Drinking water safety improvement and future challenge of lakes and reservoirs

To meet the Sustainable Development Goal(SDG)target 6.1,China has undertaken significant initiatives to address the uneven distribution of water resources and to enhance water quality.Since 2000,China has invested heavily in the water infrastructure of numerous reservoirs,with a total storage capacity increase of 4.704×1011m3(an increase of 90.8%).These reservoirs have significantly enhanced the available freshwater resources for drinking water.Concurrently,efforts to improve water quality in lakes and reservoirs,facilitated by nationwide water quality monitoring,have been successful.As a result,an increasing lakes and reservoirs are designated as centralized drinking water sources(CDWSs)in China.Among the 3441 CDWSs across all provinces,40.8%are sourced from lakes and reservoirs,32.6%from rivers,and 26.6%from groundwater in 2023.Notably,from 2016 to 2023,the percentage of lakes and reservoirs categorized as CDWSs has increased consistently across all 29 provinces.This progress has enabled561.4 million urban residents to access improved drinking water sources in 2022,compared to 303.4 million in 2004.Our findings underscore the pivotal role of water infrastructure construction and water quality improvement jointly promoting lakes and reservoirs as vital drinking water sources.Nevertheless,the nationwide occurrence of algal blooms has surged by 113.7%from the 2000s to the 2010s,which is a considerable challenge to drinking water safety.Fortunately,algal blooms have been markedly alleviated in past four years.However,it is still crucial to acknowledge that lakes and reservoirs face the challenges of algal blooms,and associated toxic microcystin and odor compounds.

Effects of artificially induced complete mixing on dissolved organic matter in a stratified source water reservoir

Naturally complete mixing promotes the spontaneous redistribution of dissolved oxygen(DO),representing an ideal state for maintaining good water quality,and conducive to the biomineralization of organic matter.Water lifting aerators(WLAs)can extend the periods of complete mixing and increase the initial mixing temperature.To evaluate the influence of artificial-induced continuously mixing on dissolved organic matter(DOM)removal performance,the variations of DOM concentrations,optical characteristic,environmental factors were studied after approaching the total mixing status via WLAs operation.During this process,the dissolved organic carbon reduced by 39.18%,whereas the permanganate index decreased by 20.47%.The optical properties indicate that the DOM became more endogenous and its molecular weight decreased.Based on the results of the Biolog Eco Plates,the microorganisms were maintained at a relatively high metabolic activity in the early stage of induced mixing when the mixing temperature was relatively high,whereas DOM declined at a high rate.With the continuous decrease in the water temperature,both the metabolic capacity and the diversity of aerobic microorganisms significantly decreased,and the rate of organic matter mineralization slowed down.The results of this study demonstrate that the artificial induced mixing largely enhanced the removal DOM performance by providing a long period of aerobic conditions and higher initial temperature.