Disinfection By-products Research Articles

Mixed exposure to haloacetaldehyde disinfection by-products exacerbates lipid aggregation in the liver of mice

Haloacetaldehyde disinfection by-products (HAL-DBPs) are among the top three unregulated DBPs found in drinking water. The cytotoxicity and genotoxicity of HALs are much higher than that of the regulated trihalomethanes and haloacetic acids. Previous studies have mainly focused on the toxic effects of single HAL, with few examining the toxic effects of mixed exposures to HALs. The study aimed to observe the effects of mixed exposures of 1∼1000X the realistic level of HALs on the hepatotoxicity and lipid metabolism of C57BL/6J mice, based on the component and concentration of HALs detected in the finished water of Shanghai. Exposure to realistic levels of HALs led to a significant increase in phosphorated acetyl CoA carboxylase 1 (p-ACC1) in the hepatic de novo lipogenesis (DNL) pathway. Additionally, exposure to 100X realistic levels of HALs resulted in significant alterations to key enzymes of DNL pathway, including ACC1, fatty acid synthase (FAS), and diacylglycerol acyltransferase 2 (DGAT2), as well as key proteins of lipid disposal such as carnitine palmitoyltransferase 1 (CPT-1) and peroxisome proliferator activated receptor α (PPARα). Exposure to 1000X realistic levels of HALs significantly increased hepatic and serum triglyceride levels, as well as total cholesterol, low-density lipoprotein, alanine aminotransferase, aspartate transaminase, alkaline phosphatase, and lactate dehydrogenase levels, significantly decreased high-density lipoprotein. Meanwhile, histopathological analysis demonstrated that HALs exacerbated tissue vacuolization and inflammatory cell infiltration in mice livers, which showed the typical phenotypes of non-alcoholic fatty liver disease (NAFLD). These results suggested that the HALs mixture is a critical risk factor for NAFLD and is significantly highly toxic to C57BL/6J mice.

Formation potential of disinfection byproducts during chlorination of petroleum hydrocarbon-contaminated drinking water

Recent leaks of underground fuel storage tanks in the Pearl Harbor region have led to direct release of un-weathered petroleum hydrocarbons (PHCs) into drinking water sources, which then directly underwent chlorination disinfection treatment. Since the control of disinfection byproducts (DBPs) traditionally focuses natural organic matters (NOM) from source water and little is known about the interactions between free chlorine and un-weathered PHCs, laboratory chlorination experiments in batch reactors were conducted to determine the formation potential of DBPs during chlorination of PHC-contaminated drinking water. Quantitative analysis of regulated DBPs showed that significant quantities of THM4 (average 3,498 μg/L) and HAA5 (average 355.4 μg/L) compounds were formed as the result of chlorination of un-weathered PHCs. Amongst the regulated DBPs, THM4, which were comprised primarily of chloroform and bromodichloromethane, were more abundant than HAA5. Numerous unregulated DBPs and a large diversity of unidentified potentially halogenated organic compounds were also produced, with the most abundant being 1,1-dichloroacetone, 1,2-dibromo-3-chloropropane, chloropicrin, dichloroacetonitrile, and trichloracetonitrile. Together, the results demonstrated the DBP formation potential when PHC-contaminated water undergoes chlorination treatment. Further studies are needed to confirm the regulated DBP production and health risks under field relevant conditions.

MnO2-based capacitive system enhances ozone inactivation of bacteria by disrupting cell membrane

The application of ozone (O3) disinfection has been hindered by its low solubility in water and the formation of disinfection by-products (DBPs). In this study, capacitive disinfection is applied as a pre-treatment for O3 oxidation, in which manganese dioxide with a rambutan-like hollow spherical structure is used as the electrode to increase the charge density on the electrode surface. When a voltage is applied, the negative-charged microbes are attracted to the electrodes and killed by electrical interactions. The contact between microbes and capacitive electrodes leads to changes in cell permeability and burst of reactive oxygen species, thereby promoting the diffusion of O3 into the cells. After O3 penetrates the cell membrane, it can directly attack the cytoplasmic constituents, accelerating fatal and irreversible damage to pathogens. As a result, the performance of the capacitance-O3 process is proved better than the direct sum of the two individual process efficiencies. The design of capacitance-O3 system is beneficial to reduce the ozone dosage and DBPs with a broader inactivation spectrum, which is conducive to the application of ozone in primary water disinfection.

Sunlight enhanced the formation of tribromomethane from benzotriazole degradation during the sunlight/free chlorine treatment in the presence of bromide

The coexistence of free chlorine and bromide under sunlight irradiation (sunlight/FC with Br−) is unavoidable in outdoor seawater swimming pools, and the formation of brominated disinfection byproducts could act more harmful than chlorinated disinfection byproducts. In this study, benzotriazole was selected as a model compound to investigate the degradation rate and the subsequent formation of disinfection byproducts via sunlight/FC with Br− process. The rate constants for the degradation of benzotriazole under pseudo first order conditions in sunlight/FC with Br− and sunlight/FC are 2.3 ± 0.07 × 10−1 min−1 and 6.0 ± 0.7 × 10−2 min−1, respectively. The enhanced degradation of benzotriazole can be ascribed to the generation of HO•, bromine species, and reactive halogen species (RHS) during sunlight/FC with Br−. Despite the fact that sunlight/FC with Br− process enhanced benzotriazole degradation, the reaction results in increasing tribromomethane (TBM) formation. A high concentration (37.8 μg/L) of TBM was detected in the sunlight/FC with Br−, which was due to the reaction of RHS. The degradation of benzotriazole was notably influenced by the pH value (pH 4 − 11), the concentration of bromide (0 − 2 mM), and free chlorine (1 − 6 mg/L). Furthermore, the concentration of TBM increased when the free chlorine concentrations increased, implying the formation potential of harmful TBM in chlorinated seawater swimming pools.

Exploring Prenatal Exposure to Halogenated Compounds and Its Relationship with Birth Outcomes Using Nontarget Analysis.

Halogenated organic compounds (HOCs) are a class of contaminants showing high toxicity, low biodegradability, and high bioaccumulation potential, especially chlorinated and brominated HOCs (Cl/Br-HOCs). Knowledge gaps exist on whether novel Cl/Br-HOCs could penetrate the placental barrier and cause adverse birth outcomes. Herein, 326 cord blood samples were collected in a hospital in Jinan, Shandong Province from February 2017 to January 2022, and 44 Cl/Br-HOCs were identified with communicating confidence level above 4 based on a nontarget approach, covering veterinary drugs, pesticides, and their transformation products, pharmaceutical and personal care products, disinfection byproducts, and so on. To our knowledge, the presence of closantel, bromoxynil, 4-hydroxy-2,5,6-trichloroisophthalonitrile, 2,6-dibromo-4-nitrophenol, and related components in cord blood samples was reported for the first time. Both multiple linear regression (MLR) and Bayesian kernel machine regression (BKMR) models were applied to evaluate the relationships of newborn birth outcomes (birth weight, length, and ponderal index) with individual Cl/Br-HOC and Cl/Br-HOCs mixture exposure, respectively. A significantly negative association was observed between pentachlorophenol exposure and newborn birth length, but the significance vanished after the false discovery rate correction. The BKMR analysis showed that Cl/Br-HOCs mixture exposure was significantly associated with reduced newborn birth length, indicating higher risks of fetal growth restriction. Our findings offer an overview of Cl/Br-HOCs exposome during the early life stage and enhance the understanding of its exposure risks.

The removal of pathogenic bacteria and dissolved organic matter from freshwater using microporous membranes: insights into biofilm formation and fouling reversibility

Pathogenic bacteria in drinking-water pose a health risk to consumers, as they compromise the quality of portable water. Chemical disinfection of water containing dissolved organic matter (DOM) causes harmful disinfection by-products. In this work, 4-hydroxybenzoic acid (4-HBA) blended polyethersulfone membranes were fabricated and characterised using microscopic and spectroscopic techniques. The membranes were evaluated for the removal of bacteria and DOM from synthetic and environmental water. Permeate flux increased from 287.30 to 374.60 l m−2 h−1 at 3 bars when 4-HBA increased from 0 to 1.5 wt.%, suggesting that 4-HBA influenced the membrane’s affinity for water. Furthermore, 4-HBA demonstrated antimicrobial properties by inhibiting bacterial growth. The membrane with 1 wt.% 4-HBA recorded 99.4 and 100% bacteria removal in synthetic and environmental water, respectively. Additionally, DOM removal of 55–73% was achieved. A flux recovery ratio (FRR) of 94.6% was obtained when a mixture of bacteria and humic acid was filtered, implying better fouling layer reversibility during cleaning. Furthermore, 100% FRR was achieved when a multimedia granular filtration step was installed prior to membrane filtration. The results illustrated that the membranes had a high permeate flux with low irreversible fouling. This indicated the potential of the membranes in treating complex feed streams using simple cleaning protocols.

Chlorite and bromate alter the conjugative transfer of antibiotic resistance genes: Co-regulation of oxidative stress and energy supply

The widespread use of disinfectants during the global response to the 2019 coronavirus pandemic has increased the co-occurrence of disinfection byproducts (DBPs) and antibiotic resistance genes (ARGs). Although DBPs pose major threats to public health globally, there is limited knowledge regarding their biological effects on ARGs. This study aimed to investigate the effects of two inorganic DBPs (chlorite and bromate) on the conjugative transfer of RP4 plasmid among Escherichia coli strains at environmentally relevant concentrations. Interestingly, the frequency of conjugative transfer was initially inhibited when the exposure time to chlorite or bromate was less than 24 h. However, this inhibition transformed into promotion when the exposure time was extended to 36 h. Short exposures to chlorite or bromate were shown to impede the electron transport chain, resulting in an ATP shortage and subsequently inhibiting conjugative transfer. Consequently, this stimulates the overproduction of reactive oxygen species (ROS) and activation of the SOS response. Upon prolonged exposure, the resurgent energy supply promoted conjugative transfer. These findings offer novel and valuable insights into the effects of environmentally relevant concentrations of inorganic DBPs on the conjugative transfer of ARGs, thereby providing a theoretical basis for the management of DBPs.

Molecular-weight dependent promotion and competition effects of natural organic matter on dissolved black carbon removal by coagulation

Dissolved black carbon (DBC) is the ubiquitous component of dissolved organic matter pools with the high reactivity for disinfection byproducts formation. However, it is unknown that the influence of molecular weight (MW) of natural organic matter (NOM) on the DBC removal from potable water sources. Therefore, it was studied that the DBC removal by coagulation in the presence of the NOM with various molecular weights. The DBC removal was promoted due to the presence of NOM and the promotion degree decreased with decreasing MW of NOM. Furthermore, the removal ratio of humic-like component increased as the MW of NOM decreased, suggesting that the competition between DBC and NOM increased with decreasing MW. The functional groups after coagulation were the same with that before coagulation as the MW of NOM varied, suggesting that the molecular structure was not the key factor of influencing the DBC removal. This study will give the deep insight into the prediction of the DBC removal ratio by coagulation based on the MW of NOM in water sources.

Comparative analysis of chlorinated disinfection byproducts formation from 4-nitrophenol and 2-amino-4-nitrophenol during UV/post-chlorination

Nitrophenol compounds (NCs) are widely distributed in water environments and regarded as important precursors of disinfection byproducts (DBPs). Herein, 4-nitrophenol and 2-amino-4-nitrophenol were selected as representative NCs to explore chlorinated DBPs (Cl-DBPs) formation during UV/post-chlorination. Dichloronitromethane (DCNM), trichloronitromethane (TCNM), dichloroacetonitrile (DCAN), and trichloromethane (TCM) were formed from 4-nitrophenol and 2-amino-4-nitrophenol during UV/post-chlorination, and the yields of individual Cl-DBPs from 2-amino-4-nitrophenol were higher than those from 4-nitrophenol. Meantime, increasing chlorine contact time, UV fluence, and free chlorine dose could enhance Cl-DBPs formation, while much higher values of the three factors might decrease the yields of Cl-DBPs. Besides, alkaline pH could decrease the yields of halonitromethane (HNMs) and DCAN but increase the yields of TCM. Also, higher concentrations of 4-nitrophenol and 2-amino-4-nitrophenol would induce more Cl-DBPs formation. Subsequently, the possible formation pathways of DCNM, TCNM, DCAN, and TCM form 4-nitrophenol and 2-amino-4-nitrophenol during UV/post-chlorination were proposed according to transformation products (TPs) and density functional theory (DFT) calculation. Notably, Cl-DBPs formed from 2-amino-4-nitrophenol presented higher toxicity than those from 4-nitrophenol. Among these generated Cl-DBPs, DCAN and TCNM posed higher cytotoxicity and genotoxicity, respectively. Furthermore, 4-nitrophenol, 2-amino-4-nitrophenol, and their TPs exhibited ecotoxicity. Finally, 4-nitrophenol and 2-amino-4-nitrophenol presented a high potential to produce DCNM, TCNM, DCAN, and TCM in actual waters during UV/post-chlorination, but the Cl-DBPs yields were markedly different from those in simulated waters. This work can help better understand Cl-DBPs formation from different NCs during UV/post-chlorination and is conducive to controlling Cl-DBPs formation.

Underestimated role of hydroxyl radicals for bromate formation in persulfate-based advanced oxidation processes

In persulfate-based advanced oxidation processes (PS-AOPs), sulfate radicals (SO4•-) have been recognized to play more important roles in inducing bromate (BrO3−) formation rather than hydroxyl radicals (HO•) because of the stronger oxidation capacity of the former. However, this study reported an opposite result that HO• indeed dominated the formation of bromate instead of SO4•-. Quenching experiments were coupled with electron paramagnetic resonance (EPR) detection and chemical probe identification to elucidate the contributions of each radical species. The comparison of different thermal activated persulfates (PDS and PMS) demonstrated that the significant higher bromate formation in HEAT/PMS ([BrO3−]/[Br−]0 = 0.8), as compared to HEAT/PDS ([BrO3−]/[Br−]0 = 0.2), was attributable to the higher concentration of HO• radicals in HEAT/PMS. Similarly, the bromate formation in UV/PDS ([BrO3−]/[Br−]0 = 1.0), with a high concentration of HO•, further underscored the dominant role of HO•. As a result, we quantified that HO• and SO4•- radicals accounted 66.7% and 33.3% for bromate formation. This controversial result can be reconciled by considering the critical intermediate, hypobromic acid/hypobromate (HOBr/BrO−), involved in the transformation of Br− to BrO3−. HO• radicals have the chemical preference to induce the formation of HOBr/BrO− intermediates (contributing ∼ 60%) relative to SO4•- radicals (contributing ∼ 40%). This study highlighted the dominant role of HO• in the formation of bromate rather than SO4•- in PS-AOPs and potentially offered novel insights for reducing disinfection byproduct formation by controlling the radical species in AOPs.

Development and validation of a GC-MS/MS method for the determination of iodoacetic acid in biological samples.

Iodoacetic acid (IAA) is a halogenated disinfection by-product of growing concern due to its high cytotoxicity, genotoxicity, endocrine disruptor effects, and potential carcinogenicity. However, the data on distribution and excretion of IAA after ingestion by mammals are still scarce. Here, we developed a reliable and validated method for detecting IAA in biological specimens (plasma, urine, feces, liver, kidney, and tissues) based on modified QuEChERS sample preparation combined with gas chromatography-tandem triple quadrupole mass spectrometry (GC-MS/MS). The detection method for IAA exhibited satisfactory recovery rates (62.6-108.0%) with low relative standard deviations (RSD < 12.3%) and a low detection limit for all biological matrices ranging from 0.007 to 0.032ng/g. The study showed that the proposed method was reliable and reproducible for analyzing IAA in biological specimens. It was successfully used to detect IAA levels in biological samples from rats given gavage administration. The results indicated that IAA was found in various tissues and organs, including plasma, thyroid, the liver, the kidney, the spleen, gastrointestinal tract, and others, 6h after exposure. This study provides the first data on the in vivo distribution inand excretion of IAA by mammals following oral exposure.

Sulfonamide disinfection byproducts exhibited severe toxicity to human commensal bacteria

Many antibiotic disinfection byproducts have been detected but their toxicity has not been evaluated adequately. In this report, the chlorination reaction kinetics of five common sulfamides (SAs), reaction intermediates and their toxicity were investigated. Chlorination of sulfapyridine (SPD), sulfamethazine (SMT), sulfathiazole (STZ), and sulfisoxazole (SIZ) followed the second-order kinetics, and were degraded completely within 10 min. A large number of reaction intermediates were deteced by LC-MS, among which a total of 16 intermediates were detected for the first time. Toxicity of the five SAs chlorination solutions was evaluated separately by examining their effects on the growth rate of S. salivarius K12, a commensal bacterium in the human digestive system. After 30 min chlorination, solutions of SMT, STZ and sulfadiazine (SDZ) each exhibited severe toxicity by inhibiting the bacteria growth completely, whereas the inhibition was only 50 % and 20 % by SIZ and SPD respectively. Based on the comparison between toxicity test results and mass spectra, three SA chlorination intermediates, m/z 187.2 (C10H10N4), m/z 287.2 (C9H7N3O4S2) and m/z 215 (C7H10N4O2S/C12H14N4) were proposed to be the primary toxicants in the chlorination products. Our study demonstrated the power of combined approach of chemical analysis and toxicity testing in identifying toxic disinfection byproducts, and highlighted the ne ed for more research on the toxicity evaluation and risk assessment of antibiotic disinfection byproducts.

Degradation of prometryn during UV/persulfate process: Kinetics and disinfection by-product formation

Prometryn is one of the commonly used triazine herbicides and is also widely used for algae removal in aquaculture. This study investigated the degradation kinetics of prometryn via UV/persulfate (PS) oxidation and confirmed its adherence to pseudo-first-order kinetics, with a calculated rate constant (kobs) of 0.2358 min−1. The impact of PS concentration, water matrix (including background ions of Cl− and Br− and natural organic matter (NOM)), and solution pH on prometryn degradation were assessed. Results indicated an increase in prometryn degradation with raising concentrations of PS, Cl−, and Br−, especially evident at a PS concentration of 400 μm where complete degradation was achieved. Conversely, degradation decreased with increasing NOM concentration and pH. Radical scavenging experiments affirmed the promotion of prometryn degradation in UV/PS by both HO• and SO4−•, with SO4−• contributing over 70 % of the total free radical contribution. Evaluation of disinfection by-product (DBP) formation revealed trichloromethane (TCM) as the predominant DBP in non‑bromine water and tribromomethane (TBM) in bromine water. Thus, this study offers a theoretical foundation for UV/PS degradation of triazine herbicides in aqueous environments. The obtained results hold significance for controlling DBPs in subsequent water treatment processes, ensuring the provision of safe drinking water to the public and meeting the sustainable development goal 6.

A Delicate Balance: Water Disinfection and By-Product Immunotoxicity.

Mouse macrophages and human blood cells exposed to very high levels of three trihalophenols showed changes in RNA methylation, pointing to one mechanism by which disinfection by-products may harm health, even as disinfection protects it in other ways.

Cytotoxicity of emerging halophenylacetamide disinfection byproducts in drinking water: Mechanism and prediction

Halophenylacetamides (HPAcAms) have been identified as a new group of nitrogenous aromatic disinfection byproducts (DBPs) in drinking water, but the toxicity mechanisms associated with HPAcAms remain almost completely unknown. In this work, the cytotoxicity of HPAcAms in human hepatoma (HepG2) cells was evaluated, intracellular oxidative stress/damage levels were analyzed, their binding interactions with antioxidative enzyme were explored, and a quantitative structure-activity relationship (QSAR) model was established. Results indicated that the EC50 values of HPAcAms ranged from 2353 μM to 9780 μM, and the isomeric structure as well as the type and number of halogen substitutions could obviously induce the change in the cytotoxicity of HPAcAms. Upon exposure to 2-(3,4-dichlorophenyl)acetamide (3,4-DCPAcAm), various important biomarkers linked to oxidative stress and damage, such as reactive oxygen species, 8‑hydroxy-2-deoxyguanosine, and cell apoptosis, exhibited a significant increase in a dose-dependent manner. Moreover, 3,4-DCPAcAm could directly bind with Cu/Zn-superoxide dismutase and induce the alterations in the structure and activity, and the formation of complexes was predominantly influenced by the van der Waals force and hydrogen bonding. The QSAR model supported that the nucleophilic reactivity as well as the molecular compactness might be highly important in their cytotoxicity mechanisms in HepG2 cells, and 2-(2,4-dibromophenyl)acetamide and 2-(3,4-dibromophenyl)acetamide deserved particular attention in future studies due to the relatively higher predicted cytotoxicity. This study provided the first comprehensive investigation on the cytotoxicity mechanisms of HPAcAm DBPs.

Algal-Rich Drinking Source Water: Effects of Chlorine Pre-oxidation on Algal Growth, Algal Organic Matter, and the Potential of Disinfection By-Products

Algal-Rich Drinking Source Water: Effects of Chlorine Pre-oxidation on Algal Growth, Algal Organic Matter, and the Potential of Disinfection By-Products

Selection of membrane for production of drinking water from surface and groundwater by nanofiltration

The aim of the work was to select a nanofiltration membrane that would ensure effective simultaneous co-removal of pollutants present in surface and groundwater, including contaminants such as bisphenol A and PFAS compounds. Series of membrane filtrations was carried out using 12 commercial nanofiltration membranes (NFX, NFG, NF270, NF90, DK, DL, TS80, SB90, TS40, XN45, NPO30, NPO10) under various operating parameters. The conducted tests showed that among tested membranes the membrane most suitable for the production of drinking water from model waters is the NF90 membrane by Dow Filmtec. Regardless of the composition of the water, its pH and transmembrane pressure, the water produced using NF90 membrane each time met the legal requirements in terms of heavy metals (chromium total, silver, nickel, lead, arsenic), iron, manganese, sulfates, chlorides, fluorides, nitrates, sodium, PFAS, tetrachlorethylene, bisphenol A and KMnO4 index. In addition, tests carried out to verify the susceptibility of the produced water to the formation of disinfection by-products (DBP - ∑THM and halogenoacetic acids) showed that DBP concentrations in produced water did not exceed the values permitted by law.

Using transcriptome analysis to reveal the effects of bromoacetamide at drinking water ambient concentrations on the transformation of eDNA carrying ARGs

Antibiotic resistance genes (ARGs) are frequently detected in drinking water. Transformation of extracellular antibiotic resistance genes (eARGs) is an important pathway for horizontal gene transfer, which facilitates the spread of ARGs among different species. Although most studies have pointed out that the presence of some common carbon-containing disinfection by-products, such as trihalomethanes, can increase the frequency of transformation by increasing the content of reactive oxygen species (ROS), nitrogen-containing disinfection by-products (N-DBPs), such as bromoacetamide (BAcAm), can also induce bacterial resistance to antibiotics by stimulating ROS. However, it is unclear whether such N-DBPs can similarly promote the transformation of ARGs in bacteria. In this study, the effect of BAcAm on the transformation of eDNA carrying ARGs was investigated, and found that DNA integration and repair (ruv, rec), efflux pumps (emr), and genes related to membrane proteins (bam, opm) were up-regulated in E. coli after addition of BAcAm. Furthermore, in addition to analyzing common functional genes, in terms of metabolic gene expression, which is usually overlooked, the genes related to amino acid biosynthesis (pot, arg, lys) were up-regulated while genes related to sulfur metabolism, which has a higher metabolic cost (thi, sssu) were down-regulated, which suggests that E. coli is able to effectively defend itself against the threat posed by BAcAm to its survival. In conclusion, the factors affecting the conversion of eDNA carrying ARGs into E. coli cells by BAcAm were suggested and elaborated that E. coli carrying ARGs can adapt to various unfavorable environments by regulating relevant metabolic mechanisms and survive in drinking water environment for a long period of time.

Degradation Strategy and Mechanism of Nitrogenous Disinfection By-products in Three-dimensional Electrochemical System

Nitrosopyrrolidine (NPYR) is a nitrogenous disinfection by-products (N-DBPs) that has attracted much attention due to its high toxicity and resistance to treatment. The removal of NPYR using a three-dimensional aerated electrochemical reactor (3DAER) was investigated. The artificial neural network (ANN) method was employed for the first time to optimize the operating parameters of NPYR degradation with the 3DAER system. Compared to manual parameter optimization, the NPYR degradation parameters generated with the ANN increased the degradation rate by 8.20% to 86.67%. The inhibition rate of the treated water sample used to treat luminescent bacteria was reduced by 49.16%. Mechanistic studies revealed that ·OH and ·O2- were involved in the reaction, and ·OH attacked nucleophilic sites and ·O2- targeted the electrophilic sites of NPYR. Gas chromatographymass spectrometry (GC–MS), combined with Fukui index analyses, was used to elucidate the pathway for NPYR degradation. This confirmed lower biological toxicities for the intermediate products formed during NPYR degradation. In conclusion, the MgFe-LDH/3DAER electrochemical process mitigated the environmental hazards associated with NPYR. This study offers theoretical insights and practical guidance for controlling water disinfection by-products.

Photothermal assisted space-confined chlorine activation for removal of pharmaceuticals and personal care products coupled with disinfection by-products control

The solar/chlorine process provides an energy-efficient technique for the abatement of some pharmaceuticals and personal care products (PPCPs) but it is inefficient in degrading PPCPs lacking electron-donating group and suffers high formation of disinfection byproducts (DBPs). In this study, a photothermal approach is developed to promote chlorine activation (photothermal/chlorine) under solar radiation to effectively remove a wide range of structurally diverse PPCPs and to control DBPs formation. To this end, a carbon black (CB) coated 3D porous melamine sponge (MS), namely CB@MS, is developed for the photothermal/chlorine application, achieving significantly enhanced PPCPs degradation with an ibuprofen (IBU) removal rate constant (0.22 min−1) 3.76 times that of the solar/chlorine process (0.058 min−1). Mechanistic investigations revealed that CB@MS confines the thermal energy within the 3D porous structure to achieve high localized heating for boosting PPCPs degradation in the confined space, which is equivalent to the thermal effect achieved by the solar/chlorine process at constant solution temperature of around 70 °C. Moreover, the photothermal/chlorine process reduces TOCl and DBPs formation by 77.6 % and 67.5 %, ascribed to adsorption by CB@MS, less chlorine exposure, and altered PPCPs degradation pathways. The broad applicability in various water matrices, and good reusability and stability of the photothermal/chlorine system also ensure its excellent practicality. This study offers in-depth mechanisms and practical insights into the development of a novel photothermal/chlorine process for PPCPs abatement and DBPs control.