Surface Water Quality Research Articles

Comparative evaluation of spatiotemporal variations of surface water quality using water quality indices and GIS

AbstractThere is a need for a comprehensive comparative analysis of spatiotemporal variations in surface water quality, particularly in regions facing multiple pollution sources. While previous research has explored the use of individual water quality indices (WQIs), there is limited understanding of how different WQIs perform in assessing water quality dynamics in complex environmental settings. The objective of this study is to evaluate the effectiveness of three WQIs (Canadian Council of Ministers of the Environment (CCME), National Sanitation Foundation (NSF) and System for Evaluation of the Quality of rivers (SEQ-Eau) and a national water quality regulation in assessing water quality dynamics. The pilot study area is the Acısu Creek in Antalya City of Turkey, where agricultural practices and discharge of treated wastewater effluents impair the water quality. A year-long intensive monitoring study was conducted includig on-site measurements, analysis of numerous physicochemical and bacteriological parameters. The CCME and SEQ-Eau indices classified water quality as excellent/good at the upstream, gradually deteriorating to very poor downstream, showing a strong correlation. However, the NSF index displayed less accuracy in evaluating water quality for certain monitoring stations/sessions due to eclipsing and rigidity problems. The regulatory approach, which categorized water quality as either moderate or good for different sampling sessions/stations, was also found less accurate. The novelty of this study lies in its holistic approach to identify methodological considerations that influence the performance of WQIs. Incorporating statistical analysis, artificial intelligence or multi-criteria decision-making methods into WQIs is recommended for enhanced surface water quality assessment and management strategies.

Influence of Land Use and Land Cover on the Quality of Surface Waters and Natural Wetlands in the Miranda River Watershed, Brazilian Pantanal

Water quality assessment stands as a fundamental step in water resource management. In addition to substances and organisms present in the water, land use and land cover are two factors also affecting water quality. This study analyzed the correlation and influence between water quality and land use and land cover in the Miranda River Basin (MRB) and the natural wetlands in the Pantanal Biome. Using a watershed-wide approach, results suggested that water quality management policies can be considered in terms of sub-basins (smaller planning units). The Water Quality Index (WQI) was considered GOOD or EXCELLENT throughout the MRB. It was observed that the natural wetlands have the capacity to contribute to improving the WQI, with reductions in thermotolerant coliforms and turbidity; however, high values were found for thermotolerant coliforms, a temporal increasing trend of biochemical oxygen demand (BOD), and a reduction in dissolved oxygen and total phosphorus. Conversely, in these flooded areas, trends of a decrease in dissolved oxygen and an increase in BOD levels were found. Natural wetlands play important hydrological and ecological roles in water quality, storing, removing, and cycling nutrients. They are highly relevant areas for defining watershed management and conservation strategies, environmental protection, and providing ecosystem services.

THE SALINITY ORIGIN OF THE SURFACE WATER IN THE WATERSHED DAM ZARDEZAS, EASTERN ALGERIA

: The deterioration of the physico-chemical quality of surface waters in the Algerian Northeast is caused by several factors. Our study aims to fill the knowledge gap on the control of hydro-chemical evolution of surface waters in wetlands. The main focus is on major elements in surface waters of the Skikda region in northeastern Algeria. To address this issue, we received 45 samples during the 09 campaigns conducted during the period of low and high water of the year 2015-2016, distributed over five points, namely the tributary Oued Khemakhem, Oued Bouadjeb, Oued Safsaf, reservoir of the Zerdazas dam and the downstream of the Zerdazas dam. First, we studied the variation of physical elements such as pH and EC. Then, using PCA and FA, we characterized the physicochemical properties of the water to demonstrate the relationship between the elements and the factors controlling the distribution of the major elements and the heavy metals Pb2+, Fe2+ and Sr2+. The specific formula of the dominance of the different concentrations in the surface waters of the study area followed the sequence: Ca-Mg-Na-K and Cl-SO4-HCO3 from which a predominant specific facies emerges on 67% of the samples, is of the chloride and sulfate-calcoMagnesian facies.

Assessment of surface water quality in the Siversky Donets river within Kharkiv region in 2023

Purpose. Provide an assessment of the quality of the massif of surface waters of the Siverskyi Donets River within the Kharkiv region in 2023 based on the determination of water quality indices. Methods. The methods of the modified water pollution index (WPI) and the combinatorial water pollution index (CWPI). Results. State of the river water at the observation point of the v. Pechenigy according to the method of the modified water pollution index WPIF is estimated as II class characterized as "clean", WPIH - I class, "very clean"; according to the method of the combinatorial index of water pollution CWPIF - class III a, "dirty", CWPIH - class I, "slightly polluted". State of the river water at the observation point of the v. Eschar according to the method of the modified water pollution index of WPIF is estimated as III class characterized as "moderately polluted", WPIH - II class, "clean"; according to the method of the combinatorial index of water pollution CWPIF - class III b, "dirty", CWPIH - class II, "polluted". State of the river water at the observation point of the v/ Zadonetskyi according to the method of the modified index of water pollution, WPIF is estimated as III class characterized as "moderately polluted", WPIH is II class, "clean"; according to the method of the combinatorial index of water pollution CWPIF - class III b, "dirty", CWPIH - class I, "slightly polluted". Conclusions. It was determined that there are changes in water quality along the watercourse of the Siverskyi Donets River within the Kharkiv Region in 2023. There is a deterioration of water quality after the confluence of the Uda River, by 1.69 times the magnitude of the index change, then the state of water quality improves by 1.25 times the magnitude index changes, probably due to self-cleaning processes and lower anthropogenic load. The quality of water according to WPI indicators varies from 0.25 to 1.47 (from "very clean" to "moderately polluted"). The quality of water according to the CWPI indicators varies from 1.0 to 3.83 (from "slightly polluted" to "dirty"). It was established that according to both assessment methods and both standards, the quality of water in the Pechenigy reservoir, p. Pechenegs the best, and the worst water quality in the Siverskyi Donets River below the mouth of the Uda River, village Eschar.

Effects of residential self-taxing districts on urban surface water quality

An extensive literature documents the economic benefits associated with improving the quality of inland surface waters, including lakes, streams, and rivers. Efforts to do so in urban U.S. landscapes are often limited due to laws restricting the use of property taxes for surface water management. However, programs in several states allow homeowners to establish residential self-taxing districts through referendum to fund management and improvement activities. This study investigates the effectiveness of self-taxing districts for improving lake water quality, focusing upon a long-standing program in Orange County, Florida. Results from dynamic panel data models estimated with annual measures of total nitrogen and phosphorus concentrations, secchi disk depth, and trophic state from >250 lakes over 1970–2018 indicate significant differences in mean annual water quality emerge over time between taxing district lakes and un-managed lakes and that particular district objectives and best management practices are associated with significant reductions in nitrogen and phosphorus concentrations.

Assessing environmental pollutionfrom shrimp farming activities in Soc Trang province

The study aimed to evaluate the level of environmental pollution from shrimp farming in coastal areas of Soc Trang province. A total of 10 shrimp farming households and 50 neighbouring households were interviewed about emissions and environmental sanitation conditions. At the end of the shrimp season, pond water samples were collected from 5 semi-intensive ponds and 5 intensive ponds, bottom sediment samples were collected from 5 semi-intensive ponds to evaluate the level of pollution. Interview results indicated that wastewater and bottom sediment from shrimp farming are the main causes of declining surface water quality and reducing the number of wild fish; pollution levels are likely to increase in the future. The pH, total suspended solid (TSS), BOD5, and chemical oxygen demand (COD) values of pond water samples are suitable for shrimp farming (except TSS of water samples in Cu Lao Dung and Long Phu); total Kjeldahl nitrogen (TKN) and total phosphorus (TP) contents fluctuate widely between sampling ponds. The metal content in the bottom sediment is lower than the allowable discharge threshold of sediment quality standards. Solid waste generated in farming areas has not been properly collected and treated. To sustainably develop the shrimp industry, local authorities need to encourage shrimp farmers to apply proper waste treatment technologies in addition to state management solutions.

Simultaneous Determination of Chemical Oxygen Demand, Total Nitrogen, Ammonia, and Phosphate in Surface Water Based on a Multielectrode System.

A technique for monitoring chemical oxygen demand (COD), total nitrogen (TN), ammonia (N-NH4), and phosphate (P-PO4) in surface water with a targeted signal multielectrode system (Cu, Ir, Rh, Co(OH)2, and Zr(OH)4 electrodes) is proposed for the first time. Each water quality index is specifically detected by at least two electrodes with distinct selectivity sensing mechanisms. Cyclic voltammetry and electrochemical impedance measurements are employed for multidimensional signal acquisition, complemented by normalization and Least Absolute Shrinkage and Selection Operator (LASSO) for principal feature extraction and dimension reduction. Multiple linear regression (MLR), partial least-squares (PLS), and eXtreme Gradient Boosting (XGBoost) were employed to evaluate the established prediction model. The precisions of the multielectrode system are ±10%/±5 ppm of COD, ±10%/±0.2 ppm of TN, ±5%/±0.1 ppm of N-NH4, and ±5%/±0.01 ppm of P-PO4. The analysis time of the multielectrode system is reduced from hours to minutes compared with traditional analysis, without any sample pretreatment, facilitating continuous online monitoring in the field. The developed multielectrode system offers a feasible strategy for online in situ monitoring of surface water quality.

Interactive Changes in Climatic and Hydrological Droughts, Water Quality, and Land Use/Cover of Tajan Watershed, Northern Iran

In response to novel and complex uncertainties, the present research is conducted to characterize the most significant indicators of watershed health including drought, water quality, and vegetation for the Tajan watershed, Mazandaran, Iran. The Standardized Precipitation Index (SPI) and Streamflow Drought Index (SDI) are, respectively, used to quantify the meteorological and hydrological droughts in the present (1993–2020) and future (2023–2050) employing optimistic RCP2.6 and pessimistic RCP8.5 scenarios. To concoct discharge data for the future, IHACRES v1.0 software is used with a Nash–Sutcliffe coefficient (NSE) of 0.48 and a coefficient of determination (R2) of 0.58. Maps of land use and Normalized Difference Vegetation Index (NDVI) are also prepared using Landsat images. Subsequently, the surface water quality is assessed using AqQA v1.1.0 software. The results show the difference in the severity of future meteorological droughts in different stations. In addition, the predominance of non-drought (SDI ≥ 0) or mild drought (−1 ≤ SDI < 0) is indicated for future hydrology. The land use changes show a decrease in rangeland (−5.47%) and an increase in residential land (9.17%). The water quality analysis also indicates an increase in carbonate ions in the watershed outlet. Communicating the relationships between study indicators, which is a big gap in the current watershed management approach, avoids future failures and catastrophes.

Recent advances in vertical temperature profiler instrumentation and flux estimation methods facilitate groundwater – Surface water exchange studies in environments with strong discharge zones

Groundwater fluxes to many surface water systems are spatially heterogeneous with discharge focused into discrete, high-flux zones. Quantifying fluxes in these preferential discharge zones is critical to a range of surface water habitat and water quality processes, but characterization can be difficult due to short-scale spatial and temporal variability. Passive heat-as-a-tracer methods employing vertical temperature profiler (VTP) data can provide the necessary spatial and temporal resolution, but upward fluid flow strongly attenuates the thermal signals used for estimating fluxes. In preferential discharge zones it becomes difficult to measure the signals in the subsurface and the flux parameter can become insensitive in the analysis models, leading to large uncertainties. We use data from a high-flux site of contaminant-loaded groundwater discharge to the Quashnet River on Cape Cod, Massachusetts, USA, to demonstrate how recent advances in VTP instrumentation that allow for the acquisition of high-resolution (0.001 °C) temperature data at short (1 cm) offsets near the ground surface, combined with advances in flux estimation methods that exploit the information content of the high-resolution data, facilitate heat-as-a-tracer approaches for characterizing groundwater-surface water exchanges and make it possible to obtain accurate and statistically robust results in a preferential discharge zone with a specific discharge of ∼1 m/d.

Spatial and seasonal variation of microplastics and surface water quality of the Njoro River and Lake Nakuru ecosystems, Kenya

High levels of plastic pollutants threaten aquatic habitats as the plastic materials are ingested by aquatic organisms as food. This study assessed seasonal variations of microplastics and the water quality of the Njoro River and Lake Nakuru, Kenya. Selected water physico-chemical parameters were measured. Microplastic (MP) abundance in the surface water samples in the dry season was recorded as 47–649 MPs 300 l−1 for sampling points in the Njoro River, and 54–508 MPs 300 l−1 at Fisher’s Point in Lake Nakuru. Abundances during the rainy season were measured as 8–389 MPs 300 l−1 and 28–259 MPs 300 l−1 for the Njoro River and Lake Nakuru, respectively. Our study observed a significant contribution of microplastics from polymers, namely polyester (40%), polypropylene (25%), polyethylene (20%) and polyethylene terephthalate (10%). Recorded ranges of the water parameters were: salinity 0.085–2.59 ± 0.03 ppt; temperature 14.22–23.69 ± 0.07 °C; pH 8.8–9.3; turbidity 13.95–36.03 ± 0.35 NTU; total nitrogen 5.9–8.57 ± 3.24 mg l−1; total phosphorus 7.49–9.41 ± 1.84 mg l−1; electrical conductivity 73.3–533.3 ± 0.64 μs cm−1; and total dissolved solids 46.67–243.33 ± 0.11 ppm. These ranges were within the standards recommended by WHO and U.S. EPA. The results indicate the possibility for the quantity and mass of microplastic particles in Lake Nakuru to surpass those in the Njoro River.

THE ECOLOGICAL ASSESSMENT OF SMALL RIVERS IN UKRAINE UNDER CONDITIONS OF INTENSIVE WAR IMPACT

Aquatic ecosystems are perpetually exposed to anthropogenic sources of pollution, wherein the quality of subterranean and surface waters undergoes influence from both natural and anthropogenic processes. This interaction results in environmental predicaments and, occasionally, environmental crises. Small rivers, in particular, bear a pronounced impact from human interventions on the environment. The investigation undertaken by the researchers commenced in 2021 with the primary objective of scrutinizing the ecological condition of the Irsha River. Regrettably, due to the military aggression of the Russian Federation, the regions through which the river courses were temporarily occupied, subjecting it to considerable anthropogenic disturbances. Specifically, two bridges spanning the Irsha River in the Malyn area were demolished, and military operations transpired along the riverbanks, leading to the accumulation of damaged military equipment. Consequently, it was deemed imperative during the course of our study to conduct an analysis of the natural water in the Irsha River subsequent to the military activities. The outcomes of a comprehensive assessment of surface water quality, employing a graphical method, revealed that, during the period of 2021-2022, the river waters within the Irsha River exhibited an overall failure to meet quality standards in both monitoring locations. Elevated values of Maximum Permissible Concentration (MPC) exceeding the norm were noted for the Chemical Oxygen Demand (COD) indicator, the dissolved oxygen indicator, as well as the general iron and iron of permanganate oxidizability parameters in both samples. The highest degree of pollution was discerned in the Malyn Reservoir, whereas the Irsha Reservoir manifested comparatively lower pollution levels in the aquatic environment.

A four-season exploration of surface water quality and trophic status in the highly dynamic waters of Karun-4 Dam Lake, SW Iran

This study explores seasonal fluctuations in water quality and phytoplankton communities within Karun-4 Dam Lake, the largest double-arch dam in the Middle East situated in Iran. Employing a systematic approach, 26 sampling stations were strategically selected to collect surface water samples at a depth of 50 cm during the midpoints of each season throughout 2019. Significant seasonal variations in water quality parameters and phytoplankton composition were observed. Predominant species included Chrysophyceae (38%) and Bacillariophyceae (32%), indicative of nutrient-rich conditions, particularly during spring and summer, as evidenced by the eutrophic state (Carlson Trophic State Index: 59.43 and 53.96, respectively). Summer exhibited the highest diversity (Shannon–Wiener Index = 2.27) and lowest evenness (Pielou’s Evenness Index = 0.21). PCA and CCA analyses revealed season-specific preferences for nutrients and ions among phytoplankton species. Water temperature emerged as a crucial factor in spring and summer, while environments with elevated bicarbonate and alkalinity levels were less favorable during winter and fall. This study provides essential insights into Karun-4 Lake's dynamic ecological conditions, underscoring the necessity for ongoing monitoring to discern long-term trends and anthropogenic impacts for effective ecosystem management.

Occurrence, transport and sources of metals and metalloids in the Bangpakong River in the eastern economic corridor area of Thailand

The occurrence of elements in river water is affected by various factors, including mobility, weathering and transport processes and anthropogenic contributions. A total of six water sampling campaigns were conducted from 2021 to 2022 to study the factors affecting the occurrence of twelve elements (Al, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn and Se) in the Bangpakong River. The total concentrations of all the elements were within the levels set by the national surface water quality standard. Comparisons of dissolved elemental concentrations in the study area with the global average for dissolved elemental concentrations in pristine rivers indicated contamination with Al, As, Co, Mn, Zn and Se in the river water. Based on the percentage of each element in particulates to the total concentration, Al (80.6 %), Cr (71.9 %), Cu (69.9 %), Fe (95.6 %), Mn (76.6 %), Pb (74.7 %), and Zn (70.6 %) were mainly transported in the particulate phase in both the dry and wet seasons. However, As (65.5 %), Co (60.3 %), and Se (77.6 %) were mainly transported in the dissolved phase in both seasons. The ratios of the dissolved Se concentration in river water to the Se concentration in the Earth's crust indicated significant and high mobility, especially in downstream sites, likely due to Se leaching from alluvial sediments. Seawater intrusion is likely the cause of As and Zn contamination in the dry season. Weathering of rocks and soils likely causes Al, Co, and Mn contamination in the wet season. The anthropogenic sources of contamination include the discharge of Mn and Zn from fertilizers in agriculture and the use of formulated feed in aquaculture. Approximately 52.98, 25.23, 5.68 and 0.63 tons of Fe, Al, Mn and Zn, respectively, are estimated to be transported from the river into the Gulf of Thailand each year.

Impact of lifestyle, human diet and nutrient use efficiency in food production on eutrophication of global aquifers and surface waters

A spatially explicit (0.5 degree resolution) analysis is presented of the impact of human lifestyle, diet and nutrient use efficiency in food production and wastewater treatment on exceedance of threshold concentrations for nitrate in groundwater, and total N and total P concentrations in surface water, as well as criteria for their ratio. This analysis starts from the middle-of-the-road (SSP2) and the sustainability (SSP1) Shared Socio-economic Pathways (SSP), focusing on the year 2050. The scenarios with changed lifestyle assume a reduction of food wastage and a low-meat diet for all world inhabitants, implying large reductions of meat and milk consumption and production in industrialized countries. Scenarios with improved nutrient use efficiencies assume maximum achievable efficiencies under practical conditions. The SSP2 scenario combined with assumptions on lifestyle and human diet leads to improvement in industrialized countries only, and increased levels in many other regions. A strong improvement is achieved in SSP1, but not in many developing countries, and SSP1 combined with changed lifestyle leads to improvement of groundwater and surface water quality in industrialized countries only. Therefore, changed lifestyle needs to be combined with efforts to improve the efficiency in food production systems and wastewater treatment to achieve reductions of the area affected by groundwater contamination and eutrophication of surface waters. Reduction strategies need to find a balance between N and P, since it is easier to reduce N in rivers to levels below the threshold than P.

MICROBIAL CONTAMINATION OF THREE RIVERS CROSSING SOFIA CITY

Water is an important factor for all living creatures. In some organisms, it makes up 90% of body weight. In humans, its percentage varies between 55-65%. Water covers about 71% of the planet's surface. That is why it is necessary to protect it from various types of pollution with physical, chemical and biological substances. Rivers are the main sources because they provide water for drinking-domestic water supply, industry, animal husbandry, agriculture, etc. Attention should be paid to the quality of surface waters, an adequate assessment of microbiological contamination and their sanitary condition should be made. However, antimicrobial resistance is constantly increasing. The number of deaths is expected to rise from 700,000 in 2014 to 10 million by 2025. This is the first report of the microbial contamination of three rivers crossing Sofia city – Darvenishka River, Vladayska River (before the Wastewater Treatment Plant (WWTP) near Kubratovo) and Iskar River (after WWTP Kubratovo). According the REGULATION №12 from 18.06.2002 and the number of colony forming units in 100 ml the waters of the Darvenishka River belong to Category 2 according to the contents of fecal streptococci and Category 3 – according to the contents of E. coli and coliforms. The waters of the Vladayska River fall into Category 2. The waters of the Iskar River at the sampling point are classified as Category 3 according to the total coliform and Category 2 according to the fecal streptococci content. We isolated 12 single bacterial cultures from water and sludge of Darvenishka River and characterized theme biochemically by BD Phoenix M50. According the EUCAST cut-off values we determined their susceptibility against 8 groups of antibiotics and most of them were multiresistant.

Application of Mesoporous Silicas for Adsorption of Organic and Inorganic Pollutants from Rainwater.

Precipitation is an important factor that influences the quality of surface water in many regions of the world. The pollution of stormwater runoff from roads and parking lots is an understudied area in water quality research. Therefore, a comprehensive analysis of the physicochemical properties of rainwater flowing from parking lots was carried out, considering heavy metals and organic micropollutants. High concentrations of zinc were observed in rainwater, in addition to alkanes, e.g., tetradecane, hexadecane, octadecane, 2,6,10-trimethyldodecane, 2-methyldodecane; phenolic derivatives, such as 2,6-dimethoxyphenol and 2,4-di-tertbutylphenol; and compounds such as benzothiazole. To remove the contaminants present in rainwater, adsorption using silica carriers of the MCF (Mesostructured Cellular Foams) type was performed. Three groups of modified carriers were prepared, i.e., (1) SH (thiol), (2) NH2 (amino), and (3) NH2/SH (amine and thiol functional groups). The research problem, which is addressed in the presented article, is concerned with the silica carrier influence of the functional group on the adsorption efficiency of micropollutants. The study included an evaluation of the effects of adsorption dose and time on the efficiency of the contaminant removal process, as well as an analysis of adsorption isotherms and reaction kinetics. The colour adsorption from rainwater was 94-95% for MCF-NH2 and MCF-NH2/SH. Zinc adsorbance was at a level of 90% for MCF-NH2, and for MCF-NH2/SH, 52%. Studies have shown the high efficacy (100%) of MCF-NH2 in removing organic micropollutants, especially phenolic compounds and benzothiazole. On the other hand, octadecane was the least susceptible to adsorption in each case. It was found that the highest efficiency of removal of organic micropollutants and zinc ions was obtained through the use of functionalized silica NH2.

Effects of landscape changes on water quality: A global meta-analysis

Landscape changes resulting from anthropogenic activities and climate changes severely impact surface water quality. A global perspective on understanding their relationship is a prerequisite for pursuing equity in water security and sustainable development. A sequent meta-analysis synthesizing 625 regional studies from 63 countries worldwide was conducted to analyze the impacts on water quality from changing landscape compositions in the catchment and explore the moderating factors and temporal evolution. Results exhibit that total nitrogen (TN), total phosphorus (TP), and chemical oxygen demand (COD) in water are mostly concerned and highly responsive to landscape changes. Expansion of urban lands fundamentally degraded worldwide water quality over the past 20 years, of which the arid areas tended to suffer more harsh deterioration. Increasing forest cover, particularly low-latitude forests, significantly decreased the risk of water pollution, especially biological and heavy metal contamination, suggesting the importance of forest restoration in global urbanization. The effect size of agricultural land changes on water quality was spatially scale-dependent, decreasing and then increasing with the buffer radius expanding. Wetland coverage positively correlated with organic matter in water typified by COD, and the correlation coefficient peaked in the boreal areas (r=0.82, p<0.01). Overall, the global impacts of landscape changes on water quality have been intensifying since the 1990s. Nevertheless, knowledge gaps still exist in developing areas, especially in Africa and South America, where the water quality is sensitive to landscape changes and is expected to experience dramatic shifts in foreseeable future development. Our study revealed the worldwide consistency and heterogeneity between regions, thus serving as a research roadmap to address the quality-induced global water scarcity under landscape changes and to direct the management of land and water.

Ultrafiltration and reverse osmosis integrated to conventional drinking water treatment to ensure human right to water in dam break scenarios: From bench- to pilot-scale

Previous events of tailing dam failures were associated with impacts in the water sources of drinking water treatment plants, which involves elevated concentrations of suspended solids and metal(oid)s. This study assesses the effectiveness of conventional treatment processes at a lab-scale, highlighting their limited robustness in treating water with different physicochemical qualities. Subsequently, it validates the integration of ultrafiltration (UF) and reverse osmosis (RO) into an existing water treatment plant to enhance its performance. The processes were conducted at a pilot scale, operating for 660 h under varied turbidity (<2 – 200 NTU) and contaminant (iron, manganese, and arsenic) concentrations. The membranes operated steadily with an average permeate flux of 38.6 ± 0.9 L/m2h and 19.6 ± 0.8 L/m2h for UF and RO, respectively. UF fouling was primarily related to internal pore blocking and attributed to organic matter and inorganic compounds, identified using excitation-emission matrix and energy-dispersive X-ray mapping across the cross-section of its fibers. Due to the limitations of UF in removing dissolved species, RO became necessary and ensured that all parameters analyzed met drinking water standards. The UF-RO contributes to higher robustness to conventional treatment processes and addresses operational challenges associated with a dam rupture event such as the unforeseen alteration in the quality of surface water that hinders the optimization of pre-oxidants and coagulants in conventional treatment process. To reduce costs, energy requirements, and the size of membrane-based systems, a blending strategy was proposed with a focus on achieving drinking water standards. The suggested blends include effluent from sand filters and RO permeate in a 1:1 ratio. That was only possible due to the high quality achieved for RO permeate. Apart from creating more compact systems, the blending strategy promotes the remineralization of RO permeate, mitigating undesirable characteristics such as corrosiveness, taste, and odor. For the concentrate, UF concentrate could be recycled back into the treatment process, improving water recovery in the drinking water facility, while the concentrate from RO adheres to discharge limits. Overall, the study advances investigations on integrating ultrafiltration and reverse osmosis with conventional drinking water treatment to address water quality issues from tailing dam ruptures.

Linking wastewater treatment plant effluents to water quality and hydrology: Effects of multiple stressors on fish communities

Wastewater treatment plants (WWTPs) are essential for maintaining a good water quality of surface waters. However, WWTPs are also associated with water quality deterioration and hydro-morphological alteration. Riverine communities respond to these stressors with changes in their community structure, abundance and diversity. In this study, we used a dataset of 94 monitoring sites across North Rhine-Westphalia, Germany to investigate the influence of WWTPs on the water quality and hydro-morphological quality in river sections downstream of WWTP effluents. More specifically, we analyzed the effects of the percentage of WWTP effluents (in relation to median base flow) on four stressor groups (physico-chemistry, micropollutants, hydrological and morphological alteration) using Linear Mixed Models (LMM). Furthermore, we assessed the impact of a selection of twelve ecologically relevant stressor variables reflecting water quality deterioration and hydro-morphological alteration on reference fish communities using Canonical Correspondence Analysis (CCA). The percentage of WWTP effluents was correlated with water quality, especially with toxic units of a wide range of pharmaceuticals including diclofenac, venlafaxine and sulfamethoxazole (R² up to 0.54) as well as specific pesticides (e.g., terbutryn: R² = 0.33). The correlation of percent WWTP effluents with hydro-morphological alteration was weaker and most pronounced for the frequency of high flow (R² = 0.24) and flow variability (R² = 0.19). About 40 % of the variance in the fish community structure were explained by 12 stressor variables in the CCA models. Water quality and hydrological, but not morphological stressors showed strong albeit highly variable effects on individual fish species. The results indicate that water quality degradation and hydrological alteration are important factors determining the ecological status of fish communities. In this context, WWTP effluents can impose relevant point sources of pollution that affect water quality but also cause alterations of the hydrological regime. Further management measures addressing both stressor groups are needed to improve the ecological status.

Understanding watershed sources of pollution in Vinh Long Province, Vietnamese Mekong Delta

We explore point source (PS) and non-point source (NPS) pollution impacts on surface water quality in Vinh Long Province, Vietnam. We used data from 60 surface water quality monitoring stations across dry, transitional, and wet seasons from 2017 to 2021, in addition to sampling data collected from 12 wastewater outlets from June to October 2021 to determine the sources of pollution loads. Surface water quality was assessed using both the water quality index (WQI) and the Vietnamese standards QCVN 08:2015, whilst cluster analysis (CA) and principal components analysis (PCA) were used to evaluate spatial variation and key influencing factors. We observed seasonal variation in surface water quality, with a decline in quality during the rainy season. Moreover, the water quality parameters such as chemical oxygen demand (COD), biochemical oxygen demand (BOD5), total nitrogen (TN), and total phosphorus (TP) frequently exceeded the QCVN 08:2015 standard. Across, the different monitoring fixed points and seasons, COD levels were found to range from 8.94 to 15.14 mg/L, while TN levels varied between 0.24 and 0.53 mg/L. The cluster analysis categorized the monitoring fixed points into three groups, based on their water quality parameters, while PCA identified four principal components that explain 69% of the variance, distinguishing between pollution sources and seasonal factors. Our findings emphasize that poor water quality in many areas is affected by non-point source pollution, underscoring the need for watershed and land management. The results and applied methodologies provide insights for watershed management, policy development, and adaptation, applicable to regions facing similar environmental challenges.