Solidification / Stabilization (S/S)

The terms solidification and stabilization (S/S) are commonly used together in the environmental cleanup and waste processing industries. Despite the similarities or the goals that solidification / stabilization may share, it’s important to understand their differences and when each process is applicable for treating waste materials.

Certain conditions may require the use of both S/S processes to properly treat a waste material to meet a treatment standard or change the physical characteristics for handling purposes. Treatment is often accomplished by using reagents that have cementitious properties that combine with the waste to create a solid, and in some cases, a material with monolithic properties. At other times, solidification or stabilization alone will accomplish the treatment objective for a specific type of waste.

Occasionally, there is some debate in the field about a specific solidification application that should not be classified as treatment. A clear understanding from a regulatory perspective of what constitutes treatment is required to maintain compliance. In the early stages of developing the environmental regulations, USEPA (United States Environmental Protection Agency) established a broad definition for the term treatment. As published in the Code of Federal Regulations at 40 CFR 260.10 the regulations define treatment as: “any method, technique, or process, including neutralization, designed to change the physical, chemical, or biological character or composition of any hazardous waste so as to neutralize such waste, or so as to recover energy or material resources from the waste, or so as to render such waste non-hazardous, or less hazardous; safer to transport, store, or dispose of; or amenable for recovery, amenable for storage, or reduced in volume.”

What is Liquid Waste Solidification?

USEPA defines stabilization as a process that chemically reduces the hazard potential of a waste by converting the contaminants into stable and less toxic forms. Stabilization reduces the solubility and the mobility of the contaminates within the waste matrix. Depending on the reagents selected for the stabilization process a change in the physical characteristics of the treated waste may or may not be noticeable.

Solidification refers to a treatment process that encapsulates and transforms the waste into a solid form that has some structural integrity. Although some beneficial chemical interactions with the contaminates may occur, it is not the objective of this waste treatment technique to target specific contaminants. The resulting product from solidification can range from a granular consistency to a monolithic solid. This is entirely dependent on the reagent used, the dose rate and the physical / chemical characteristics of the waste material being solidified. Bench testing with different dose rates of reagents can produce valuable information to optimize operations, production levels and overall project cost.

When is Solidification used?

Solidification of difficult-to-handle waste materials can be the best treatment and management option available. Specific waste types that fall into the group may include contaminated sediments from dredging, oil and gas exploration wastes, drilling muds, multi-phase liquids, sludges, non-reclaimable tank bottom sludges and other waste mixtures that are not compatible with conventional treatment technology. Other considerations where a solidification process may be the most viable option include:

  • Situations where no additional value can be obtained from the waste material through product recovery, recycling, direct reuse, or feedstock to another process
  • Converting a liquid / sludge waste material to a solid form for safe handling and transport
  • Physical/chemical treatment technology is not compatible with the waste material
  • Other treatment options are cost prohibitive from a technology and / or logistics perspective
  • The waste volume is too large for a disposal facility to handle with free liquids present in the material
  • The disposal facility is not permitted to handle a specific type or classification of waste as designated by regulations
  • Chemical spill cleanup and other emergency situations. Using solidification products that are compatible with the waste can be a quick and effective way to contain, immobilize as well as reduce further impacts to the environment
  • To meet strength requirements and add structural integrity to a waste material for proper disposal at a landfill or approved beneficial reuse application
  • In some applications, converting the waste into a monolithic mass can reduce leaching and mobility of specific contaminants of concern more effectively than where other processes

What types of products are used for Solidification?

Some of the most common reagents / binders that are readily available in the market include: Lime, Lime Kiln Dust, Cement, CKD, Fly Ash, and select industrial by-products and custom blends of these materials. Proper selection of reagents and binders for any solidification process requires lab testing and bench trials. A general understanding of how the waste was generated, chemistry and the variability in the physical / chemical characteristics is critical information for any solidification process. Some key points to consider in reagent selection should include:

  • Lab testing to evaluate chemical compatibility and observe desired and any undesirable changes with the waste
  • Time required for the reagents to reach the desired outcome
  • Consideration for reagent performance based on weather conditions in the field versus a controlled setting in the lab
  • Mixing techniques that will be used in the field
  • Cure time at full production levels in the field and any variables that could impact the process
  • The preferred reagent of choice is acceptable by permit at the disposal facility including a backup facility
  • Reagent supply and seasonal shortfalls that could impact project schedules
  • Delivery options, packaging, and lead times to fulfill orders and facilitate ramp up timelines for large scale projects
  • Reagent cost
  • The solidified waste meets all DOT requirements for safe transport
  • The solidified waste meets the disposal facilities strength and operational concerns as received. Off specification charges to further process the waste can be expensive

Why choose Mintek Resources to supply your next project?

  • Cost effective
  • Multiple product delivery options
  • Strategic supply locations and terminals
  • Established network of truck and rail shipping options
  • Technical resources and research laboratory
  • Decades of field experience
  • Proven product performance
  • Consistent product quality

What to expect?

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