqueous phase. This means high capital investments and is the major reason why the technology has not been acceptable to a small user until now Over the past seven years, ARS has developed an improvement in LIX@/LX handling equipment. Mr. George Galik, the Technical Director of ARS, has developed improvements which significantly reduce the required footprint for the LIX*/LX system and improves the kinetics and contact time between the LIX@/LX and the metal bearing water. These improvements are so unique that two patents are issued. These improvements enable the LIX@/LX technology to be utilized in confined spaces and thus be utilized in individuai operating plants within the metal finishing and circuit board shop arena for wastewater treatment. The system is called METCON or metal concentrator. To place these improvements in proper perspective an analogy is in order. LIX@/LX is like a powerful software package that historically could only operate on large mainframe computers which required large areas and high initial cost. Then a company developed a small desktop computer that could operate this

3 powerful software - thus making the software available for a wide range of users. The system developed and patented by George Galik represents this small desktop computer. The first METCON unit was installed at a circuit board shop in 1982 (over seven years ago). A second installation was completed and started nearly two years ago. Both these installations incorporated at- source pollution control techniques in addition to installation of the METCON. Results have been excellent. Both facilities report: Significantly reduced water usage - up to 60% (with no effect on product quality or manufacturing throughput). Reduction in the amount of water requiring treatment by over 95%. No sludge disposal. Decidedly reduced wastewater treatment costs. Minimum operator time and maintenance expense. The third and fourth METCON systems are currently coming on-stream. LIX@/LX SYSTEMS VERSUS RESIN ION EXCHANGE (RIX) SYSTEMS The METCON system employing LIX@/LX technology offers significant improvements over existing resin ion exchange technologies. Both systems meet wastewater discharge requirements and reduce, if not eliminate, sludge transportation, disposal and liability problems (which is a key consideration). However, the METCON system offers significant operating advantages and cost saving results compared to existing resin ion exchange technologies. The reason for these vast improvements is the significant operating advantages LIX@/LX technology presents. These advantages are listed in Table LIX@/LX utilizes two metal removal technologies (ion exchange and liquidliquid extraction). Other treatment systems, specifically resin ion exchange systems employ only one removal technology -- ion exchange. 2. LIXB/LX is moved (pumped). Thus the METCON is a true continuous system. Resin ion exchange systems (RIX) are truly batch operations. RIX systems are start-stop type eperations. The resin bed "loads ~ p" md is taken off he f~r regeneration. The METCON system is never "taken off-line" since the liquid ion exchanger is continuously regenerated after extracting the metals. This can be done because the LIX@/LX is a liquid and by itself can be moved (whereas a resin cannot be moved). It is a well known engineering fact that a continuous svstem is much more efficient than a batch operation - resulting in significant lower operating costs - which METCON has achieved in over seven (7) vears of plant operation.

4 powerful software -- thus making the software available for a wide range of users. The system developed and patented by George Galik represents this small desktop computer. The first METCON unit was installed at a circuit board shop in 1982 (over seven years ago). A second installation was completed and started nearly two years ago. Both these installations incorporated at- source pollution control techniques in addition to installation of the METCON. Results have been excellent. Both facilities report: Significantly reduced water usage - up to 60% (with no effect on product quality or manufacturing throughput). Reduction in the amount of water requiring treatment by over 95%. No sludge disposal. Decidedly reduced wastewater treatment costs. Minimum operator time and maintenance expense. The third and fourth METCON systems are currently coming on-stream. LIX@/LX SYSTEMS VERSUS RESIN ION EXCHANGE (RIX) SYSTEMS The METCON system employing LIXB/LX technology offers significant improvements over existing resin ion exchange technologies. Both systems meet wastewater discharge requirements and reduce, if not eliminate, sludge transportation, disposal and liability problems (which is a key consideration). However, the METCON system offers significant operating advantages and cost saving results compared to existing resin ion exchange technologies. The reason for these vast improvements is the significant operating advantages LIXB/LX technology presents. These advantages are listed in Table LD(@/LX utilizes two metal removal technologies (ion exchange and liquidliquid extraction). Other treatment systems, specifically resin ion exchange systems employ only one removal technology -- ion exchange. 2. LIXB/LX is moved (pumped). Thus the METCON is a true continuous system. Resin ion exchange systems (RIX) are truly batch operations. RIX systems iire start-stop type operations. The resin bed ads ~ p" md is taken eff h e fm regeneration. The METCON system is never "taken off-line" since the liquid ion exchanger is continuously regenerated after extracting the metals. This can be done because the LIX@/LX is a liquid and by itself can be moved (whereas a resin cannot be moved). It is a well known engineerinp - fact that a continuous svstem is much more efficient than a batch oderation -- resulting: in simificant lower operating costs -- which METCON has achieved in over seven (7) years of plant operation.

5 3. METCON can treat waste steams and effluents containing significant higher metal concentrations than other treatment systems. RIX systems can only treat streams containing metal concentrations below 150 to 200 mg/l (on a continuous, steady state basis). LIX@/LX systems not only have treated concentrated batch dumps directly but have treated spent etchant solutions ( which contain metal concentrations around 200,000 mg/l). Thus, METCON, emploving: LIX@ /LX can treat effluents containing - metal concentrations 500 times greater than RIX svstems. The METCON's continuous counter current operation makes for better chemical efficiency and mass transfer. METCON uses the advantages of liquid ion exchange and liquid-liquid extraction which presents 100% active exchange media with as many stages as required to do the job. 4. Any upset in the METCON will not produce an instantaneous breakthrough in metal concentration (which would happen in a resin ion exchange system). The METCON would produce a gradual increase in copper concentration, if an upset did occur. For example, if the effluent was running at 0.5 mg/l copper and an upset occurred, the copper concentration would slowly begin to rise from 0.5 mg/l to 0.6 mg/l to 0.7 mg/l, etc. This provides time for any required adjustments. 5. LIX@/LX is selective. There are over 100 different LIX@/LX compounds available from HENKEL (the manufacturer of the material). Each LIX@/LX material is formulated to extract a specific metal cation or group of metal cations. Thus LIX@/LX does not waste capacity on extracting ions that need not be extracted. Resin systems are not as selective. They pull not only the cations which must be extracted from the water but also cations that need not be extracted. This wastes resin bed capacity. 6. LIX@/LX systems are more resilient than resin (RIX) systems. LIX@/LX systems are operated and have operated in the mining industry for over 30 years. These systems process mine tailings with all the contaminations (including rocks and other debris) associated with these operations. RIX systems are very susceptible to resin fouling, breakage and other malfunctions. For a specific comparison between a typical resin ion exchange system versus a LU@/LX system please refer to Figures 2 and 3. Both systems remove metals from aqueous streams, concentrate these metals in an acidic (regenerate) solution o ~ the t =et& i~ an e!e~tro~<~~iifig 4 1 (:hiis <oiiveitifig the ~lietds to a non-hazardous form). Operation of a Tmical Resin Ion Exchange Svstem Figure 2 shows a schematic of a typical resin ion change system for the treatment of circuit board plant wastewater. First, resin ion exchange (RIX) systems are designed to treat the low concentration, high volume rinse waters from a circuit board plant operation. Dilute rinse waters in metal finishing operations such as a

6 printed circuit board shop contains metal concentrations between ten (10) and thirty (30) mg/l. These dilute rinse waters are adequate for a resin ion exchange systems, i.e., high volume, low metal concentration streams. However, the rinses from these operations contain only 10% to 15% of the metal problem. For example, an average printed circuit board (PCB) shop discharges about 25 lbs of copper per day. But the rinse waters contain only 2 to 3 lbs. of copper per day. The vast majority of copper discharged from a PCB facility is generated from the concentrated batch dumps (about 20 to 22 lbs./day of copper). These batch dumps are low volume but high metal concentrations (often exceeding 5,000 mg/l). Because of these high concentrations, the batch dumps must be carefully metered into the influent streams to the RIX systems. This metering is required so the overall metal concentration in the feed to the lux system does not exceed 150 to 200 mg/l on a steady state basis. Thus careful monitoring of the influent feed to a RIX system is required -- requiring instrumentation, management time and operator attendance. Also, to insure the maximum allowable metal concentration in the feed is not exceed, RIX systems prefer to treat the maximum amount of water - this insures maximum dilution and the lowest possible influent metal concentration. However, every gallon of water treated costs money. Thus, the inefficiency of the RIX systems costs a metal finishing facility extra operating expenses. The key is to minimize the amount of water requiring treatment -- not maximize. Additionally, RIX systems require separate resins (and separate resin columns/systems) to treat the chelated metal bearing wastewaters. This adds not only operating cost but capital costs. The second limitation is RIX systems require a narrow ph range to operate effectively. Thus the influent wastewater must be pre-treated before treatment. Typically these ph ranges are approximately 4.0 to 5.5. This results is the following disadvantages: Additional capital equipment is required( ph meters, chemical addition equipment, process controls/instrumentation, etc.) Added operating expense since chemicals are purchased to adjust the ph (acids as well as caustics). Increased liability exposure since employees must handle these hazardous chemicals. The next Em-itatinn in a t-icd RIX svstem is the basic operation. RIX systems - are batch operations. Thus, they are not as effiaent as continuous systems. Although resin systems continuously treat the wastewater from a circuit board shop or metal finishing facility, the resin column itself is a batch operation. After the resin capacity is exhausted (loads-up) the bed is taken off line and the following steps are implemented:

7 The bed is backwashed. This adds additional water requiring treatment. Acid is added to regenerate the resin. Rinse water is added to remove traces of acid from the resin bed. This adds to the amount of water requiring treatment. Note that steps 1 and 3, above, add water to the amount already requiring treatment. Thus resin systems not only do not promote water conservation - but by their very nature increase water usage and increase wastewater treatment cost. A batch system, which is constantly opening and closing values, starting and stopping motors, has higher maintenance costs than a continuous system. Simply put a batch system places more strain and fatigue on mechanical equipment - which results in greater maintenance costs over the life of the system (versus a continuous system). Also RIX systems require more auxiliary controls, instrumentation and micro-processors to monitor the operation. This increases capital cost and again creates potential problems in failure of this equipment because no monitoring equipment is infallible. For example, the micro-processors that control the system can fail. This is what happened to AT&T in January 1990 when their micro processors failed - disrupting the telephone system in the Northeast section of the United States. The next inefficiency is in the electrowinning cell. The electrowinning cell is also a batch operation. After each resin bed regeneration, the regeneration solution contains a high metal concentration (2 to 3 oz/gal). This solution is passed through an electrowinning cell where the metal (primarily copper in a PCB facility) is plated out at the cathode. Thus, the metal is converted to a non-hazardous form. The metal concentration in the regeneration solution (or electrowinning cell feed solution) is initially high. As the metal plates out at the cathode, the concentration decreases in the regeneration solution. As the concentration falls, the electrowinning cell efficiency decreases which increases operating cost (electrical costs). The resins used in RD( systems, although somewhat selective, extract other multivalent cations in addition to metals, e.g., calcium (Ca+2) and Magnesium (Mgf2). These divalent cations such as calcium are not plated out during the electrowinning step. Thus, the concentrations of these dissolved solids (salts) increase in the regeneration solution to a point where the solution cannot be reused. This means the solution must be recycled and retreated. This results in two inefficiencies: 1) A portion of the toxic metals must be treated twice not just once; and 2) Fresh regeneration acid must be added to the system (which increases operating cost).

8 The METCON Utilizing Technolonv Figure 3 shows a schematic of the METCON system for treatment of effluents generated by a circuit board plant and other metal finishing operations. The treatment of a typical printed circuit board (PCB) plant effluent is used for purposes of this discussion. As with a RIX system, the METCON treats both the rinse waters as well as the concentrated batch dumps. However, before the actual treatment system is installed a thorough examination of the sources of metal wastewater generated is performed. This study called a "Design Basis Report", recommends minor plant operating changes which, after implementation, will reduce water usage up to 60%, and reduce the amount of water requiring treatment up to 95%. This is a key difference between LIX@/LX and RIX. ub/lx svstems allow the implementation of at-source pollution reduction and control practices. These practices reduce the amount of water requiring treatment. However, the same quantity of metal (lbs./day) is discharged. The result of these in-plant pollution reduction practices is condensing the same pounds per day of metals into a much smaller volume of water. This drastically increases the metal concentration in the wastewater stream requiring treatment (to a level exceeding 1,000 mg/l). All other metal treatment systems (including resin ion exchange) cannot handle these high metal concentration effluents. These other treatment systems actually inhibit the implementation of atsource pollution control practices. METCON only treats the wastewater that requires treatment. This amounts to 95% less water requiring treatment than in a typical resin system. The result is a significantly reduced operating cost for waste treatment. Cost savings that fall right to the "bottom line". METCON also treats the chelated metal waste without a separate system. Most resin ion exchange systems require a distinct type of resin to treat the chelated metal (increasing capital cost as well as operating expenses). METCON employing LIX@/LX does not require a separate system. The chelated wastes are combined with the other wastewaters for treatment in one system. The second point is the LIX@/LX extracts metals very efficiently over a very wide ph range (this range is ph 2 to 14). The ph of most wastewaters from a circuit hoard shop or metal finishing facility is hetween 3 and 6- Thusi METCON does not require ph monitoring equipment for the wastewater feed or chemical addition. This saves capital as well as operating cost. The next point is the basic operation of the system. METCON is a true continuous system. The wastewater is combined with the LIX@ in the extraction stage where the metals are removed from the water. From the extraction stage the wastewater is discharged to the sewer. The LIX@ which contains the heavy metals exits the extraction stage and is transferred to the stripping stage. In the stripping

9 stage the is blended with acid (typically sulfuric acid) and the metals are stripped from the The is then returned to the extraction stage to treat additional water, all on a continuous basis. The continuous basis allows for a very simple operation which has a very low operating cost plus low maintenance. The METCON system does not require micro-processors or complicated servo valves or other costly instruments. METCON requires very little maintenance because there are very little moving parts -- only the small electric motors which operate the patented turbo-mixers. Chemical cost, electrical cost, maintenance cost, and manpower requirements are almost nil. The final key advantage is in the electrowinning cell operation The metal concentration in the regeneration tank is approximately three to four ounces per gallon. With the METCON system, this high metal concentration is maintained at all times (versus the RIX systems where this metal concentration is depleted). The reasons the system can operate this way is two fold: 1)The system is truly continuous; and, 2) The LIX@ is selective - the LIX@ does not extract other divalent or other multivalent cations. All cations extracted from the aqueous phase are plated out in the electrowinning cell. Thus, there is no buildup of dissolved solids in the regeneration solution -- the solution is recycled indefinitely. This also saves chemical cost because the acid, formed at the cathode continuously replenishes the acid content needed in the stripping stage. Thus, very little, if any, fresh acid is required. To better understand this particular step in the operation a closer look at the regeneration solution storage tank is required. There are two liquid streams or loops entering and leaving this tank. The first loop interfaces the regeneration storage tank as well as the stripping stages of the METCON unit. In this loop metal is being added to the regeneration solution storage tank. The second loop interfaces the regeneration solution storage tank and the electrowinning cell. In this loop, metal concentration is being depleted or decreased. Together these two loops, one adding metal to the regeneration solution storage tank the other depleting metal from the storage tank, create a steady state condition where the metal concentration is maintained at a high level ( 3 to 4 oz/gal). Because the metal concentration is always high, the electrowinning cell, for the METCON system, is very simple - less initial cost plus less operating cost than cells employed in a resin ion exchange system. The overall conclusion is the METCON, utilizing LIX*/LX technology is less costly to own and operate. Table 2 lists operating cost comparison for a typical PCB plant using three different treatment methods, resin ion exchange, LD<@/LX, and chemical precipitation. As shown, LIX@/LX is the most economical alternative by $40,700 versus a typical RIX system and over $144,000 per year versus a typical chemical precipitation system. This translates to cumulative savings over a five (5) year period of over $200,000 versus a RIX system and $722,000 versus a chemical precipitation system.

10 TREATMENT ALTERNATIVES Using -/LX technology, Advanced Recovery Systems (ARS) employs three basic treatment schemes or methods depending on the objectives of the circuit board facility or metal finishing facility. These are listed in Table 3. The first method consists of condensing or consolidating the toxic metal containing wastewaters into a point source or very small volume. Typically the amount of wastewater requiring treatment is reduced to approximately five percent of the total water usage (this represents a 95% reduction in the quantity of water requiring treatment). The metal concentration in this point source wastewater volume typically exceeds 1,000 mg/l. No other system, to our knowledge, exists which can treat these extremely high concentrations, on a steady state basis. The second method ARS employs consists of a METCON system treating the batch dumps from a circuit board shop or metal finishing facility. The batch dumps in a metal finishing facility comprise approximately eighty five percent of the metal bearing problem (on a pounds per day basis). The dilute rinse waters, although they makeup the majority of the flow volume, account for only 10% to 15% of the actual metal problem. Some firms recognize this fact and, rather than dismantle their existing and expensive chemical precipitation systems, choose to treat the batch dumps using METCON. This reduces the following: Their chemical costs for treatment (up to 80%). Their cost of transporting and disposing of the sludge created in the chemical precipitation system (about BO%).. Liability exposure for generating, transporting and disposing of hazardous wastes. - The third treatment method or altemative is a water recycle option. The METCON is employed along with a reverse osmosis (or nanofiltration) system. The reverse osmosis system treats the dilute rinse water streams. The product water from the reverse osmosis system is recycled back to the head of the plant for reuse. The reject or concentrated stream generated by the reverse osmosis system is treated in the METCON system. These metal concentrations, in the reverse osmosis reject stream, are typically 1,000 mg/l or higher. Additionally, the concentrated batch dumps are treated directly by the METCON system. This altemative is attractive in areas where water rationing is a problem, make-up water costs and sewer use charges are high, or where discharge requirements are so stringent that a company is wise to consider recycling the water treated rather than discharging into a sewer. Treatment Alternative I The driving force behind Alternative I is an economic one. It is an economic fact that the more water a faality has to treat the greater its waste water treatment

11 costs. An important objective is to reduce the amount of water requiring treatment. This is what is accomplished using Altemative I. Minor changes are implemented which, when completed, save operating cost. ARS employs a two step process to achieve this goal. The first is waste minimization, the second is waste segregation. Waste minimization is accomplished by conserving water (water conserved is waste saved). This not only reduces water cost but reduces the amount of water requiring treatment. Actual operating data show water usage can be reduced 40% to 60% with no adverse effect in product quality. These are accomplished by utilizing better rinse techniques. The second step is waste segregation. Waste segregation means separating the water that requires treatment from the water which does not require treatment. Results from actual plant operations, using proper M se technology, show the majority of water generated by rinsing operations does not require treatment. These studies show the metal concentration of these streams (representing 95% of the flow volume) are less than 1.0 mg/l and typically less than 0.5 mg/l. Rinsing Ouerations Rinsing is required in a metal finishing shop or circuit board facility to isolate the chemical steps and prevent cross contamination of the processes. The mechanism of rinsing is controlled by two factors: I) The removal rate of water film,which contains the total dissolved solids, from the material requiring rinsing (for example the circuit board); and 2) Removal of the total dissolved solids from the rinse tank by dilution with fresh water. In most facilities the rinsing operations are very inefficient - requiring large quantities of water to achieve the desired results. Rinsing inefficiencies are caused in most facilities because of two factors: a) utilizing poorly designed spray nozzles, and b) poor plant hydraulics which result in insufficient pressure at each spray nozzle. Insufficient pressure at each nozzle results in a low velocity of water leaving each nozzle. Most operators, in order to correct this problem, increase the flow volume to each rinse tank. Thus, a large amount of water is used (water maximization, not conservation) which increases the load on the wastewater treatment system (increasing operating costs). Most operators think a large volume of water is required to rinse effectively. Detaiied examination of rinsing operations show optimum results are achieved by fist flushing the water film from the circuit board (or other material being rinsed) with a high velocity, but low volume, burst of water. This is achieved by using a high velocity, timed, spray rinse. This spray rinse step is followed by immersion of the circuit board in a conventional two stage counter flow cascade rinse tank.

12 The key point is : Merely dipping a circuit board in a rinse tank and increasing water flow (volume) does not produce effective rinsing. The important aspect is the velocity of the water across the circuit board, not water volume. Efficient rinsing to accomplish reduction in the amount of water requiring treatment is summarized in four (4) points: 1. Rinse first with a high velocity, high impact, timed spray rinse to remove the vast majority of film. This spray rinse is followed by two stage counter-flow cascade rinse tanks. 2. Design the cascade rinse tanks so the volume differential between the work load and the rinse tank is large enough to allow work to flow smoothly but not so large as to require lengthy turn over times for the tank. 3. Drag as little dissolved solids as possible, from tank-to-tank, by allowing the excess, contaminated water, to drain off between rinse tanks. 4. Design racks for holding the work (materials) for optimum draining, that is, use small round surfaces rather than flat or rectangle areas. Figure 4 shows a schematic of the recommended operation. The first tank employs the use of a timed spray rinse. Each burst of water typically lasts ten (10) seconds. The effluent from this spray rinse tank is highly concentrated, but low in volume. This effluent is discharged to the METCON treatment system. The material (circuit board, etc.) is next rinsed in a conventional, two stage counter-flow cascade rinse operation. The cascade step is a high volume (3 to 5 gpm) rinse. Because the vast majority of metals (contained in the film on the material) are sprayed off the work in the first timed spray rinse operation, the wastewater leaving the cascade rinse tank operation contains less than 1.0 mg/l and typically less than 0.5 mg/l. Thus this wastewater is discharged directly to the sewer. The key methodology for waste minimization is improved rinsing techniques and waste segregation. Low metal contaminated water (containing less than 1.0 mg/l metals) is segregated from high metal content water (containing metal concentration exceeding 1.0 mg/l). The overall conclusion is this: It is economical to eliminate and/or reduce the quantity of water at its source in the manufacturing plant prior to treatment. This is done with proven rinse technology and waste segregation techniques. Previously, even if a metal finishing operation installed these techniques, the resulting wastewater contained metal concentrations too high for conventional systems. Thus, it did not pay to improve rinse operations and segregate the wastewaters. Conventional treatment systems (including resin ion exchange) could not handle the high metal concentrations -- thus the end-of-pipe systems limited the at-source pollution control techniques which a metal finishing facility could utilize. They were forced to spend needless money on treating large volumes of water because of the inherent inefficiencies of the existing waste treatment systems.

13 The key reason is reducing the amount of water requiring treatment does not eliminate the amount of metals requiring treatment. The amount (pounds) of metals stays the same. However, these metals are condensed into a smaller volume, resulting in a significant increase in metal concentration. Other treatment systems cannot treat these high concentrations. Only METCON, employing LIX@/LX technology can treat these high concentrations. Thus METCON allows a circuit board facility or metal finishing facility to employ solid environmental and process engineered solutions to save water and reduce the amount of water requiring treatment. This saves operating cost. Figure 5 shows the effect on metal concentration after conserving water and minimizing the amount of water requiring treatment. Figure 5 lists data from a typical circuit board plant. The plant initially had twenty five pounds of copper per day contained in ninety thousand gallons per day. This resulted in an average effluent metal concentration equal to 33 mg/l. Improving rinse operation resulted in saving 50,000 gallons of water the per day (GPD). Saving this water does not reduce the amount of metals. Thus the resulting metal concentration in the 40,000 GPD is 60 mg/l. The last step is segregating the low contaminated wastewater (less than 1.0 mg/l) from the wastewaters containing metals exceeding 1.0 mg/l. All other treatment systems cannot implement this step since these systems cannot treat the resulting high metal concentration wastewaters. Employing these waste segregation practices results in only having to treat 2,500 GPD of wastewater. However, this wastewater contains metal concentrations exceeding 1,200 mg/l. This is why all other system cannot implement this step. Results from actual circuit board plants are listed in Tables 4 and 5. Plant A reduced water consumption by thirty five percent and plant B forty percent reduction. Additionally, Plant A treats only 4.5% of the water usage, while Plant B treats only 3.3% of the water used. METCON utilizing LIX@/LX technology in concert with sound waste minimization and waste segregation practices provides a synergistic solution to metal bearing waste water problems. TREATMENT ALTERNATIVE 11. METCON can ireat directiy (with no diiutionj the batch dumps, which amount to 85% of total pounds per day of metal generated by a metal finishing or circuit board facility. Because METCON can treat these high concentrated, low volume flows - the low metal content, but high volume rinse water can still be treated in existing treatment systems. This alternative avoids a facility having to

14 The key reason is reducing the amount of water requiring treatment does not eliminate the amount of metals requiring treatment. The amount (pounds) of metals stays the same. However, these metals are condensed into a smaller volume, resulting in a significant increase in metal concentration. Other treatment systems cannot treat these high concentrations. Only METCON, employing LIX@/LX technology can treat these high concentrations. Thus METCON allows a circuit board facility or metal finishing facility to employ solid environmental and process engineered solutions to save water and reduce the amount of water requiring treatment. This saves operating cost. Figure 5 shows the effect on metal concentration after conserving water and minimizing the amount of water requiring treatment. Figure 5 lists data from a typical circuit board plant. The plant initially had twenty five pounds of copper per day contained in ninety thousand gallons per day. This resulted in an average effluent metal concentration equal to 33 mg/l. Improving rinse operation resulted in saving 50,000 gallons of water the per day (GPD). Saving this water does not reduce the amount of metals. Thus the resulting metal concentration in the 40,000 GPD is 60 mg/l. The last step is segregating the low contaminated wastewater (less than 1.0 mg/l) from the wastewaters containing metals exceeding 1.0 mg/l. All other treatment systems cannot implement this step since these systems cannot treat the resulting high metal concentration wastewaters. Employing these waste segregation practices results in only having to treat 2,500 GPD of wastewater. However, this wastewater contains metal concentrations exceeding 1,200 mg/l. This is why all other system cannot implement this step. Results from actual circuit board plants are listed in Tables 4 and 5. Plant A reduced water consumption by thirty five percent and plant B forty percent reduction. Additionally, Plant A treats only 4.5% of the water usage, while Plant B treats only 3.3% of the water used. METCON utilizing LIX@/LX technology in concert with sound waste minimization and waste segregation practices provides a synergistic solution to metal bearing waste water problems. TREATMENT ALTERNATIVE 11. METCON can treat directiy (with no diiutionj the batch dumps, which amount to 85% of total pounds per day of metal generated by a metal finishing or circuit board facility. Because METCON can treat these high concentrated, low volume flows - the low metal content, but high volume rinse water can still be treated in existing treatment systems. This alternative avoids a facility having to

15 dismantle a treatment system which they perhaps just purchased. Alternative 11 drastically reduces the problem by eliminating 85% of the metal problem which causes high chemical usage, sludge hauling and disposal cost, and liability cost. By employing the METCON about 80% to 85% of the cost is eliminated. TREATMENT ALTERNATIVE I11 There is a significant need for water recycling in todays environment. Key points that drives this need for water recycle are listed in Table 6. Advanced Recovery Systems employs reverse osmosis (nanofiltration) technology to achieve this water recycling option. Previously, reverse osmosis systems had difficulty treating metal finishing plant effluents. Current technology mitigates the previous problems encountered when reverse osmosis is used to treat metal bearing effluents. These mitigating steps are listed in Table 7. The two key points listed in Table 7 are numbers 3 and 4. In previous treatment schemes, the reverse osmosis system had to treat the batch dumps as well as the dilute rinse. This resulted in severe membrane fouling and frequent membrane replacement. With the METCON, these concentrated batch dumps are not treated by the reverse osmosis unit. These concentrated batch dumps are discharged directly to the METCON system. This saves membrane fouling and replacement. Additionally there were problems with disposing of the concentrated (reject) stream created by the reverse osmosis system. No other treatment system could handle this high metal concentration reject stream. However, the METCON system, utilizing UX@/LX technology, can. Figure 6 shows a schematic of the system for employing the technology of reverse osmosis along with the METCON. If a shop chooses to do so, it can employ the use of a METCON system initially and purchase a reverse osmosis system for water recycle in the future. The future installation of the reverse osmosis system is easily integrated with the METCON system. CONCLUSION In-plant pollution control techniques, in metal finishing plants, rinse methods and waste segregation techniques can be employed to reduce water usage and minimize waste treatment requirement. Water use reductions up to 60% have been demonstrated with no effect on product quality. Additionally, waste water requiring treatment can be reduced up to 95%. In order to achieve these reductions

16 a treatment system is required to effectively handle wastewater containing high metal concentrations (exceeding 1,000 mg/l). A new system, utilizing liquid-liquid extraction/liquid ion exchange technology effectively treats these high metal concentration waste water and converts the toxic heavy metals to a non-hazardous form. This new treatment system, the METCON, in concert with sound waste minimization and waste segregation practices provides a synergistic and cost effective solution to metal bearing waste water problems. This technology provides the following. Water conservation. Reduced operating cost (not only in waste water treatment but in overall manufacturing). Minimize the quantity of water requiring treatment. Conversion of Heavy Metals into Non-Hazardous Metallic Sheets. At-Source Pollution Control.

17 Figure 1. Photo of Metcon Unit

18 Table 1. Advantages of 1. Combines advantages of liquid ion exchange with I i q u i d-i i q u id extraction. 2. LIX@/LX is not fixed - it can be pumped Treats waste streams containing metal concentrations af 200,000 mg/l times higher than resin ion exchange. 4. LIX@/LX is.sdective - much more selective than resin c 6. LIX@/LX systems do not produce an instantaneous breakthrough in metal concentration.

19 ~ Table 2. Cost Comparison (Con t.) SYSTEM - THE MOST ECONOMICAL ALTERNATIVE I The ILIX@ System is less costly (per year) by $40,700 versus a typcial RIX System! I The LIX@ System is less costly (per year) by $144,400 versus a conventional precipitation system! THIS TFWNSLATE TO A TOTAL SAVINGS (over a 5 year period) OF: $203,500 compared to a resin (RIX system) - $722,000 compared to a sludge system

20 .- n 0 I cn n E a 0 m!= 3 0 U a n c3 0-0 I 0 0 m 0 b 00" e 0 0 w 05- w e

21 c: Acid Caustic I Maintenance Effluent I b b Collection Solution Containing Copper (k200 m a) which must be re-treated L 4 Resin Ion Exchange Regeneration Solution Specialized Electrow in Cell Metallic Copper Sheets Acid k Figure 2. Schematic of Resin Ion Exchange System

22 *j Collection ;I I -Effluent 1' Stripping Column Collection rl- No ph Adjustment Required Regenerated LIX 1 1 Regeneration Solution [CuS04mS04 Electrowin Cell Generated H2S04 Copper Sheet Figure 3. Schematic of Liquid Extraction/Liquid Ion Exchange System

23 Table 3. Treatment Alternatives ARS TREATMENT METHOD I Condense the amount of wastewater requiring treatment to approximately 3% to 5% of the total water usag e. ARS TREATMENT METHOD II Use the METCON to treat the batch dumps (which are 85% of the heavy metal problem) and, use the existing treatment system to treat the high volume, low metal content rinses (which are only 10 to 15% of the heavy metal problem). ARS TREATMENT METHOD 111 Plant water recycle using Reverse Osmosis (nanofiltration) and the MFrTCON treating the high metal content RO reject stream plus the batch dumps.

24 Flow of Material 2 Stage Counter-Flow Cascade Rinse Tanks 1 st Spray Rinse 2nd Rinse I 7 3rd Rinse High Velocity, Timed + Spray Rinse (1 0 sec) Low Wastewater Volume to Treatment 1 t High Volume (3-5 gph) Wastewater L containing < 1.0 mg/l to Sewer 0.06 to 0.49 mg/l copper concentration Figure 4. Optimum Rinsing Operation

25 EXAMPLE: EFFECT OF WATER CONSERVATION, WASTE MINIMIZATION AND SEGREGATION PRACTICES ON METAL CONCENTRATION INITIALLY: 25 Ibs. of Cu/day and 90,000 GPD treatable effluent Cu Concentration: 33 mg/l 1. Water Conservation through Proper Rinse Techniques 25 Ibs. of Cu/day and 50,000 GPD treatable effluent Cu Concentration: 60 mg/l 2. Waste Minimization through Segregation 25 Ibs. of Cu/day and 2,500 GPD treatable effluent Cu Concentration: 200 mg/l Figure 5. Effect of Water Conservation

26 Table 4. Examples - Water Conservation WATER CONSERVATION SPECIFIC CIRCUIT BOARD PLANTS EXAMPLES / Initial Water Usage: 75,000 gal/day After implementing water conservation techniques recommended by ARS... Water Usage: 45,000 gal/day A 35% REDUCTION [ PLANTB Initial Water Us age: 100,000 gal/day After implementing water conservation techniques recommended by ARS... Water Usage: 60,000 gal/day A 40 % REDUCTION

27 / Table 5. Examples - Waste Minimization WASTE MINIMIZATION SPECIFIC CIRCUIT BOARD PLANTS EXAMPLES [ PLANTA: Reduced from 45,000 gal/day to 2,000 gal/day... or 4.5% of total volume Reduced from 60,000 gal/day to 2,000 gal/day... or 3.3% of total volume.

28 Table 6. Key Points for Water Recycle THE NEED FOR WATER RECYCLE 1) Stringent Wastewater Discharge Limitations. 2) Public Image - Public Concern over Safe Drinking Water. 3) Economics - The High Cost of Water. 4) Water Availability and Sewer Usage Limitations. 5) Improved Water Quality.

29 Table 7. Mitigation Steps for RO Usage REVERSE OSMOSIS Mitigation Steps to Previous Usage 1) Improved Membrane Technology 2) Adequate Pretreatment of the Influent 3) Heavy Concentrated Dumps are Handled Directly by the METCON Unit not by the Reverse Osmosis Unit. 4) Disposal of the Concentrated Reject Stream from the Reverse Osmosis Unit is Treated by the METCON Unit.

30 k t T I 0 a, v) L a, > v) v) W u 0 2 I 1 u