Hazardous Waste Treatment Agents

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WHAT THEY CAN DO

HAZCO Division products can solidify almost any waste - liquids, sludges, soils, dry solids, or suspensions. At the same time, they can chemically stabilize heavy metals and many organic compounds in the waste to meet EPA Land Disposal Restrictions (LDR's, 40 CFR 268). They offer, to the user, three principal advantages over traditional cement/pozzolan methods:

1. Low Volume/Weight Expansion

Solidification of wastes which are to be land-disposed, or stored after treatment, expands both the volume and the weight of the waste. The degree of expansion will have a direct effect on the dollar cost of final disposal, as well as on the cost of transportation to the disposal site. For any given degree of stabilization, as measured by the EPA's TCLP, HAZCO technologies will result in much lower expansion than those processes which are primarily based on cement and/or pozzolans. Typical volume expansion coefficients with HAZCO stabilizers will run between 1.05 and 1.35. For cement/pozzolan stabilizers, the coefficients will run between 1.50 and 2.50.

A recent example is a barium-contaminated sludge which, if treated with portland cement, required 1.5 tons of portland cement per ton of sludge to drop its barium TCLP leachability from 1600 mg/l to 30 mg/l. This would have produced a volume expansion factor of 2.50, or an addition of 150% in volume. Treatment with a HAZCO product was accomplished by the addition of only 0.2 tons of stabilizer per ton of sludge, and resulted in a barium TCLP reading of only 0.36 mg/l, and an expansion factor of only 1.2 This sludge was in two ponds, and was treated in-situ with HAZCO's products.

2. Simultaneous Stabilization of Both Inorganic (Heavy Metal) and Organic Toxins

Wastes (soils in particular) often contain both heavy metals and toxic organic compounds. Cement-based stabilization can capture the heavy metals, but will not stabilize organic toxins. A separate operation would thus be required (such as thermal treatment) to deal with the organics. With HAZCO materials, both the metals and the organics often can simultaneously be stabilized in a single treatment. The accompanying data sheets show some examples.

3. Low Temperature Rise in Mixing

Cement and pozzolan reactions are strongly exothermic, and can cause the volatile and semi-volatile organic components of a waste to be "cooked-out" into the atmosphere during the mixing process. HAZCO product reactions are, in contrast, almost totally non-exothermic. A recent test run by Dr. Neville Kingham of Kiber Associates in Atlanta on a typical PC/Pozzolan mix with soil showed a net temperature rise of about 26E C (start at 22E C, finish at 48E C!). In this test, Dr. Kingham was particularly looking into VOC release, and found that the measured VOC discharge was substantial.

Using the same waste (a badly contaminated soil), and the same mixing procedures, but with a HAZCO blend of stabilizers, the temperature rise was less than 3E C. VOC kickout was correspondingly reduced.

WHAT THEY ARE?

The several HAZCO products are each based upon one of more carefully selected and purified clays. Certain of these clays are chemically modified for specific tasks, and may also be pre-mixed with other components to achieve specific goals. Most applications can be completed with one of these products. In some cases, two or more HAZCO products may be either pre-mixed or applied in sequence. Most HAZCO products are dry powders which are to be mixed with the waste being treated. Two are granular, and when used with clear, aqueous waste, do not require mixing.

PRODUCT DESCRIPTIONS

They are slightly alkaline, non-flammable, non-reactive and non-corrosive, and are not biodegradable.

These reagents immobilize wastes (liquid, sludge, or solid) through the action of complex bonding mechanisms and ion exchange reactions. The end result is a homogeneous solid with excellent leach resistance.

LIQUI-SET Liqui-Set is a water-activated, granular solidification/stabilization agent used for treatment of aqueous liquids containing small amounts of dissolved and suspended solids, detergents, chelating agents, resins, and up to 5% oils. Liqui-Set does not require stirring, and is utilized by simple addition to the aqueous liquid waste. Typically, 100 to 150 pounds of Liqui-Set are required to solidify 45 to 48 gallons of liquid waste in a 55-gallon drum.

LIQUI-BOND, LIQUI-BOND II Liqui-Bond is chemically similar to granular Liqui-Set, but instead is a finely-divided powder. Its application requires power mixing, either with an impeller (drum mixing) or a ribbon-blender or pugmill (continuous or bulk mixing). It thus can be used to treat wastes with high solids content, including heavy sludges. With the addition of water, dry solid wastes can be successfully treated to meet TCLP leach-resistance standards.

Liqui-Bond II is used with the same range of wastes for which Liqui-Bond is used. Unlike Liqui-Bond, Liqui-Bond II sets up to a hard matrix. Load‑bearing strengths over 5 tons per square foot (69 psi, or 48.8 metric tons per square meter) can be achieved. It sets up slower than Liqui-Bond.

CHEM-BOND, CHEM-BOND II Chem-Bond is a powdered solidification/stabilization agent used either alone or in combination with Liqui-Bond or Petro-Lock. Chem-Bond finds its greatest utility in the solidification/stabilization of aqueous solutions very high in dissolved solids, such as neutralized acids and bases, and those organic liquids that are water soluble or miscible. Example of organic liquids in this category include alcohols, glycols and low molecular weight ketones. Mixtures of Chem-Bond and Petro-Lock are ideal when the above liquids are present in combination with oils and/or greases. Use of Chem-Bond requires power mixing equipment. Chem-Bond can also be used to treat sludges and soils contaminated with metals and/or water soluble or miscible organics, since it can stabilize heavy metals.

Chem-Bond II is used with the same range of wastes for which Chem-Bond is used. Unlike Chem-Bond, Chem-Bond II sets up to a hard matrix. Load‑bearing strengths over 5 tons per square foot (69 psi, or 48.8 metric tons per square meter) can be achieved. It sets up slower than Chem-Bond

PETRO-LOCK Petro-Lock is a finely ground solidification/stabilization agent for organic compounds. It is used in the treatment of wastes some or all of whose liquid components are not water-miscible (such as oils). Treatment of wastes which have both water-miscible and water immiscible components is accomplished through the use of a combination of Petro-Lock with Liqui-Bond, or Petro-Lock with Chem-Bond.

Petro-Lock, used alone, will not solidify nor chemically stabilize the aqueous phases of waste. With the addition of Chem-Bond or Liqui-Bond as described above, heavy metal contaminants in the aqueous phase of a two-phase waste will be chemically stabilized simultaneously with the organic components. Power mixing is required.

CURING

With two exceptions (Liqui-Bond II and Chem-Bond II) HAZCO solidifiers/stabilizers cure to a stiff putty-like consistency during mixing, depending upon the nature of the raw waste and its matrix, and the loading rate used. Liqui-Bond II and Chem-Bond II are chemically equivalent to their respective namesakes. They differ in that they cure more slowly (48 to 96 hours), and result in a hard end product. Again depending on the makeup of the raw waste, and the reagent loading rate, typical 28-day Penetrometer readings will be well over 3.6 tons per square foot (50 PSI).

MIXING

With the exception of Liqui-Set, which is a granular product designed for use on predominantly clear liquid wastes with negligible solids, all of the HAZCO products are finely-divided powders (200 mesh). Good dispersion of the stabilizer material within the waste matrix is essential to ensure that there are no "islands" of untreated waste. Since these materials begin to "catch" or clot the waste rather quickly, good shear action is desirable to break down over-treated clots, and to achieve good dispersion.

In drums, a simple four-blade impeller, slightly smaller in OD than the ID of the drum, works well. Means should be provided to raise and lower the impeller during mixing. Bulk mixing can be done in a ribbon blender, pugmill, or similar apparatus.

In-situ treatment of soils and sludges can be accomplished with backhoes, rotary tillers, augers, or other equipment.

SUMMARY

These brief product descriptions are presented as general guidelines in the use of HAZCO stabilization media. Because of nearly endless waste varieties, determination of a waste-specific media recipe is essential to achieve optimum balance of efficiency and economy. The amount of solidifiers required for a given waste will vary with the type and concentration of contaminants present, as well as the character of the matrix. HAZCO has laboratory facilities to serve customer needs in developing the most efficient and cost effective waste treatment recipes.

HOW THEY ARE APPLIED

SITE REMEDIATION

For in-situ remediation projects, backhoes, augers, rotary tillers, or other equipment may be used. Another option (which gives better control of mixing) is removal of the soil or sludge, treatment in a mobile plant positioned nearby, and return of the treated waste to its original place. Pugmills and ribbon blenders are suitable treatment mixers.

BULK TREATMENT

Pugmills or ribbon blenders may be used for mixing.

DRUM TREATMENT

Waste can be treated in DOT 17H drums, using a vertical-shaft mixer with a four-blade propeller-type blade. A 5-horsepower air or hydraulic motor is adequate.

GENERAL CONSIDERATIONS

The treater should have available a thorough characterization of the raw waste, both physical and chemical, in order to design an appropriate treatment procedure.The Waste Acceptance Criteria of the facility which will be next to receive the treated waste must be known and taken into consideration in planning the treatment. The following table displays typical match-ups between waste types and HAZCO materials. The loading rates shown are by no means either maxima or minima. Rather, they represent conservative starting points for bench testing.