Disinfection By-product Formation Potential Research Articles

Reaction mechanisms of chlorinated disinfection byproducts formed from nitrophenol compounds with different structures during chlor(am)ination and UV/post-chlor(am)ination

Nitrophenol compounds (NCs) have high formation potentials of disinfection byproducts (DBPs) in water disinfection processes, however, the reaction mechanisms of DBPs formed from different NCs are not elucidated clearly. Herein, nitrobenzene, phenol, and six representative NCs were used to explore the formation mechanisms of chlorinated DBPs (Cl-DBPs) during chlor(am)ination and UV/post-chlor(am)ination. Consequently, the coexistence of nitro and hydroxy groups in NCs facilitated the electrophilic substitution to produce intermediates of Cl-DBPs, and the different positions of nitro and hydroxy groups also induced different yields and formation mechanisms of Cl-DBPs during the chlorination and UV/post-chlorination processes. Besides, the amino, chlorine, and methyl groups significantly influenced the formation mechanisms of Cl-DBPs during the chlorination and UV/post-chlorination processes. Furthermore, the total Cl-DBPs yields from the six NCs followed a decreasing order of 2-chloro-3-nitrophenol, 3-nitrophenol, 2-methyl-3-nitrophenol, 2-amino-4-nitrophenol, 2-nitrophenol, and 4-nitrophenol during chlorination and UV/post-chlorination. However, the total Cl-DBPs yields from the six NCs during chloramination and UV/post-chloramination followed a quite different order, which might be caused by additional reaction mechanisms, e.g., nucleophilic substitution or addition might occur to NCs in the presence of monochloramine (NH2Cl). This work can offer deep insights into the reaction mechanisms of Cl-DBPs from NCs during the chlor(am)ination and UV/post-chlor(am)ination processes.

Disinfection by-product formation potential in response to variability in dissolved organic matter and nutrient inputs: Insights from a mesocosm study

Changes in rainfall patterns driven by climate change affect the transport of dissolved organic matter (DOM) and nutrients through runoff to freshwater systems. This presents challenges for drinking water providers. DOM, which is a heterogeneous mix of organic molecules, serves as a critical precursor for disinfection by-products (DBPs) which are associated with adverse health effects. Predicting DBP formation is complex due to changes in DOM concentration and composition in source waters, intensified by altered rainfall frequency and intensity. We employed a novel mesocosm approach to investigate the response of DBP precursors to variability in DOM composition and inorganic nutrients, such as nitrogen and phosphorus, export to lakes. Three distinct pulse event scenarios, mimicking extreme, intermittent, and continuous runoff were studied. Simultaneous experiments were conducted at two boreal lakes with distinct DOM composition, as reflected in their color (brown and clear lakes), and bromide content, using standardized methods. Results showed primarily site-specific changes in DBP precursors, some heavily influenced by runoff variability. Intermittent and daily pulse events in the clear-water mesocosms exhibited higher haloacetonitriles (HANs) formation potential linked to freshly produced protein-like DOM enhanced by light availability. In contrast, trihalomethanes (THMs), associated with humic-like DOM, showed no significant differences between pulse events in the brown-water mesocosms. Elevated bromide concentration in the clear mesocosms critically influenced THMs speciation and concentrations. These findings contribute to understanding how changing precipitation patterns impact the dynamics of DBP formation, thereby offering insights for monitoring the mobilization and alterations of DBP precursors within catchment areas and lake ecosystems.

Control of chlorination disinfection by-products in drinking water by combined nanofiltration process: A case study with trihalomethanes and haloacetic acids

Disinfection by-products (DBPs) are prevalent contaminants in drinking water and are primarily linked to issues regarding water quality. These contaminants have been associated with various adverse health effects. Among different treatment processes, nanofiltration (NF) has demonstrated superior performance in effectively reducing the levels of DBPs compared to conventional processes and ozone-biological activated carbon (O3-BAC) processes. In this experiment, we systematically investigated the performance of three advanced membrane filtration treatment schemes, namely "sand filter + nanofiltration" (SF + NF), "sand filter + ozone-biological activated carbon + nanofiltration" (SF + O3-BAC + NF), and "ultrafiltration + nanofiltration" (UF + NF), in terms of their ability to control disinfection by-product (DBP) formation in treated water, analyzed the source and fate of DBP precursors during chlorination, and elucidated the role of precursor molecular weight distribution during membrane filtration in relation to DBP formation potential (DBPFP). The results indicated that each treatment process reduced DBPFP, as measured by trihalomethane formation potential (THMFP) and haloacetic acid formation potential (HAAFP), with the SF + O3-BAC + NF process being the most effective (14.27 μg/L and 14.88 μg/L), followed by the SF + NF process (21.04 μg/L and 16.29 μg/L) and the UF + NF process (26.26 μg/L and 21.75 μg/L). Tyrosine, tryptophan, and soluble microbial products were identified as the major DBP precursors during chlorination, with their fluorescence intensity decreasing gradually as water treatment progressed. Additionally, while large molecular weight organics (60–100,000 KDa) played a minor role in DBPFP, small molecular weight organics (0.2–5 KDa) were highlighted as key contributors to DBPFP, and medium molecular weight organics (5–60 KDa) could adhere to the membrane surface and reduce DBPFP. Based on these findings, the combined NF process can be reasonably selected for controlling DBP formation, with potential long-term benefits for human health.

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.

Far-UVC Photolysis of Peroxydisulfate for Micropollutant Degradation in Water.

Increasing radical yields to reduce UV fluence requirement for achieving targeted removal of micropollutants in water would make UV-based advanced oxidation processes (AOPs) less energy demanding in the context of United Nations' Sustainable Development Goals and carbon neutrality. We herein demonstrate that, by switching the UV radiation source from conventional low-pressure UV at 254 nm (UV254) to emerging Far-UVC at 222 nm (UV222), the fluence-based concentration of HO• in the UV/peroxydisulfate (UV/PDS) AOP increases by 6.40, 2.89, and 6.00 times in deionized water, tap water, and surface water, respectively, with increases in the fluence-based concentration of SO4•- also by 5.06, 5.81, and 55.47 times, respectively. The enhancement to radical generation is confirmed using a kinetic model. The pseudo-first-order degradation rate constants of 16 micropollutants by the UV222/PDS AOP in surface water are predicted to be 1.94-13.71 times higher than those by the UV254/PDS AOP. Among the tested water matrix components, chloride and nitrate decrease SO4•- but increase HO• concentration in the UV222/PDS AOP. Compared to the UV254/PDS AOP, the UV222/PDS AOP decreases the formation potentials of carbonaceous disinfection byproducts (DBPs) but increases the formation potentials of nitrogenous DBPs.

Application and environmental impact of loose nanofiltration in surface water treatment

Loose nanofiltration (LNF) membranes with a molecular weight cutoff (MWCO) of about 1000 Da have great potential for high selectivity between natural organic matter (NOM) and mineral salts. Therefore, they are interesting for treatment plants for purifying oligotrophic lake waters with an elevated NOM concentration. This study was conducted to determine the design and operational expenses as well as the environmental impact of an LNF-based drinking water treatment process that removes NOM from Finnish surface water. Two LNF membranes with similar MWCOs were selected, and the results were compared to ultrafiltration, nanofiltration, and conventional treatment. One LNF membrane demonstrated a rejection rate of NOM higher than 95 % and a low rejection rate of hardness at about 40 %, while the other LNF membrane performed similarly to an ultrafiltration membrane. The LNF-based treatment process would increase operational expenses by 53—69 % but at the same time decrease the environmental impact by >18 %. Improved removal of aromaticity and low molecular weight compounds could lower the disinfection byproduct formation potential and microbial growth in the network, thus reducing the required chlorine dosage in the network and possibly bringing further cost savings.

Hydrology Predominates Over Harvest History and Landscape Variation to Control Water Quality and Disinfection Byproduct Formation Potentials in Forested Pacific Coast Watersheds.

Despite the global importance of forested watersheds as sources of drinking water, few studies have examined the effects of forestry on drinking water treatability. Relatively little is known about how the interaction between landscape variation and flow impacts source water quality and what this interaction means for drinking water treatability. To address this knowledge gap, we examined variability in sediments, dissolved organic matter, and disinfection byproduct formation potentials (DBP-FPs) across a range of flow conditions in four small watersheds with contrasting forest harvest histories and soil characteristics on Vancouver Island. Storm event-driven change in streamflow was the primary driver of water quality and DBP-FPs at our sites, with greater changes during stormflow (e.g., a 3-fold increase in dissolved organic carbon concentrations) than those across contrasting watersheds. Flow-driven changes in water quality and DBP-FPs were not significantly different across watersheds with different harvest histories; muted responses may be attributed to widespread second growth forests (i.e., recent harvesting effects may be confounded by historical harvest), forestry practices (e.g., slash burning), or soils with low organic carbon storage. This study suggests that variation in hydrology predominates over harvest history and soil characteristics to drive water quality and DBP-FPs on the east coast of Vancouver Island.

Changes of characteristics and disinfection by-products formation potential of intracellular organic matter with different molecular weight in metalimnetic oxygen minimum

Metalimnetic oxygen minimum (MOM) occurs in reservoirs or lakes due to stratification and algal blooms, which has low dissolved oxygen (DO) levels and leads to the deterioration of water quality. The transformation mechanism and the impact on the water quality of intracellular organic matter (IOM) derived from algae are poorly understood under MOM conditions. In this study, IOM extracted by Microcystis aeruginosa was divided into five components according to molecular weight (MW), and the changes of characteristics and correlated disinfection by-products formation potential (DBPFP) were analyzed and compared under MOM conditions. The removal efficiency of dissolved organic carbon (DOC) in the <5 kDa fraction (66.6%) was higher than that in the >100 kDa fraction (41.8%) after a 14-day incubation under MOM conditions. The same tendency also occurred in Fmax and DBPFP. The decrease in Fmax was mainly due to the decline in tryptophan-like and tyrosine-like for all IOM fractions. The diversity of microorganisms degrading the MW > 100 kDa fraction was lower than others. Besides low MW fractions, these findings indicated that more attention should be paid to high MW fractions which were resistant to biodegradation under MOM conditions during water treatment.

Application of EEM fluorescence spectroscopy for characterizing organic DBP precursors in different water sources: a review

Abstract Disinfection by-products (DBPs), generated from the reaction of disinfectants with DBP precursors, have been found to pose unintentional risks to human health. Considering that the concentration and speciation of DBPs formed during disinfection will be affected by the content and composition of dissolved organic matter (DOM), widespread concern about the characteristics of DBP precursors in water sources have been prompted. Three-dimensional excitation–emission matrix (EEM) can quickly and efficiently determine the properties and composition of DOM in water, and thus is generally used to investigate the origin of DBP precursors in water sources. This study overviews the fluorescent properties of different DBP precursors, summarizes the application of different EEM interpretation methods in DBP precursors and analyses the key factors affecting the correlation between the fluorescent components and DBP precursors (e.g., natural organic matter, algal organic matter, effluent organic matter and organic matter derived from other sources). A series of factors, including composition of fluorophores, bromide concentration, spatio-temporal characteristics and disinfectant types, could impact the correlation between DBP formation potential and fluorescent components. As for future research needs, it is of significance to select suitable fluorescence analysis methods and investigate the combination of EEM with other characterization technologies based on different situations.

Disinfection by-products control in wastewater effluents treated with ozone and biological activated carbon followed by UV/Chlor(am)ine processes

Sequential utilization of ozone (O3) and biological activated carbon (BAC) followed by UV/chlor(am)ine advanced oxidation process (AOP) has drawn attention in water reuse. However, the formation of disinfection by-products (DBPs) in this process is less evaluated. This study investigated the DBP formation and the relevant toxicity during the O3-BAC-UV/chlor(am)ine treatment of sand-filtered municipal secondary effluent. DBP formation in UV/chlorine and UV/dichloramine (NHCl2) processes were compared, where the impact of key operational parameters (e.g., UV wavelength, pH) on DBP formation were comprehensively evaluated. O3-BAC significantly reduced DBP formation potential (DBPFP) (58.2 %). Compared to UV/chlorine AOP, UV/NHCl2 AOP reduced DBP formation by 29.7 % in short-time treatment, while insignificantly impacting on DBPFP (p > 0.05). UV/NHCl2 AOP also led to lower calculated cytotoxicity (67.7 %) and genotoxicity (55.9 %) of DBPs compared to UV/chlorine AOP. Compared to 254 nm UV light, the utilization of 285 nm UV light decreased the formation of DBPs in wastewater treated with the UV/chlorine AOP and UV/NHCl2 AOP by 31.3 % and 19.2 %, respectively. However, the cytotoxicity and genotoxicity in UV/NHCl2 AOP using 285 nm UV light increased by 83.4 % and 58.5 %, respectively, compared to 254 nm. The concentration of DBPs formed in the UV/NHCl2 AOP at pH 8 was 54.3 % lower than that at pH 7, suggesting a better control of DBPs at alkaline condition. In the presence of bromide, UV/NHCl2 AOP tended to generate more brominated DBPs than UV/chlorine AOP. Overall, UV/NHCl2 AOP resulted in lower concentration and toxicity of DBPs compared to UV/chlorine AOP.

Spatiotemporal dynamics of dissolved organic matter and disinfection by-products formation potential of Shengzhong Lake in southwest China.

The quality and quantity of dissolved organic matter (DOM) in lakes as well as its environmental effects associated with the unintended disinfection by-products (DBPs) have received continuous attention. This work investigated the spatiotemporal dynamics of DOM in Shengzhong Lake in southwest China and the formed DBPs during the chlorine disinfection process. The results showed that lake water in summer had significantly higher dissolved oxygen and dissolved organic carbon than that in winter. In contrast, DOM in winter demonstrated an obviously higher aromaticity and molecular weight than that in summer. Four fluorescence components, i.e., terrestrial humic-like substances (C1), protein-like substances (C2), and microbial humic-like substances (C3 and C4), were identified, and their relative abundance followed in the order of C3 > C4 > C2 > C1 in winter and C4 > C3 > C1 > C2 in summer. The formation potential of trihalomethanes and haloacetic acids in winter was higher and lower than that in summer, which was mainly ascribed to the content of aromatic and hydrophobic substances. Compared to the significant seasonal dynamic, the spatial variation of DOM and the formed DBPs was not obvious. This work sheds light on the spatial-temporal distribution of DOM and the potentially formed DBPs in Shengzhong Lake, and will be helpful for understanding the biogeochemical cycle of carbon and assessing the drinking water safety.

Disinfection byproduct formation from chlorination of agricultural reuse water sources

Treatment of reuse water sources is critical for achieving proper water quality for the desired end-use. Disinfection is often achieved through chlorination, but this leads to the formation of toxic disinfection byproducts (DBPs). During reuse for agricultural purposes, it is important to reduce the potential for contamination of food crops and thereby minimize DBP production from treatment processes. This study evaluates the DBP formation potential from various reuse water sources under different reaction conditions to determine the implications of chlorination-derived DBPs for agricultural water reuse. Chlorination experiments were conducted on wastewater, stormwater, and farm lagoon water at pH 5, 6, 7, and with Br− addition. DBP concentrations were then evaluated in conjunction with initial concentrations of dissolved organic carbon (DOC), total nitrogen (TN), initial bromide, and specific UV-absorbance (SUVA). The most abundantly formed DBP class for nearly all sources was trihalomethanes (THMs), followed by nitrogenous DBPs (N-DBPs). Despite a high DOC concentration of 37.8 mg/L, lagoon source 2 only formed a total of 4.15 µg/L DBPs, likely due to oxidation of the inorganic nitrogen (54.8 mg/L TN) inhibiting DBP formation. Stormwater sources (DOC range 3.0-15.3 mg/L) had the highest DBP formation potential, with chloroform concentrations reaching up to 92 µg/L. Waters with lower DOC, TN and bromide and at lower pH ranges had less DBP formation potential for the compounds evaluated in this study. While SUVA did not prove to be a strong indicator of DBP formation, with increasing Br/UVA, there was an exponential increase in bromine substitution factor for THMs (R2=0.927, p < 0.0001) across all reuse sources. Toxicity-weighted DBP concentrations were also evaluated for all sources. Waters with higher TN and bromide content produced more toxic N-DBPs, mainly dichloroacetonitrile and dibromoacetonitrile.

Response mechanism of soil leachate and disinfection by-product formation to extreme precipitation events under continuous drought scenario

In this study, a rainfall simulation device was employed to investigate the response mechanism of soil leachate and disinfection by-products formation potential (DBPsFP) to extreme precipitation events. The results revealed that the aromaticity of dissolved organic matter (DOM) and the concentration of hydrophobic DOM containing aromatic carbon groups in leachate decreased with rising temperature. The humification degree of DOM decreased at 25 °C (99 mm/h), while the humification degree and protein-like level of DOM increased under high temperatures droughts (45 °C and 65 °C). Higher temperatures resulted in the leach of more microbial-derived humus and low molecular phenolic compounds from soil and broadened the range of molecular weight distribution. Increasing temperature increased DBPsFP and DBPs species and caused the precursors of haloacetic acids (HAAs) in leachate to become more hydrophobic, while the precursors of trihalomethanes (THMs) became more hydrophilic. Most importantly, the increased temperature attenuated the rainfall-mediated dilution of organic pollutant concentration, and temperature has a more significant effect than extreme rainfall in DOM abundance and the formation potential (or species) of DBPs. The results help to better understand the impact of climate change on the physicochemical processes of water quality.

Using machine learning to trace the pollution sources of disinfection by-products precursors compared to receptor models

To increase the efficiency of managing backup water resources, it is critical to identify and allocate pollution sources. Source apportionment of dissolved organic matter (DOM) was investigated in our work. Parallel factor analysis (PARAFAC) and the Spearman correlation analysis were used for source identification. After that, a newly hybrid model applying the fuzzy c-means and support vector regression (FCM-SVR) was employed for source apportionment compared to receptor models. The results demonstrated that the FCM-SVR model exhibited excellent generalization, and only required standardization and normalization as pre-processing steps for dataset. According to the results, microbial sources played a key role (28.1 %) in the formation potential of disinfection byproducts (DBPFPs). Additionally, shipping marine sources exhibited a substantial contribution (21.2 %) to DBPFPs. The prediction accuracy of DBPFPs was matched or exceeded receptor models, and the R2 of DOC (0.884) was significantly high. Therefore, we recommend the FCM-SVR model combined with PARAFAC to trace the source of DBPFPs as its significant effectiveness in source identification, source apportionment, and prediction accuracy, possessing the potential for further applicability in tracking more organic compounds. Environmental implicationThe disinfection byproducts precursors in water sources, which were thought to be hazardous materials in this study, are proved to be chlorinated into carcinogenic disinfection byproducts (DBPs) during drinking water treatment, However, the source apportionment methods of DBPs are not well developed compared to other inorganic matter, e.g., heavy metals and ammonia nitrogen. We proposed a new FCM-SVR model to trace the source of DBPs, which required easier pre-treatment and resulted a better source apportionment and prediction accuracy. As a result, it could provide a different prospect and useful management advices to trace the source of DBPs.

Synergistic disinfection effects and reduction of disinfection by-products in water treatment using magnetic quaternized cyclodextrin polymer combined with chorine disinfection process

Disinfection is vital in ensuring water safety. However, the traditional chlorine disinfection process is prone to producing toxic and harmful disinfection by-products (DBPs). The combination of quaternary ammonium polymer and the chlorine disinfection process can solve this shortcoming. Currently, research on the control of DBPs through the combined process is not systematic and the control effect between reducing the dosage of disinfectants and DBPs remains to be studied. Quaternized cyclodextrin polymers have attracted increasing attention due to their excellent adsorption and antibacterial properties, but their synergistic effect with chlorine disinfection is still unclear. In this study, a magnetic quaternized cyclodextrin polymer (MQCDP) is synthesized in an ionic liquid green system, and a combined process of MQCDP treatment and chlorine disinfection is established. The disinfection performance of the combined process on the actual water body along with its reducing effect on the amount of chlorine disinfectant as well as the trihalomethanes (THMs) and haloacetic acids (HAAs) DBPs are explored. MQCDP has a porous structure with a specific surface area of 825 m2 g−1 and is easily magnetically separated. MQCDP can remove most of the natural organic matter (UV254 absorbance decreased by 97 %) in the water at the dosage of 1 g L−1 and kill bacteria with a sterilization rate of 85 %. Compared with disinfection using chlorine alone, the combined process has higher disinfection efficiency and significantly reduces the amount of disinfectant used. A concentration of 5 mg/L of NaClO was needed to meet the standard by chlorine disinfectant alone, while only 2 mg/L of NaClO can meet the standard for the combined process, indicating 60 % of the chlorine demand was reduced. More importantly, the combined process can significantly reduce the generation potential of DBPs. When 10 mg/L of NaClO is added, the THMs and HAAs generated by the combined process decreased by 65 % and 34 %, respectively, compared with the levels produced by single chlorine disinfection. The combined process can reduce the dosage of chlorine disinfectant and MQCDP can adsorb humic acid DBP precursors in raw water, thus lowering the generation of DBPs during disinfection. In summary, MQCDP has excellent separation and antibacterial ability, and its synergistic effects combined with the chlorine disinfection process are of great significance for controlling the amount of disinfectant and the formation potential of DBPs, which has potential applications in actual water treatment.

Characterization of dissolved organic matter and disinfection by-product formation potentials during the metalimnetic oxygen minimum in deep reservoirs

Abstract Dissolved oxygen (DO) is strongly linked to the origin and transformation of dissolved organic matter (DOM) in reservoirs. During metalimnetic oxygen minimum (MOM), the reservoir is divided into four regions: surface oxygen-rich (SOR), middle anoxic (MA), middle oxygen (MO), and bottom anoxic (BA). This article focuses on the link between DOM and disinfection by-product (DBP) precursors and DO in reservoirs. The DOM in SOR was characterized by the highest proportion of protein-like components, lowest humification and aromaticity, which was indicated mainly affected by algae blooms. The DOM in MO was affected by terrestrial, with the highest ratio of humic and fulvic-like fluorescent and the highest extent of humification and aromaticity. The humification and aromaticity in MA and BA were between MO and SOR water. Moreover, according to redundancy analysis, the dominant DBPs, including trichloromethane and haloacetic acid precursors, mainly originate from a high degree of humification and aromaticity in DOM, suggesting that the terrestrial-derived DOM was a dominant source of DBP precursors. This study provides the distribution in DOM characteristics and its driven DBPs in the Sanhekou Reservoir during the MOM, which is of great significance for selecting appropriate water intake regions for subsequent water treatment.

Nontargeted identification of disinfection by-product precursors from soluble microbial products in municipal secondary effluent

As soluble microbial products (SMPs) can serve as precursors for disinfection by-products (DBPs), the release of SMPs from municipal secondary effluent has the potential to increase the health hazards associated with reused water. Nontargeted identification of DBPs precursors from SMPs in municipal secondary effluent was explored in the present research. The hydrophobic (HPO) fraction that constituted the major portion of the SMPs was 48.0%, and the majority of organic SMPs were composed of low molecular weight (LMW) compounds. The results showed that the HPO fraction with MW < 1 kDa component has the highest disinfection by-product formation potentials (DBPFPs). X-ray photoelectron spectroscopy (XPS) results showed that the HPO fraction with MW < 1 kDa component was mainly composed of OC–OH (40.2%) and amide/peptide N (46.7%) functional groups. This finding was in line with the results showing the highest yields of DBPFPs in terms of HAAs (haloacetic acids) and trichloroacetamide (TCAcAm). Ultra-performance liquid chromatography coupled with tandem quadrupole-time-of-flight mass spectrometry (UPLC-Q-ToF-MS) data revealed that phospholipids, fatty acids, fatty acyls-fatty amides, phosphatidylcholine, glycosides, fatty acid esters, glycolipid, and steroids were the main chemical classes in SMPs. Among these chemical classes, phospholipids containing amino acids structures and fatty acids containing carboxyl functional groups with the maximum abundance could promote the formation of HAAs. This research offers a thorough characterization of SMPs derived from municipal secondary effluent. These results enable the implementation of targeted methods to decrease the formation of DBPs by identifying potential precursors of DBPs.

Aging of polystyrene microplastics by UV/Sodium percarbonate oxidation: Organic release, mechanism, and disinfection by-product formation

The occurrence and transformation of microplastics (MPs) in environment has attracted considerable attention. However, the release characteristics of MP-derived dissolved organic matter (MP-DOM) under oxidation conditions and the effect of DOM on subsequent chlorination disinfection by-product (DBP) still lacks relevant information. This study focused on the conversion of polystyrene microplastics (PSMPs) in the advanced oxidation of ultraviolet-activated sodium percarbonate (UV/SPC-AOP) and the release characteristics of MP-DOM. The DBP formation potential of MP-DOM was also investigated. As a result, UV/SPC significantly enhanced the aging and fragmentation of PSMPs. Under UV irradiation, the fluorescence peak intensity and position of humus-like and protein-like components of MP-DOM were correlated with SPC concentration. The aging MP suspension was analyzed by gas chromatography–mass spectrometry (GC-MS), and various alkyl-cleavage and oxidation products were identified. Quenching experiments and electron paramagnetic resonance (EPR) detection confirmed that carbonate and hydroxyl radicals jointly dominated the conversion of PSMPs. The formation of DBP was related to the components of MP-DOM. Overall, these results help to understand the aging behavior of MPs in AOP. Moreover, MP-DOM released by MPs after AOP oxidation may be a precursor of DBPs, which deserved more attention.

Modeling source water disinfection byproducts formation potential using environmental variables

AbstractPredictive models of disinfection byproducts (DBPs) formation in treated drinking water have been widely used to guide operational decisions. However, very few studies have addressed the issue of managing DBPs through watershed protection programs and proactive management of water supply systems through predictive modeling of DBP formation potential in source waters. Here, we propose a two‐component, simple statistical approach to predict the formation potentials of the sum of five haloacetic acids (HAA5fp) and total trihalomethanes (TTHMfp) in source water streams using environmental variables and ultraviolet absorbance at 254 nm wavelength (UV254) as a surrogate for DBP precursors. In the first component of the model, using three feature selection regression models and cross‐validation of subsets of the selected predictors, we identified three commonly monitored variables—streamflow, soil temperature, and total phosphorus for predicting UV254. In the second component, HAA5fp and TTHMfp are predicted from UV254. The approach is successfully demonstrated for two source water streams of the New York City water supply system (R2 was 0.8, and 0.7–0.8 for the two model components). Long‐term predictions of HAA5fp and TTHMfp showed distinct seasonal patterns that are linked to differences in land uses of the two watersheds. Moreover, sensitivity analysis showed that transport processes were important in one watershed whereas production processes were more important in the other.

Effective control of DBPs formation and membrane fouling in catalytic ozonation membrane reactor for municipal wastewater reclamation

This study aimed to evaluate the performance of different ceramic membranes, namely CuMn2O4 (CMO), g-C3N4 (CN), and CuMn2O4/g-C3N4 (CMO/CN) ceramic membrane (CM), in a catalytic ozonation membrane reactor (COMR) for municipal wastewater reclamation. The results demonstrated that CMO/CM and CMO/CN/CM used in the COMR exhibited high performance in terms of flux, removal efficiency of effluent organic matter (EfOM), control of disinfection by-products formation potential (DBPs-FP), and mitigation of membrane fouling. Notably, catalytic ozonation by CMO/CM showed superior reduction in DBPs formation (40.6 % of nitrogenous DBPs, 83.4 % of halogenated hydrocarbons, 36.6 % of haloacetic acids). Furthermore, significant inhibition of both organic fouling and biofouling was observed in the COMR. The addition of O3 altered the membrane fouling mechanism from gel layer formation to intermediate blocking. Ozonation primarily reduced the physically reversible fouling while catalytic ozonation additionally mitigated physically irreversible fouling. In addition to the almost complete removal of total cells and proteins, catalytic ozonation by CMO/CM further cleaned the α-polysaccharides and β-polysaccharides on the membrane surface, resulting in a 55.3 % reduction in biofilm thickness and demonstrating strong self-cleaning properties. These findings have important implications for enhancing the overall performance and durability of COMR systems in municipal wastewater reclamation.