Naturally occurring and found in surface water, Geosmin and MIB are produced by bacteria in soil and algae blooms and typically have an earthy or musty odor similar to that of rich soils.
When algae or bacteria naturally increase in source water due to seasonal shifts, Geosmin and MIB readings can rise above that of the taste and odor threshold which leads to unsatisfactory drinking water (while taste and odor of the water is poor, the water does remain safe to drink).
Humans can detect the smell of geosmin at about 15 parts per trillion (15 nanograms per liter). To further illustrate, if you poured a teaspoon of geosmin into the amount of water that could fit into 200 olympic-sized swimming pools, you could still smell it.
Aulick Partners With Independent Lab And Utility To Test Powdered Activated Carbons Based On Performance
- Scope of testing was to analyze 3 PACs for MIB and geosmin removal
- Including – MIB 4-point dose removal curve and resulting performance factors
- Raw water from WTP was supplied to Lab
The resulting design for the testing was as follows:
- MIB and geosmin was spiked to an initial concentration of approx. 90 ng/L. The initial concentration of MIB and geosmin will not impact the dose removal curve of the PAC studies as the generation of these curves are independent of starting concentration.
- The jar tests were run by a procedure that’s part of the AWWA PAC Standard (B600).
- PAC doses of 10, 15, 20, and 30 mg/L, along with a blank, were used to generate dose removal curves for MIB.
- For graphing purposes all results below the minimum reporting of 1.0 ng/L were recorded at 0.99 ng/L.
Discussion And Conclusion
All 3 carbons resulted in the targeted 80% removal of MIB using PAC doses ranging from 9.55 – 15.55 mg/L. Overall, however, Aulick’s Activated Carbon performed best with 80% removal at the lowest PAC dose of 9.55 mg/L.
The performance factor ranking utilized the following scenario:
- MIB was chosen as the primary factor over the other odor causing compounds due to its persistence in the effluent vs. its counterparts.
- 80% removal of MIB was sufficient to capture the majority of the MIB with typical PAC doses.