Electrochemical biofilm control by remolding microbial community in agricultural water distribution systems

Authors: SONG, PENG - China Agricultural University; XIAO, YANG - China Agricultural University; Brooks, John; FREGUIA, STEFANO - China Agricultural University; ZHOU, BO - Chinese Academy Of Sciences; LI, YUNKAI - China Agricultural University

Submitted to: Journal of Hazardous Materials
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/26/2020
Publication Date: 7/27/2020
Citation: Song, P., Xiao, Y., Brooks, J.P., Freguia, S., Zhou, B., Li, Y. 2020. Electrochemical biofilm control by remolding microbial community in agricultural water distribution systems. Journal of Hazardous Materials. 403. Article 123616. https://doi.org/10.1016/j.jhazmat.2020.123616.
DOI: https://doi.org/10.1016/j.jhazmat.2020.123616

Interpretive Summary: Smaller scale irrigation systems require specialized cleaning approaches, one of which is to use electrochemical, or electrically activating reactive chemicals in water systems to remove bacteria from the interior surface of irrigation systems as well as prevent bacteria from attaching to these surfaces. Chemicals such as chlorine can be used to control these bacteria and reduce groups of bacteria on surfaces, known as biofilms. This study aimed to understand the effect of these cleaning systems and how they reduce and change the bacterial members on surfaces of drip irrigation tubing. Bacteria on the irrigation tubing surface was quantified and qualified using DNA sequencing approaches to determine the changes to the bacterial populations. The cleaning system formed active chlorine which reduced the bacterial population on the surface. Some bacterial members changed within the population, indicating that there was some adaptation to the cleaning approach. Additionally, the cleaning also reduced the total amount of the biofilm. The system may be useful to clean irrigation systems employing wastewater or other unconventional water sources.

Technical Abstract: Electrochemical treatment has become one of the most effective methods to control biofilm due to its obvious bactericidal effect and eco-friendliness. Understanding the mechanism of electrochemical biofilm control is the key to further improving its efficiency. In this paper, the upflow electrochemical processor with Ti/IrO2+RuO2 anode and stainless-steel cathode is used to inhibit and remove the non-electrode target surface with no-biofilm and biofilm, respectively. Illumina Miseq high-throughput sequencing technology, combined with molecular ecological network analysis methods, were applied to investigate the effects of electrochemical treatment on attached biofilm microbial communities and microbiological mechanisms systematically. It was found that the electrochemically formed active chlorine migrated to the non-electrode target surface with the test water, and effectively reduced the complexity and stability of the microbial network of attached biofilm; key bacteria and biomarkers are linearly related to extracellular polymer and biofilm content play an inhibitory role in significantly reducing the amount of biofilm, which was more than 53.0%. For the two electrochemical modes, the biofilm controlling treatment“remove” (biofilm attached) was obviously better than that of “inhibition” (no-biofilm attached) , mainly because the frequent “inhibition” type electrochemical treatment selected for bacteria which were chlorine- and electric-resistant. This study can provide a theoretical reference for more efficient control of biofilm growth in membrane bioreactors, wastewater treatment, and unconventional water irrigation.