Assessment of the municipal water cycle in China

The negative-positive feedback transition thresholds of meteorological drought in response to agricultural drought and their dynamics

There are complex bidirectional feedback relationships among different types of droughts (e.g., meteorological and agricultural droughts). As agricultural drought intensifies, meteorological drought response to agricultural drought may be changed from negative to positive feedback. Nevertheless, the negative-positive feedback transition thresholds of meteorological drought in response to agricultural drought and their dynamics have remained unsolved. Herein, we proposed a new quantitative method to characterize the mutual feedback between meteorological drought and agricultural drought based on the vine copula function for the first time in this study. The negative-positive feedback transition threshold and the sensitivity of the feedback were quantified under certain drought conditions. In order to investigate the feedback relationship dynamics under a changing environment, the total study period was evenly divided into two stages: stage 1 (1982-1999) and stage 2 (2000-2018). Finally, the random forest method was used to explore the dominant factors on the transition threshold. Results indicate that: (1) the negative-positive feedback transition thresholds in August is generally lower than June and July in mainland China, the basin with large threshold is the Southwest River Basin; (2) the sensitivity of meteorological drought in response to agricultural drought was higher in positive feedback than in negative feedback; (3) the transition thresholds of stage 2 was mostly reduced, while the feedback sensitivity of positive feedback was mostly increased; and (4) compared with the single factor, the land-meteorological coupling strength (the correlation between precipitation and soil moisture) dominants the negative-positive feedback transition threshold. This study sheds new insights into droughts feedback.

The occurrence, ecological risk, and control of disinfection by-products from intensified wastewater disinfection during the COVID-19 pandemic

Increased disinfection of wastewater to preserve its microbiological quality during the coronavirus infectious disease-2019 (COVID-19) pandemic have inevitably led to increased production of toxic disinfection by-products (DBPs). However, there is limited information on such DBPs (i.e., trihalomethanes, haloacetic acids, nitrosamines, and haloacetonitriles). This review focused on the upsurge of chlorine-based disinfectants (such as chlorine, chloramine and chlorine dioxide) in wastewater treatment plants (WWTPs) in the global response to COVID-19. The formation and distribution of DBPs in wastewater were then analyzed to understand the impacts of these large-scale usage of disinfectants in WWTPs. In addition, potential ecological risks associated with DBPs derived from wastewater disinfection and its receiving water bodies were summarized. Finally, various approaches for mitigating DBP levels in wastewater and suggestions for further research into the environmental risks of increased wastewater disinfection were provided. Overall, this study presented a comprehensive overview of the formation, distribution, potential ecological risks, and mitigating approaches of DBPs derived from wastewater disinfection that will facilitate appropriate wastewater disinfection techniques selection, potential ecological risk assessment, and removal approaches and regulations consideration.

Fluorescence analysis of centralized water supply systems: Indications for rapid cross-connection detection and water quality safety guarantee

Better insight into non-potable reclaimed water and drinking water can produce more reliable risk assessment and help to achieve sustainable water reuse in the long-term. This study illustrates the effectiveness of fluorescence excitation-emission matrix (EEM) for rapid cross-connection detection. Based on samples collected from three different sites of China, it is identified that the overall fluorescence intensity was 6-31 times of reclaimed to drinking water in water samples at all FRI regions. This is shown to be highly sensitive over conventional water quality parameters. Furthermore, based on parallel factor analysis (PARAFAC), humic acid and tryptophan are considered as the main components contributing to fluorescence both in secondary and tertiary effluents. Total fluorescence intensities as well as fluorescence peaks of EEM pairs were investigated. Under different mixing scenarios, it is found that the signal is distinguishable as low as 20% of reclaimed water. This study also offers possibility of exploring portable devices with identified fluorescence peaks in EEM regions for risk prevention and water quality monitoring at end user sites.

Feasibility of containing shigellosis in Hubei Province, China: a modelling study

Background

The transmission features and the feasibility of containing shigellosis remain unclear among a population-based study in China.

Methods

A population–based Susceptible – Exposed – Infectious / Asymptomatic – Recovered (SEIAR) model was built including decreasing the infectious period (DIP) or isolation of shigellosis cases. We analyzed the distribution of the reported shigellosis cases in Hubei Province, China from January 2005 to December 2017, and divided the time series into several stages according to the heterogeneity of reported incidence during the period. In each stage, an epidemic season was selected for the modelling and assessing the effectiveness of DIP and case isolation.

Results

A total of 130,770 shigellosis cases were reported in Hubei Province. The median of R_eff was 1.13 (range: 0.86–1.21), 1.10 (range: 0.91–1.13), 1.09 (range: 0.92–1.92), and 1.03 (range: 0.94–1.22) in 2005–2006 season, 2010–2011 season, 2013–2014 season, and 2016–2017 season, respectively. The reported incidence decreased significantly (trend χ² = 8260.41, P <  0.001) among four stages. The incidence of shigellosis decreased sharply when DIP implemented in three scenarios (γ = 0.1, 0.1429, 0.3333) and when proportion of case isolation increased.

Conclusions

Year heterogeneity of reported shigellosis incidence exists in Hubei Province. It is feasible to contain the transmission by implementing DIP and case isolation.

Urban River Health Analysis of the Jialu River in Zhengzhou City Using the Improved Fuzzy Matter-Element Extension Model

Urban rivers are valuable elements of urban ecosystems and play a key role in urban socio-economic development. Unfortunately, the functional integrity of urban rivers is being threatened by extensive human activities associated with the social development. Urban river health evaluation is important, as it may provide policy makers with information that is fundamental for river governance and the protection of urban ecosystems. To this purpose, we first constructed an urban river health assessment index system based on the pressure–state–response (PSR) framework. Secondly, we developed an urban river health index (uRHI) using the improved fuzzy matter–element extension assessment model. Finally, we used the uRHI to assess the health state of the Jialu River from 2008 to 2017 in Zhengzhou City, China. The results indicate that the health state of the Jialu River was improved from an unhealthy state in 2008 to a sub-healthy state in 2017. The pressure, state, and response subsystems developed towards a healthier state from 2008 to 2017, thanks to the implementation of a number of actions by the local government. However, the overall health status of the Jialu River is still relatively low. The Jialu River also faces several pressures, such as substantial Chemical Oxygen Demand (COD) emissions and sewage discharge. This paper concludes that it is necessary to further strengthen the health management of the Jialu River and the protection of Zhengzhou’s water environment.

Identification of urban drinking water supply patterns across 627 cities in China based on supervised and unsupervised statistical learning

Urbanization, one of the predominant trends of the 21st century, places great stress on urban water supply networks. This paper aimed to identify the most important variables driving urban water supply patterns in China, a region which has seen rapid urban growth in the last few decades. In addition, a principal component analysis-informed urban water sustainability index was developed in order to benchmark cities. The research involved applying statistical learning and other analytical methods to 12 years of urban water supply data for 627 cities across China. The findings were as follows: (1) PCA showed that approximately 46.8% of variability in the data could be explained by two principal components. Component 1 (37.26%) was more closely associated with variables related to water supply and sale, supply pipelines, and water supply finance. C2 (9.51%) was clearly related to urban water prices and average per capita water use. (2) Random forest and XGBoost algorithms were effective in classifying cities according to their region, with model testing accuracies of 87.69% and 88.32% respectively. (3) Chinese cities have consistently suffered water loss/leakage rates above 20% since 2001, and water prices are closely associated with leakage. (4) China's urban water sustainability has increased by just 3.56% between 2001 and 2013; Southwest China saw the highest growth rate in urban water supply sustainability. The implications of our research effort will be useful for decision makers in water-stressed urban areas around the world who are seeking novel insights in how to leverage statistical learning techniques to gain insights into urban drinking water supply patterns.