Board of Public Works
City of Los Angeles
Hazardous & Toxic Materials Project - Board of Public Works
Rev 5/90
City Hall
200 AL Spring Street Room 353
Los Angeles, CA 990012
(213) 237-1209
Waste Minimization Fact Sheet
Getting rid of metal finishing wastes is expensive, and the situation looks like it's only going to get worse. The high cost of land disposal of hazardous wastes has made It critical for many industries to find alternative management practices for their waste streams. While standard treatment methods for such wastes as electroplating sludges reduce the volume of the stream, most shops still pay large fees each year to transport and dispose of dewatered sludges. Many treatment/storage/disposal (TSD) facilities will not accept F006 sludges due to their frequent inability to meet federal and state leachate limits. Sometimes sludges must be shipped 1,000 miles or more to landfills that will accept them. What's more, the corporations that own the landfills are often under pressure by concerned citizen's groups to close their doors to highly toxic wastes.
Once the "land ban" takes effect In May of 1990, sludge disposal costs will go up even more, because metal sludges will have to be stabilized before land disposal In order to meet the strict new leachate requirements. Some land disposal sites offer stabilization capabilities, but they charge very high prices for this service.
What cost-saving alternatives exist for generators of metal-bearing sludges?
Waste generators can use three types of strategies for reducing their waste management costs:
"Pollution prevention" strategies involve using less toxic raw materials, altering manufacturing processes and work practices, and recovering plating chemicals and reusing them in shop operations. These strategies not only save the shop money through reduced wastes and associated waste management costs; they also reduce the amount of raw materials needed and the cost associated with converting these raw materials into waste.
Specific waste minimization approaches include:
Waste minimization strategies can reduce the amount of sludge generated, but usually cannot eliminate it entirely. New technologies have been developed to manage this sludge in more economical ways they are also more protective of the environment. In May of 1990, strict new regulations will take effect that limit the amount of hazardous metals or cyanides that can be leached out of sludges, if they are to be sent to land disposal areas. If your shop can stabilize its wastes to meet these new standards, you can save paying waste management companies high rates to do it for you. Better still, if you can detoxify the sludges, they can be disposed of inexpensively as non-hazardous "municipal" waste, or be recycled.
Two high temperature stabilization/recycling technologies that appear promising for on-site applications are:
Thermal bonding is quite simple in concept. You mix dewatered sludge with clay, then heat it The primary goal of the alumina-silicate bonding process is to detoxify hazardous metal sludges by fixating the metals in a leach-resistant ceramic matrix. A secondary aim is to convert metal waste sludges into a salable raw material for construction applications.
Rohr Industries in San Diego is one company that has successfully implemented a "sludge conversion" system. Rohr mixes a clay called montmorillonite with its metal sludges. The sludge contains 25% solids, typical for sludges that have been squeezed through a filter press. Four parts of clay are used for every one part (dry weight) of sludge. The alumina-silicate materials in the clay form weak "coordinate" bonds with the metals in the sludge soon after mixing. String chemical bonds are formed after firing the mixture in a kiln at temperatures up to I 100c) C. This process generates a salable ceramic aggregate whose strength is considerably enhanced by the metal in it.
The Rohr process demonstrates that heavy metal sludges can be detoxified and help to generate a useful material when mixed with clay. But because Rohr's system employs a rotary kiln to fire the mixture, it is beyond the budgets of most plating shops.
A company called Ceramic Bonding, Inc. (CBI) of Mountain View, California has taken the waste conversion concept and designed a much more affordable system around it. As in the Rohr process, the CBI system involves four continuous operations:
The major difference between the Rohr and CBI processes is in the ceramic drying and firing steps. CBI has replaced Rohr's rotary dryer and rotary kiln with a compact thermal processing unit that is continuously fed with clay/sludge pellets. 'Me thermal processor is designed to be completely filled with pellets, and so is much smaller and uses far less energy than the rotary kiln, which operates only 5% full The footprint of CBI's smallest thermal processor, which handles two dry tons of sludge per day, is only 6 feet by 8 feet The energy draw is 80,000 Btu per hour, approximately that of a domestic water heater.
After four hours in the thermal processor unit at temperatures reaching I 1000 C, metals in the sludge become so firmly locked into the clay matrix that even when the pellets are crushed and hot nitric acid is poured on them, the metals stay bound up.
Toxic air emissions from the thermal processor appear to be very low. After the air passes through the driest pellets on the bottom, the particles it picks up are to a great extent scrubbed from it as it passes through the closely packed wet pellets in the top of the chamber.
The cost of the CBI system, including mixer, extruder, and thermal processor, ranges from $100,000 to $250,000 for systems capable of processing 100 tons per year of dewatered sludge, and $450,000 to $750,000 for 1500 torn/year systems. Operating costs for the clay additive, gas, electricity and labor range from $60 to $130 per ton of sludge. Exact costs depend on sludge characteristics, and the type of pretreatment it receives.
Fired pellets from the CBI process are designed to be used as a lightweight high strength construction aggregate. Addition of the metal sludge noticeable increases the aggregate's strength, and reduces its weight by 7%. Both of these features raise the market value of the product.
To receive more information on CBI's services and on the appropriate regulatory requirements governing waste conversion, contact the company directly. The address and phone number are:
Ceramic Bonding Inc.
939 San Rafael Avenue, Suite C
Mountain View, CA 94043
(415) 940-1146
Sludge stagging is very similar to thermal bonding except that much of the nickel, iron, copper and other metals contained in the sludge can be recovered and sold. Another advantage of this system is that the volume of waste is reduced by as much as 94%, according to manufacturer's claims. The resulting slag can be crushed and sold as aggregate to concrete block manufacturers.
Rostoker, Inc. of Burnham, Illinois has developed a novel process which utilizes custom designed slagging systems for the needs of the particular shop. The Rostoker technology is suitable for many types of waste sludges, including those from electroplating operations, chemical milling, and pickling The Rostoker system consists of five parts:
The carbon content needed for reduction of metal oxides to their elemental form often comes from the high content of organics contained in many sludges. The high temperatures of the Rostoker process pyrolize the organics into carbon. For sludges with low organic contents, coke can be added.
Sludges containing predominantly nickel and iron oxides reduce to a ferro-nickel alloy containing some carbon. This low melting point cast iron can be poured off the slag and cast as an ingot. Copperrich sludges generate molten copper, often containing some zinc, nickel, and cadmium. The remaining slag is mostly sodium silicate. This slag can be reused to supply soda and silica to new batches of sludge.
For a small shop generating 80 tons per year of sludge, the capital cost of the Rostoker process is about $80,000. A facility generating 1,000 tons a year could set up the system for $400,000. The highest price piece of equipment is the furnace. A small tilt-pouring unit can be obtained for $25,000 to $45,000. Operating costs for a small system are typically $1,500 per month for fuel, electricity, furnace refractory replacements and additives for the slagging process. The Rostoker process is marketed exclusively by Enviroscience, Inc.
Enviroscience, Inc. is currently negotiating permitting requirements with the State of California. This sludge slagging process is now available in many other states.
For more information, contact the company's local representative:
Grant Ryan
431 West Alton, Suite H
Santa Ana, CA 92707
(714) 641-7580
If hazardous metal sludge must be transported off-site, recycling alternatives now exist that are financially mom have than land disposal, and mom protective of the environment as wen. These recycling alternatives include hydrometallurgical processing, and converting the sludge to smelter feed.
Hydrometallurgical recycling methods use wet chemistry to extract usable metals from sludges. While these methods have been in use for many years, they are currently receiving attention due to their ability to extract and reuse metals in sludges.
RECONTEK, Inc. is completing construction of a hydrometallurgical plant that will have the capacity to manage sludges from many California shops. In one of its processes, metal hydroxide sludges are digested in sulfuric acid and converted to less soluble sulfates. These metal sulfates are then extracted using filtration, distillation, selective precipitation, electrowinning, ion exchange and other processes. Copper, nickel, chromium, zinc and other metals commonly found in electroplate sludges can be separated.
For more information on these processes, contact:
Wayne Rosenbaum, Executive Vice President
RECONTEK, Inc.
11770 Bernardo Plaza Court, Suite 351
San Diego, CA 92128
(619) 592-0286
Pacific Chemicals Engineering, Ltd. (PCE) is another company relying on hydrometallurgical processes for its metal recovery services. PCE uses strong acids and bases to selectively leach out metals of commercial interest from sludges and other wastes.
Information about PCE can be obtained from:
Dr. James R. Wolfe
President Pacific Chemicals Engineering Ltd.
200 Union Boulevard, Suite G 18
Flood, Colorado 8022
Electroplating sludges frequently contain metals that can be used as for smelters. World Resources Company (WRC) of Phoenix, Arizona is a recycling company that receives non-organic metal-bearing sludges from California and other states, dries the sludges, and sends them for metal recovery to various smelters, depending on the types of metals they contain. Using a broker such as WRC can benefit an electroplater in several ways. For one thing, according to vendor claims, the generator has no future liability for waste managed in this manner. Secondly, if the concentration of certain metals (such as copper) am high enough, the waste management fee can be quite low.
WRC has long-term contracts with smelters in the United States, Canada, Europe and the Far East. These smelters use WRC's sludges as substitutes for their standard smelting feedstock of ore concentrates In order to supply these smelters with useful materials, WRC must be selective in the types of F006 sludges that it accepts.
Metals in the sludge that are not recovered during the smelting process are encapsulated in a silica-rich smelting slag. According to WRC, this slag is not considered hazardous under RCRA regulations.
To find out more about WRC's capabilities, contact:
Orme Lewis, Jr., Vice President
World Resources Company
4250 East Camelback Road, Suite 175-K
Phoenix, Arizona 85018
(602) 952-1411
Some additional publications available from the Hazardous and Toxic Materials Project that may be helpful are:
City of Los Angeles
Board of Public Works
Hazardous and Toxic Materials Project
200 N. Spring Street, Room 353
Los Angeles, California 90012
For further information and assistance or to request additional publications please contact the HTM Project at:
City of Los Angeles
Board of Public Works
Hazardous and Toxic Materials Project
200 N. Spring Street, Room 353
Los Angeles, California 90012
(213) 237-1209
The Board of Public Works Hazardous and Toxic Materials Project was established by the Los Angeles City Council in 1988. The purpose of this program is to promote the National policy of minimizing hazardous waste generation and ensure citywide compliance with hazardous materials and waste requirements. Technical assistance Is provided to City agencies and Industry through on-site consultation, information dissemination, and waste assessments.
Last Updated: January 9, 1996