Extreme rainfall and urban flooding pose escalating risks to public health by mobilizing sewage and pathogenic microorganisms. In July 2021, record-breaking rainfall in Henan Province, China, caused catastrophic flooding, yet the microbial health risks associated with such events remain poorly quantified. Here, we applied high-throughput qPCR arrays to detect 21 pathogenic bacteria in floodwater and postflood tap water, and used quantitative microbial risk assessment (QMRA) to estimate infection probabilities for exposed residents. Our results showed that in floodwater, 21 pathogenic bacteria were detected, with Cryptosporidium spp. (579.8 gc/L) and Pseudomonas aeruginosa (13,500.9 gc/L), being prominent, which were also identified in tap water. Floodwater exposure substantially increases infection risks, highlighting ingestion and inhalation as primary pathways. Simple protective measures, such as avoiding contact with contaminated water, can significantly reduce risks. This study provides the first integrated molecular and risk-based assessment of microbial hazards during an extreme flood event. The findings underscore the importance of water quality monitoring, improved sewage and drainage management, and timely public health interventions such as boil water advisories. As climate change intensifies the frequency of extreme rainfall events, proactive surveillance and international collaboration will be essential to prevent waterborne disease outbreaks and protect vulnerable populations.

Treated drinking water is delivered to customers through drinking water distribution systems (DWDSs). Although studies have focused on exploring the microbial ecology of DWDSs, knowledge about the effects of different water treatments on the bacterial community of biofilm and loose deposits in DWDS is limited. This study assessed the effects of additional treatments on the bacterial communities developed in 10 months’ old pilot DWDSs. The results showed a similar bacterial community in the pipe-wall biofilm, which was dominated by Novosphingobium spp. (20–82 %) and Sphingomonas spp. (11–53 %), regardless of the treatment applied. The bacterial communities that were retained in the distribution systems (including pipe-wall biofilm and loose deposits) were similar to the particle-associated bacteria (PAB) in the corresponding supply water. The additional treatments showed clear effects of the removal and/or introduction of particles. The genera Aeromonas spp., Clostridium spp., Legionella spp., and Pseudomonas spp., which contain opportunistic pathogenic species, were only detected among the PAB in ion exchange system. Our study demonstrated that the biofilm community is consistent across treatments, and the contribution from bacteria in loose deposits is important but can be controlled by removing particles. These findings offer more insight into the origin and development of microbial ecology in DWDSs and suggest paths for further research on the possibility of managing the microbial ecology in distribution systems.

Hydrothermal carbonization (HTC) liquor of waste activated sludge generated during urban sewage biotreatment contains high concentrations of phosphate and thus is an appropriate resource for phosphorus recovery. The influence of proteins in the HTC liquor on vivianite crystallization, as a promising phosphorus recovery method, was investigated in this study from the perspectives of removal efficiencies and product properties. The proteins in the HTC liquor were observed to remain in unhydrolyzed forms with free amino acids having a negligible concentration. For vivianite crystallization in the synthetic HTC liquor with bovine serum albumin (BSA) mimicking the unhydrolyzed proteins, the efficiencies of phosphorus removal and crystallization at pH 6 decreased by 13.5 % and 18.4 %, respectively, compared with the BSA-free controls. The strong interaction between Fe and the proteins was suggested to be responsible for the reduced efficiency of vivianite formation and the variation of crystal growth mode from spirally expanding to x/z-axis extending.