A Tale of Two Water Supplies in China: Finding Practical Solutions to Urban and Rural Water Supply Problems

Trihalomethanes in global drinking water: Distributions, risk assessments, and attributable disease burden of bladder cancer

This study aimed to assess the global spatiotemporal variations of trihalomethanes (THMs) in drinking water, evaluate their cancer and non-cancer risks, and THM-attributable bladder cancer burden. THM concentrations in drinking water around fifty years on a global scale were integrated. Health risks were assessed using Monte Carlo simulations and attributable bladder cancer burden was estimated by comparative risk assessment methodology. The results showed that global mean THM concentrations in drinking water significantly decreased from 78.37 μg/L (1973-1983) to 51.99 μg/L (1984-2004) and to 21.90 μg/L (after 2004). The lifestage-integrative cancer risk and hazard index of THMs through all exposure pathways were acceptable with the average level of 6.45 × 10-5 and 7.63 × 10-2, respectively. The global attributable disability adjusted of life years (DALYs) and the age-standardized DALYs rate (ASDR) dropped by 16% and 56% from 1990-1994 to 2015-2019, respectively. A big decline in the attributable ASDR was observed in the United Kingdom (62%) and the United States (27%), while China experienced a nearly 3-fold increase due to the expanded water supply coverage and increased life expectancy. However, China also benefited from the spread of chlorination, which helped reduce nearly 90% of unsafe-water-caused mortality from 1998 to 2018.

Assessment of microbial population in integrated CW-MFC system and investigation of organics and fecal coliform removal pathway

The current study is focused on understanding the operational mechanism of an integrated constructed wetland-microbial fuel cell (CW-MFC) reactor emphasizing fecal coliform (FC) removal. Few studies are available in the literature investigating the inherent mechanisms of pathogen inactivation in a CW-MFC system. Raw domestic wastewater was treated in three vertical reactors, one planted constructed wetland (R1), one planted CW-MFC (R2), and one unplanted CW-MFC (R3). Spatial analysis of treated effluents showed a considerable amount of organics and fecal coliform removal at the vicinity of the anode in R2. Assessment of the microbial population inside all the reactors revealed that EABs (Firmicutes, Bacteroidetes, and Actinobacteria) were more abundant in R2 compared to R1 and R3. During the activity study, biomass obtained from R2 showed a maximum substrate utilization rate of 1.27 mg COD mgVSS-1 d-1. Kinetic batch studies were carried out for FC removal in all the reactors, and the maximum first order FC removal rate was obtained at the anode of R2 as 2.13 d-1 when operated in closed circuit mode. This value was much higher than the natural die-off rate of FCs in raw wastewater which was 1.16 d-1. Simultaneous bioelectricity monitoring inferred that voltage generation can be correlated to faster FC inactivation, which was probably due to EABs outcompeting other exogenous microbes in a preferable anaerobic environment with the presence of an anode. Reactor R2 was found to be functioning as a symbiotic bio-electrochemical mesocosm.

Study on characteristic and mechanism involved in the formation of N-nitrosodimethylamine precursors during microbial metabolism of amino acids

Amino acid metabolism by microorganisms is a new but important pathway for the formation of NDMA precursors in water. We investigated the properties of nitrosamine precursors produced through microbial metabolism of amino acids by polarity rapid assessment method and molecular weight fractionation by ultrafiltration method. The PRAM results showed that the positively charged fraction and the non-polar fraction accounted for most (45 %-79 % and 6 %-82 %, respectively) of the NDMA precursors. The MW fractionation results also indicate the dominant precursors had MWs <1 kDa or over 10 kDa. NDMA precursors produced through amino acid metabolism were identified and quantified. Dimethylamine, N-methyl-alanine and alanine methyl ester were produced during the metabolism of alanine and peptone. Together, N-methyl-alanine and dimethylamine averagely contributed 24 % (12 %-44 %) of the NDMA precursors in the alanine medium. The NDMA precursor formation pathway during alanine metabolism involves the methylation of alanine to form N-methyl-alanine and the decomposition of alanine anabolism products to form dimethylamine. Nitrosamine precursors are generally formed through anabolism or methylation, but biogenic amines or NH₃ can be produced through catabolism before nitrosamine precursor synthesis. Microbial community analysis was performed and Ralstonia was found to be a likely key genus contributing to NDMA precursor formation during alanine metabolism.

Bubbleless aerated-biological activated carbon as a superior process for drinking water treatment in rural areas

Drinking water supply in rural areas remains a substantial challenge due to complex natural, technical and economic conditions. To provide safe and affordable drinking water to all, as targeted in the UN Sustainable Development Goals (2030 Agenda), low-cost, efficient water treatment processes suitable for rural areas need to be developed. In this study, a bubbleless aeration BAC (termed ABAC) process is proposed and evaluated, involving the incorporation of a hollow fiber membrane (HFM) assembly within a slow-rate BAC filter, to provide dissolved oxygen (DO) throughout the BAC filter and an increased DOM removal efficiency. The results showed that after a 210-day period of operation, the ABAC increased the DOC removal by 54%, and decreased the disinfection byproduct formation potential (DBPFP) by 41%, compared to a comparable BAC filter without aeration (termed NBAC). The elevated DO (> 4 mg/L) not only reduced secreted extracellular polymer, but also modified the microbial community with a stronger degradation ability. The HFM-based aeration showed comparable performance to 3 mg/L pre-ozonation, and the DOC removal efficiency was four times greater than that of a conventional coagulation process. The proposed ABAC treatment, with its various advantages (e.g., high stability, avoidance of chemicals, ease of operation and maintenance), is well-suited to be integrated as a prefabricated device, for decentralized drinking water systems in rural areas.

Drinking Water in Rural China: Water Sources, Treatment, and Boiling Energy

Access to safe drinking water is a major public concern in China. A national survey of 57 029 households was conducted to fill major knowledge gaps on drinking water sources, end-of-use treatment methods, and energy used to boil water. Herein, we show that surface water and well water were frequently used by >147 million rural residents living in low-income inland and mountainous areas. Driven by socioeconomic development and government intervention, the level of access to tap water in rural China increased to 70% by 2017. Nevertheless, the rate was considerably lower than that in cities and unevenly distributed across the country. Approximately 90% of drinking water was boiled, an increase from 85% a decade ago. The contribution of electricity, mainly electric kettles, to the boiling of water was 69%. Similar to cooking, living conditions and heating requirements are the main influencing indicators of energy used to boil water. In addition to socioeconomic development, government intervention is a key factor driving the transition to safe water sources, universal access to tap water, and clean energy. Further improvement in drinking water safety in poor and remote rural areas remains challenging, and more intervention and more investment are needed.

Study on electrochemical reduction mechanisms of iron oxides in pipe scale in drinking water distribution system

Iron release from pipe scale is an important reason for water quality deterioration in drinking water distribution systems (DWDS) globally. Disruption of pipe scale, release and transformation of iron compounds are hot topics in the field of water supply. The aim of this study is to determine whether and how ferric components in pipe scale be reduced under anoxic condition. In this study, new investigation approaches were applied, which include simplifying the complex scale into electrode pairs, developing novel simulating reactors and conducting tailored electrochemical assays. A galvanic cell reactor with anode of metallic iron (Fe⁰) and various cathode made of certain iron oxide (FeO_x) was firstly developed to simulate the complex niche and components of pipe scale. Electrochemical methods were used to study the reduction characteristics of scale. The results proved that reduction of iron oxide scale did occur under anoxic condition. Electromotive forces between various electrodes match the Nernst Equation quite well. As main components in pipe scale, lepidocrocite (γ-FeOOH) was found to be the most reducible iron oxide but at low rate, while goethite (α-FeOOH) has weak reducibility but can be quickly reduced. As a result of electrochemical reactions, goethite in pipe scale was transformed into magnetite (Fe₃O₄). By these means, electrochemical reaction mechanisms of pipe scale disruption were revealed, which is helpful to restrain pipe corrosion and water deterioration in DWDS.

Quality assessment and prediction of municipal drinking water using water quality index and artificial neural network: A case study of Wuhan, central China, from 2013 to 2019

The sanitary security of drinking water is closely related to human health, but its quality assessment mainly focused on limited types of indicators and relatively restricted time span. The current study was aimed to evaluate the long-term spatial-temporal distribution of municipal drinking water quality and explore the origin of water contamination based on multiple water indicators of 137 finished water samples and 863 tap water samples from Wuhan city, China. Water quality indexes (WQIs) were calculated to integrate the measured indicators. WQIs of the finished water samples ranged from 0.24 to 0.92, with the qualification rate and excellent rate of 100 % and 96.4 %, respectively, while those of the tap water samples ranged from 0.09 to 3.20, with the qualification rate of 99.9 %, and excellent rate of 95.5 %. Artificial neural network model was constructed based on the time series of WQIs from 2013 to 2019 to predict the water quality thereafter. The predicted WQIs of finished and tap water in 2020 and 2021 qualified on the whole, with the excellent rate of 87.5 % and 92.9 %, respectively. Except for three samples exceeding the limits of free chlorine residual, chloroform and fluoride, respectively, the majority of indicators reached the threshold values for drinking. Our study suggested that municipal drinking water quality in Wuhan was generally stable and in line with the national hygiene standards. Moreover, principal component analysis illustrated that the main potential sources of drinking water contamination were inorganic salts and organic matters, followed by pollution from distribution systems, the use of aluminum-containing coagulants and turbidity involved in water treatment, which need more attention.

Drinking water behavior and willingness to use filters by middle-aged and elderly residents in rural areas: A cross-sectional study in Tengchong, China

Access to safe drinking water is critical to health and development issues, and residents' drinking behavior reflects their awareness of health and water hygiene. Random sampling and face-to-face questionnaires were used to investigate the drinking water behavior, sanitation and perceptions of drinking water among middle-aged and elderly residents in Tengchong, southwest Yunnan from July 1 to July 28, 2021. Differences between groups were assessed using the Chi-square test and t-test. Two binary logistic regression analyses were conducted to explore the influencing factors of drinking unboiled tap water and willingness to use filters. Results show that 35% of residents drink unboiled tap water, and 29.8% of respondents indicated a willingness to use filters. The model results showed a strong correlation between 60 and 79 years old (OR: 0.510, 95% CI: 0.303-0.858), 80 and above years old (OR: 0.118, 95% CI: 0.038-0.365), drinking water at a regular interval (OR: 0.397, 95% CI: 0.257-0.612), wanting to gain knowledge about drinking water (OR: 0.198, 95% CI: 0.099-0.395), Perceived health risks (PHR) (OR: 0.847, 95% CI: 0.771-0.929), having kidney stones (OR: 2.975, 95% CI: 1.708-5.253) and drinking unboiled tap water (p < 0.05). 60-79 years old (OR: 0.446, 95% CI: 0.244-0.815), 80 and above years old (OR: 0.228, 95% CI: 0.064-0.812), water storage (OR: 0.088, 95% CI: 0.026-0.300), middle school and above (OR: 2.238, 95% CI: 1.289-3.883), household water treatment (HWT) (OR: 33.704, 95% CI: 9.726-116.791), Perceived health risks (PHR) (OR:1.106, 95% CI: 1.009-1.213), water authority satisfaction (WAT) (OR:0.857, 95% CI: 0.769-0.956) and willingness to use filters were correlated (p < 0.05). Our findings suggested that a certain proportion of permanent middle-aged and elderly residents in rural areas still drink unboiled tap water, and residents are less willing to use filters. Residents' perception of drinking water can reflect residents' drinking water behavior and willingness to a certain extent. It is recommended that the government and Centers for Disease Control (CDC) should strengthen relevant measures such as knowledge popularization and health education, and regulate the water use behavior of middle-aged and elderly residents. Promote safe, economical and effective household water filtration facilities to ensure public health safety.

Review on corrosion and corrosion scale formation upon unlined cast iron pipes in drinking water distribution systems

The qualified finished water from water treatment plants (WTPs) may become discolored and deteriorated during transportation in drinking water distribution systems (DWDSs), which affected tap water quality seriously. This water stability problem often occurs due to pipe corrosion and the destabilization of corrosion scales. This paper provides a comprehensive review of pipe corrosion in DWDSs, including corrosion process, corrosion scale formation, influencing factors and monitoring technologies utilized in DWDSs. In terms of corrosion process, corrosion occurrence, development mechanisms, currently applied assays, and indices used to determine the corrosion possibility are summarized, as well as the chemical and bacterial influences. In terms of scale formation, explanations for the nature of corrosion and scale formation mechanisms are discussed and its typical multilayered structure is illustrated. Furthermore, the influences of water quality and microbial activity on scale transformation are comprehensively discussed. Corrosion-related bacteria at the genus level and their associated corrosion mechanism are also summarized. This review helps deepen the current understanding of pipe corrosion and scale formation in DWDSs, providing guidance for water supply utilities to ensure effective measures to maintain water quality stability and guarantee drinking water safety.

Coagulation combined with ultraviolet irradiation activated sodium percarbonate as pretreatment prior to ultrafiltration: Analysis of free radical oxidation mechanism and membrane fouling control

Novel pre-coagulation-sedimentation integrated with ultraviolet activated sodium percarbonate (SPC) (Fe(III)-UV/SPC) processes are promising methods for ultrafiltration (UF) pretreatment to ensure the safety of rural drinking water and mitigate UF membrane fouling. The process of surface water purification using the integrated coagulation-advanced oxidation processes (AOPs)-UF system relies on the idea that pre-coagulation can remove hydrophobic macromolecular organic compounds, thus facilitating the oxidation of hydrophilic molecules or medium-sized macromolecules to improve the utilization efficiency of free radicals in AOPs. Compared with the UV/SPC process, the removal rates of UV₂₅₄ and DOC in the Fe(III)-UV/SPC process (Fe(III) = 0.1 mM, SPC = 0.5 mM) were increased from 87.39 % to 41.45 %-93.56 % and 52.51 %, respectively. Furthermore, the dosage of SPC was reduced from 0.75 mM in UV/SPC process to 0.5 mM due to effects of pre-coagulation. The free radical quenching experiment showed that a significant radical sink of reactions with organic contaminants was formed by •OH and CO₃^•- in the UV/SPC process, rather than a single specific radical. The destruction of the cake layer structure, reduction in contaminant concentration, and appearance of many permeable holes on the membrane surface were the main reasons for the alleviation of UF membrane fouling. Finally, the trans-membrane pressure and reversible membrane resistance decreased from 22.33 kPa to 3.68 × 10¹¹ m^-1 to 18.28 kPa and 0.93 × 10¹¹ m^-1, respectively. These results provide new insights into the behavior of membrane fouling control and offer technical references for the long-term stable operation of the UF process.

To centralize or to decentralize? A systematic framework for optimizing rural wastewater treatment planning

Untreated rural sewage seriously affects the universal access to clean water of rural residents. The lack of decision-support tools in rural sewage treatment (RuST) planning makes it difficult for RuST system to achieve the expected results and is not conducive to the optimal allocation of limited funds. Hence, there is an urgent need to develop a decision-support framework for large-scale RuST planning. For the first time, RuST planning decision-support framework was developed using divide-and-conquer strategy based on rural residents' spatial pattern (RESP) and the optimal pattern of RuST. This framework can be transferred to other countries/regions easily by correcting RESP dataset according to the spatial and environmental characteristics. We confirmed that the variation of RESP made the ideal RuST pattern varied significantly under different topography. And community-based pattern could be the optimal pattern for large-scale RuST planning, when spatial obstacle and RESP were fully considered. The price of onsite sewage treatment facility is the most significant factor for RuST planning. In our selected case, requited onsite facility accounted for 65.51%. For the total investment, the cost of sewer systems accounted for 56.01%, and the average investment in plains, hills, platforms and mountains was 1401, 1803, 1903 and 1859 USD/household, respectively. We expect this research could provide reference for RuST planning in other developing countries/regions all around the world.

Disinfection by-product (DBP) research in China: Are we on the track?

Disinfection by-products (DBPs) formed during water disinfection has drawn significant public concern due to its toxicity. Since the first discovery of the trihalomethanes in 1974, continued effort has been devoted on DBPs worldwide to investigate the formation mechanism, levels, toxicity and control measures in drinking water. This review summarizes the main achievements on DBP research in China, which included: (1) the investigation of known DBP occurrence in drinking water of China; (2) the enhanced removal of DBP precursor by water treatment process; (3) the disinfection optimization to minimize DBP formation; and (4) the identification of unknown DBPs in drinking water. Although the research of DBPs in China cover the whole formation process of DBPs, there is still a challenge in effectively controlling the drinking water quality risk induced by DBPs, an integrated research framework including chemistry, toxicology, engineering, and epidemiology is especially crucial.

Nanofiltration for drinking water treatment: a review

In recent decades, nanofiltration (NF) is considered as a promising separation technique to produce drinking water from different types of water source. In this paper, we comprehensively reviewed the progress of NF-based drinking water treatment, through summarizing the development of materials/fabrication and applications of NF membranes in various scenarios including surface water treatment, groundwater treatment, water reuse, brackish water treatment, and point of use applications. We not only summarized the removal of target major pollutants (e.g., hardness, pathogen, and natural organic matter), but also paid attention to the removal of micropollutants of major concern (e.g., disinfection byproducts, per- and polyfluoroalkyl substances, and arsenic). We highlighted that, for different applications, fit-for-purpose design is needed to improve the separation capability for target compounds of NF membranes in addition to their removal of salts. Outlook and perspectives on membrane fouling control, chlorine resistance, integrity, and selectivity are also discussed to provide potential insights for future development of high-efficiency NF membranes for stable and reliable drinking water treatment.

NDMA formation during ozonation of metformin: Roles of ozone and hydroxyl radicals

Metformin, a high-consumed pharmaceutical for diabetes, has been reported to generate carcinogenic nitroso-dimethylamine (NDMA) during treatment of its containing wastewater. However, whether it would produce NDMA during ozonation or not is unclear, let alone discriminate roles of ozone (O₃) and hydroxyl radicals (OH). In this paper, effects of ozonation on NDMA formation from metformin were investigated, roles of O₃ and OH were also distinguished by adding tert-butyl alcohol (tBA) as OH scavenger. Moreover, various influencing factors and reaction mechanisms were demonstrated. The results indicated that NDMA could be directly formed from metformin during ozonation, the addition of OH scavenger significantly enhanced its formation (0-46.2 ng/L vs 0-139.1 ng/L). The formation of NDMA by O₃ and OH was more affected by bromide and HCO₃^- than those with only O₃; while the impacts of pH and sulphate on the latter were more notable. No matter without/with tBA in the solution, the formed NDMA during ozonation of metformin increased with raising pH (from 5 to 9) and achieved the maximum 69.6 ng/L and 235.9 ng/L at pH 9, respectively; small amount of bromide (0.1 μM) promoted NDMA production, high levels of bromide (10 μM) inhibited its formation; the existence of HCO₃^- enhanced the amounts of NDMA from 44.5 to 73.5 ng/L (raised by 65.2%) by O₃ and OH and from 102.9 to 130 ng/L with only O₃ (raised by 26.3%); with the addition of sulphate, NDMA concentration raised by 43.8% by O₃ and OH, while the value was high up to 134.6% with only O₃. Based on the result of UPLC-Q-TOF and density functional theory, the oxidation intermediates were identified and possible transformation pathways of metformin during ozonation were proposed. The findings in this paper would provide reference when treating metformin-containing water in future.

China's drinking water sanitation from 2007 to 2018: A systematic review

Regular monitoring of drinking water in China is carried out by the Centers for Disease Control and Prevention at all levels and some articles were published for the public to understand the status of drinking water. However, these published articles were limited to small areas and reported almost exclusively in Chinese. In order to give the public a comprehensive understanding of the situation of drinking water sanitation in China and provide specific directions for ensuring drinking water safety in the future, we review the sanitation status of drinking water in different regions of China from 2007 to 2018, the changes over time and the factors affecting drinking water quality by means of systematic review for the first time. Our results show that the quality of drinking water in China has shown an upward trend from 2007 to 2018. The qualification rate of urban drinking water (85.51%) was much higher than that of rural drinking water (51.12%), and the dry season (56.93%) was higher than the wet season (50.54%), and the terminal tap water (59.88%) was higher than the outlet water of waterworks (55.87%). In addition, the regions with low qualification rate of water quality in China were mainly distributed in several southern provinces, such as Yunnan, Guizhou, Hainan, etc. What's more, the qualified rate of the three microbiological indicators was the lowest, all below 85%. All the results indicate that the sanitation status of drinking water in China is unsatisfactory, and the biggest risk affecting water safety is microbial pollution. The central and local governments should work hard to improve people's drinking water quality and continue to strengthen the treatment and supervision of drinking water, especially in rural areas and undeveloped southern areas.

Intake of volatile nitrosamines by Chinese residents in different provinces via food and drinking water

N-nitrosamines are potent carcinogens, particularly N-nitrosodimethylamine (NDMA) and N-nitrosodiethylamine (NDEA), which are commonly found in a variety of foods and drinking water. We calculated the food and drinking water intakes of NDMA, NDEA, and total volatile nitrosamines (TVNA) by Chinese residents in different provinces by multiplying the reported total diet study results by the nitrosamine contents in food and drinking water. The weighted content of nitrosamines in each category of foods and the concentration of nitrosamines in drinking water was obtained through literature review. The exogenous NDMA, NDEA and TVNA intakes of adult residents in 20 provinces ranged from 171 to 425 ng/d, 41 to 140 ng/d and 373 to 1028 ng/d, respectively. The main contributors to NDMA and TVNA intakes were vegetables, cereals, aquatic products, and meats while the main sources of NDEA intake were vegetables and cereals. The average total NDMA intake per capita in China (251 ng/d) was similar to that in Germany in 1991 (231 ng/d) but higher than that in the United States (136 ng/d), Canada (87.6 ng/d) and France (188 ng/d). Large differences in nitrosamine intakes were observed between the coastal provinces and inland provinces. Drinking water was estimated to contribute 13.1%, 1.3% and 10.8% of the exogenous intakes of NDMA, NDEA and TVNA, respectively. Based on our results, we recommend setting the NDMA drinking water criterion of 40 ng/L. Overall, this study presents basic information regarding nitrosamines intake via food and drinking water in China that will facilitate risk assessment, generation of health advisories and policy making.

Geographic information system-based health risk assessment of rural drinking water in Central China: a case study of You County, Hunan

This study assessed potential human health hazards posed by drinking water from centralized water supply systems in rural You County, along with its spatial distribution. While most previous studies have focused on source water or urban drinking water, this study evaluated the health risk posed by 20 common pollutants (arsenic, cadmium, chromium(VI), lead, mercury, selenium, cyanide, fluoride, nitrate nitrogen, trichloromethane, tetrachloromethane, chlorite, aluminum, iron, manganese, copper, zinc, ammonia nitrogen, chlorine dioxide, and volatile phenols) in rural terminal tap water. The assessment adopted the model recommended by the US Environmental Protection Agency (EPA) and was combined with the geographic information system (GIS) analysis to explore the spatial distribution of risk factors. Water samples were collected from 13 townships in You County across four quarters of 2019. The results indicated that the average carcinogenic risk of the rural drinking water was 2.45 × 10^-5, ranging from 1.80 × 10^-5 to 3.89 × 10^-5, which never exceeded the maximum acceptable range recommended by the US EPA (1.0 × 10^-4 ~ 1.0 × 10^-6). The average hazard index (HI), which reflects noncarcinogenic risk levels, was 0.75 and ranged from 0.34 to 1.74. Throughout the year, some townships presented HI > 1, indicating a non-carcinogenic risk. The GIS analysis indicated that noncarcinogenic risks were mainly distributed in the north, followed by the east and west. This is generally consistent with the spatial distribution of chlorite concentrations, which contribute most strongly to noncarcinogenic risk levels. The northern You County should therefore be prioritized for health risk control, followed by the eastern and western regions. Chlorite is the priority pollutant for control.

Challenges for Safe and Healthy Drinking Water in China

PURPOSE OF REVIEW

Rapid economic growth and its huge population are putting tremendous pressure on water sustainability in China. Ensuring clean drinking water is a great challenge for public health due to water shortage and pollution. This article reviews current scientific findings on health-related issues on drinking water and discusses the challenges for safe and healthy drinking water in China.

RECENT FINDINGS

From literature published since 2010, a variety of emerging contaminants were detected in drinking water, including disinfection byproducts (DBPs), pharmaceuticals and personal care products (PPCPs), endocrine-disrupting compounds (EDCs), antibiotic resistance genes, and pathogens. Arsenic and fluoride are still the two major contaminants in groundwater. Microcystins, toxins produced by cyanobacteria, were also frequently detected in surface water for drinking. Health effects of exposure to arsenic, fluoride, nitrates, DBPs, and noroviruses in drinking water have been reported in several epidemiological studies. According to literature, water scarcity is still a severe ongoing issue, and regional disparity affects the access to safe and healthy drinking water. In addition, urbanization and climate change have strong influences on drinking water quality and water quantity. Multiple classes of contaminants of emerging concern have been detected in drinking water, while epidemiological studies on their health effects are still inadequate. Water scarcity, regional disparity, urbanization, and climate change are the major challenges for safe and healthy drinking water in China.

Ceramic membrane based hybrid process for the upgrade of rural water treatment plants: A pilot study

An integrated process with ozonation, ceramic membrane ultrafiltration, and activated carbon filtration is investigated for the treatment of drinking water in the rural area of China. A pilot-scale experiment with a capacity of 20 m³ /d is conducted, and a number of water quality parameters are evaluated, such as turbidity, color, organic matter (COD_Mn ), manganese (Mn), geosmin (GSM), 2-methylisoborneol (2-MIB), and 37 kinds of pharmaceutical and personal care products (PPCPs). The result shows that the removal efficiency of all the evaluated parameters of this integrated process is much higher than that of the conventional treatment processes. In particular, the removal rate of PPCPs achieves 52.5%, which is twice higher than that of the conventional process. Moreover, ozone can oxidize manganese ions, degrade organic matters, and reduce membrane fouling. It is believed that the integrated treatment process developed in this study is efficient in upgrading the existing water treatment plants and ensuring the safety of drinking water in the rural areas around the world.

Households with unimproved water sources in Ethiopia: spatial variation and point-of-use treatment based on 2016 Demographic and Health Survey

Background

Improved water sources are not equally available in all geographical regions. Populations dependent on unsafe water sources are recommended to treat their water at point-of-use using adequate methods to reduce associated health problems. In Ethiopia, the spatial distribution of households using unimproved water sources have been incomplete or ignored in most of the studies. Moreover, evidence on the point-of-use water treatment practice of households dependent on such water sources is scarce. Therefore, the current study is intended to analyze the spatial distribution of unimproved water sources by wealth quintiles at country level and point-of-use treatment (POU) practices using nationally representative data.

Method

The data of 2016 Ethiopian Demographic and Health Survey (EDHS) conducted on 16650 households from 643 clusters were used for the analysis. For spatial analysis, the raw and spatially smoothed coverage data was joined to the geographic coordinates based on EDHS cluster identification code. Global spatial autocorrelation was performed to analyze whether the pattern of unimproved water coverage is clustered, dispersed, or random across the study areas. Once a positive global autocorrelation was confirmed, a local spatial autocorrelation analysis was applied to detect local clusters. The POU water treatment is analyzed based on reported use of either boiling, chlorine (bleach), filtration, or solar disinfection (SODIS).

Results

There were 5005 households using unimproved water sources for drinking purposes. Spatial variation of unimproved water coverage was observed with high coverage observed at Amhara, Afar, Southern Nations Nationalities and People and Somalia regions. Disparity in unimproved water coverage between wealth quintiles was also observed. The reported point-of-use water treatment practice among these households is only 6.24%. The odds of POU water treatment among household heads with higher education status is 2.5 times higher (95% CI = 1.43-4.36) compared to those who did not attend education.

Conclusion

An apparent clustering trend with high unimproved water coverage was observed between regions and among wealth quintiles hence indicates priority areas for future resource allocation and the need for regional and national policies to address the issue. Promoting households to treat water prior to drinking is essential to reduce health problems.

Spatial, temporal variability and carcinogenic health risk assessment of nitrosamines in a drinking water system in China

Nitrosamines, as a class of emerging frequently detected nitrogenous disinfection byproducts (N-DBPs) in drinking water, have gained increasing attention due to their potentially high health risk. Few studies focus on the occurrence variation and carcinogenic health risk of nitrosamines in drinking water systems. Our study aimed to investigate the spatial and temporal variability of nitrosamines in a drinking water system and to conduct a carcinogenic health risk assessment. Three types of water samples, including influent water, treated water and tap water, were collected monthly during an entire year in a drinking water system utilizing a combination of chlorine dioxide and chlorine in central China, and 9 nitrosamines were measured. The nitrosamine formation potentials (FPs) in influent water were also determined. N-nitrosodimethylamine (NDMA) was the most prevalent compound and was dominant in the water samples with average concentrations ranging from 2.5 to 67.4 ng/L, followed by N-nitrosodiethylamine (NDEA) and N-nitrosopiperidine (NPIP). Nitrosamine occurrence varied monthly, and significant seasonal differences were observed in tap water (p < .05). There were decreasing mean NDMA, NDEA and NPIP concentrations from influent water to treated water to tap water, but no significant spatial variability was observed within the water distribution system (p > .05). The average and 95th percentile total lifetime cancer risks for the three main nitrosamines were 4.83 × 10^-5 and 4.48 × 10^-4, respectively, exceeding the negligible risk level (10^-6) proposed by the USEPA. Exposure to nitrosamines in drinking water posed a higher cancer risk for children than for adults, and children aged 0.75 to 1 years suffered the highest cancer risk. These results suggest that nitrosamine occurrence in tap water varied temporally but not spatially. Exposure to drinking water nitrosamines may pose a carcinogenic risk to human health, especially to children.

Formation of N-nitrosodimethylamine precursors through the microbiological metabolism of nitrogenous substrates in water

N-nitrosodimethylamine (NDMA) as one emerging disinfection by-product has been investigated globally since 1990s. However, its main precursors are still unclear. We found that NDMA formation potential (NDMAFP) of various water samples increased firstly and then decreased gradually during incubation with microorganism. We hypothesized that NDMA precursors could be produced through metabolism of nitrogenous components and then gradually be biodegraded. To verify this hypothesis, six amino acids (AAs), peptone and ammonium were separately incubated with microorganism and NDMAFP was measured regularly. The average molar yield of the substrates to NDMAFP were 60-200 × 10^-6 for the AAs, 350 × 10^-6 for peptone under aerobic condition. The extracellular fraction with molecular weight (MW) less than 1 k Dalton contributed the majority to NDMAFP in the peptone experiment, followed by that with MW between 10 k and 0.22 μm and the intracellular materials. Dimethylamine and methylamine were detected during the experiments but their contribution to NDMAFP is quite limited. The results indicate that the nitrosamine precursors may not be the direct metabolite of AAs or peptones but the excretion of living bacteria or the components in dead bacteria body. Our results inferred that AA metabolism may give an NDMAFP of 0.12 nmol/L (maximum) or 0.09 nmol/L (average) in water under aerobic condition. This estimation of NDMAFP from AA metabolism can account for 38% (maximum) or 27% (average) of the median NDMAFP in waters of China (0.32 nmol/L) reported before.

Fouling Mechanisms Analysis via Combined Fouling Models for Surface Water Ultrafiltration Process

Membrane fouling is still the bottleneck affecting the technical and economic performance of the ultrafiltration (UF) process for the surface water treatment. It is very important to accurately understand fouling mechanisms to effectively prevent and control UF fouling. The rejection performance and fouling mechanisms of the UF membrane for raw and coagulated surface water treatment were investigated under the cycle operation of constant-pressure dead-end filtration and backwash. There was no significant difference in the UF permeate quality of raw and coagulated surface water. Coagulation mainly removed substances causing turbidity in raw surface water (including most suspended particles and a few organic colloids) and thus mitigated UF fouling effectively. Backwash showed limited fouling removal. For the UF process of both raw and coagulated surface water, the fittings using single models showed good linearity for multiple models mainly due to statistical illusions, while the fittings using combined models showed that only the combined complete blocking and cake layer model fitted well. The quantitative calculations showed that complete blocking was the main reason causing flux decline. Membrane fouling mechanism analysis based on combined models could provide theoretical supports to prevent and control UF fouling for surface water treatment.

Equity in Essential Maternal, Newborn, and Child Health Interventions in Northeastern China, 2008 to 2018

Objectives: We aim to analyze equity in maternal, newborn, and child health (MNCH) interventions in Jilin, a northeastern province of China, 2008–2018.

Study design: Cross-sectional study.

Methods: We used provincially representative survey data from 2008, 2013, and 2018. We included 18 essential MNCH interventions, analyzed equity, and calculated the composite coverage score. We used logistic and multiple linear regressions to adjust sampling clusters and covariates.

Results: Coverage of hospital-based interventions, such as hospital delivery and antenatal B-ultrasound tests, was nearly universal in Jilin province. Cesarean sections persisted at alarmingly high rates (57.6%). Enormous unmet needs and rural–urban inequalities existed for community-based interventions, such as improved drinking water sources (85.4 vs. 97.9%, p < 0.01), improved sanitation facilities (52.5 vs. 94.2%, p < 0.01), four government-funded antenatal care services (55.8 vs. 84.1%, p < 0.01), and at least eight antenatal care sessions (26.8 vs. 46.3%, p < 0.05). Compared to rural–urban inequity, individual-level disparities across income and education were either small in scale or statistically insignificant. The inequity in coverage of maternal and newborn care shrank during 2008–2018.

Conclusions: Despite its success in reducing mortality, China's unique obstetrician-led safe motherhood strategy may come at the cost of over-medicalization and health inequity. Jilin province's recent efforts to revitalize primary health care show the potential to make a change. An integrated system that links families, communities, and all levels of health care organizations seems to be the most effective and efficient model to offer continuing MNCH care.

Early period corrosion and scaling characteristics of ductile iron pipe for ground water supply with sodium hypochlorite disinfection

The corrosion and scaling phenomenon have crucial impact on drinking water distribution systems (DWDS), which might lead to pipe blockage or leakage, colored water and other chemical stability issues. In this study, a simulating pipe system with continuous water flow was prepared to investigate the characteristics of corrosion and scaling on ductile iron pipe transporting ground water with sodium-hypochlorite (NaOCl) disinfection. Electrochemical assays, such as polarization curves and electrochemical impedance spectra were applied to monitor the corrosion and scaling process. Results showed the morphology and components of scale were closely related with the electrochemical analysis results. The corrosion current density decreased continuously as corrosion and scaling proceeded. The process could be divided into three stages. During Stage I (0-20 days), the corrosion current intensity of low NaOCl dosage experiments (1, 2 mg/L) were higher than those of high NaOCl dosage experiments (5, 10 mg/L). The difference could be explained by different oxidation potentials, pH and CaCO₃ deposition. During Stage II (20-80 days), higher proportions of Fe₃O₄ in scale in experiments with no or low NaOCl dosages restrained the corrosion process and presented smaller corrosion current. Subsequently, the ductile iron surface became passivated and the difference of various NaOCl dosages affecting corrosion and scaling process turned to be negligible during Stage III (80-90 days). A negative linear relationship between the proportion of stable scale component and the corrosion current density was established. Besides the direct corrosion reaction with iron substrate, NaOCl dosing was accompanied by an increase in pH and calcium carbonate precipitation potential values, which affected the early period corrosion and scaling phenomenon greatly.

Intermittent Water Supply Management, Household Adaptation, and Drinking Water Quality: A Comparative Study in Two Chinese Provinces

Intermittent water supply (IWS) is a relatively common phenomenon across the world as well as in rural and peri-urban areas across China, though there has been little IWS-focused research from China published to date. IWS consumers typically adopt a range of strategies to cope with insufficient water supply, poor drinking water quality, and associated inconveniences. In this study, we collected a range of data from small-scale utilities and households in two IWS systems and two continuous water supply (CWS) systems, as well as from comparison groups, in Shandong and Hubei provinces. Data collection included water quality testing, interviews, and surveys on behavioral adaptations, coping strategies, water-related health perceptions, and other metrics of consumer satisfaction. Overall, we found that the IWS coping strategies employed in northern China (Shandong) were associated with generally safe, but inconvenient, water access, whereas adaptation strategies observed in southern China (Hubei) appeared to improve convenience, but not water quality. Compared to the CWS comparison groups, we did not observe significant differences in water- and sanitation-related behaviors in the IWS groups, suggesting interventions to increase adaptive and protective behaviors at the household level might further improve safe water access for households living with IWS. Overall, although the water supply infrastructure in these study areas appeared to be in relatively good condition, in contrast to reported data on IWS systems in other countries, we observed multiple risk factors associated with the water treatment and distribution processes in these IWS systems. Among policy recommendations, our results suggest that the implementation of Water Safety Plans in China would likely improve the management of drinking water treatment and, by extension, safe drinking water supply under conditions of IWS.

Contributions of volatilization, photolysis, and biodegradation to N‑nitrosodimethylamine removal in conventional drinking water treatment plants

N‑nitrosodimethylamine (NDMA) was detected in the source water of some Chinese drinking water treatment plants (DWTPs), which decreased in concentration along the treatment train. Volatilization, photolysis, and/or biodegradation were suspected of being capable of attenuating NDMA. In this study, the contribution of these mechanisms to NDMA removal was investigated by a field study in a conventional DWTP with aerated bio-pretreatment, as well as in laboratory-based experiments. The effluent of each unit process (i.e., aerated bio-pretreatment tank, horizontal sedimentation tank, sand filter) of this DWTP was sampled in the winter and summer, and the concentration of NDMA, its formation potential, and other water quality parameters were measured. NDMA removal by volatilization and biodegradation was simulated in batch experiments, and that by photolysis was calculated with parameters reported in the literature. The sampling results indicated that the aerated biofilm reactor of this DWTP removed 48% of the NDMA in August and 22% in December. According to modeling results, it could be well explained by photolysis (NDMA removal of 51% in summer and 25% in winter) and biotreatment (NDMA removal of 0.2-12% in summer and 0.1-6.1% in winter), with little contribution from aeration (NDMA removal of 0.8%). The sampling results indicated that the sedimentation tank removed 19% of NDMA in August and 9.2% in December. According to modeling results, it could be well explained by photolysis (NDMA removal of 16% in August and 9.4% in December), but little by volatilization. Thus, photolysis was shown to be the most important process for NDMA removal in this DWTP. Further investigation is needed to better understand NDMA removal during biotreatment.

Making Rainwater Harvesting a Key Solution for Water Management: The Universality of the Kilimanjaro Concept

Rainwater is conventionally perceived as an alternative drinking water source, mostly needed to meet water demand under particular circumstances, including under semi-arid conditions and on small islands. More recently, rainwater has been identified as a potential source of clean drinking water in cases where groundwater sources contain high concentrations of toxic geogenic contaminants. Specifically, this approach motivated the introduction of the Kilimanjaro Concept (KC) to supply fluoride-free water to the population of the East African Rift Valley (EARV). Clean harvested rainwater can either be used directly as a source of drinking water or blended with polluted natural water to meet drinking water guidelines. Current efforts towards the implementation of the KC in the EARV are demonstrating that harvesting rainwater is a potential universal solution to cover ever-increasing water demands while limiting adverse environmental impacts such as groundwater depletion and flooding. Indeed, all surface and subsurface water resources are replenished by precipitation (dew, hail, rain, and snow), with rainfall being the main source and major component of the hydrological cycle. Thus, rainwater harvesting systems entailing carefully harvesting, storing, and transporting rainwater are suitable solutions for water supply as long as rain falls on earth. Besides its direct use, rainwater can be infiltrating into the subsurface when and where it falls, thereby increasing aquifer recharge while minimizing soil erosion and limiting floods. The present paper presents an extension of the original KC by incorporating Chinese experience to demonstrate the universal applicability of the KC for water management, including the provision of clean water for decentralized communities.