Introduction - Stabilization and Solidification of Hazardous, Radioactive, and Mixed Wastes - page 3

in 1976, few companies investigated the S/S of industrial liquid wastes. Chemfix
Inc. discovered and patented a method using sodium silicate solution and portland
cement for S/S of mine drainage sludge. During the same time period, Conversion
System Inc. (CSI) developed a lime-fly ash process for the treatment of sludge from
power plant flue gas desulfurization. Dravo Corporation used blast furnace slag for
solidification of high-volume sludge from electric power plants. Crossford Pollution
Control (later Stablex) in England began commercialization of its cement-fly ash
process for solidification of inorganic waste streams at central treatment sites. The
USEPA funded a few projects to evaluate S/S processes for hazardous waste treat-
ment. Despite the lack of regulations, a considerable amount of waste was solidified
during this time period. Reportedly, Chemfix solidified more than 375 ML (100
million gallons) of sludge from 1970 to 1976. CSI and Dravo installed several flue-
gas desulphurization gypsum (FDG) treatment systems and treated much larger
quantities of waste. In 1974, about 47,000 tonnes of sludge containing mercury were
solidified and then disposed in the ocean (ocean disposal of treated radioactive,
hazardous, or mixed waste has been banned by most countries since this time).

1.3 POST-RCRA DEVELOPMENT OF S/S TECHNOLOGY

AND ORGANIZATION OF THE TOPIC

After the passage of RCRA in 1976, S/S began to receive attention from govern-
mental agencies, waste generators, and engineering firms. The USEPA began to fund
research and development on S/S technologies not only at USEPA laboratories, but
also with contractors and universities. During this time period, extensive research
and development activities on various aspects of S/S were conducted. Many inor-
ganic and organic binders, including those listed in Table 1.1, were developed for

TABLE 1.1
List of Binders Used for S/S

Inorganic Binder Systems Organic Binder Systems

Portland cement
Portland slag cement
Portland pozzolan cement
Portland cement-silicate system
Polymer modified cement
Masonry cement
Lime-pozzolan cement
Calcium aluminate cement
Alkali-activated slag cement
Alkali-activated pozzolan cement
Phosphates
Gypsum
Sulfur polymer cement
Alkali silicate minerals

Bitumen
Urea formaldehyde
Polybutadiene
Polyester
Epoxy
Polyethylene