SOIL, SEDIMENT AND SLUDGE: EX-SITU BIOLOGICAL TREATMENT
Bio-piles
Typical Biopile for Solid Phase Bioremediation
Excavated soils are mixed with soil amendments and placed in aboveground enclosures. This process also includes leachate collection systems & is used to reduce concentrations of petroleum constituents in excavated soils through the use of biodegradation. It is an aerated static pile composting process in which compost is formed into piles and aerated with blowers or vacuum pumps.
Uses
Limitations:
Costs are dependent on the contaminant, procedure to be used, need for additional pre- and post-treatment, and need for air emission control equipment. Biopiles are relatively simple and require few personnel for operation and maintenance. Typical costs with a prepared bed and liner are approx $190 per cubic metre.
- Moisture, heat, nutrients, oxygen, and pH can be controlled to enhance biodegradation.
- The treatment area will generally be covered or contained with an impermeable liner to minimize the risk of contaminants leaching into uncontaminated soil.
- The drainage itself may be treated in a bioreactor before recycling.
- The air distribution system is typically buried under the soil & passes air through the soil either by vacuum or by positive pressure.
- Soil piles may be covered with plastic to control runoff, evaporation, and volatilisation and to promote solar heating.
- If VOCs are in the soil - these will volatilise into the air stream, thus air treatment would be required.
- Biopile is a short-term technology (few weeks - several months).
Uses
- Treats non-halogenated VOCs, fuel hydrocarbons, halogenated VOCs, SVOCs, & pesticides.
- The process effectiveness will vary and may be applicable only to some compounds within these contaminant groups.
Limitations:
- Excavation of contaminated soils is required.
- Treatability tests required to determine the biodegradability of contaminants and appropriate oxygenation and nutrient loading rates.
- Questionable effectiveness for halogenated compounds.
- Similar batch sizes require more time to complete cleanup than slurry phase processes.
- Static treatment processes may result in less uniform treatment than processes that involve periodic mixing.
Costs are dependent on the contaminant, procedure to be used, need for additional pre- and post-treatment, and need for air emission control equipment. Biopiles are relatively simple and require few personnel for operation and maintenance. Typical costs with a prepared bed and liner are approx $190 per cubic metre.