Most companies lack the basics of plating, finishing and pollution prevention...
During 1994, 1996 and 1997, I visited 17 captive Latin American plating shops varying in size from small to medium. I was selected by the client and CESO to act as an advisor on improving finishing and plating processes as well as optimizing pollution prevention control. Also, the client asked that I provide guidance on a variety of existing and newer pollution prevention technologies as well as conventional destructive treatment methods such as cyanide oxidation and chromium reduction
During the last assignment of 1997, I visited 13 captive shops in one city during a four-week period. Previously, in another six-week assignment, three captive plating factories were assessed and analyzed. In the third project that lasted four weeks, only one captive company was evaluated.
Table I summarizes finishing and plating processes involved in the 17 shops. Both rack and barrel plating systems are used in some shops. In addition, one company does automatic vacuum metallizing over plastic and zinc die-cast parts. Another company has a modern automatic electrostatic painting department for finishing plated steel wire products.
All the companies have hand-operated plating lines except one large hot-dip galvanizing company, which has a self-designed automatic zinc cyanide plating line for steel tubes. Two other companies have manual hoist lines for zinc, nickel and chromium plating. All but one of these lines had improper tank arrangements with cross contamination. All of the 17 plating departments, except three shops, had shops resembling those of the 1940's to 1970's, with aged or tapped rectifiers, dark rooms, little or no ventilation, no proper tank arrangement, broken or rotten wooden catwalks and water covering the floor.
None of the 17 enterprises met metal finishing industry regulations for hazardous waste discharge. All discharge numbers were greater than their country's and/or U.S. or Canadian environmental laws and regulations. The 13 captive enterprises discharged mixed wastewater streams into the sewer, which runs into the city's river. The remaining shops discharge into the municipal sewer system. None of the companies (except one) use simple dragin and dragout technology, except electrowinning on three gold-plating operations because of the value of gold.
Some of the major problems in the facilities are as follows:
Other essential information about these companies includes:
Products plated. A wide range of styles and products are plated for household, commercial or industrial use. Substrates include steel, plastic and zinc die cast and items such as locks, boxes, keys, screws, frames, electrical metal parts, appliance parts, wire fabricated items, bicycle and motorcycle parts and hot-dip galvanized parts such as tubes, wire bundles, cable trays, beams, large plates, ladders and telephone poles.
Problems. The major concernsfaced by the plating shops were inadequate or improper housekeeping; basic oil removal; inadequate cleaning and pretreatment; little or no training/education; little or no knowledge of health and safety aspects; poor or unsatisfactory plating practices; no close process controls; no preventive maintenance, including no or inadequate filtration; no temperature control; no waste segregation; no environmental equipment; improper tank arrangements; poor connections; and a build-up of deposits on the home-made racks and hooks.
Because of time constraints, I could not sample and analyze (before and after laboratory filtration) the wastewater streams before they entered the sewer. However, a shop representative committee, including a project coordinator and two chemical engineers from a university industrial development agency, analyzed the samples before my visit. The reported results are shown in Table II. Some data were not clarified, and some were found inaccurate.
It should be noted that this Latin American country's three levels of Government (Federal, Provincial and Local) have analyzed 60 different effluent river wastes from small streams that flow into the main river, and have long- and short-term projects (more than $400 million dollars) for cleaning this river through collectors and interceptors. The removal of many houses in nearby tent towns located along the river is a big obstacle facing the governments.
Solutions and recommendations. The proposed suggestions were made to the various companies as follows:
Set-up, cleaning and pretreatment.
Processes change. Consider alternative plating chemistries to reduce wastes and avoid conventional cyanide destruction and chromium reduction treatments. For steel parts, use one of the following:
Equipment and technology for pollution control. First, evaluate pollution control methods before implementing them. These were some of the suggestions made:
It appeared to me that only a couple of enterprises were interested in making changes and improvements. Many were not willing to spend or invest the money. However, it is our Volunteer Advisors' duty to provide the necessary information and advise. Whether to implement or not depends upon the CESO's clients.
|Table I — Finishing Processes at Latin American Plating Shops|
|Neutralizer Pickle||Copper Acid||Copper Cyanide||Zinc Acid||Zinc Cyanide||Chromating yel/blue/cl||Bright Nickel|
|Table I — Finishing Processes at Latin American Plating Shops (continued from above)|
|Company Name||Brass Cyanide||Chrome Hexavalent||Bright Tin||Gold Cyanide||Silver Cyanide||Arsenic As||Phosph-
|Yellow Iriditing||Hot Dip Galvanizing|
|Table II — Reported Industrial Wastewater Discharge Stream Analysis|
|Company||ph||Grease and Oil||Total Solids||Suspended Solids||Solid Sediment||CN||Cu||Pb||Cr||Zn||Ni|
|IW: Industrial Wastewater|