SOIL, SEDIMENT AND SLUDGE: EX-SITU CHEMICAL/PHYSICAL TREATMENT
Solidification/Stabilization
Typical Ex Situ Solidification/ stabilisation Process Flow Diagram
Process:Contaminants are physically bound or enclosed within a stabilised mass (solidification) or chemical reactions are induced between the stabilising agent and contaminants to reduce their mobility (stabilisation).
(As for in situ solidification/stabilization (S/S))
Ex situ S/S, however, typically requires disposal of the resultant materials.
Typical ex situ S/S is a short- to medium-term technology.
Uses:
- The target contaminant group: inorganics (including radionuclides).Usually less effective for organics and pesticides (unless vitrification).
Limitations:
- Long-term immobilisation of contaminants needs environmental approval, may cause later problems.
- Certain wastes are incompatible with different processes.
- Organics are generally not immobilised.
- Long-term effectiveness is not widely known.
- Cost is dependent on type & volume of waste, moisture content & size of the S/S system required.
Note:
Many adaptions of the conventional process exist, however each modified system is directed to encapsulate/immobilise the harmful constituents and in some way process the contaminated soil. Modified systems include (1) bituminisation, (2) emulsified asphalt, (3) modified sulphur cement, (4) polyethylene extrusion, (5) pozzolan/Portland cement, (6) radioactive waste solidification, (7) sludge stabilisation, (8)soluble phosphates, and (9) vitrification/molten glass.
http://www.frtr.gov/matrix2/section4/4-21.html#top See link for further information.