Biofilm formation in drinking water distribution systems is primarily managed by disinfectants such as free chlorine (FC) and monochloramine (MC). However, there is limited understanding of their long-term and dynamic effects on biofilm development. To address this, a 56-week study was conducted to comprehensively assess biofilm development in terms of microbial quantity and community under different disinfection regimes: no chlorine (NC), FC (0.1 mg/L), and MC (0.4 mg/L). The results showed that both FC and MC significantly inhibited biofilm growth compared to the NC condition while shaping distinct biofilm communities. Notably, FC drastically reduced biofilm biomass and community diversity, resulting in a more uniform biofilm community predominantly composed of Proteobacteria (e.g., Rhizobacter spp., Pseudomonas spp., and Hyphomicrobium spp.), indicating stronger selection pressures on the microbial population. In contrast, though MC effectively reduced the biofilm biomass to a level comparable to that of FC, it maintained a high diversity comparable to that of NC (dominated by Sphingobium spp. and Nocardioides spp.), reflecting weaker selection pressure on bacterial community. Temporally, biofilm communities under all conditions started from nearly identical states. From week-19 and week-36 onwards, deterministic processes predominantly governed biofilm formation under FC and NC conditions, signifying that these biofilms reached a stable state. Differently, under MC condition, the community assembly was continually influenced by stochastic processes, with the biofilm not achieving stability until week-56. Overall, this study provides valuable insights into the long-term dynamics of biofilm development and evidenced that FC is better than MC in controlling biofilm formation, particularly from the community diversity perspective. This challenges classical views that MC is more effective than FC in penetrating and controlling biofilm, which may change the popularity of MC as a disinfectant in water utilities.

Correction to: Nature Waterhttps://doi.org/10.1038/s44221-023-00191-5, published online 8 February 2024. In the version of the article initially published, there was an error in the title: the phrase “submicrometre particles released during washing” originally appeared as “released submicrometre particles released during washing”. This has now been corrected in the HTML and PDF versions of the article.

Synthetic textiles are a significant source of microplastic fibre pollution. While the microplastic fibre release mechanism during the washing of textiles is well studied, little is known about the release of nanoplastics. The first investigations on the nanoplastic fraction released during the washing and abrasion of polyester textiles have been published; however, questions were raised regarding the chemical composition of the observed submicrometre particles. Using a combination of analytical methods, we show here that 12 different polyester textiles released 4.6 × 10¹⁰ to 8.9 × 10¹¹ particles per gram of textile during washing, with a mean size of 122–191 nm. The number of released submicrometre particles was not significantly influenced by the cutting method nor by the textile structure, but positively correlated (P < 0.01) with the number of submicrometre particles present on the fibre surface before washing. We found that 34–89% of the extracted submicrometre particles were soluble in ethanol. These particles are most likely water-insoluble poly(ethylene terephthalate) oligomers. Our results clearly show the urgent need to better understand the contribution of water-insoluble oligomer particles to the pollution of the environment by anthropogenic nanoplastics.

The occurrence and removal of microplastics (MPs) in drinking water treatment plants (DWTPs) have been evaluated based on particle number, while the mass concentration and removal characteristics based on the mass of MPs, and especially nanoplastics (NPs), remain unknown. This study employed pyrolysis gas chromatography-mass spectrometry (Py-GC/MS) to determine the mass concentration of MPs and NPs with different size ranges (0.01-1, 1-50, and 50-1000 μm) across the entire treatment process in a DWTP. The total polymers were measured at 9.63 ± 1.52 μg/L in raw water and 0.77 ± 0.05 μg/L in treated water, with the dominant polymers being polypropylene and polyethylene terephthalate. NPs (0.01-1 μm) accounted for only 3.2-5.3% of the total polymers, with an average concentration of 0.38 μg/L in raw water and 0.04 μg/L in treated water. Notably, NPs and sub-MPs (1-50 μm) demonstrated relatively low efficiency in the DWTP at 88.9 ± 3.2 and 88.0 ± 2.5%, respectively, compared with that of the large MPs (50-1000 μm) at 92.9 ± 0.3%. Overall, this study examined the occurrence of MPs and NPs, in a DWTP, emphasizing the significance of considering the mass concentration of MPs and NPs when assessing their pollution levels and removal characteristics.

Premise plumbing plays an essential role in determining the final quality of drinking water consumed by customers. However, little is known about the influences of plumbing configuration on water quality changes. This study selected parallel premise plumbing in the same building with different configurations, i.e., laboratory and toilet plumbing. Water quality deteriorations induced by premise plumbing under regular and interrupted water supply were investigated. The results showed that most of the water quality parameters did not vary under regular supply, except Zn, which was significantly increased by laboratory plumbing (78.2 to 260.7 µg/l). For the bacterial community, the Chao1 index was significantly increased by both plumbing types to a similar level (52 to 104). Laboratory plumbing significantly changed the bacterial community, but toilet plumbing did not. Remarkably, water supply interruption/restoration led to serious water quality deterioration in both plumbing types but resulted in different changes. Physiochemically, discoloration was observed only in laboratory plumbing, along with sharp increases in Mn and Zn. Microbiologically, the increase in ATP was sharper in toilet plumbing than in laboratory plumbing. Some opportunistic pathogen-containing genera, e.g., Legionella spp. and Pseudomonas spp., were present in both plumbing types but only in disturbed samples. This study highlighted the esthetic, chemical, and microbiological risks associated with premise plumbing, for which system configuration plays an important role. Attention should be given to optimizing premise plumbing design for managing building water quality.