Water quality assessment and pollution threat to safe water supply for three river basins in Malaysia

Rapid visual dual-mode detection of Zr(IV) based on L-histidine functionalized gold nanoparticles

Heavy metal pollution has always been a great threat to human health and safety. Compared with other heavy metals, although zirconium ion (Zr(IV)) is equally harmful, due to the lack of research on Zr(IV) in the biological systems and environment, its detection does not seem to have received the attention it deserves. Herein, a rapid visual dual-mode detection (colorimetric and chrominance method) of Zr(IV) based on L-histidine functionalized gold nanoparticles (HIS-AuNPs) has been reported. AuNPs and HIS-AuNPs before and after adding Zr(IV) were characterized by UV-Vis, TEM, DLS, Zeta potential, EDS and FT-IR, etc. These results showed that L-histidine was successfully modified on the surface of AuNPs by forming a stable Au-N bond, and its modification had little effect on the dispersion degree of AuNPs. After the addition of Zr(IV), interaction of this metal ion with the imidazolyl group on L-histidine can obviously cause the aggregation of HIS-AuNPs within 12 min, and the dispersion state and particle size of HIS-AuNPs can be significantly changed. These two detection modes were established by means of absorbance and color change of solution, and being used in addition and recovery experiments of Zr(IV) in natural water. Under the optimal conditions, these two modes exhibited good linearity within 15-70 and 20-100 μmol L-1, and limit of detection of 2.62 and 6.25 μmol L-1. The proposed method was highly sensitive and selective, which provided a new convenient way to realize the detection of Zr(IV).

Downflow sponge biofilm reactors for polluted raw water treatment: Performance optimisation, kinetics, and microbial community

Water outages caused by elevated ammonium (NH4+-N) levels are a prevalent problem faced by conventional raw water treatment plants in developing countries. A treatment solution requires a short hydraulic retention time (HRT) to overcome nitrification rate limitation in oligotrophic conditions. In this study, the performance of polluted raw water treatment using a green downflow sponge biofilm (DSB) technology was evaluated. We operated two DSB reactors, DSB-1 and DSB-2 under different NH4+-N concentration ranges (DSB-1: 3.2-5.0 mg L-1; DSB-2: 1.7-2.6 mg L-1) over 360 days and monitored their performance under short HRT (60 min, 30 min, 20 min, and 15 min). The experimental results revealed vertical segregation of organic removal in the upper reactor depths and nitrification in the lower depths. Under the shortest HRT of 15 min, both DSB reactors achieved stable NH4+-N and chemical oxygen demand removal (≥95%) and produced minimal effluent nitrite (NO2--N). DSB system could facilitate complete NH4+-N oxidation to nitrate (NO3--N) without external aeration energy requirement. The 16S rRNA sequencing data revealed that nitrifying bacteria Nitrosomonas and Nitrospira in the reactor were stratified. Putative comammox bacteria with high ammonia affinity was successfully enriched in DSB-2 operating at a lower NH4+-N loading rate, which is advantageous in oligotrophic treatment. This study suggests that a high hydraulic rate DSB system with efficient ammonia removal could incorporate ammonia treatment capability into polluted raw water treatment process and ensure safe water supply in many developing countries.

A unified deep learning framework for water quality prediction based on time-frequency feature extraction and data feature enhancement

Deep learning methods exhibited significant advantages in mapping highly nonlinear relationships with acceptable computational speed, and have been widely used to predict water quality. However, various model selection and construction methods resulted in differences in prediction accuracy and performance. Hence, a unified deep learning framework for water quality prediction was established in the paper, including data processing module, feature enhancement module, and data prediction module. In the established model, the data processing module based on wavelet transform method was applied to decomposing complex nonlinear meteorology, hydrology, and water quality data into multiple frequency domain signals for extracting self characteristics of data cyclic and fluctuations. The feature enhancement module based on Informer Encoder was used to enhance feature encoding of time series data in different frequency domains to discover global time dependent features of variables. Finally, the data prediction module based on the stacked bidirectional long and short term memory network (SBiLSTM) method was employed to strengthen the local correlation of feature sequences and predict the water quality. The established model framework was applied in Lijiang River in Guilin, China. The maximum relative errors between the predicted and observed values for dissolved oxygen (DO), chemical oxygen demand (CODMn) were 12.4% and 20.7%, suggesting a satisfactory prediction performance of the established model. The validation results showed that the established model was superior to all other models in terms of prediction accuracy with RMSE values 0.329, 0.121, MAE values 0.217, 0.057, SMAPE values 0.022, 0.063 for DO and CODMn, respectively. Ablation tests confirmed the necessity and rationality of each module for the established model framework. The established method provided a unified deep learning framework for water quality prediction.

Does tourism development contribute to the green water-use efficiency of the Yellow River Basin in China?

The coordination between economic development as well as water resources conservation in ecologically fragile areas is the basis for achieving sustainable development in developing countries. Nonetheless, the existing literature pays little attention to such an issue. The purpose of this quantitative study is to explore the causal relationship between tourism development and green water-use efficiency in the Yellow River Basin (YRB) of China. The findings are as follows: (1) Tourism development can significantly enhance the green water-use efficiency in the YRB; For every 1% increase in tourism revenue, the green water-use efficiency will increase by 4.38%. (2) Tourism affects the green water-use efficiency by increasing the intensity of water pollution and decreasing the intensity of water use; For every 1% increase in tourism revenue, the green water-use efficiency will decrease by 0.2% and increase by 0.9% respectively by increasing the intensity of water pollution and decreasing the intensity of water use. (3) Strengthening environmental regulation and improving service facilities will further enhance the positive impact of tourism development; An increase of one standard deviation in the intensity of environmental regulation or one standard deviation in the level of service facilities will increase the impact of tourism on green water-use efficiency by 1.1% or 1.7%, respectively. The aforementioned findings provide enlightenment for effectively promoting the coordination between economic development and water resources protection in ecologically fragile areas of developing countries.

New approach into human health risk assessment associated with heavy metals in surface water and groundwater using Monte Carlo Method

This study assessed the environmental and health risks associated with heavy metals in the water resources of Egypt's northwestern desert. The current approaches included the Spearman correlation matrix, principal component analysis, and cluster analysis to identify pollution sources and quality-controlling factors. Various indices (HPI, MI, HQ, HI, and CR) were applied to evaluate environmental and human health risks. Additionally, the Monte Carlo method was employed for probabilistic carcinogenic and non-carcinogenic risk assessment via oral and dermal exposure routes in adults and children. Notably, all water resources exhibited high pollution risks with HPI and MI values exceeding permissible limits (HPI > 100 and MI > 6), respectively. Furthermore, HI oral values indicated significant non-carcinogenic risks to both adults and children, while dermal contact posed a high risk to 19.4% of samples for adults and 77.6% of samples for children (HI > 1). Most water samples exhibited CR values exceeding 1 × 10-4 for Cd, Cr, and Pb, suggesting vulnerability to carcinogenic effects in both age groups. Monte Carlo simulations reinforced these findings, indicating a significant carcinogenic impact on children and adults. Consequently, comprehensive water treatment measures are urgently needed to mitigate carcinogenic and non-carcinogenic health risks in Siwa Oasis.

Occurrence, distribution, source apportionment, ecological and health risk assessment of heavy metals in water, sediment, fish and prawn from Ojo River in Lagos, Nigeria

The study investigates the occurrence and bioaccumulation of heavy metals in water, sediment, fish, and prawn from the Ojo River with a view to identify the source of origin and the associated ecological and human health risks. The result shows that heavy metal concentrations in water [As = 0.010, Cd = 0.001, Cr = 0.041, Cu = 0.019, Co = 0.050, Fe = 0.099, Pb = 0.006, Ni = 0.003, and Zn = 0.452(mg/L)] were within the acceptable limits. The heavy metals in the sediment [As = 0.050, Cd = 0.287, Cr = 0.509, Cu = 0.207, Co = 0.086, Fe = 33.093, Pb = 0.548, Ni = 0.153 and Zn = 4.249 (mg/kg)] were within their respective background levels or earth's crust and the TEL and PEL standard limits. The bioaccumulation of heavy metals in fish and prawn tissues are in this hierarchical form: Fe > Zn > Cu > Cr > Ni > Co > Pb > Ar > Cd and Fe > Zn > Cu > Cr > Pb > Ar > Ni > Co > Cd, respectively. The bioaccumulation factors of heavy metals in fish ranged from 0.893 - 16.611 and 1.056 - 49.204 in prawn, which were higher than the biota-sedimentation factors (BSAF) values, inferring that the fish and prawns of this study ingested heavy metals highly from water column. The aggregated BSAF scores (fish = 5.584 and prawn = 9.137) showed that these organisms are good concentrators of heavy metals in sediments. The water quality index and other pollution indices (Single pollution index, Heavy metal assessment index, and Heavy metal pollution index) demonstrates slightly clean water, with a moderate level of contamination. The HI values of heavy metals in water, fish, and prawn were lower than 1, implying non-carcinogenic risk in children or adults. The ADD and EDI values of the metals were within their respective oral reference doses (RfD). The TCR values showed that exposure to water, either by ingestion or dermal absorption and the consumption of P. obscura and M. vollenhovenii from the Ojo River would not induce cancer risks in people, though As, Cr, Cd, and Pb showed carcinogenic potentials. The sediment contamination indices such as CF, mCd, EF, and Igeo showed a moderate level of pollution. The ecological risk values (NMPI, mCd = 0.068, PLI = 0.016, and R.I = 86.651) of heavy metals implies "no-moderate risk" except for Cd, which showed high risk. The ecotoxicological parameters,  m-PEL-Q (0.024) and m-ERM-Q (0.016) denotes low contamination and no probability of acute toxicity. The CV analysis showed high dispersions and variabilities in the distributions of the heavy metals in water. Other source analyses (Pearson's correlation matrix, PCA, and HCA) showed that both natural processes and anthropogenic activities are responsible for the occurrence of heavy metals in water and sediment from the Ojo River.

Preparation of N-doped porous biochar with high specific surface area and its efficient adsorption for mercury ion from aqueous solution

Herein, a new type of super active nitrogen-doped biochar sheet (SNBC) was prepared by two-step pyrolysis and KOH chemical activation with melamine and cherry kernel powder as precursors of nitrogen and carbon source for removing Hg2+ from wastewater. The N2 adsorption/desorption and scanning electron microscope characterization revealed that the resulted SNBC under 600 °C calcination owned huge specific surface area of 2828 m2/g and plenty of well-developed micropores, and X-ray photoelectron spectroscopy and Fourier transform-infrared spectroscopy analysis testified the existence of functional groups containing N and O, which could provide adsorption sites for Hg2+. The SNBC-600 showed high adsorption capacity for Hg2+ even at low pH, and interfering cations had little effect on the adsorption. The adsorption process was rapid and dynamic data fit the pseudo-second-order dynamic model well. The maximum adsorption capacity of Hg2+ on SNBC-600 calculated by Langmuir model was 230 mg/g. After six times of reuse, the adsorption capacity still exceeded 200 mg/g, exhibiting good reusability. The designed microfiltration membrane device base on SNBC-600 could remove low concentration of Hg2+ effectively from solution. This study provided a simple and environment-friendly method for manufacturing nitrogen-doped biochar sheet, which was of great significance in the practical application of Hg2+ pollution treatment.

Impacts of seasonal variations and wastewater discharge on river quality and associated human health risks: A case of northwest Dhaka, Bangladesh

Surface water pollution caused by the discharge of effluents from industrial estates has become a major concern for Dhaka (Bangladesh). This study aims to have a concise look at the severe river water pollution, mainly from effluents discharged from the tannery village. Effluent samples were collected from five ejected points, including the central effluent treatment plant (CETP), twenty adjacent river water, and two pond water nearby Hemayetpur, Savar. Thirty-one parameters have been observed at these sampling points for three seasons, from April 2021 to January 2022. The results obtained from water quality indices, i.e., water quality index (WQI), entropy water quality index (EWQI), and irrigation water quality index (IWQI), show that most studied surface water samples ranked "unsuitable" for consumption, irrigation, and anthropogenic purposes. The highest health risk was observed downstream of Hemayetpur city at the Savar CETP discharge site, indicating higher levels of heavy metal in the river water following the tannery village. Carcinogenic and non-carcinogenic human health risks could be triggered mainly by water consumption as concentrations of arsenic (As), chromium (Cr), nickel (Ni), and lead (Pb) exceeded the upper benchmark of 1 × 10^-4 for adults and children. The results of the carcinogenic risk assessment revealed that children were more vulnerable to health hazards, and quick corrective action is required to control the increased levels of heavy metals at all sample locations. Therefore, through bioaccumulation, human health and the environment are affected in these areas. Using river water for consumption, household work, or even irrigation purposes is not advisable. This study's result highlighted that properly implementing compatible policies and programs is required to improve effluent treatment methods and provide biodegradability to the Dhaleshwari River.

Occurrence of per- and polyfluoroalkyl substances in aquatic environments and their removal by advanced oxidation processes

Per- and polyfluoroalkyl substances (PFAS), one of the main categories of emerging contaminants, are a family of fluorinated organic compounds of anthropogenic origin. PFAS can endanger the environment and human health because of their wide application in industries, long-term persistence, unique properties, and bioaccumulation potential. This study sought to explain the accumulation of different PFAS in water bodies. In aquatic environments, PFAS concentrations range extensively from <0.03 (groundwater; Melbourne, Australia) to 51,000 ng/L (Groundwater, Sweden). Additionally, bioaccumulation of PFAS in fish and water biota has been stated to range from 0.2 (Burbot, Lake Vättern, Sweden) to 13,900 ng/g (Bluegill samples, U.S.). Recently, studies have focused on PFAS removal from aqueous solutions; one promising technique is advanced oxidation processes (AOPs), including microwaves, ultrasound, ozonation, photocatalysis, UV, electrochemical oxidation, the Fenton process, and hydrogen peroxide-based and sulfate radical-based systems. The removal efficiency of PFAS ranges from 3% (for MW) to 100% for UV/sulfate radical as a hybrid reactor. Therefore, a hybrid reactor can be used to efficiently degrade and remove PFAS. Developing novel, efficient, cost-effective, and sustainable AOPs for PFAS degradation in water treatment systems is a critical area of research.

Hydrophilic ZnO/C nanocomposites with superior adsorption, photocatalytic, and photo-enhanced antibacterial properties for synergistic water purification

Owing to the numerous potential applications of ZnO nanomaterials, the development of ZnO-based nanocomposites has become of great scientific interest in various fields. In this paper, we are reporting the fabrication of a series of ZnO/C nanocomposites through a simple "one-pot" calcination method under three different temperatures, 500 ℃, 600 ℃, and 700 ℃, with samples labeled as ZnO/C-500, -600, and -700, respectively. All samples exhibited adsorption capabilities and photon-activated catalytic and antibacterial properties, with the ZnO/C-700 sample showing superior performance among the three. The carbonaceous material in ZnO/C is key to expanding the optical absorption range and improving the charge separation efficiency of ZnO. The remarkable adsorption property of the ZnO/C-700 sample was demonstrated using Congo red dye, and is credited to its good hydrophilicity. It was also found to exhibit the most notable photocatalysis effect due to its high charge transfer efficiency. The hydrophilic ZnO/C-700 sample was also examined for antibacterial effects both in vitro (against Escherichia coli and Staphylococcus aureus) and in vivo (against MSRA-infected rat wound model), and it was observed to exhibit synergistic killing performance under visible-light irradiation. A possible cleaning mechanism is proposed on the basis of our experimental results. Overall, this work presents a facile way of synthesizing ZnO/C nanocomposites with outstanding adsorption, photocatalysis, and antibacterial properties for the efficient treatment of organic and bacterial contaminants in wastewater.

Snapshot of the pollution-driven metabolic and microbiota changes in Carassius gibelio from Bucharest leisure lakes

In the last decades, increased intakes of contaminants and the habitats' destruction have produced drastic changes in the aquatic ecosystems. The environmental contaminants can accumulate in aquatic organisms, leading to the disturbance of the antioxidant/prooxidant balance in fish. In this context, we evaluated the level of organic, inorganic and microbiological pollutants in four leisure lakes (Chitila, Floreasca, Tei and Vacaresti) from Bucharest, the largest city of Romania, in order to compare their effects on hepatopancreas and gills metabolism and antioxidant defense mechanisms in Carassius gibelio, the most known and widespread freshwater fish in this country. The lowest level of oxidative stress was recorded in the case of fish collected from the Vacaresti lake, a protected wetland area where aquatic organisms live in wild environmental conditions. In contrast, significant oxidative changes were observed in the hepatopancreas and gills of fish from the Chitila, Floreasca and Tei lakes, such as reduced glutathione S-transferase activity and glutathione level, and increased degree of lipid peroxidation, being correlated with elevated levels of pesticides (such as 2,4'-methoxychlor) and Escherichia coli load in these organs. Although different patterns of pollutants' accumulation were observed, no important interindividual variations in cytosine methylation degree were determined. In conclusion, the presence and concentrations of metals, pesticides and antibiotics varied with the analyzed tissue and sampling site, and were correlated with changes in the cellular redox homeostasis, but without significantly affecting the epigenetic mechanisms.

Interactive Allocation of Water Pollutant Initial Emission Rights in a Basin under Total Amount Control: A Leader-Follower Hierarchical Decision Model

The initial emission rights allocation is the key measure to achieve the goal of total amount control and deepen the emission trading system. Although many studies have focused on the modeling of initial emission rights allocation, such as using game theory and multi-objective optimization methods, few studies have observed the hierarchical relationship of mutual interference and restriction between watershed management agency and local governments in each subarea during allocation. This relationship directly affects the rationality of the results of regional emission rights allocation. In this study, a leader-follower hierarchical decision model (LFHDM) for allocating initial emission rights in a basin is developed. Based on the bilevel programming approach, the model simulates the interactive decision-making process between the watershed management agency of the upper-level model (LFHDM-U) and the local government of the lower-level model (LFHDM-L) in the allocation under total amount control. A case study of China's Yellow River Basin is conducted to demonstrate the feasibility and practicality of the model. Findings reveal that, compared with the single-level model, the developed LFHDM has higher satisfaction with the allocation scheme. Under different scenarios, the overall satisfaction of the configuration schemes of COD and NH3-N in each province and autonomous region remains above 0.9. In addition, the allocation volumes of COD and NH3-N in each province of the Yellow River Basin in planning year increase with the enhancement of allowable assimilative capacity of water bodies, but the interval gap of satisfaction with allocation schemes gradually narrows. It shows that when the allowable assimilation capacity of a water body is low, the decision-making of the allocation scheme needs to be more cautious. Moreover, for the Yellow River Basin, apart from Qinghai and Sichuan, the task of reducing water pollutants in other provinces in the next few years is very arduous. The average reduction of total COD and NH3-N in the basin is about 48% and 46%, respectively.

Nutrients and Environmental Factors Cross Wavelet Analysis of River Yi in East China: A Multi-Scale Approach

The accumulation of nutrients in rivers is a major cause of eutrophication, and the change in nutrient content is affected by a variety of factors. Taking the River Yi as an example, this study used wavelet analysis tools to examine the periodic changes in nutrients and environmental factors, as well as the relationship between nutrients and environmental factors. The results revealed that total phosphorus (TP), total nitrogen (TN), and ammonia nitrogen (NH4+-N) exhibit multiscale oscillation features, with the dominating periods of 16-17, 26, and 57-60 months. The continuous wavelet transform revealed periodic fluctuation laws on multiple scales between nutrients and several environmental factors. Wavelet transform coherence (WTC) was performed on nutrients and environmental factors, and the results showed that temperature and dissolved oxygen (DO) have a strong influence on nutrient concentration fluctuation. The WTC revealed a weak correlation between pH and TP. On a longer period, however, pH was positively correlated with TN. The flow was found to be positively correct with N and P, while N and P were found to be negatively correct with DO and electrical conductance (EC) at different scales. In most cases, TP was negatively correlated with 5-day biochemical oxygen demand (BOD₅) and permanganate index (COD_Mn). The correlation between TN and COD_Mn and BOD₅ was limited, and no clear dominant phase emerged. In a nutshell, wavelet analysis revealed that water temperature, pH, DO, flow, EC, COD_Mn, and BOD₅ had a pronounced influence on nutrient concentration in the River Yi at different time scales. In the case of the combination of environmental factors, pH and DO play the largest role in determining nutrient concentration.

Removal of Dye from Aquatic Environments: State-of-the-Art and Future Perspectives

Surface water sources play a vital role in numerous aspects of societal demand, including as sources of drinking water and water used for agricultural and industrial purposes [...]

Preparation and Adsorption Properties of Graphene-Modified, Pitch-Based Carbon Foam Composites

In view of the good adsorption properties of graphene and carbon foam, they were combined to achieve the optimal matching of microstructures. Taking mesophase pitch as a raw material, pitch-based carbon foam was prepared by the self-foaming method. Graphene gel was prepared as the second phase to composite with the carbon foam matrix; graphene-modified, pitch-based carbon foam composites were finally obtained. Graphene gel was dispersed in the rich pore structure of carbon foam to improve its agglomeration and the porosity, and the active sites of the composite were further increased; the adsorption properties and mechanical properties of the composites were also significantly improved. The microstructure and morphology of the composites were studied by SEM, XRD and Raman spectroscopy; the compressive property and porosity were also tested. Methylene blue (MB) solution was used to simulate a dye solution for the adsorption test, and the influence of the composite properties and MB solution on the adsorption property was studied. Results showed that the compressive strength of the composite was 13.5 MPa, increased by 53.41%, and the porosity was 58.14%, increased by 24.15%, when compared to raw carbon foam. When the mass of the adsorbent was 150 mg, the initial concentration of the MB solution was 5 mg/L, and the pH value of the MB solution was 11; the graphene-modified carbon foam composites showed the best adsorption effect, with an adsorption rate of 96.3% and an adsorption capacity of 144.45 mg/g. Compared with the raw carbon foam, the adsorption rate and adsorption capacity of the composites were increased by 158.18% and 93.50%, respectively.