Search Results (52)

Trihalomethanes (THMs) are a class of disinfectant by-products present in chlorinated tap water. Mainly due to their carcinogenic potential, their concentration in drinking water is now limited by regulations. In Romania, little is known about their distribution in urban drinking water supply systems, their magnitude, or their seasonal variation. Drinking water suppliers periodically adapt and optimise their water treatment methods for economic reasons and in response to regulatory changes and technological developments. The formation of THMs is influenced by the physicochemical parameters of water (pH, temperature, total organic carbon—TOC) and by environmental factors (geographical, climatological). Most of these factors have significant seasonal variations that lead to the formation of THMs in variable concentrations. In this study, we analysed the seasonal trends in surface water quality (considering variations in temperature, pH, and TOC) and correlated them with the concentration of THMs in drinking water over two calendar years. Water samples were collected from the Arges River, in a geographical area comprised of plains. The results show that the formation of THMs is enhanced by increasing temperature over the course of a year, with the highest concentrations being obtained in July 2022 (98.7 µg/L THMs at 30.5 °C) and in August 2023 (81.9 µg/L THMs at 30.4 °C). The main parameters that trigger the formation of THMs are the organic matter content and the disinfectant dose; the pH has a moderate effect, and its effect is correlated with the concentration of organic matter. There were noted strong seasonal changes in the concentration of THMs, with the maximum peak being in the middle and late summer and the minimum peak being in winter. This indicates the possibility that the quality of drinking water may change as a result of climate change. In addition, monitoring and chlorination experiments have established that the concentration of THMs is directly proportional with the TOC. Full article

Natural organic matter (NOM) in surface waters is a major challenge for drinking water treatment due to its role in the formation of disinfection byproducts (DBPs) during chlorination. This study evaluated the performance of chitosan, a biodegradable coagulant, dissolved in acetic, lactic, and L-ascorbic acids for NOM removal under three turbidity levels (403, 1220, and 5038 NTU). Jar tests were conducted using raw water from the Río Grande de Añasco (Puerto Rico), and TOC, DOC, and UV₂₅₄ were measured at multiple time points. TOC removal ranged from 39.8% to 74.3%, with the highest performance observed in high-turbidity water treated with chitosan–L-ascorbic acid. DOC and UV₂₅₄ reductions followed similar trends, with maximum removals of 76.4% and 76.2%, respectively. Estimated THM formation potential (THMFP) was reduced by up to 81.6%. Across all acids, flocculation efficiencies exceeded 95%. Compared to conventional aluminum-based coagulants, chitosan demonstrated comparable performance, while offering environmental benefits. These results confirm the potential of chitosan–acid systems for effective organic matter removal and DBP control, supporting their application as sustainable alternatives in drinking water treatment. Full article

Enhanced or engineered geothermal systems (EGSs), or non-hydrothermal resources, are highly notable among sustainable energy resources because of their abundance and cleanness. The EGS concept has received worldwide attention and undergone intensive studies in the last decade in the US and around the world. In comparison, hydrothermal reservoir resources, the ‘low-hanging fruit’ of geothermal energy, are very limited in amount or availability, while EGSs are extensive and have great potential to supply the entire world with the needed energy almost permanently. The EGS, in essence, is an engineered subsurface heat mining concept, where water or another suitable heat exchange fluid is injected into hot formations to extract heat from the hot dry rock (HDR). Specifically, the EGS relies on the principle that injected water, or another working fluid, penetrates deep into reservoirs through fractures or high-permeability channels to absorb large quantities of thermal energy by contact with the host hot rock. Finally, the heated fluid is produced through production wells for electricity generation or other usages. Heat mining from fractured EGS reservoirs is subject to complex interactions within the reservoir rock, involving high-temperature heat exchange, multi-phase flow, rock deformation, and chemical reactions under thermal-hydrological-mechanical (THM) processes or thermal-hydrological-mechanical-chemical (THMC) interactions. In this paper, we will present a THM model and reservoir simulator and its application for simulation of hydrothermal geothermal systems and EGS reservoirs as well as a methodology of coupling thermal, hydrological, and mechanical processes. A numerical approach, based on discretizing the thermo-poro-elastic Navier equation using an integral finite difference method, is discussed. This method provides a rigorous, accurate, and efficient fully coupled methodology for the three (THM) strongly interacted processes. Several programs based on this methodology are demonstrated in the simulation cases of geothermal reservoirs, including fracture aperture enhancement, thermal stress impact, and tracer transport in a field-scale reservoir. Results are displayed to show geomechanics’ impact on fluid and heat flow in geothermal reservoirs. Full article

The prevention of human infectious diseases associated with waterborne pathogens is reliant on the effective disinfection of water supplies by drinking water treatment plants and adequately maintained distribution networks. For decades, the chlorination of water has safeguarded public health, where chlorine is broadly applied in both water disinfection and food production facilities, including the dairy industry, from farm to fork. The identification of chlorine disinfection byproducts in water supplies and dairy food produce is of great concern, however, due to their cytotoxic, genotoxic, mutagenic, teratogenic, and potential endocrine-disrupting activity. The association between the trihalomethanes (THMs) and haloacetic acids (HAAs) and tumour formation is documented and has led to the implementation of maximum contaminant levels enforced by the European Union. Furthermore, chlorine resistance in bacterial species is associated with multidrug resistance in clinically relevant pathogens, where antibiotic- and biocidal-resistant genes are also environmental pollutants. Increasing the concentration of chlorine to surmount this resistance will ultimately lead to increasing concentrations of byproducts in both water and food products, exceeding the EU requirements. This article provides insight into chlorine DBPs as a toxicological public health risk and the relationship between chlorine resistance and antibiotic resistance in microbes relevant to dairy food production. Full article

Dissolved organic carbon (DOC) is a critical parameter in water quality management due to its interaction with disinfectants, leading to the formation of disinfection byproducts (DBPs) during water treatment. Forest ecosystems are key contributors of DOC to surface waters, stemming from soil leachate. This study is the first to use DOC solutions directly extracted from soil to examine the formation of trihalomethanes (THMs) during chlorination and chloramination under varying environmental conditions. For this purpose, soil samples from a densely forested upland Cedar Lake watershed in Illinois were processed to extract DOC, which was then subjected to controlled disinfection experiments under varying pH, temperature, disinfectant dose, and reaction time. The results demonstrate that chlorination produces significantly higher levels of THMs compared to chloramination, with THM concentrations ranging from 31.996 μg/L to 62.563 μg/L for chlorination and 0.508 μg/L to 0.865 μg/L for chloramination. The yields of DBPs determined by chloramination increased approximately 4, 5, and 10 times with a higher DOC concentration, disinfectant concentration, and reaction time, respectively. For chlorination, these increases were approximately 5, 8, and 3 times, respectively. The presence of bromide in the DOC solutions influenced the concentration of brominated THMs (Br-THMs). The results indicate that a high formation of THMs, during both disinfection processes, occurred in the pH range of 7–8 and temperature range of 20–25 degrees Celsius. Furthermore, all tested water quality indicators (DOC, total dissolved solids, turbidity, and UV254), except for pH and Specific Ultraviolet Absorbance (SUVA), exhibited a strong positive correlation with THM levels during chlorination. In contrast, these parameters displayed a moderate to weak correlation with THM levels in the chloramination process. These findings highlight the critical role of DOC characteristics and disinfection conditions in controlling THM formation, providing valuable insights for optimizing water treatment processes. Full article

Water chlorination, fundamental for its microbiological safety, generates by-products, such as trihalomethanes (THMs), potentially associated with carcinogenic and reproductive risks. This study determined the levels of chloroform (CHCl₃) in drinking water in Cuenca, Ecuador, a topic that has been little explored in the region. During five months, water samples were collected from three water treatment systems (Cebollar, Tixan, and Sustag), and in situ measurements of physicochemical parameters such as free chlorine, pH, temperature, electrical conductivity, and turbidity were performed in the storage and distribution area. The determination of CHCl₃ was performed following the Hach protocol. For data analysis, the Kruskal–Wallis test was employed, followed by Dunn’s post hoc method and Spearman’s correlation coefficient. The results revealed a progressive decrease in free residual chlorine throughout the distribution systems. CHCl₃ concentrations ranged from 11.75 µg/L to 21.88 µg/L, remaining below the Ecuadorian regulatory limit of 300 µg/L. There was no consistent correlation between CHCl₃ and physicochemical parameters. These findings align with previous research, suggesting that the variability in CHCl₃ formation is associated with different water treatment conditions and environmental variables. This study highlights the importance of monitoring disinfection processes to minimize THMs and other DBPs, ensure public health, and contribute to sustainable drinking water management in Ecuador. Full article

The area of Cunninghamia lanceolata forests in China is expansive, the soil PhytOC(phytolith-occluded organic carbon) stock of Cunninghamia lanceolata forests is a vital carbon reservoir on the global scale. Soil from the Cunninghamia lanceolata forests was collected, and the soil physicochemical indexes and phytoliths and PhytOC content were measured to explore the accumulation characteristics of PhytOC in the 0–10, 10–20, and 20–30 cm soil layers at different stand ages. The results are as follows: (1) soil phytolith content (11.98–32.60 g·kg⁻¹), PhytOC content (0.48–1.10 g·kg⁻¹), PhytOC/TSOC (1.90%–6.93%), soil PhytOC stock (0.446–1.491 t·hm⁻²), and mature forest > middle–aged forest > Huitou-sha forest > young forest. The soil PhytOC accumulation was significantly affected by stand age. Huitou-sha is not an advantageous afforestation way of Cunninghamia lanceolata. (2) the soil physicochemical properties and stand conditions had significant effects on soil PhytOC accumulation. High–silicon, carbon-rich, acidic soil environment and appropriate thinning are conducive to phytolith formation and PhytOC sequestration. (3) the accumulation potential of soil PhytOC in the Cunninghamia lanceolata forest is relatively large, and its importance as a forest carbon sink cannot be ignored. Soil PhytOC stock in Cunninghamia lanceolata forests of different stand ages will lay a foundation for accurate estimation of forest carbon sink. Full article

The control of waterborne diseases through water disinfection is a significant advancement in public health. However, the disinfection process generates disinfection by-products (DBPs), including trihalomethanes (THMs), which are considered to influence the occurrence of cancer. This analysis aims to quantitatively evaluate the relationship between blood concentrations of THMs and cancer. Additionally, the relationship between blood chloroform concentration and cancer is analyzed separately. Following PRISMA guidelines, we conducted a thorough search in the PubMed, Web of Science, and CNKI databases. Statistical analysis was performed using Review Manager 5.4 software. After screening, seven studies meeting the evaluation criteria were included. A total of 1027 blood samples from patients with cancer and 7351 blood samples from the control group were collected. The average concentration of THMs in the blood of the experimental group was 46.71 pg/mL, while it was 36.406 pg/mL in the control group. The difference between the two groups was statistically significant (SMD = −0.36, 95% CI: −0.45 to −0.27, p < 0.00001). However, due to the limited research data on the relationship between blood THMs and cancer, the conclusions drawn exhibit high heterogeneity. Additionally, we discussed the carcinogenic mechanisms of THMs, which involve multiple biological pathways such as oxidative stress, DNA adduct formation, and endocrine disruption, with variations in accumulation and target sites potentially leading to different cancer types, for which evidence is currently lacking. In the future, further epidemiological and animal model studies on THMs should be conducted to obtain more accurate conclusions. Full article

This study focuses on optimizing the ozonation process in drinking water production from Lake Butoniga to ensure safe water quality while minimizing disinfection by-products (DBPs). Laboratory simulations were conducted using the Box–Behnken design to model the effects of ozone dose and treatment duration on bromate formation, trihalomethanes (THMs), haloacetic acids (HAAs) and specific UV absorption (SUVA). Two ozonation strategies were tested: Strategy 1 aimed to minimize all DBPs, while Strategy 2 focused on controlling bromate levels while keeping THMs, HAAs and SUVA below 80% of maximum contaminant levels. Results showed that Strategy 2 reduced ozone consumption while maintaining water quality within regulatory standards, providing a cost-effective and environmentally sustainable treatment approach. Seasonal and depth-dependent variations in water quality had a significant impact on treatment efficiency and required adjustments to operational settings. The study also addressed discrepancies between laboratory and real plant results and suggested recalibration methods that improved the accuracy of model predictions. These results highlight the potential for integrating predictive modelling and dynamic treatment strategies into large-scale water treatment processes. Full article

The organic material from cyanobacteria is a significant precursor to the generation of disinfection byproducts. This study’s aim was to evaluate the formation of assimilable organic carbon (AOC) in water contaminated with cyanobacteria. Furthermore, the formation of AOC was related to the generation of trihalomethanes (THMs) and dissolved organic carbon (DOC). The advanced oxidation process was caISOrried out by exposing Microcystis aeruginosa cells (250,000 cells mL⁻¹) to different peroxide dosages (10 to 100 mg L⁻¹) under ultraviolet radiation. Pseudomonas fluorescens (P-17), Spirillum sp. (NOX), and flow cytometry were used to determine the AOC concentration. The formation of AOC and THMs during the UV/H₂O₂ process was not directly related. The AOC concentration increased with low H₂O₂ doses and decreased at higher concentrations, while the levels of THMs decreased regardless of the AOC formed. After oxidation, the DOC concentration decreased, along with the concentration of THMs. Additionally, it was observed that the behavior of DOC and AOC is inversely proportional. These results suggest that the oxidation process has a complex effect on organic matter, influencing byproduct formation and AOC availability. Moreover, these findings highlight the importance of carefully monitoring and controlling the oxidation processes to better understand their impact on water treatment and byproduct formation. Full article

The prevalence of disinfection by-products in drinking water supplies is a global concern due to their carcinogenicity. However, the monitoring of DBPs such as trihalomethanes (THMs) and haloacetic acids (HAAs) in drinking water supplies is non-existent in many developing Asian, South American, and African countries. The formation of THMs during disinfection arises from a reaction between the disinfectant and natural organic matter in the water, particularly, dissolved organic carbon (DOC). This reaction is hastened by increases in temperature, high levels of disinfectant doses or residual, elevated water pH, long disinfection contact times, and high DOC concentrations. However, the inclusion of a granular activated carbon adsorption process in the water treatment process is the most effective method for the removal of the main precursor (DOC) for the formation of THMs in treated water. The Barekese WTP, which disinfects with chlorine, has no adsorption process for DOC removal, and supplies over 80% of pipe-borne water to the city of Kumasi in Ghana, was assessed for the THM formation potential (THMFP). A THM predictive model was used to determine the potential THM concentration in the final water. The THMFP at the Barekese WTP ranged between 22.42 and 38.94 µg/L, which was below the 100 µg/L threshold set by the WHO. The lifetime average daily doses were 3.9494 × 10⁻⁴ µg/Kg/d and 3.9294 × 10⁻⁴ µg/Kg/d for male and female consumers, respectively. The lifetime integrative cancer risks associated with consumption of the water were 1.817 × 10⁻⁵ and 1.808 × 10⁻⁵ for males and females, respectively. The cancer risk posed was acceptably low. However, direct measurement of DBPs is required to corroborate these findings and verify the cancer risk posed to the consumers of treated water from the Barekese WTP to inform policies, regulations, public health interventions, and investment. Full article

Rice is a staple food crop that feeds billions globally. Addressing Zn deficiency in rice is crucial for improving nutrition and food security. Zn deficiency in rice is a widespread issue, especially in purple tidal mud substrates, which often exhibit low Zn availability. The objective of this two-year pot study was to explore the relationship between Zn content, yield components, and Zn absorption in rice grown in purple tidal mud substrate with varying amounts of Chinese milk vetch (Astragalus sinicus L.) incorporation. The experimental design consisted of seven treatments: an unfertilized control, a Chinese milk vetch control, a chemical fertilizer control, and four treatment variations incorporating Chinese milk vetch alongside chemical fertilizer applications. The results indicated that planting and applying Chinese milk vetch improved the grain yield of rice in purple tidal mud substrate, and the yield increased with higher levels of Chinese milk vetch applied. The increased grain yield resulted in higher Zn absorption in rice grains. The application of Chinese milk vetch, both solely and in combination with chemical fertilizers, had varying effects on zinc uptake and grain zinc formation efficiency in early and late rice, with the control and low-level Chinese milk vetch treatments generally exhibiting the highest performance across the two-year period. By introducing Chinese milkvetch following the use of chemical fertilizers, the Zn content in rice grains increased starting from the second year. The treatment with Chinese milkvetch applied at a rate of 2.25 t/hm² showed the best results in increasing the Zn content in rice grains. The increase in Zn content and Zn uptake by the rice plants gave rise to a lowering of the DTPA-extractable Zn content in the purple tidal mud substrate. Sole Chinese milk vetch application and using Chinese milk vetch following chemical fertilizer application both increased Zn content extracted by DTPA in purple tidal mud substrate. Full article

Eutrophication in water reservoirs releases algal organic matter (AOM), a key precursor to the formation of disinfection by-products (DBPs) during the disinfection process. Typical drinking water treatment is not efficient for AOM removal, and advanced treatments are necessary for the removal of residual AOM before chlorination. UV-based technology with PS and TiO₂ is widely used as a pre-oxidation step in water treatment; however, no publications have focused on them for AOM degradation. In this context, this work investigated the effect of oxidant concentration (0.1 to 0.5 g∙L⁻¹) and pH (6 to 10) on AOM degradation with TiO₂/UV and persulfate (PS)/UV using response surface methodology. In general, PS/UV was more effective in removing protein, while TiO₂/UV was more effective in carbohydrate degradation. TiO₂/UV removals varied from 27 to 57% for protein and from 48 to 86% for carbohydrates. The optimal condition (57% for protein and 86% for carbohydrates) was obtained using 0.5 g∙L⁻¹ TiO₂ at pH 10. PS/UV removals varied from 33 to 81% for protein and from 24 to 53% for carbohydrates. The optimal condition (81% for protein and 53% for carbohydrates) was obtained using 0.5 g∙L⁻¹ PS concentration at pH 8. Degradation kinetics showed a good fit to the pseudo-first-order model (R² > 95%) for both processes. The DBP formation reductions observed with TiO₂/UV—trihalomethane (THM) (85 to 86%) and chloral hydrate (CH) (94 to 96%)—were similar to the efficiencies observed for PS/UV—THM (87 to 89%) and CH (83 to 88%). These results show the efficiency of UV-based technology for AOM degradation and the control of DBP formation. Full article

All water destined for human consumption must be subjected to disinfection processes via chlorination with the aim of eliminating the risk of the transmission of waterborne diseases. However, the treatment of water using this method leads to the formation of trihalomethanes (THMs), which are toxic compounds that may be ingested, inhaled, or absorbed by the skin, increasing the risk of carcinogenic and mutagenic processes. High trihalomethane concentrations in water may be directly related to physicochemical properties, such as temperature, pH, hardness, and potentially toxic metal concentrations. In this work, physicochemical characterization was performed and water quality was assessed with regard to the presence of trihalomethanes in 17 samples collected from points before and after storage in reservoirs. Atomic absorption spectroscopy to determine potentially toxic metals and the measurement of physicochemical properties demonstrated that all results were in accordance with the standards established by Brazilian legislation. Gas chromatography–mass spectrometry was used to determine levels of trihalomethanes in the water samples (trichloromethane, bromodichloromethane, chlorodibromomethane, and bromoform), which were also in accordance with the limits established by Brazilian legislation. Hierarchical clustering on principal components confirmed changes in the water quality depending on location. This work constitutes a paradigm for future studies on the monitoring of toxic organic compounds in water to avoid health problems in humans and animals. Full article

The mechanical behavior of unsaturated porous media under non-isothermal conditions plays a vital role in geo-hazards and geo-energy engineering (e.g., landslides triggered by fire and geothermal energy harvest and foundations). Temperature increase can trigger localized failure and cracking in unsaturated porous media. This article investigates the shear banding and cracking in unsaturated porous media under non-isothermal conditions through a thermo–hydro–mechanical (THM) periporomechanics (PPM) paradigm. PPM is a nonlocal formulation of classical poromechanics using integral equations, which is robust in simulating continuous and discontinuous deformation in porous media. As a new contribution, we formulate a nonlocal THM constitutive model for unsaturated porous media in the PPM paradigm in this study. The THM meshfree paradigm is implemented through an explicit Lagrangian meshfree algorithm. The return mapping algorithm is used to implement the nonlocal THM constitutive model numerically. Numerical examples are presented to assess the capability of the proposed THM mesh-free paradigm for modeling shear banding and cracking in unsaturated porous media under non-isothermal conditions. The numerical results are examined to study the effect of temperature variations on the formation of shear banding and cracking in unsaturated porous media. Full article