Science Inventory

Dynamics of the Physiochemical and Community Structures of Biofilms under the Influence of Algal Organic Matter and Humic Substances

Citation:

Li, L., Y. Jeon, S. Lee, H. Ryu, J. Santodomingo, AND Y. Seo. Dynamics of the Physiochemical and Community Structures of Biofilms under the Influence of Algal Organic Matter and Humic Substances. WATER RESEARCH. Elsevier Science Ltd, New York, NY, 158:136-145, (2019). https://doi.org/10.1016/j.watres.2019.04.014

Impact/Purpose:

The frequent occurrence of harmful algal blooms (HABs) by cyanobacteria poses adverse effects to drinking water supplies. Physiochemical treatments such as coagulation and sedimentation have been commonly used to address the suddenly increased load of algal cells and algal organic matter (AOM) during HAB outbreaks. AOM and humic substances (HS) in water can cause taste and oder issues and are linked to the formation of toxic disinfection by products. Furthermore, as organic substrates, AOM may promote the growth of microbial biofilms in oligotrophic drinking water distribution systems (DWDS). Biofilm formation causes a series of problems, such as biocorrosion, nitrification, and consumption of residual disinfectants in DWDS. More importantly, biofilm can serve as temporary or long-term reservoirs for opportunistic pathogens. An understanding of how biofilm develops and matures under unchlorinated conditions is crucial to minimize the accumulation and transmission of pathogens in DWDS. To our best knowledge, no research has been conducted to study the impacts of AOM on biofilm growth. Furthermore, in-depth knowledge of how HS and AOM-impacted bulk water differently affect the physical and microbial community structure of biofilm succession is also missing. To have better insights for biofilm control, a comprehensive understanding of how biofilms develop in response to complex nutrient sources in DWDS is imperative.

Description:

This study aims to investigate the effects of AOM and HS-impacted water in biofilm development under unchlorinated drinking water distribution system (DWDS) conditions. Simulated DWDSs were constructed and operated for 168 days. The formation, development, physiochemical characteristics, and bacterial community structure of biofilms exposed to algal organic matter (AOM) or to humic substances (HS) were continuously monitored and compared using confocal laser-scanning microscopy (CLSM) and 16S rRNA gene sequencing analysis. For the first time, this study examined the dynamic changes of biofilm in response to AOM and HS-impacted bulk water. Biofilms grown for 168 days under AOM-impacted bulk water (BFAOM) had relatively thinner and heterogeneous structures with lower extracellular polymeric substance (EPS) production, while biofilms grown under HS-impacted bulk water (BFHS) had thicker and homogeneous structures with higher EPS accumulation. Analyses of bacterial community structure indicated that higher bacterial diversity was observed in the BFAOM and that bacterial diversity generally tended to increase as biofilm matured. Family Comamonadaceae was the most dominant in biofilm samples but showed different temporal dynamics depending on the organic matter composition of bulk water. In addition, BFAOM showed to possess a higher percentage of unique core microbiome compared to BFHS and was enriched with Rhodobacteraceae and Sphingomonadaceae. Overall, this study revealed that the organic matter composition in bulk water significantly influences the dynamics of physical and bacterial community structure of DWDS biofilm.