GROUNDWATER AND LEACHATE: EX-SITU CHEMICAL/PHYSICAL TREATMENT
Adsorption/Absorption
Typical Adsorption/Absorption System
Process:
Process involves either:
Adsorbents:
Granulated activated carbon is most common (GAC - explained later); others include:
1. Activated alumina:
Limiting Factors/Reduced effectiveness:
Cost:
Typical costs for 1 year period depend on how frequently replacement of absorbent unit is required.
For heavy metal contaminated ground water, the Forager Sponge technology is approximately $280/1000 gallons.
- Contaminated water enters system.
- Solutes concentrate at the surface of a sorbent, reducing their concentration in the contaminated water.
- Treated effluent then collected.
- Continuous process used until absorbence unit requires replacement.
Process involves either:
- Physical adsorption: weak Van der Waals forces provide the driving force
- Chemi-sorption: chemical bond forms between the compound and the surface of the solid
- Electrostatic adsorption (or ion exchange): adsorption of ions through Coulombic forces.
Adsorbents:
Granulated activated carbon is most common (GAC - explained later); others include:
1. Activated alumina:
- Porous and highly absorptive
- Effectively removes fluoride, arsenic, and selenium
- Requires periodic cleaning.
- Open-celled cellulose sponge with an amine polymer
- Selectively absorbs dissolved heavy metals as both cation and anions.
- Adsorptive surface allowing molecular adhesion of organic, inorganic and heavy metal contaminants
- Used to treat waste streams.
- Better suited for explosives
- Resistant to deactivation (due to the adsorption of dissolved solids)
- More expensive than GAC, but greater adsorption capacity & more resistant to abrasion - longer life.
Limiting Factors/Reduced effectiveness:
- Water-soluble/small particulates are not adsorbed well.
- High cost if used as the primary treatment for high contaminant concentration levels - would require very frequent replacement of absorbent unit.
- Not used for oily substances.
- Contaminated media often requires further treatment or disposal as hazardous wastes.
Cost:
Typical costs for 1 year period depend on how frequently replacement of absorbent unit is required.
For heavy metal contaminated ground water, the Forager Sponge technology is approximately $280/1000 gallons.