Citation:

Jeon, Y., L. Li, J. Calvillo, H. Ryu, J. Santo Domingo, O. Choi, J. Brown, AND Y. Seo. Impact of algal organic matter on the performance, cyanotoxin removal, and biofilms of biologically-active filtration systems. WATER RESEARCH. Elsevier Science Ltd, New York, NY, 184:116120, (2020). https://doi.org/10.1016/j.watres.2020.116120

Impact/Purpose:

The occurrence of harmful algal blooms dominated by toxic cyanobacteria can induce continuous loadings of algal organic matter (AOM) and toxins in drinking water treatment plants. However, little is known about the behavior of AOM and microcystin-LR (MC-LR) as well as their influence on biofilm formation in biological filtration systems using granular-activated carbon (GAC). This study highlights the performances of conventional biological filters on the removal of AOM components including MC-LR and the key changes of microbial community structures driven by AOM. The results of this study suggest that microorganisms in biofilms play an important role in removing MC-LR, humic-like substances, and protein-like substances of AOM. Even though the community structures showed a rapid adaptation to AOM, it appears that there is a limitation in removing all AOM components, which may increase concerns regarding finished water quality. For the next step, it is necessary to understand how infiltrated AOM affects downstream processes (e.g., disinfection) and impact community structures and biofilm formation in drinking water distribution systems.

Description:

In this study, five parallel laboratory-scale columns were used to investigate the impacts of AOM on the performance and bacterial community structure of GAC filters at different empty bed contact times (EBCTs). The results of excitation and emission matrix analysis indicated that terrestrial humic- and protein-like fractions were dominant in AOM. When AOM was loaded into biological filters, terrestrial humic-like substances were preferably eliminated than protein-like substances. AOM-related substances and MC-LR were not completely removed, showing the strong correlation between the removal of MC-LR and the removal of the terrestrial humic-like component. Moreover, the filtration performance for the removal of AOM and MC-LR significantly decreased with an EBCT (10 min) and deactivation of biofilms. The bacterial community analysis results revealed that the community structure of biofilms responded to AOM where the dominance of Rhodocyclaceae, Saprospiraceae, and Comamonadaceae was closely associated with the removal of aromatic carbon compounds and protein-like substances in AOM. Overall, this study provides deeper insights into the responses of biofilm and the fate of AOM and MC-LR in conventional biological filters.

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