Environmental Science: Water Research & Technology最新文献

Peroxymonosulfate (PMS)-based advanced oxidation processes (AOPs) effectively degrade persistent and emerging organic pollutants in water. Although chloride ions were once dismissed as inhibitors due to radical scavenging, research now reveals their dual role: at low levels they inhibit reactions, but at higher concentrations they enhance degradation via reactive chlorine species, singlet oxygen, and high-valent metal-oxo species. These intermediates heighten treatment efficacy across applications like disinfection, ammonia removal, membrane cleaning, and emerging contaminant breakdown. However, chloride can also generate chlorinated by-products (CBPs) and absorbable organic halides (AOXs), raising ecological concerns. While the toxicity of some chlorinated products may initially increase, prolonged treatment typically mitigates these risks. The key lies in optimizing chloride concentration and treatment conditions to ensure both efficiency and environmental safety.

Drinking water quality is a key factor in public health and the long-term operation of water supply systems. This article considers topical issues of iron and manganese removal from underground water, since exceeding the maximum permissible concentrations of iron and manganese negatively affects the organoleptic properties of water and causes corrosion of pipelines and clogging of water supply systems. This work covers the main criteria for selecting filter materials, including their physicochemical parameters, resistance to pollution, and durability. An analysis of existing filter media of natural, synthetic, and modified origin, such as quartz sand, activated carbon, anthracite, zeolite, and catalytic materials with manganese oxides, is carried out. Particular attention is paid to modern methods of modifying materials that improve their adsorption properties and increase the efficiency of iron and manganese removal. The findings emphasize the promise of using modified filter materials made from inexpensive or recycled waste. Such technologies can reduce water treatment costs and environmental impact and ensure high purification efficiency. The presented results and recommendations may be useful in developing new materials and technologies for water treatment.

A novel metal organic framework (MOF) was fabricated on the surface of an open cell nickel foam and employed as a selective sorbent for Hg²⁺ dissolved in surface water. Two organic ligands (2-amino-teraphthalate and 4,4-dipyridyl) were combined with Ni(NO₃)₂ and grown on a Ni foam (95% porosity) to generate a P4₁ symmetric MOF with an internal 2.487 Å pore size and an active amino moiety serving as a binding site for Hg²⁺ and other heavy metals, characterized by XRD, and a lenticular crystal habit producing relatively well distributed spherical crystals, characterized by SEM-EDX. Adsorption experiments were conducted in both deionized water and mercury spiked into river water at concentrations typical for polluted areas ([Hg²⁺] ∼ 4, 40, and 400 ppb). The adsorption effect was characterized by Au-stabilized ICP-MS, finding highly favorable adsorptive efficacy, exhibiting adsorption capacities of 201.31 mg g⁻¹, 25.68 mg g⁻¹, and 3.017 mg g⁻¹, at initial concentrations of 400 ppb, 40 ppb, and 4 ppb, respectively. The coating of the MOF on the metal foam modulated the adsorption behavior of the MOF, maximizing the effective surface area of the adsorbent and thereby reversing the otherwise inverse relationship of % adsorbed with respect to increasing C_i.

Free nitrous acid (FNA) pretreatment has emerged as an effective strategy for enhancing short-chain fatty acid (SCFA) production from waste-activated sludge (WAS). However, a comprehensive understanding of how individual pretreatment parameters influence fermentation performance remains limited. This study systematically optimized FNA dose, pre-treatment temperature, pH, and duration to enhance SCFA yield. It also introduces a different mechanistic perspective highlighting the fate of NO₂⁻–N as a key determinant in modulating fermentation pathways. FNA doses of 3.7–7.3 mg L⁻¹, temperatures between 5 and 20 °C, and pH levels of 5.5–6.0 minimized NO₂⁻–N decomposition during pre-treatment and increased its exposure to anaerobic bacteria during fermentation, which was favorable for enhancing SCFA production by suppressing methanogens. The findings underscore that residual NO₂⁻–N concentration, which is governed by the extent of NO₂⁻–N decomposition during the pre-treatment phase, critically influences fermentation performance. The study also found that shorter pre-treatment durations (12–24 h) and lower temperatures (5 °C) produced SCFA yields comparable to those from 48 h treatments at 20 °C. These conditions reduce the need for heating and allow smaller tank sizes, making the process more energy- and cost-efficient, especially in colder climates. Under optimal conditions (FNA dose: 2.4 mg L⁻¹, pH: 6.0, temperature: 5 °C, duration: 24 h), the FNA reactor yielded 141 mg COD g⁻¹ VSS of SCFA, 4.4 times higher than the control. Microbial community analysis revealed that FNA-induced fermentation suppressed SCFA-consuming bacteria while enriching SCFA-producing bacteria. This study provides critical insights for optimizing FNA pre-treatment and scaling up sludge fermentation across diverse environmental conditions.

The harvesting microalgae is a challenging process that requires innovative and efficient technologies to make large-scale cultivation economically viable. This study investigated the effectiveness of electrochemical methods for harvesting microalgae Chlorella vulgaris. The operational parameters, such as electrolysis time, electrical current, and pH, were optimized using the response surface methodology based on the Box–Behnken design. The boron-doped diamond (BDD), aluminum (Al), and iron (Fe) electrodes were tested and compared. BDD–Al showed 99.3% of harvesting efficiency (time: 20 min, current: 100 mA, pH: 9), which is the highest value and a pH of 9. The physicochemical properties of the harvested algae, including lipids, proteins, carbohydrates, total suspended solids, and chlorophyll-a content, were examined. The content of harvested algae was found as 41.07–46.63% for protein, 5.5–16.9% for lipid, and 9.02–12.08% for carbohydrates (sugar). The chlorophyll-a concentrations varied from 6.7 to 8.36 μg mL⁻¹. Optimized operating conditions for electrolysis time, pH, and current were determined, and harvesting efficiency was achieved at more than 99%. Energy consumptions for the highest harvesting efficiencies were found to be 0.2, 0.35, and 0.4 kWh kg⁻¹ for BDD–Al, Al–Al, and Al–BDD electrode pairs, respectively. These values were lower than those of conventional algae harvesting methods. The results showed that the electrochemical harvesting techniques are promising alternatives with a high harvesting efficiency and low energy consumption.

Groundwater is a vital water source, providing drinking water to at least 50% of the world's population and accounting for 43% of water used in irrigation. In Sri Lanka, 39.6% of the population rely on groundwater for drinking purposes, with 72% of this group residing in rural areas. In several of these regions, groundwater quality is affected by geogenic contaminants such as excessive fluoride, hardness, and salinity, which are linked to chronic health issues. These ion-related problems highlight the need for selective separation technologies, with electrodialysis (ED) emerging as a promising and sustainable option. However, membrane fouling and scaling remain significant challenges. This study aims to investigate the mechanisms of membrane fouling and scaling in ED systems and develop effective cleaning strategies to restore membrane performance. The fouling process involves two stages: organic fouling dominant in the initial stages, followed by inorganic scaling. Pearson correlation analysis revealed a strong negative correlation of −0.94 for organic fouling and −0.63 for inorganic fouling. A similar two-stage fouling behavior was also observed in a one-year field experiment conducted in Sri Lanka, further supporting these findings. An integrated acid–base cleaning method was developed, with acidic cleaning effectively removing inorganic scales and alkaline cleaning addressing organic fouling. The acid–base cleaning approach stands out as a sustainable solution to tackle fouling in ED systems, making it suitable for decentralized groundwater treatment in Sri Lanka.

This study elucidates the competitive adsorption dynamics of ciprofloxacin (CIP) and acetaminophen (ACE) onto coffee husk activated with potassium (CH–KOH, BET surface area = 1145 m² g⁻¹, pH_PZC = 7.36), providing mechanistic insights into the removal of pharmaceuticals in complex aqueous matrices. The Modified Langmuir multicomponent isotherm effectively captured the competitive equilibrium behavior (deviation = 25.8%), showing a higher affinity for ACE (η_ACE = 0.7) than for CIP (η_CIP = 4.9), the qT was 1.25 mmol g⁻¹ across the entire evaluated concentration range, which is similar to the observed in mono-component systems, Q_max 1.26 mmol g⁻¹ for ACE and 0.58 mmol g⁻¹ for CIP, with removal efficiencies of 91–99% and 75–99%, respectively. In real matrices such as synthetic hospital wastewater and urine, high efficiencies (84–97%) were maintained. Fixed-bed column studies confirmed the strong performance under continuous-flow conditions, with saturation capacities (q_s) up to 1.46 mmol g⁻¹ for ACE and 0.61 mmol g⁻¹ for CIP, mass transfer zones ranging from 0.42 to 1.53 cm, and breakthrough times between 91 and 1463 min depending on flow rate (1–3 mL min⁻¹) and bed height (1–3 cm). The Thomas model accurately predicted breakthrough curves, revealing faster kinetics for ACE. Physisorption predominates, involving synergistic π–π stacking interactions, hydrogen bonding networks, and hydrophobic association, with ACE showing greater selectivity in both mono and multicomponent systems. CH–KOH exhibited high stability and reusability, stabilizing at approximately 70% of its initial capacity by the third cycle, with no further decrease observed in the fourth cycle. Comprehensive physicochemical characterization revealed that physisorption predominates, involving synergistic π–π stacking interactions, hydrogen bonding networks, and hydrophobic associations. These results confirm the potential of CH–KOH as a sustainable adsorbent for pharmaceutical contaminant removal in real-world scenarios, integrating circular economy principles into advanced water treatment.

Retraction of ‘Extraction of metal ions from water using a novel liquid membrane containing ZIF-8 nanoparticles, an ionic liquid, and benzo-18-crown-6’ by Arash Adhami et al., Environ. Sci.: Water Res. Technol., 2025, https://doi.org/10.1039/d4ew00694a.

In the present study, a novel pilot ozone contactor configuration was employed using hydrogen peroxide (H₂O₂) and multiple ozone diffusion zones in an over-under contactor for testing three wastewater effluents. With a 1 : 1 molar H₂O₂ : O₃ dose, splitting the ozone dose between three diffusers reduced bromate formation by as much as 93% compared to the traditional single diffuser control condition. The required H₂O₂ dose for similar bromate levels was decreased by more than 90%. 1,4-Dioxane was used as a representative contaminant and hydroxyl radical (·OH) probe compound. H₂O₂ addition significantly improved 1,4-dioxane removal, and removal was similar between different diffuser conditions for the same total ozone dose. Detailed ozone residual and ozone exposure measurements showed that, with H₂O₂, similar ozone exposure was provided between the single and multi-diffuser H₂O₂ experiments. This indicates that minimization of local ozone concentration, rather than exposure, is vital for preventing the O₃–Br· reaction which controls bromate formation and may be beneficial for removal of ozone reactive contaminants and disinfection. Ozone decay, both with and without H₂O₂, was extremely sensitive to pH. Bromate formation increased by a factor of nearly two from pH 6 to 8 in the control condition, while the effect was less pronounced with H₂O₂. 1,4-Dioxane removal was unaffected by pH or temperature, while bromate formation decreased with increasing temperature.

Iodinated disinfection by-products (I-DBPs) are of growing concern due to their elevated toxicity compared to their chlorinated counterparts, with links to adverse health effects such as bladder cancer and miscarriages. Medical imaging agents like iohexol, commonly used in healthcare facilities, introduce iodine into wastewater systems. This study investigates the photodegradation of iohexol and the subsequent formation of products, including I-DBPs, during simulated final wastewater treatment under chlorination and sunlight exposure. Experiments were conducted with solutions containing 30 μM iohexol, 3 mg L⁻¹ humic acids, and 5.5 mg L⁻¹ hypochlorite. Samples were irradiated at λ ≥ 295 nm and subject to ion chromatography monitoring of I⁻, IO₃⁻, Cl⁻, and ClO₃⁻, providing mechanistic insight into the fate of iodide released from iohexol. UV-visible spectroscopy was employed to monitor the degradation profile of iohexol and the concurrent release of iodide. Electrospray ionization mass spectrometry (ESI-MS) identified a range of anionic products based on their mass-to-charge ratios (m/z), including low molecular weight carboxylic acids, their carcinogenic haloacetic derivatives (chloroacetic acid (m/z 93), iodoacetic acid (IAA, m/z 185), and hydroxyiodoacetic acid (m/z 201)) as well as phenolic halides. Notably, IAA was present at a concentration of 0.16 μM at the conclusion of the reaction. These findings elucidate photodeiodination-coupled radical attack, photooxidative cleavage, and halogenation transformation pathways of iodinated compounds during disinfection and underscore the potential risks associated with their presence in wastewater. The results provide valuable insights for medical facilities and wastewater treatment plants aiming to mitigate the formation of hazardous I-DBPs.