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Comparison of Physical and Community Structure of Biofilm under the Influence of Humic Substances and Algal Organic Matter in Simulated Drinking Water Distribution Systems
Citation:
Li, L., S. Lee, H. Ryu, J. Santodomingo, AND Y. Seo. Comparison of Physical and Community Structure of Biofilm under the Influence of Humic Substances and Algal Organic Matter in Simulated Drinking Water Distribution Systems. WQTC 18, Toronto, Ontario, CANADA, November 11 - 15, 2018.
Impact/Purpose:
The growth of microorganisms is one of the great challenges for safe drinking water delivery. In drinking water distribution systems (DWDS), about 95% of bacteria tend to attach to the pipe interior surface to form biofilms. The biofilm occurrence in the DWDS might cause a series of issues such as nitrification, biocorrosion, and the proliferation of opportunistic pathogens. Hydraulics regime, pipe materials, disinfectants (i.e. type and concentration), and temperature are commonly documented to affect the biofilm formation in the DWDS. Additionally, the characteristics of bulk water have also been suggested to shape the growth of biofilm. It is reported that biofilm developed in the higher organic loading showed to have a thick and heterogeneous structure. The excessive amount of nitrogen might stimulate the growth of autotrophic bacteria and form a dense structure.
Description:
The growth of microorganisms is one of the great challenges for safe drinking water delivery. In drinking water distribution systems (DWDS), about 95% of bacteria tend to attach to the pipe interior surface to form biofilms. The biofilm occurrence in the DWDS might cause a series of issues such as nitrification, biocorrosion, and the proliferation of opportunistic pathogens. Hydraulics regime, pipe materials, disinfectants (i.e. type and concentration), and temperature are commonly documented to affect the biofilm formation in the DWDS. Additionally, the characteristics of bulk water have also been suggested to shape the growth of biofilm. It is reported that biofilm developed in the higher organic loading showed to have a thick and heterogeneous structure. The excessive amount of nitrogen might stimulate the growth of autotrophic bacteria and form a dense structure. In the DWDS, because of the limitations of conventional water treatment processes, there are often two different sources of natural organic matter (NOM) widely present. The allochthonous NOM, which derived from anthropogenic sources (i.e. humic substance (HS)), is one dominant form. In addition to HS, due to the increased frequency of harmful algal blooms (HABs) in freshwater systems, the autochthonous NOM (i.e. algal organic matter (AOM)) originated from algae is also commonly spread in the DWDS. Studies found that AOM is comprised of more small molecules, hydrophilic fraction, and nitrogenous compounds, compared to HS. Both HS and AOM are important energy sources to support the growth of biofilm. However, no studies have been carried out to understand the different impacts of HS and AOM on biofilm formation in the DWDS yet. Moreover, given the fact that developing biofilm control strategies are indispensable for producing microbiologically stable drinking water, understanding the biofilm development patterns under the influence of HS or AOM, and designing inhibition approaches accordingly are essential for the operation of DWDS. Therefore, this study aims to investigate the dynamic changes of biofilm under the influence of HS and AOM in regard to the physical and community structure in the simulated DWDS. Biofilm was grown in Centers for Disease Control and Prevention (CDC) biofilm reactors with removable polyvinyl chloride (PVC) coupons and fed with AOM collected from Lake Erie or prepared HS respectively. The PVC coupons were periodically taken from the reactors to monitor various biofilm parameters. The biofilm physical structure was observed using a confocal laser scanning microscope (CLSM), while 16S rRNA Illumina sequencing was applied to characterize the variety of biofilm community structure.