Effect of oxidation ditch and anaerobic-anoxic-oxic processes on CX3R-type disinfection by-product formation during wastewater treatment

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 IMPLICATION: The 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.

Perspectives and understanding on the occurrence, toxicity and abatement technologies of disinfection by-products in drinking water

Disinfection by-products (DBPs) are one of the significant emerging contaminants that have caught the attention of researchers worldwide due to their pervasiveness. Their presence in drinking water, even in shallow concentrations (in levels of parts per billion), poses considerable health risks. Therefore, it is crucial to understand their kinetics to understand better their formation and persistence in the water supply systems. This manuscript demonstrates different aspects of research carried out on DBPs in the past. A systematic approach was adopted for the bibliographical research that started with choosing appropriate keywords and identifying the most relevant manuscripts through the screening process. This follows a quantitative assessment of the extracted literature sample, which included the most productive and influential journal sources, the most widely used keywords, the most influential authors active in the research domain, the most cited articles, and the countries most actively engaged in the research field. Critical observations on the literature sample led to the qualitative assessment, wherein the past and current research trends were observed and reported. Finally, we identified the essential gaps in the available literature, which further led to recommending the course ahead in the research domain. This study will prove fruitful for young and established researchers who are or wish to work in this emerging field of research.

Smart Stimulation Response of a Pyrene-Based Lanthanide(III) MOF: Fluorescence Enhancement to HX (F and Cl) or R-COOH and Artificial Applicable Film on HCl Vapor Sensing

Toxic acids produced by industries are major hazards to the environment and human health, and luminescent pyrene-based crystalline metal-organic frameworks (MOFs) demonstrate promising performance in the detection of toxic acids. Herein, two novel isostructural 3D porous lanthanide MOFs, H3O·[Ln3(TBAPy)2(μ2-H2O)2(OH)2]·2DMA·2Diox·6.5H2O (Ln = Pr (1) and Ce (2); H4TBAPy (1,3,6,8-tetrakis(p-benzoic acid)pyrene); and DMA: N,N-dimethylacetamide) were synthesized, which showed alb topology. Based on the protonation and hydrogen bond mechanism, complex 1 could be used as a fluorescence recognition sensor for HX (X = F, Cl, Br, and I) acid solutions with different luminescence behaviors. It is worth noting that complex 1 exhibited high sensitivity in the fluorescence enhancement sensing of hydrofluoric acid, oxalic acid, and trichloroacetic acid. In particular, complex 1 had a low limit of detection (LOD) for OA (0.1 μM) and was applied to real monitoring of orange fruit samples. In addition, the PVA@1 film could selectively, sensitively, and quantitatively respond to hydrochloric acid (HCl) vapor through fluorescent quenching; due to its protonation and adsorption capacity, the LOD was 0.18 ppm. Therefore, the portable optical device, the PVA@1 film, can detect HCl gas in trace amounts, achieving the ultimate goal of real-time and rapid detection, which has potential application value for industrial production safety.

Characteristics in dissolved organic matter and disinfection by-product formation during advanced treatment processes of municipal secondary effluent with Orbitrap mass spectrometry

Dissolved organic matter (DOM) is reported to be a precursor to disinfection by-products (DBPs), which have adverse effects on human health. Therefore, it is crucial to effectively remove DOM before water disinfection. Characteristics of DOM and DBPs formation during advanced treatment processes including coagulation, adsorption, ultraviolet (UV) irradiation, and ozone (O3) oxidation in municipal secondary effluent were investigated in this research. DOM was characterized by Fourier transform infrared spectroscopy (FTIR), excitation-emission matrix fluorescence spectroscopy (EEM), and Orbitrap mass spectrometry (Orbitrap MS). Moreover, DBPs formation potential under different advanced treatment processes was also discussed. FTIR results indicated that various functional groups existing in DOM may react with the disinfectant to form toxic DBPs. EEM analysis indicated that DOM in all water samples was dominated by soluble microbial product-like (SMPs) and humic acid-like (HA) substances. The municipal secondary effluent was abundant with DOM and rich in carbon, hydrogen, oxygen, and nitrogen atoms, contained a certain dosage of phosphorus and sulfur atoms, and the highest proportion is lignin. Most of the precursors (CHO features) had positive double bond equivalent subtracted oxygen per carbon [(DBE-O)/C] and negative carbon oxidation state (Cos) in all four different advanced treatment processes. DBPs formation potential (DBPFP) of coagulation, adsorption, UV irradiation, and O3 oxidation advanced treatment processes were 487 μg L-1, 586 μg L-1, 597 μg L-1, and 308 μg L-1, respectively. And the DBPs precursors removal efficiency of coagulation, adsorption, UV irradiation, and O3 oxidation advanced treatment processes were 50.8%, 40.8%, 39.8%, and 69.0%, respectively. This study provides in-depth insights into the changes of DOM in municipal secondary effluent at the molecular level and the removal efficiency of DBPs precursors during coagulation, adsorption, UV irradiation, and O3 oxidation advanced treatment processes.

Insight into suppression of dibutyl phthalate on DOM removal during municipal sewage treatment using fluorescence spectroscopy with PARAFAC and moving-window 2D-COS

Dibutyl phthalate (DBP) has been widely detected in municipal and industrial wastewater, which could indirectly inhibit pollutant removals, especially degradation of dissolved organic matter (DOM). Here, the inhibition of DBP on DOM removal from wastewater in pilot-scale A2O-MBR system was investigated by fluorescence spectroscopy with two-dimensional correlation (2D-COS) and structural equation modeling (SEM). Seven components were extracted from DOM using parallel factor analysis, i.e., tryptophan-like (C1 and C2), fulvic-like (C4), tyrosine-like (C5), microbial humic-like (C6) and heme-like (C7). The tryptophan-like had a blue-shift at DBP occurrence, defined as blue-shift tryptophan-like (C3). DBP with 8 mg L^-1 exhibited a stronger inhibition on removals of DOM fractions, extraordinarily tyrosine-like and tryptophan-like in anoxic unit than DBP of 6 mg L^-1 by moving-window 2D-COS. The indirect removals of C1 and C2 through the C3 removal were more strongly inhibited by 8 mg L^-1 DBP than those by 6 mg L^-1 DBP, while the former exhibited a weaker inhibition on the direct degradation of C1 and C2 than the latter via SEM. Based on metabolic pathways, abundances of key enzymes secreted by microorganism in anoxic unit, degrading tyrosine-like and tryptophan-like, were higher in wastewater with 6 mg L^-1 DBP than those with 8 mg L^-1 DBP. These could provide a potential approach for online monitoring of DBP concentrations in wastewater treatment plants, which could rectify operating parameters, and then enhance the treatment efficiencies.

Potential Disrupting Effects of Wastewater-Derived Disinfection Byproducts on Chinese Rare Minnow (Gobiocypris rarus) Transthyretin: An In Vitro and In Silico Study

The available information about whether wastewater-derived disinfection byproducts (DBPs) could elicit potential endocrine-related detrimental effects on aquatic organisms was scarce. Herein, the potential disrupting effects and underlying binding mechanism of 14 wastewater-derived aliphatic and aromatic DBPs and 12 other substances on Chinese rare minnow (Gobiocypris rarus) transthyretin (CrmTTR) were tested and revealed by in vitro and in silico methods. The amino acid sequences of CrmTTR were determined, and the recombinant CrmTTR with a molecular mass of 66.3 kDa was expressed and purified. In vitro assay results indicated that eight selected aromatic DBPs exhibited detectable CrmTTR disrupting ability. Meanwhile, six aliphatic DBPs were not CrmTTR binders. Molecular modeling results implied that hydrophobic hydrogen bonds and/or ionic pair interactions were non-negligible. Four binary classification models with high classification performance were constructed. A significant positive linear relationship was observed for the binding affinity data from CrmTTR and human TTR (n = 18, r = 0.922, p < 0.0001). However, the binding affinity for 13 out of 18 tested compounds with CrmTTR was higher than that with human TTR. All the results highlighted that some wastewater-derived DBPs may be potential disruptors on the aquatic organism endocrine system, and interspecies variation should not be neglected in future determination of the potential endocrine disrupting effects of wastewater-derived DBPs.

The characteristic of N-nitrosodimethylamine precursor release from algal organic matter and degradation performance of UV/H2O2/O3 technology

Seasonal cyanobacterial blooms in eutrophic water releases algal organic matter (AOM), which contains large amount of dissolved organic nitrogen (DON) and is difficult to be removed effectively by conventional treatment processes (e.g., coagulation and sand filtration) because of its high hydrophilicity. Moreover, N-nitrosodimethylamine (NDMA) can be generated by the reaction of AOM with disinfectants in the subsequent disinfection process. In this study, the formation of NDMA from different AOM components was explored and the control of algal-derived NDMA precursors by UV/H₂O₂/O₃ was evaluated. The results showed that the hydrophilic and polar components of AOM with the low molecular weight had higher NDMA yields. UV-based advanced oxidation process (AOPs) is effective in degrading NDMA precursors, while the removal rate can be affected greatly by UV doses. The removal rate of NDMA precursors by UV/H₂O₂/O₃ is higher than by UV/H₂O₂ or UV/O₃ which can reach 95% at the UV dose of 400 mJ/cm². An alkaline environment reduces the oxidation efficiency of UV/H₂O₂/O₃ technology, while an acidic environment is conducive to its function. Inorganic anions such as HCO₃^-, SO₄^2-, Cl^- and NO₃^- are potential to compete with target algal-derived NDMA precursors for the oxidants reaction and inhibit the degradation/removal of these precursors. The degradation of algal-derived NDMA precursors by UV/H₂O₂/O₃ is mainly accomplished by the oxidation of DON with secondary amide groups, and the main degradation mechanism by UV/H₂O₂/O₃ was through the initial decomposition of macromolecular organic compounds such as biopolymers and humic substances and the further degradation of resulting small molecular components.

Transformation of antiviral ribavirin during ozone/PMS intensified disinfection amid COVID-19 pandemic

Due to the spread of coronavirus disease 2019 (COVID-19), large amounts of antivirals were consumed and released into wastewater, posing risks to the ecosystem and human health. Ozonation is commonly utilized as pre-oxidation process to enhance the disinfection of hospital wastewater during COVID-19 spread. In this study, the transformation of ribavirin, antiviral for COVID-19, during ozone/PMS‑chlorine intensified disinfection process was investigated. •OH followed by O₃ accounted for the dominant ribavirin degradation in most conditions due to higher reaction rate constant between ribavirin and •OH vs. SO₄•^- (1.9 × 10⁹ vs. 7.9 × 10⁷ M^-1 s^-1, respectively). During the O₃/PMS process, ribavirin was dehydrogenated at the hydroxyl groups first, then lost the amide or the methanol group. Chloride at low concentrations (e.g., 0.5- 2 mg/L) slightly accelerated ribavirin degradation, while bromide, iodide, bicarbonate, and dissolved organic matter all reduced the degradation efficiency. In the presence of bromide, O₃/PMS process resulted in the formation of organic brominated oxidation by-products (OBPs), the concentration of which increased with increasing bromide dosage. However, the formation of halogenated OBPs was negligible when chloride or iodide existed. Compared to the O₃/H₂O₂ process, the concentration of brominated OBPs was significantly higher after ozonation or the O₃/PMS process. This study suggests that the potential risks of the organic brominated OBPs should be taken into consideration when ozonation and ozone-based processes are used to enhance disinfection in the presence of bromide amid COVID-19 pandemic.

Risks, characteristics, and control strategies of disinfection-residual-bacteria (DRB) from the perspective of microbial community structure

The epidemic of COVID-19 has aroused people's particular attention to biosafety. A growing number of disinfection products have been consumed during this period. However, the flaw of disinfection has not received enough attention, especially in water treatment processes. While cutting down the quantity of microorganisms, disinfection processes exert a considerable selection effect on bacteria and thus reshape the microbial community structure to a great extent, causing the problem of disinfection-residual-bacteria (DRB). These systematic and profound changes could lead to the shift in regrowth potential, bio fouling potential, as well as antibiotic resistance level and might cause a series of potential risks. In this review, we collected and summarized the data from the literature in recent 10 years about the microbial community structure shifting of natural water or wastewater in full-scale treatment plants caused by disinfection. Based on these data, typical DRB with the most reporting frequency after disinfection by chlorine-containing disinfectants, ozone disinfection, and ultraviolet disinfection were identified and summarized, which were the bacteria with a relative abundance of over 5% in the residual bacteria community and the bacteria with an increasing rate of relative abundance over 100% after disinfection. Furthermore, the phylogenic relationship and potential risks of these typical DRB were also analyzed. Twelve out of fifteen typical DRB genera contain pathogenic strains, and many were reported of great secretion ability. Pseudomonas and Acinetobacter possess multiple disinfection resistance and could be considered as model bacteria in future studies of disinfection. We also discussed the growth, secretion, and antibiotic resistance characteristics of DRB, as well as possible control strategies. The DRB phenomenon is not limited to water treatment but also exists in the air and solid disinfection processes, which need more attention and more profound research, especially in the period of COVID-19.