Marek Kieszkowski Institute of Precision Mechanics 00-967 Warsaw, Poland Gilbert S. Jackson EBON Research Systems Washington, D.C. 20001
With regard to electroplating, two scientists-one f r o m Warsaw, the other f r o m Washington-explain how that industry is engaged in
In the past decade, Poland has emphasized large-scale industrialization with accelerating levels of capital investment. Most of the planned or current expansion relates to industries that are substantial users of metal finishing technoIogy. These include the automobile, machinery, agricultural equipment, shipbuilding, electrical and electronics, and other specialized industries. The total surface area covered by such industries in Poland in 1977, with electroplated and organic coatings for anticorrosion and decorative purposes, was about 45 million m2. The 1990 estimate is 115 million m2. The organic coatings industry (paint and plastic coatings) produces 75% of the total coatings performed in Poland. However, there are more than 1000 metal finishing shops of different sizes in the country. About 80 of these are large-scale shops, mainly in the automobile, electronics and agricultural equipment industries. They produced about 25% of the total coatings.
The major problems The major environmental problems in the metal finishing industry consist of wastewater pollution and air pollution, as well as large amounts of metal-bearing sludge from effluent treatment processes. During the period of industrial expansion, the scarce waters of the country became increasingly polluted by increased waste loading. The total annual wastewater discharge from metal finishing shops was 90 million m3 last year (1977); 85% consisted of acidic or alkaline wastes, 10% of chromium, and 5% of cyanide-bearing wastes. On the other hand, in the organic coatings industry, with an overall paint production of about 500 000 t/y, emissions to the atmosphere consisted of approximately 200 000 t/y of organic solvents from surface preparation, paint spraying stations, and paint baking. The sludge disposed of annually from metal finishing operations amounts to about 8000 t/y (dry weight), but very often it is discharged as 98% water slurry. Thus, the total weight is generally about 0.4 million t/y. Inadequate management and disposal of such a watered sludge could cause serious contamination of surface and underground waters. In order to protect natural water resources, as well as to promote proper
water
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use of municipal sewage works, certain national guidelines were developed and legally established for all effluent discharges. These cover: discharge limitations into municipal treatment systems (pretreatment standards) discharge limitations into natural water bodies. For the second type of guidelines, all Polish natural waters were segregated into three classes of purity with specific concentration limitations; first-class purity waters are devoted to drinking and recreation purposes. Effluent discharge into natural waters must not raise the concentration of various species above the limit values. Some typical Polish national effluent limitations are summarized in Table 1. Wastewater treatment The wastewaters produced in metal finishing operations contain many toxic pollutants, such as cyanides, chromates, heavy metals, mineral acids, alkalis, oils, greases, detergents, and organic solvents. The most common and generally emloyed effluent treatment technology consists of well-known, conventional chemical procedures that can be done both continuously and batch-wise. It can involve several operations; for example:
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alkaline chlorination of segregated cyanide solutions reduction of segregated chromate solutions final neutralization of mixed effluents and precipitation of metal hydroxides followed by landfill disposal. Generally, sodium hypochlorite solution is employed for cyanide oxidation, and sodium bisulfite for hexavalent chromium reduction. Only a few plants utilize liquid chlorine or sulfur dioxide. Lime, or sometimes sodium hydroxide, is generally used for final neutralization and metal precipitation. Most of the larger plants use sludge dewatering equipment, such as filter presses or vacuum filters. Lagooning is only occasionally used for sludge-thickening purposes. Over the last few years, much more attention has been paid to proper rinse technology with drag-out tanks, multiple (2- or 3-) counter-flow rinse tanks, or spray-rinse devices. Also, some new plating technologies are being developed for better pollution control and water conservation. These include non-cyanide solutions for zinc and copper plating; substitution of low-concentration solutions for highconcentration baths; trivalent chromium solutions for zinc and cadmium passivation; and the like. ..
Shop equipment Most of the large plating shops are equipped with fully or partially automatic continuous, conventional effluent treatment plants. Figure 1 presents a schematic diagram of a metal finishing effluent treatment plant (OXY Effluent Control Ltd., England) in a large Fiat automobile factory in Warsaw. The plating shop consists of several large automatic plating lines, mainly for coppernickel-chromium plating of bumpers, hubcaps, and other automobile parts. The total water flow through the effluent treatment plant is about 400 m3/h (100 gpb). Wastewaters are segregated into four streams, with recovery of precipitated nickel carbonate from the nickel-bearing stream. Some of the large- and mediumscale plating shops in Poland utilize integrated effluent treatment systems, with design and facilities supplied by Zugil-Poland, and by Lancy Laboratories Ltd. (England). Chemical rinse operations with sodium hypochlorite or hydrazine reagents are utilized to deal with cyanide and chromate wastes; partial recirculation of rinse water allows recovery of some more valuable metals, such as nickel and copper. Few other Polish plating shops employ ion-exchange systems with recir-
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Rinse tank. Part of acyanide treatment/metal recouery system culation of rinse water, but for these shops, equipment is supplied by Zugil-Poland, or by some foreign companies. One such shop uses ionexchange columns for effluent treatment with water recirculation (Degrkmont, France) at the K Z A factory in Krak6w. Two double-line ion-exchange systems are used for separate treatment of acid-chromate, and cyanide-bearing waters. Each line consists of a sand-filter column, a strongly acidic cation exchanger, and a medium or strongly basic anion exchanger. Regeneration solutions, and other strong, dumped metal-finishing solutions are treated in a small conventional, continuously-operated effluent treatment unit; metal hydroxides sludge is then separated and filtered. The majority of medium and small job type plating shops use conventional batch effluent systems. Typical difficulties with final effluent purity standards- generally stem from 0.2ppm copper limitations, and 300-ppm suspended solids, and sulfate limitations. Air pollution and sludge As far as air pollution control in plating shops is concerned, normally, dry scrubbers are used to deal with chromic acid mist from chrome plating operations, However, sometimes wet scrubbers are used to absorb nitrogen 898
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Ion exchange columns. They clean water at plant in Krak6w
oxide fumes from brass bright-dip The IMP operations. The applied research for the Polish But much more important air pol- metal finishing industry is conducted lution problems are encountered in the by thednstitute of Precision Mechanics organic coatings industry, especially in (Instytut Mechaniki Precyzyjnej, or paint shops. For the moment, not very IMP), Warsaw. The Institute has ormuch is being done in this field for ganized an environmental protection existing shops. However, new organic department as part of its metal fincoatings shops are normally equipped ishing division. The main activity of with special air pollution control fa- this group is the application of research cilities, mainly to adsorb or destroy projects to industry, and direct convolatile hydrocarbons and other or- sulting with industry, planning buganic solvents from paint-baking op- reaus, and project offices. IMP speerations. Frequently employed paint- cialists are concerned with approxispray booths are generally equipped mately 50% of the total national efwith a water curtain-type air washing fluent discharge from Polish metal system to capture the excess spray finishing operations. The Institute paint material in a water solution. A enjoys a high technical reputation coagulation agent may be added, and among Polish industries. closed-loop water recirculation might In the past five yeais, fifteen to be used. twenty new environmental technoloA very serious environmental gies developed at IMP were introduced problem is created by the increasing into Polish industry. Some of them are amounts of heavy metals contained in now in use in other countries, as watered sludge from effluent treat- well-Czechoslovakia, for example. ment operations, as well as organic About 40 treatment technologies have sludges from spray paint application. been developed since 1967 by the InAs was mentioned, such more-or-less stitute. Roughly 250 plants all over watered sludges are generally disposed Poland have adopted I M P technoloof upon the land, thereby creating gies. They consist predominantly of the secondary water pollution prob- larger metal finishing operations. lems. Moreover, in some industrial New directions areas, the plating industry has difficulSeveral newer concepts, which perties in finding secured locations for landfill disposal of the sludge pro- mit water and bath constituents recovery in treatment of metal finishing duced.
effluents, are suitable to Polish industrial conditions. But it has been recognized that before improvement of treatment or recovery technology, the waste problem can be drastically reduced by in-plant modifications and by proper in-plant control techniques (ES&T, March 1977, p 234). The primary goals for these in-plant modifications are to reduce dragout of bath chemicals into the rinse waters, and to conserve water by reduction of rinsewater volume discharged to waste treatment. Of course, all modifications and changes can and should be made at a minimum cost, without affecting final product quality and production throughput. In the beginning of 1977, a special United Nations Industrial Development Organization (UNIDO) project was launched, in order to assist the I M P in developing effective technology to apply to the Polish metal finishing industry. Phase I of this project led to the development of a specific in-plant modification program, as one of the results of UN-designated expert Gilbert Jackson’s 2-month visit in Poland. An appropriate demonstration plant site was selected, and modifications outlined. The demonstration program, based upon UN-expert and I M P recommendations, is expected to be started this year. All in-plant modifications proposed consist mainly of simple, practical rules for minimizing dragout volume (such as slow withdrawal of plated parts, and proper racking), and application of effective spray- or fogrinse systems over the hot baths (cyanide copper, bright nickel and chrome plating baths) with positive water flow controls. Other improvements included installation of triple (or more) countercurrent rinse tanks, by modest changes within existing plating line and tank configuration; and proper management of semi-concentrated solutions from dragout tanks, for example. Estimated cost savings expected from successful application of these modifications a t the demonstration plant are on the order of $100 OOO/y (from better chemical recovery and water reduction alone), with estimated in-plant capital investment costs of about $100 000 for six automatic plating lines. Among other expected improvements are reduction in effluent toxic discharges, better final effluent quality, and reduced sludge buildUP. If successful, the project will provide a working example of relevant in-plant modifications for future adoption by the Polish metal finishing industry;
design would depend upon specific waste problems. In many plating plants, the water usage rate can be similarly reduced by 30-60% depending on the individual plant application. This approach has been favorably received by Polish industry. Promising techniques The most promising newer effluent treatment and material recovery techniques, suitable to the Polish metal finishing conditions and necessary for better environmental protection, are evaporative recovery of plating bath constituents from rinse waters, with demineralized water reuseespecially suitable for nickel- and chrome-plating solutions, as well as for some cyanide solutions reverse osmosis systems for some plating solutions, with pretreatment or preconcentration techniques, such as ion exchange or evaporation improved ion-exchange systems applied as: * * packaged mobile units for single metals recovery from separated rinse streams-after nickel plating, for instance secondary polishing systems for final effluent purification (removal of traces of heavy metals remaining in the effluent after clarification and sedimentation steps) * * rinse-water purification steps prior to evaporative recovery or reverse osmosis * * foreign metal and other impurity removal from metal finishing solutions, to extend their useful life, and to reduce waste volume ultrafiltration systems for water reclamation, and for some metal finishing solutions concentration; for example, oil emulsions, effluents from paint shops, and the like. This technique seems to be particularly suitable for paint material recovery from electro coating wastewater, as well as for oil and grease removal from some used degreasing bath solutions, increasing the useful life span of such solutions solidification of metal finishing sludges containing mixed metallic hydroxides and organic sludges from paint application operations. Application of chemical or physico-chemical fixation methods (with cement, fly ash, silicates, polymetric materials, and so on) should provide stable products encapsulating toxic heavy metals, thereby resolving safe landfill disposal problems for such sludges. All of the above-mentioned techniques are known and even applied in Poland. The actual task of IMP specialists, with U N I D O assistance, is to extend and to perfect their applications under
different metal finishing conditions. Other promising techniques include possible utilization of sulfide precipitation of heavy metals, solvent rinsing, ion flotation, carbon adsorption, and recovery of metals from hydroxide sludges by solvent extraction. Of course, all of these new effluent treatment and recovery methods need to be carefully selected for appropriateness to particular situations, with special regard to their specific effectiveness and economic factors. A common interest Nevertheless, in all cases, the common effort and interest of metal finishers and environmentalists-focused on possible changes in bath formulations, practical in-plant modification, and proper choice of effluent treatment and recovery technique-will encourage better environmental protection, more economical metal finishing operations, and rational management of natural water resources. These aims are essential not only in Poland, but all over the world. They constitute the most important necessity of the present time.
Additional reading Tuznik, F., Lis, A., Powloki Ochr., 2 (6),23 (1974). Kieszkowski, M., Electroplat. Met. Finish., 24 (5), 5 (1971). Tuznik, F., Kieszkowski, M., Electroplat. Met. Finish., 25 ( 7 ) , 10 (1972). Kieszkowski, M., Bartkiewicz, B., Met. Finish. J . , 18 (215), 385 (1972). Kieszkowski, M., Pastuszke, J., Powloki Ochr., 5 (2), 2; (3), 2 (1977).
Marek Kieszkowski (1) is chiefscientist of the plating effluent treatment department of the Institute of Precision Mechanics, Warsaw, Poland. Kieszkowski is responsible f o r research applied t o the Polish electroplating industry, with regard t o pollution control. H e has published more than 40 technical papers in the field. Gilbert. S. Jackson (r) is involved in a number ofprojects in the environment and energy fields. H e has been a consultant t o EPA, and to the United Nations Industrial Development Organization. In addition, Jackson produces an environmental radio show in the Washington, D.C. area, twice Coordinated by J J a week. Volume 12, Number 8, August 1978
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