A rapid technique for assessing assimilable organic carbon of UV/H₂O₂-treated water

Abstract

A rapid technique was adopted and customized to assess the assimilable organic carbon (AOC) content of water for UV/H₂O₂ treatment applications. Indigenous consortium was used as inoculum and cells grown were counted using flow cytometry. Residual H₂O₂ after UV/H₂O₂ treatment was found to inhibit microorganisms’ regrowth, leading to incorrect AOC measurement. Therefore, Catalase immobilized on a polymeric support was used to eliminate the residual H₂O₂ prior to the AOC bioassay without affecting the water quality and the AOC. The choice of microbial consortium was found to influence the result of the AOC bioassay, suggesting that indigenous inoculum should be used for each individual sample set. Three days of incubation at 30°C were enough for the microorganisms to reach their stationary phase. Addition of minerals was found to be necessary, affecting the outcome of the AOC test. The method presented in this article will be valuable for monitoring AOC levels at different stages of water treatment train, especially when UV/H₂O₂ is used as one of treatment steps.

Keywords:

• Assimilable organic carbon
• biological stability
• bacterial regrowth
• advanced oxidation processes
• UV/H₂O₂
• water treatment

Acknowledgments

The authors thank Drs. Siva Sarathy and Mihaela Stefan from Trojan Technologies for their cooperation and technical feedback. We also thank Dr. F. Hammes from EAWAG for his kind inputs. Andy Johnson at the biomedical research centre of UBC is also acknowledged for his assistance on the FACS machine. RES`EAU-WaterNET Strategic Network and Natural Sciences and Engineering Council of Canada (NSERC) are acknowledged for financial support.