Search Results (62)

This study develops a fully coupled thermo–hydro–mechanical (THM) finite-element model to investigate fracture-induced fluid loss in depleted formations. To address the issue of assuming a homogeneous, unfractured medium, this approach incorporates the effects of pre-existing or induced fractures. By integrating thermoelastic stresses, fluid flow, and transient heat transfer, the model provides a more accurate simulation of coupled interactions, enabling a deeper understanding of stress evolution and fracture aperture behavior under temperature variations. The results show that pressure depletion reduces horizontal principal stresses in an approximately linear manner, with the minimum horizontal stress being more sensitive. The influence of wellbore pressure is concentrated in the near-wellbore region (r/rw < 2), where it increases circumferential stress at low azimuths and exhibits an almost linear positive correlation with fracture aperture. Fracture length has a negligible effect on pore-pressure variations (≤0.19 MPa) but increases circumferential stress at high azimuths and enlarges the aperture near the wellbore. Temperature effects, through thermoelastic stresses, dominate local stress redistribution, with the 90° azimuth showing the strongest sensitivity. Higher injection temperatures increase circumferential and radial stresses while decreasing near-wellbore aperture, whereas lower temperatures produce the opposite response. Although temperature differences cause only minor changes in pore pressure and far-field stresses, they exert first-order control on near-wellbore width evolution and the likelihood of lost circulation. These findings indicate that coordinated optimization of wellbore pressure, fracture dimensions, and injection temperature under depletion conditions is important for mitigating fracture-induced fluid loss and improving drilling safety and efficiency. Full article

The Midong Block is currently a primary target for coalbed methane (CBM) exploration and development in Xinjiang. However, fracturing operations in this region generally exhibit low flowback rates, which escalate the risk of reservoir damage and ultimately suppress daily gas production. To elucidate the impact of various geological and engineering factors on flowback efficiency and permeability damage, as well as their underlying mechanisms, this study conducted fracturing fluid flowback simulation experiments. The pulse-decay permeability measurement and weighing methods were employed to quantify the variations in flowback rates and permeability damage intensities under different conditions. Experimental results indicated that the permeability damage rate in the Xishanyao Formation coal samples ranged from 3.12% to 92.86% after flowback, with 92% of the samples exhibiting a flowback rate of less than 10%. This significant impairment was primarily attributed to the synergistic effects of stress-induced fracture closure, clay mineral hydration swelling, and coal fines migration. Specifically, elevated confining pressures and prolonged soaking times exacerbated reservoir damage. A low flowback pressure differential intensified the water locking effect, hindering fluid recovery. Notably, the flowback velocity displayed a U-shaped velocity sensitivity profile. In the low-temperature regime, damage characteristics fluctuated, controlled by competitive thermal–hydro–mechanical (THM) coupling mechanisms. Full article

Active substance-based Ballast Water Management Systems (BWMS) can generate disinfection by-products (DBPs) by reacting with dissolved organic matter (DOM). However, current IMO G9-based assessments often overlook qualitative DOM variations. This study investigated DBP formation following NaDCC treatment in natural seawater dominated by the diatom Skeletonema costatum and the dinoflagellate Akashiwo sanguinea. Laboratory-cultured DOM was also analyzed using ATR-FT-IR, PCA, and 2D-COS to evaluate structural differences. In field experiments, S. costatum treatment primarily produced brominated trihalomethanes (THMs) and specific haloacetic acids (HAAs) with a limited composition. Conversely, A. sanguinea treatment yielded a diverse range of DBPs, including nitrogenous DBPs (HANs). FT-IR results, supported by 2D-COS, revealed that A. sanguinea-derived DOM underwent non-monotonic structural changes and distinct sequential functional group reactions, suggesting multiple, time-delayed precursor interactions. These findings demonstrate that phytoplankton species-specific DOM composition significantly dictates DBP profiles and temporal dynamics. Therefore, environmental risk assessments for BWMS must incorporate the qualitative characteristics of biogenic DOM and dominant species traits, particularly during coastal bloom events, to ensure more accurate management strategies. Full article

Drinking-water treatment systems must effectively control natural organic matter (NOM), a major precursor of regulated disinfection by-products (DBPs). Specific ultraviolet absorbance (SUVA) is widely used as an operational surrogate for NOM aromaticity and hydrophobicity; however, ozonation and subsequent filtration can disrupt the linear relationship between SUVA and trihalomethane formation potential (THMFP). This study evaluates whether SUVA can reliably predict THMFP under two ozonation configurations frequently applied in drinking-water treatment: pre-ozonation prior to coagulation–filtration and final ozonation following filtration. Experimental data were analyzed using conventional linear regression and artificial neural network (ANN) models, with SUVA employed as the sole predictor variable. Across all treatment configurations, reductions in SUVA were consistently more pronounced than corresponding decreases in THMFP, indicating a decoupling between chromophoric loss and chlorine-reactive precursor dynamics under ozonation-dominated conditions. Linear regression models exhibited only moderate predictive performance (R² = 0.63–0.76), reflecting the limitations of proportional surrogate-based approaches when NOM undergoes oxidative and adsorptive transformation. In contrast, single-parameter ANN models captured the nonlinear SUVA–THMFP relationship with substantially higher accuracy across both pre- and final-ozonation regimes (R² = 0.88–0.99), successfully resolving process-dependent patterns embedded within optically compressed SUVA signals. These findings demonstrate that, although SUVA alone cannot linearly represent the multistep transformation of NOM during ozonation and adsorption, it retains process-relevant structure information on DBP precursor reactivity that can be effectively extracted using nonlinear modelling. The results highlight the potential of integrating ANN-driven tools into advanced monitoring and DBP-control strategies in modern drinking-water treatment systems. Full article

Cyanobacterial blooms pose significant threats to aquatic ecosystems and drinking water safety, primarily through the release of diverse secondary metabolites. This study systematically explored the dynamics of secondary metabolites in Microcystis aeruginosa and Anabaena sp. under controlled conditions, focusing on the effects of temperature (10 °C, 25 °C, 35 °C) and growth phases (exponential, stationary, decline). Key parameters measured included cell density, dissolved organic carbon (DOC), microcystins (MC-LR, MC-RR), taste and odor compounds (β-cyclocitral, β-ionone), and disinfection by-product formation potentials (trihalomethanes (THMs) and haloacetic acids (HAAs)). Results revealed striking interspecific differences: M. aeruginosa exhibited significantly higher metabolite production, with peak DOC, extracellular MC-LR, and particulate β-cyclocitral observed in the decline phase at 25–35 °C. In contrast, Anabaena sp. showed an “early accumulation advantage” for THM precursors and “residual release” in the decline phase. Temperature played a critical regulatory role, with 25 °C as the optimal for most metabolites, while 35 °C enhanced extracellular release of dissolved β-cyclocitral in M. aeruginosa. Growth phase dynamics were consistent across species, with stationary and decline phases marked by elevated metabolite concentrations due to intensified synthesis and cell lysis, particularly for HAAs. These findings highlight species-specific metabolic strategies and their environmental drivers, providing critical insights for assessing and managing cyanobacterial bloom risks in aquatic ecosystems. Full article

Paddy field leveling is the foundation of high-yield rice cultivation. In response to the current issues of low leveling accuracy and the lack of efficient multi-operation machinery, an Integrated Multi-operation Paddy Field Leveling Machine was designed in this study. This machine can complete soil crushing, stubble burying, mud stirring, and leveling in a single pass. Combined with an adaptive control system based on Global Navigation Satellite System—Real-Time Kinematic (GNSS-RTK) technology, it enables adaptive and precise paddy field leveling operations. To verify the operational performance of the equipment, field tests were conducted. The results showed that the machine achieved an average puddling depth of 14.21 cm, a surface levelness of 2.16 cm, an average stubble burial depth of 8.15 cm, and a vegetation coverage rate of 89.33%, demonstrating satisfactory leveling performance. Furthermore, to clarify the feasibility and superiority of applying this equipment in actual rice production, experiments were conducted to investigate the effects of different field leveling methods on early rice growth, yield, and its components. One-way analysis of variance was employed to examine the differences in agronomic indicators between the different field leveling treatments. The results indicated that using this equipment for paddy field leveling, compared to traditional methods and dry land preparation, can improve the seedling emergence rate, thereby laying a solid population foundation for the formation of effective panicles. It also promoted root growth and development and increased the total dry matter accumulation at maturity, thereby contributing to high yield formation. Over the two-year experimental period, the rice yield remained above 9.8 t·hm⁻². This research provides theoretical support and practical guidance for the further optimization and development of subsequent paddy field preparation equipment, thereby promoting the widespread application of this technology in rice production. Full article

Underground pumped hydro storage (UPHS) in solution-mined salt caverns offers a promising approach to address the intermittency of renewable energy in flat geological regions such as Southern Ontario, Canada. This work presents the first fully coupled thermo-hydro-mechanical (THM) numerical model of a two-cavern UPHS system in Southern Ontario, providing a foundational assessment of long-term cavern stability and brine leakage behavior under cyclic operation. The model captures the key interactions among deformation, leakage, and temperature effects governing cavern stability, evaluating cyclic brine injection–withdrawal at operating temperatures of 10 °C, 15 °C, and 20 °C over a five-year period. Results show that plastic deformation is constrained to localized zones at cavern–shale interfaces, with negligible risk of tensile failure. Creep deformation accelerates with temperature, yielding maximum strains of 2.6–3.2% and cumulative cavern closure of 1.8–2.6%, all within engineering safety thresholds. Leakage predominantly migrates through limestone interlayers, while shale contributes only local discharge pathways. Elevated temperature enhances leakage due to reduced brine viscosity, but cumulative volumes remain very low, confirming the sealing capacity of bedded salt. Overall, lower operating temperatures minimize both convergence and leakage, ensuring greater stability margins, indicating that UPHS operation should preferentially adopt lower brine temperatures to balance storage efficiency with long-term cavern stability. These findings highlight the feasibility of UPHS in Ontario’s salt formations and provide design guidance for balancing storage performance with geomechanical safety. Full article

This study examines the potential for improved and more sustainable wastewater treatment by integrating coagulation and disinfection using polyaluminum chloride (PACl) and sodium hypochlorite (NaClO) for secondary effluent. The impacts of this integrated approach on phosphorus removal, microbial inactivation, and disinfection by-product (DBP) formation were evaluated through bench- and pilot-scale experiments under both sequential and simultaneous dosing. The results show that simultaneous dosing of PACl and NaClO achieved high phosphorus removal (>90% at 6–9 mg/L PACl), while microbial inactivation targets were met with moderate chlorine doses (3–6 mg/L). Pilot-scale tests further revealed that PACl enhanced microbial inactivation under high-intensity mixing. Importantly, the integrated process reduced DBP formation substantially, with trihalomethanes (THMs) and haloacetic acids (HAAs) lowered by up to ~50% compared to sequential treatment. By minimizing the need for separate treatment units, shortening hydraulic retention time, and lowering overall chemical consumption, this integrated coagulation–disinfection strategy provides a compact, cost-effective, and sustainable alternative to conventional wastewater treatment. Full article

The interaction of disinfectants with bromide/iodide ions and natural organic matter (NOM) generates brominated/iodinated disinfection byproducts (Br/I-DBPs), known for their heightened cytotoxicity and genotoxicity relative to chlorinated DBPs. This study investigated Br/I-DBP formation during sodium hypochlorite (NaClO) disinfection of lignin-containing synthetic water by quantifying adsorbable organic halogens (AOX) and trihalomethanes (THMs). Disinfection of bromide-containing water yielded a bromide ion (Br⁻) to adsorbable organic bromine (AOBr) conversion rate of approximately 60%, with bromine within THMs accounting for about 30% of the total AOBr, indicating significant brominated DBP formation where THMs represent a major fraction. Conversely, iodide ion (I⁻) conversion to adsorbable organic iodine (AOI) is minimal, suggesting negligible iodinated DBP formation under NaClO disinfection. Examination of key parameters revealed that brominated THM (Br-THM) formation decreased with increasing lignin concentration, while iodinated THM (I-THM) formation increased. The effect of chlorine dose differed: Br-THM formation exhibited an initial increase followed by a decrease at higher doses, whereas I-THM formation consistently decreased. Both Br-THM and I-THM formation increased with higher bromide or iodide ion concentration and with increasing pH. These results highlight the distinct pathways and influencing factors governing brominated versus iodinated DBP formation in lignin-containing waters disinfected with hypochlorite. Full article

This study examined the spatial and seasonal variations of trihalomethanes (THMs) and estimated the health risks associated with THM exposure in drinking water through various pathways. Water samples were collected from 14 distribution districts connected to the Ulutan Distribution System (UDS) and the Süleyman Bey Distribution System (SDS), which supply drinking water to Zonguldak Province, Türkiye. THMs were measured using the USEPA 551 method. The median total trihalomethanes (TTHMs) ranged from 41 μg/L to 71 μg/L, which is below the Turkish drinking water standard of 100 μg/L. Chloroform (TCM) was the most common trihalomethane in all distribution networks in UDS and SDS. On the other hand, pre-ozonation oxidation after chlorination in SDS disinfection caused the contribution of brominated THMs (62%) to THM formation to be higher than that of TCM (38%). The study on cancer risk reveals that ingestion (96%) poses the greatest risk of the investigated pathways, followed by dermal contact (3.95%), while inhalation has been found to have a negligible effect. The highest and lowest median TTHMs occurred during winter and summer. The findings of the study show that the distribution areas of Kozlu, Ömerli, Topçalı, and Uzunçayır, for both genders, exhibit an unacceptable cancer risk level according to the criteria established by the USEPA (>10⁻⁴). Bromodichloromethane (BDCM) and chlorodibromomethane (DBCM) are the main contributors to cancer risk for males and females in UDS and SDS. The hazard index (HI) data indicated that the HI value remained below one for both UDS and SDS. Sensitivity analysis of THMs demonstrated that exposure frequency (EF) was the primary parameter contributing to the maximum potential impact on the total cancer risk exposure frequency (EF), followed by body weight (BW) and exposure duration (ED). Further, the results provide valuable information for health departments and water management authorities, enabling the formulation of more specific and efficient policies to minimise THM levels in drinking water distribution networks. Full article

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