Control strategies for biofilm control in reclaimed water distribution systems from the perspective of microbial antagonism and electrochemistry

Biofilm formation in reclaimed water (RW) distribution systems presents significant technical challenges to RW utili-zation. Two main technologies to control biofilm formation, microbial antagonism (MA) and electrochemical oxida-tion (EO), are not yet widely used in drip irrigation systems (DIS) and their mechanisms of action need further clarification. In this study, we first showed that the MA and EO treatments reduced biofilm formation by about 62% and 68%,respectively, and extracellular polymeric substance (EPS) content by 14% and 49%, respectively, in biofilms compared with raw RW type 1 (R-RW1) in unused pipes, thus effectively improving the performance of DIS. When MA-RW and EO-RW were applied to already clogged systems, the degree of clogging alleviation varied depending on the severity of the original clogging. We recommend adding the antagonist, Bacillus subtilis, to RW at 25% clogging for the maximum effect and to slow the microbial adaptation process. Compared to MA, the recovery effect of EO was slower initially but lasted longer and had a significantly better alleviating effect on severely clogged pipelines. Illumina Mi-SEQ high-throughput sequencing data showed that both MA and EO resulted in a significant decrease in microbial di-versity, dynamic changes in bacterial community structure, and disruption of network interaction and network mod-ularity. Meanwhile, both treatments promoted the growth of specific microorganisms, enhanced the interaction between certain microbial components, and improved the efficiency of information, matter, and energy exchange within the modules. In summary, we verified the dredging effect of two strategies on DIS under different water condi-tions, revealed the differences in their mechanisms of action, and proposed their application scenarios. Our results will help improve the efficiency of RW in agricultural drip irrigation systems and effectively reduce maintenance costs.