Coupled chemical–microbial deterioration in stagnant fire hydrant branches threatens drinking water quality
Mengqing Fan (TU Delft - BT/Environmental Biotechnology, Chinese Academy of Sciences)
Qiang Xu (TU Delft - QN/Zandbergen Lab, Chinese Academy of Sciences)
Xiaoxuan Wang (Chinese Academy of Sciences)
Zhiwei Fang (Chinese Academy of Sciences)
Mark C.M. van Loosdrecht (TU Delft - BT/Environmental Biotechnology)
Martin Pabst (TU Delft - BT/Environmental Biotechnology)
Yu Tao (TU Delft - Sanitary Engineering)
Joan B. Rose (Michigan State University)
Walter van der Meer (TU Delft - Sanitary Engineering, TU Delft - RST/Radiation, Science and Technology, University of Twente)
Gang Liu (Chinese Academy of Sciences, TU Delft - Pavement Engineering)
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Abstract
Fire hydrants are widely installed in drinking water distribution systems, where stagnant water forms multiple ‘high-risk zones’. The stagnant water quality at hydrant terminals has been poorly studied. Here we show that stagnant water exhibited an 18-fold increase in manganese, a 40-fold increase in total cell counts, a 13-fold increase in adenosine triphosphate and enrichment of opportunistic pathogens compared with flowing water. Notable changes were also observed in microbial communities and dissolved organic matter composition, including shifts in dominant bacterial taxa, transformation of saturated oxidized compounds and generation of unsaturated reduced compounds. This study also explored the ecological mechanisms underlying the covariation of microorganisms and dissolved organic matter after water stagnation. This finding provides an additional possibility for drinking water quality deterioration in drinking water distribution systems, highlighting the potential threat posed by stagnant water in non-consumer terminals (fire hydrants) to water safety.