WASTEWATER AND LEACHATE: EX-SITU BIOLOGICAL TREATMENT
Bioreactors
Typical Rotating Biological Contactor (RBC)
Process:
Extracted waste water is mixed with microorganisms in attached or suspended growth biological reactors (RBCs):
Enhance process by:
Uses:
Limitations:
Note:
-The microbial population usually comes from the contaminant source.
-Other applications include wetland ecosystems, trickling filters and column reactors.
-Bioreactor equipment and materials are readily available
Extracted waste water is mixed with microorganisms in attached or suspended growth biological reactors (RBCs):
- In Suspended Growth Systems (e.g. activated sludge, fluidized beds, sequencing batch reactors ) - wastewater circulated in an aeration basin. In the aeration basin a microbial population aerobically degrades organic matter producing: CO2, H2O and new cells. The cells form a sludge - settled out in clarifier & recycled into aeration basin or disposed
- In Attached Growth Systems (rotating biological contractors/trickling filters) - microorganisms are established on an inert support matrix to aerobically degrade water contaminants..
Enhance process by:
- Adding activated carbon - adsorbs contaminant, slowly releasing it to the microorganisms for degradation.
- Adding nutrients to the bioreactors - supports growth of microorganisms.
Uses:
- Primary Contaminant Treatment: SVOCs, fuel hydrocarbons & any biodegradable organic material.
- Less effective for some pesticides.
- Some success has been seen with halogenated compounds e.g. PCP & chloro-benzene.
- Enhanced Bioreactors can be used to treat PCBs, halogenated VOCs, and SVOCs in extracted ground water.
- Treats both municipal and industrial wastewater (& recently contaminated water from hazardous waste sites).
Limitations:
- Very high contaminant concentrations may be toxic to microorganisms.
- Volatilisation from activated sludge process would require air pollution control.
- Low temperatures decrease bio-degradation rates - longer cleanup time & increased costs (require heating).
- Residuals from sludge processes require treatment or disposal.
- Long-term technology (several years) - clean-up time dependent on ground conditions, temperatures & rate of desorption of contaminants from soil.
- Cost is highly dependent on the chemical oxygen demand & acid/base required to neutralise the pH of the waste stream.
Note:
-The microbial population usually comes from the contaminant source.
-Other applications include wetland ecosystems, trickling filters and column reactors.
-Bioreactor equipment and materials are readily available