Monitoring Bacterial Community Dynamics in a Drinking Water Treatment Plant: An Integrative Approach Using Metabarcoding and Microbial Indicators in Large Water Volumes

Abstract

Monitoring bacterial communities in a drinking water treatment plant (DWTP) may help to understand their regular operations. Bacterial community dynamics in an advanced full-scale DWTP were analyzed by 16S rRNA metabarcoding, and microbial water quality indicators were determined at nine different stages of potabilization: river water and groundwater intake, decantation, sand filtration, ozonization, carbon filtration, reverse osmosis, mixing chamber and post-chlorination drinking water. The microbial content of large water volumes (up to 1100 L) was concentrated by hollow fiber ultrafiltration. Around 10 million reads were obtained and grouped into 10,039 amplicon sequence variants. Metabarcoding analysis showed high bacterial diversity at all treatment stages and above all in groundwater intake, followed by carbon filtration and mixing chamber samples. Shifts in bacterial communities occurred downstream of ozonization, carbon filtration, and, more drastically, chlorination. Proteobacteria and Bacteroidota predominated in river water and throughout the process, but in the final drinking water, the strong selective pressure of chlorination reduced diversity and was clearly dominated by Cyanobacteria. Significant seasonal variation in species distribution was observed in decantation and carbon filtration samples. Some amplicon sequence variants related to potentially pathogenic genera were found in the DWTP. However, they were either not detected in the final water or in very low abundance (<2%), and all EU Directive quality standards were fully met. A combination of culture and high-throughput sequencing techniques may help DWTP managers to detect shifts in microbiome, allowing for a more in-depth assessment of operational performance.

Performance of polycarbonate, cellulose nitrate and polyethersulfone filtering membranes for culture-independent microbiota analysis of clean waters

“…4). These abundance values are in agreement with what has been reported in drinking and disinfected water [36][37][38]. Gene quantification values, expressed per volume (mL) of water, ng of DNA or 16S rRNA gene copy number, were not significantly different between the three types of filtering membranes (p > 0.01) for none of TW and DW samples (Fig.…”

From Source to Tap: Tracking Microbial Diversity in a Riverbank Filtration-Based Drinking Water Supply System under Changing Hydrological Regimes

“…Water treatment, consisting of ozone oxidation, sand filtration, and chlorination further reduced both cell count and microbial diversity, in line with previous observations [27,39]. Of the above treatment processes, chlorination was shown to have the most significant impact in a water supply system using surface water abstraction [13,40]. Chlorine concentration is the main driver of separation of treated and untreated samples.…”

“…Subsequent treatment technology depends on the quality of water produced in RBF. Most water treatment plants use at least disinfection (chlorination), which has a well-documented impact on microbial communities, giving rise to chlorine-resistant taxa while eliminating sensitive microorganisms [13,14]. However, during distribution, regrowth may also occur, depending on the physicochemical characteristics of the finished water (e.g., temperature; total organic carbon (TOC) concentration; residual chlorine, ammonium, iron, or manganese concentration) and the distribution system (such as age, corrosion, scaling, or other deposit formation) [15].…”

“…Microbial diversity in drinking water supply systems is usually investigated in snapshots, i.e., single sampling events at multiple locations [17]. In a recent study, microbial community dynamics was tracked for a year in a full-scale drinking water treatment plant using surface water abstraction and complex treatment technology [13], but to the best of our knowledge no such study has been conducted yet in RBF-based drinking water supply systems. Source water quality is an important aspect, since its microbiome was shown to contribute on average 49% (ranging 0-93%) to the microbial community at the tap, depending on source water type and between 25-62% in RBF [8,18].…”