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Enumeration of coliform bacteria in wastewater solids using defined substrate technology
1Department of Civil Engineering, Texas A&M University, College Station 77843-3136, USA. tkramer@civilmail.tamu.edu
Summary
A new Colilert-QuantiTray method for enumerating coliform bacteria in waste activated sludge (WAS) shows statistically equal results to traditional methods. This easier, faster technique may be suitable for WAS bacterial analysis, pending further data.
Area of Science:
- Environmental Microbiology
- Wastewater Treatment
- Bacteriology
Background:
- Accurate enumeration of coliform bacteria in waste activated sludge (WAS) is crucial for wastewater management.
- Traditional methods like multiple-tube fermentation (MTF) are time-consuming and labor-intensive.
- Defined substrate technologies offer potential for faster and easier bacterial analysis.
Purpose of the Study:
- To evaluate the applicability of a commercially available defined substrate technology (Colilert-QuantiTray) for enumerating coliforms in WAS.
- To compare the performance of Colilert-QuantiTray with the U.S. Environmental Protection Agency (U.S. EPA)-accepted multiple-tube fermentation (MTF) method.
- To assess the method's suitability for raw and pasteurized WAS samples.
Main Methods:
- Colilert-QuantiTray system was used for bacterial enumeration in raw and pasteurized WAS.
- Results were compared against standard MTF methods using various broths (lauryl tryptose, brilliant-green lactose bile, EC, EC-MUG).
- Twenty replicates were analyzed for each sample type (raw, 15-min pasteurized, 30-min pasteurized) to ensure statistical validity.
Main Results:
- Both Colilert-QuantiTray and MTF yielded statistically equivalent total coliform most probable numbers (MPNs) across all tested WAS samples.
- Fecal coliform counts by MTF were higher than Escherichia coli (E. coli) by Colilert-QuantiTray, as expected.
- However, E. coli MPNs generated by MTF were statistically equal to those from Colilert-QuantiTray.
Conclusions:
- The Colilert-QuantiTray system demonstrates potential as a user-friendly and time-efficient alternative for coliform enumeration in WAS.
- While results for total coliforms and E. coli show statistical equivalence, further data are needed for definitive U.S. EPA acceptance.
- This study contributes to building a database for the potential acceptance of Colilert-QuantiTray in WAS bacterial analyses.