Our Technologies

Bioreactor Systems

When lime treatment is not a suitable solution, a bioreactor may solve the problem. This is often the case when a site:

• has a flow of less than 200 gallons/min;
• has low to moderate acidity;
• is remote or difficult to access; or
• requires sulfate reduction to less than 2,000 mg/L

Bioreactors remove metals and sulfate by reversing the chemistry of acid generation and promoting the growth of bacteria that reduce sulfate to sulfide. The resulting sulfide can subsequently precipitate metals as metal sulfides.

The Sulfate-Reducing Bioreactor’s Competitive Advantage

Among bioreactor systems, IWT’s sulfate-reducing, semi-passive bioreactor is often the better choice over traditional bioreactor applications and alkalinity-based bioreactors.

In traditional bioreactors, acid rock drainage is introduced to an organic substrate (such as manure compost). These bioreactors work best with low metal concentrations, low flow rates and even flow distribution. The organic substrate must be monitored and adjusted to assure levels are appropriate in light of carbon needs, sulfate or metal loading, bacterial reactions’ required residence time and vertical transport time associated with thee substrate’s composition.

Another alternate, the “Successive Alkalinity Producing Systems” (SAPS) uses a system of organic material overlying limestone. Water flows first, through organic material where oxygen and iron are removed; second, through limestone to receive alkalinity without immediate precipitation of iron hydroxides, and finally into settling ponds where it becomes re-oxidized and iron hydroxides settle out.

Unlike these alternatives, IWT’s sulfate-reducing bioreactor adds a carbon source to the influent and uses a liquid substrate reactor with larger pore spaces. Our system can remove specific concentrations of sulfate and metals based on the stoichiometric addition of the carbon source. Further, metals can be removed separate from the bioreactor.

The Benefits of IWT’s Technology:

• Longer lifespan, not limited by the carbon source in the substrate;
• Little or no plugging or short-circuiting due to substrates (manure);
• Removes specific sulfate and metals concentrations;
• Increases hydraulic conductivity
• Removes metals separate from the bioreactor to further avoid failures;
• Requires less power, labor and expense that traditional system.
• Greater reliability, not affected by flow, chemistry and equipment changes
• Remote site suitability (fewer site visits for monitoring)
• Less sludge than with lime precipitation

COLLATERAL TREATMENT OF MINE DRAINAGE WITH THE ROTATING CYLINDER TREATMENT SYSTEM™ (RCTS™) MULTIPLE APPLICATIONS RCTS-60HS™ Emergency Treatment of Acid Mine Drainage at the Leviathan Mine with the Rotating Cylinder Treatment System (RCTS™) Semi-Passive Bioreactor Design Permanganate Passivation (more resources)

Sustainable Technologies, Revolutionary Results

• RCTS™ – Rotating Cylinder Treatment System™
• Bioreactor Systems
• Permanganate Passivation