Soft Water Research Articles

Humic substances modulate bacterial communities and mitigate adverse effects of temperature stress in coral reef organisms.

In the present study, we tested if terrestrially-derived humic substances (HS) could mitigate the adverse effects of elevated temperature and UVB radiation on the bacterial communities of two hard corals (Montipora digitata and Montipora capricornis), one soft coral (Sarcophyton glaucum), sediment and water. We also examined the impact of temperature, UVB radiation and HS supplementation on coral photosynthetic activity, a proxy for coral bleaching. We performed a multifactorial experiment using a randomized-controlled microcosm setup. Coral photosynthetic efficiency was measured in vivo using a pulse amplitude modulation (PAM) fluorometer. Bacterial communities were analyzed using 16s rRNA gene sequencing. Corals in HS-supplemented microcosms had significantly higher photosynthetic activities than those in microcosms subjected to elevated temperature and UVB radiation. Additionally, HS supplementation significantly influenced the composition of sediment, water and host-associated bacterial communities. Reef organisms in HS supplemented microcosms contained distinct bacterial communities enriched with groups of potentially beneficial bacteria. In the hard coral Montipora digitata, we observed an interactive effect of HS supplementation, UVB radiation, and temperature. Our findings indicate that HS significantly modulates coral reef bacterial communities and support the hypothesis that these substances contribute to improved reef resistance to the adverse effects of elevated temperature and UVB radiation.

Design of Carbon Materials with Selective Ion Separation in Capacitive Deionisation and TheirApplications.

Capacitive deionization (CDI) isa novel, cost-effectiveand environmentally friendly desalination technology that has garneredsignificantattention in recent years. Carbon materials,owing to theirexcellent properties,have become the preferredelectrode materials forCDI. Giventhe significantdifferences betweendifferent ions, ion-selective performance has emerged as acritical aspect ofCDI applications.However, comprehensivereviewson the selective ion separation capabilities of carbon materials for CDI remain scarce. This review examines the progress in developingcarbon materials forion-selective separation in CDI,focusing onregulatory mechanisms and representativematerials.Italso discusses the applications of selective CDI carbon materialsin areas such asheavy metal removal, nutrient recovery, seawater desalination resourcing, and water softening. Furthermore, the challenges and futureprospects for advancingcarbon materials in CDIare explored.This review aims toprovide theoretical insights and practical guidance for utilisingcarbon materials in wastewater treatment and resource recovery.

Associations between domestic hard water exposure and incident psoriasis in adults: Insights from the UK Biobank cohort study.

Although exposure to hard water is associated with various inflammatory skin conditions, the specific relationship between hard water and psoriasis has not been clearly defined. We analyzed data from 486,414 participants in the UK Biobank cohort to explore the association between domestic hard water exposure and the incidence of psoriasis. Domestic water hardness, measured in calcium carbonate concentration, was obtained in 2005 from local water providers in Wales, Scotland, and England. During a median follow-up period of approximately 14 years, a total of 4801 (1.0%) participants reported psoriasis, and we observed that for every 50mg/L increase in water hardness (as CaCO₃), there was a 3% increase in the risk of psoriasis [Hazard Ratio (HR)=1.03, 95% Confidence Interval (CI) 1.01-1.06]. Individuals exposed to very hard water (>180mg/L) exhibited a 20% increased risk of psoriasis compared to those exposed to soft water (0-60mg/L) [HR: 1.20, 95% CI: 1.07-1.34]. A positive linear relationship was observed between water hardness and the risk of psoriasis. Furthermore, the polygenic risk score indicated a synergistic effect between hard water exposure and genetic risk factors in developing psoriasis. Subgroup analysis suggested that the effect of hard water on psoriasis is more pronounced in individuals with a low polygenic risk score, women, the elderly, non-obese individuals, those of high socioeconomic status or without dyslipidemia. Residential water hardness has been identified as a significant risk factor for psoriasis in adults. Sustained efforts to reduce exposure to hard water may alleviate the psoriasis burden.

Mechanical properties and failure modes of discontinuous jointed considering water softening effects

Mechanical properties and failure modes of discontinuous jointed considering water softening effects

Membrane Treatment to Improve Water Recycling in an Italian Textile District.

The textile district of Prato (Italy) has developed a wastewater recycling system of considerable scale. The reclaimed wastewater is characterized by high levels of hardness (32 °F on average), which precludes its direct reuse in numerous wet textile processes (e.g., textile dyeing). Consequently, these companies utilize ion exchange resins for water softening. However, the regeneration of the resins results in an increased concentration of chlorides in the reclaimed wastewater that exceeds the limit set by Italian regulations for the reuse of water for irrigation purposes. The objective of this study is to investigate the potential of membrane filtration as an alternative method for removing hardness from water. Therefore, an industrial-scale ultrafiltration-nanofiltration (UF-NF) pilot plant was installed to test the rejection of hardness from the reclaimed wastewater. The experiment employed two types of NF membranes and three permeate fluxes (27, 35, and 38 L·m-2·h-1) for testing. The results demonstrated that the system could remove hardness with efficiencies exceeding 98% under all conditions tested. The experimental findings indicate that the UF-NF system has the potential to be employed as a post-treatment step to render the reclaimed wastewater suitable for all textile finishing processes and to expand the scope for reuse.

The effect of calcium on acute sodium chloride toxicity in Daphnia species.

Chloride concentrations in freshwater are rising, with toxic effects on aquatic life. In temperate regions with cold winters, road salt used for deicing paved surfaces is a primary cause. There is evidence that water hardness can modify salt toxicity, but data are insufficient to inform policy. Because calcium is a primary ion influencing water hardness and there is widespread calcium decline in lakes, we examined the effects of varying calcium concentrations on acute salt toxicity in three Daphnia species to gain a greater understanding of the water hardness-salt toxicity relationship. We conducted 48-hr acute sodium chloride (NaCl) toxicity tests, using chloride concentrations as our metric, on neonates less than 24 hrs old in six calcium treatments: 1.5 to 128 mg/L (hardness ∼7 to 323 mgCaCO3/L). We determined the effective concentration of chloride that was lethal to 10%, 25%, and 50% of the sample populations from each iso-female line in each calcium treatment. Acute NaCl toxicity decreased as calcium concentrations increased. The relationship between NaCl toxicity and calcium concentration differed among Daphnia, such that Daphnia catawba and Daphnia pulex were more sensitive to NaCl in lower calcium treatments and less sensitive in higher calcium treatments compared to Daphnia pulicaria. Our results provide evidence that water quality guidelines are not protective enough for aquatic life in very soft water (≤3 mg Ca2+/L, 11.3 mg CaCO3/L) because most ECxx values we found for Daphnia were significantly lower than Canada's national guidelines for short-term chloride exposure. There are already many lakes with calcium concentrations below 3 mg/L, and global widespread calcium decline may put more aquatic ecosystems at risk of experiencing NaCl toxicity.

Dual Repurposing of End-of-Life BWRO Membranes: Ultrafiltration Membranes for Advanced Wastewater Treatment and Cation Exchange Membranes for Fungal Microbial Fuel Cells.

The objective of this study is to evaluate the degradation of end-of-life BWRO membranes sourced from a factory in France by analyzing their water permeability, roughness, and chemical composition in order to diagnose the level of degradation incurred during their first life cycle in water softening. Following this, two new applications for the end-of-life BWRO membranes were investigated: (i) as ultrafiltration membranes (UF) for domestic effluent treatment and (ii) as cation exchange membranes (CEM) for use in fungal microbial fuel cells (FMFC). The UF membrane was renovated with an acetic acid treatment and, subsequently, used for domestic effluent filtration. The cation exchange membrane was developed in two steps: (i) chlorine treatment and (ii) the deposition of an Amer Sil layer, a functional coating formed by an interpenetrating polymer network (IPN) made of sulfonated polyether sulfone (S-PES) in a cross-linked matrix of acrylic acid and divinylbenzene.

Experimental Study on Softening High-Calcium Sulfate Reverse Osmosis Concentrate Using Induced Crystallization Method

Reverse osmosis (RO) concentrate often contains high levels of sulfate and calcium ions due to the use of antiscalants, leading to significant calcium sulfate supersaturation and creating favorable conditions for induced crystallization. This study utilized a combination of static and dynamic experiments to investigate the key factors influencing the removal of calcium sulfate from RO concentrate via induced crystallization. The static experiments examined the effects of seed crystal concentration, stirring speed, reaction temperature, and the molar ratio of SO42− to Ca2+ on removal efficiency, with response surface methodology (RSM) employed to analyze the interactions among these factors. In the dynamic experiments, gypsum particles were used as seed crystals in a fluidized bed reactor to study the impact of initial seed crystal dosage and influent flow rate on the removal performance. Optimization strategies for stable operation were also explored. The static experiments revealed that seed crystal concentration was the most critical factor affecting removal efficiency. Under optimal conditions, the calcium ion concentration in the treated water could be reduced to 453 mg/L, achieving a removal rate of 63.8%. In the dynamic experiments, the effluent calcium ion concentration was reduced to 724 mg/L, with a removal rate of 52.5%. However, prolonged continuous operation led to a gradual increase in effluent calcium ion levels, which could be mitigated by recycling seed crystals from the settling zone back to the reaction zone. Characterization of the induced seed crystals and simulation calculations demonstrated that Ca2+ and SO42− reacted to form calcium sulfate crystals, primarily as CaSO4·2H2O, which adhered to the seed crystal surfaces. The growth of the seed crystals, indicated by an increase in particle size, correlated with the volume of water treated. This study provides valuable insights and data for the application of calcium sulfate-induced crystallization as a method to reduce sulfate and calcium ion concentrations in RO concentrate, offering a viable approach to water softening and resource recovery.

Addressing the Challenges of Economic Water Scarcity in Kenya: Multi-Barrier and Multilateral Integrated Approach Systems for Sustainable Access to Safe Drinking Water A Review

Accessibility to clean drinking water is essential to the quality of life of all humans. Water is also important in national development of a country. Kenya is faced with both physical water scarcity and economic water scarcity. Physical water scarcity is due to increased water demand, limited supply of water and low rainfall whereas economic water scarcity is due to lack of sufficient financial capability to support water infrastructure. Depending on the water use, there are various techniques available for removal of harmful bacteria, water softening and removing organic particulates and other contaminants from drinking water. They range from simple to sophisticated technologies. This review focused on the economic water scarcity in Kenya which is a developing country. Aspects reviewed included: water poverty index and effects of economic water scarcity. The review methodology tool used was the water poverty index assessment tool (WPI) at which elemental parameters related to water were identified and discussed. The outcome of this research was expected to contribute in the development of affordable and sustainable purification technologies and policies that can be used to deliver safe and clean drinking water. The assessment using the Water Poverty Index (WPI) found Kenya’s WPI to be low in the range of 38-45 %, which is characterised as being severe in regard to the global water stress. Kenya’s safe yield of surface water resources and ground water was estimated to be 7.4 BCM per annum and 1.0 BCM per annum respectively. Water abstractions is estimated at 1.6 BCM per annum representing 13-19% of the available water. Challenges identified include: undeveloped water resources, low financial and institutional capacity, limited access and increased demand of water in agricultural activities such as irrigation with a declining total annual renewable water per capita in the last 50 years. Recommendations proposed as solutions that can be adopted to address economic water scarcity and consequently water stress in Kenya, include exploring sustainable low-cost purification technologies, adopting multi-barrier integrated approach system and the use of multilateral economic groups support to address economic water scarcity.

Preparation of hybrid nanofiltration membranes based on Schiff base reaction for hard water softening

To obtain positively charged layer and achieve high divalent cation rejection, a novel nanofiltration (NF) membrane was successfully fabricated by utilizing polyethyleneimine (PEI), newly fabricated polyacrolein (PA) and amine silane coupling agent γ-aminopropyl triethoxysilane (APTES). The PA was synthesized via radical polymerization to avoid the migration and volatilization of small molecule in the typical coating process, making NF membranes even with great stability. On the one hand, the PEI crosslinked with PA through Schiff base reaction; on the other hand, the in-situ hydrolysis self-polycondensation of APTES generated loose networks with Si-O-Si bonds which provided the permeation channel for water and accordingly boosted the water permeance. The water permeance of the optimal PEI/PA/APTES membrane could reach 16.9 L·m-2·h-1·bar-1 and the Mg2+ and Ca2+ rejections were 98.8% and 97.3%, respectively, better than those of commercial NF membranes, breaking up the “trade off” effect. This study prepared a high-performance PEI/PA/APTES hybrid NF membrane oriented for hard water softening in tap water and brackish water via the non-interfacial macromolecule crosslinking coating method.

Water Softening Systems of Low and Medium Capacity

Water Softening Systems of Low and Medium Capacity

Large-scale field model testing of the effects of soft rock water content on the bearing performance of tunnel-type anchorages

Large-scale field model testing of the effects of soft rock water content on the bearing performance of tunnel-type anchorages

An Extensive Review of Leaching Models for the Forecasting and Integrated Management of Surface and Groundwater Quality

The present study reviews leachate models useful for proactive and rehab actions to safeguard surface and subsurface soft water, which have become even more scarce. Integrated management plans of water basins are of crucial importance since intensively cultivated areas are adding huge quantities of fertilizers to the soil, affecting surface water basins and groundwater. Aquifers are progressively being nitrified on account of the nitrogen-based fertilizer surplus, rendering water for human consumption not potable. Well-tested solute leaching models, standalone or part of a model package, provide rapid site-specific estimates of the leaching potential of chemical agents, mostly nitrates, below the root zone of crops and the impact of leaching toward groundwater. Most of the models examined were process-based or conceptual approaches. Nonetheless, empirical prediction models, though rather simplistic and therefore not preferrable, demonstrate certain advantages, such as less demanding extensive calibration database information requirements, which in many cases are unavailable, not to mention a stochastic approach and the involvement of artificial intelligence (AI). Models were categorized according to the porous medium and agents to be monitored. Integrated packages of nutrient models are irreplaceable elements for extensive catchments to monitor the terrestrial nitrogen-balanced cycle and to contribute to policy making as regards soft water management.

Developing Biodegradable Liquid Soap Detergent Solution for Domestic and Industrial Applications

Liquid soap solution is a versatile and widely used personal care product, offers a convenient and hygienic way to maintain cleanliness. This abstract summarizes the key aspects of liquid soap. This is soap in a liquid form. Generally liquid detergent are used with soft water. Where as in case of detergent powder cloths can be washed in hard as well as soft water. Liquid soap for Industrial use as well as house hold use can be manufactured by employing a very simple process. A typical formula for 1 kg of product is given below. This is called 25% liquid soap, since the acid slurry (active matter) used is 25% For lesser Concentration the quantity of acid slurry may be decreased correspondingly. The main aim of this project is to develop the liquid soap solution.

Mechanistic model advancements for optimal calcium removal in water treatment: Integral operation improvements and reactor design strategies

Drinking water softening has primarily prioritized public health, environmental benefits, social costs and enhanced client comfort. Annually, over 35 billion cubic meters of water is softened worldwide, often utilizing three main techniques: nanofiltration, ion exchange and seeded crystallization by pellet softening. However, recent modifications in pellet softening, including changes in seeding materials and acid conditioning used post-softening, have not fully achieved desired flexibility and optimization. This highlights the need of an integral approach, as drinking water softening is just one step in the drinking water treatment chain, which includes ozonation, softening, biological active carbon filtration (BACF) and sand filtration among others. In addition, pellet softening is often practiced based on operator knowledge, lacking practical key reactor performance indicators (KPIs) for efficient control. For that reason, we propose a newly and improved integral mechanistic model designed to accurately predict (1) calcite removal rates in drinking water through seeded crystallization in pellet softening reactors, (2) the saturation of the filter bed in the subsequent treatment step, (3) values for the KPIs steering the softening efficiency. Our new mechanistic model integrates insights from hydrodynamics, thermodynamics, mass transfer kinetics, nucleation and reactor engineering, focussing on critical variables such as temperature, linear velocity, pellet particle size and saturation index with respect to calcite. Our model was validated with data from the Waternet Weesperkarspel drinking water treatment plant in Amsterdam, The Netherlands, but implies universal applicability for addressing industrial challenges beyond drinking water softening. The implementation of our model proposes five effective KPIs to optimize the softening process, chemical usage, and reactor design. The advantage of this model is that it eliminates the application of numerical methods and fills a significant gap in the field by providing predictions of the carry-over (i.e., the produced CaCO3 fines leaving the fluidized bed) from water softening practices. With our model, the calcium removal rate is predicted with an average standard deviation (SD) of 40 % and the consequential clogging prediction of the BACF bed with an average SD of 130 %. Ultimately, our model provides crucial insights for operational management and decision-making in drinking water treatment plants, steering towards a more circular and environmentally sustainable process.

Emissive glutathione modified sulphur quantum dots for the sensing of lemon yellow and luminescent hydrogels/films

Lemon yellow (LY) is an azo dye which is widely used as food colorant. The continuous consumption can result in the safety concerns for both human and environmental health. This study describes a new sulphur quantum dot (SQD) based fluorescent sensor, which was facilely prepared with oxidized-glutathione (GSSG) as passivator at mild condition of 75 °C. The obtained sulphur quantum dots (GSSG-SQDs) have a relative quantum yield of 0.25, which is 2–5 times that of most SQDs. GSSG-SQDs were used as a sensor for lemon yellow in the concentration range of 0.10–70 μM and the limit of detection of 60 nM. The application was verified with the real sensing of lemon yellow in the soft drinking and tap water, having the standard recovery from 92.5 % to 105 %. Given the great luminescence and photostability, GSSG-SQDs were used as a filler for the preparation of luminescent films and hydrogels as a promising material for a wide range of applications such as information encryption and bioengineering.

Precisely regulating ion convection to counteract electro-migration for H+–OH- separation with enabling efficient electrochemical water softening

Conventional electrochemical precipitation softening often suffers from the low utilization of OH– for hardness precipitation on the cathode surface in traditional undivided electrolytic cell. In this study, an asymmetric cathode was designed to confine the occurrence of H2 evolution reaction at its backside in an undivided electrolytic cell, where the electrodes were placed aslant at an angle of 5° to facilitate the upward motion of H2 bubbles and the water flowing distribution network was used to inhibit the circumfluence of water. This specific cell configuration successfully decoupled the ion convection and electro-migration behaviors, and regulated the convection behaviors of H+ and OH– to counteract their electro-migration behaviors. Specially, theoretical calculations revealed that the OH– convection rate (Vw,b = 0.033 ∼ 0.043 cm s−1) under the combined effects of H2 gas bubbling and water flowing-through cathode at current densities of 1 ∼ 15 mA cm−2 was larger than its electro-migration rate (Ve = 0.0062 ∼ 0.019 cm s−1), which effectively promoted the transport of OH– away from the cathode backside into the bulk solution opposite to the direction toward the anode side. The H+ electro-migration toward the cathode could be also offset by the convection mediated by water flowing-through anode. Thus, the H+–OH– neutralization reaction was effectively inhibited, favoring the hardness precipitation. Under the optimum condition, the developed cell showed a Ca hardness removal efficiency of 80.8 ± 1.18 % and a current efficiency of up to 73 % at an energy consumption of 2.67 ± 0.13 kWh kg−1 CaCO3, which were superior to most electrolytic systems with or without membranes. Generally, this study provides a precisely engineered electrodes configuration for energy-efficient electrochemical water softening in circulating cooling water system.

Impact of edetate sodium on calcium carbonate scaling: Insights from molecular dynamics simulations

In order to mitigate calcium carbonate (CaCO3) scaling in oil and gas wells, antiscaling agents are commonly used. This research employed the molecular dynamics method to simulate the crystallization process of a supersaturated CaCO3 solution, with particular emphasis on examining the influence of the antiscalant edetate sodium (EDTA). Analysis of the spatial distribution of Ca2+ in proximity to CO32− revealed that EDTA effectively impedes the interaction between Ca2+ and CO32−, resulting in a reduction in the mean square displacement and diffusion coefficient of CO32−. The examination of intermolecular interaction energies indicates that the binding energy between Ca2+ and CO32− is approximately −516 kcal mol−1, while the binding energy between Ca2+ and EDTA is estimated at −718 kcal mol−1. These findings suggest that EDTA exhibits a higher affinity for binding with Ca2+ compared to CO32−, consequently hindering the formation of CaCO3.

Impact of flocculated and softened particles on UV254 inactivation of indigenous spores

AbstractUS regulatory ultraviolet (UV) disinfection credit is typically granted when turbidity is ≤1 NTU. However, studies show turbidity does not always correlate well with UV dose responses. This study examined the impact of worst‐case high turbidity scenarios at drinking water treatment plants on UV254 inactivation of indigenous spores from unfiltered source water and unsettled flocculation and softening steps. Flocculated water (turbidity = 6.49–164 NTU) had the lowest dose response with a significantly lower Geeraerd‐tail maximum inactivation rate (kmax = 0.021 cm2/mJ) and higher residual population density (Nres = 7.081 SFU/mL). Raw source water (kmax = 0.027 cm2/mJ, Nres = 1.168 SFU/mL, turbidity = 0.978–215 NTU) and softened water (kmax = 0.030 cm2/mJ, Nres = 0.216 SFU/mL, turbidity = 318–495 NTU) had similar dose responses despite significantly different water quality. Particle size and the degree of particle‐associated spores best explained the differences in dose responses. Almost all spores were associated with flocculated particles instead of free‐floating, which increased tailing and negatively impacted UV inactivation. Based on regulatory reduction equivalent dose bias factors and UV sensitivities of spiked Bacillus subtilis spores, Cryptosporidium would be 4‐log inactivated in these raw, flocculated, or softened waters if UV transmission were ≥65%, 90%, or 80%, respectively, even though turbidity was grossly >1 NTU. Depending on particle characteristics, partial inactivation credit when turbidity is >1 NTU should be considered to avoid high‐tier violations while still protecting public health.

Study on water softening characteristics and multi-stage sliding zone reactivation mechanism of old clay landslides in the Three Gorges Reservoir area subjected to groundwater

Study on water softening characteristics and multi-stage sliding zone reactivation mechanism of old clay landslides in the Three Gorges Reservoir area subjected to groundwater