Disinfection Byproducts and Their Precursors in Drinking Water Sources:Origins,Influencing Factors,and Environmental Insights

Tracing the contamination origins in water sources and identifying the impacts of natural and human processes are essential for ecological safety and public health.However,current analysis approaches are not ideal,as they tend to be laborious,time-consuming,or technically difficult.Disinfection byproducts(DBPs)are a family of well-known secondary pollutants formed by the reactions of chemical disinfectants with DBP precursors during water disinfection treatment.Since DBP precursors have various origins(e.g.,natural,domestic,industrial,and agricultural sources),and since the formation of DBPs from different precursors in the presence of specific disinfectants is distinctive,we argue that DBPs and DBP precursors can serve as alternative indicators to assess the contamination in water sources and identify pollution origins.After providing a retrospective of the origins of DBPs and DBP precursors,as well as the specific formation patterns of DBPs from different precursors,this article presents an overview of the impacts of various natural and anthropogenic factors on DBPs and DBP precursors in drinking water sources.In practice,the DBPs(i.e.,their concentration and speciation)originally present in source water and the DBP precursors determined using DBP formation potential tests—in which water samples are dosed with a stoichiometric excess of specific disinfectants in order to maximize DBP formation under certain reaction conditions—can be considered as alternative metrics.When jointly used with other water quality parameters(e.g.,dissolved organic carbon,dissolved organic nitrogen,fluorescence,and molecular weight distribution)and specific contaminants of emerging concern(e.g.,certain pharmaceuticals and personal care products),DBPs and DBP precursors in drinking water sources can provide a more comprehensive picture of water pollution for better managing water resources and ensuring human health.

Efficacy of graphene nanocomposites for air disinfection in dental clinics: A randomized controlled study

BACKGROUND Aerosols containing disease-causing microorganisms are produced during oral diagnosis and treatment can cause secondary contamination.AIM To investigate the use of graphene material for air disinfection in dental clinics by leveraging its adsorption and antibacterial properties.METHODS Patients who received ultrasonic cleaning at our hospital from April 2023 to April 2024.They were randomly assigned to three groups(n=20 each):Graphene nanocomposite material suction group(Group A),ordinary filter suction group(Group B),and no air suction device group(Group C).The air quality and air colony count in the clinic rooms were assessed before,during,and after the procedure.Additionally,bacterial colony counts were obtained from the air outlets of the suction devices and the filter screens in Groups A and B.RESULTS Before ultrasonic cleaning,no significant differences in air quality PM2.5 and colony counts were observed among the three groups.However,significant differences in air quality PM2.5 and colony counts were noted among the three groups during ultrasonic cleaning and after ultrasonic treatment.Additionally,the number of colonies on the exhaust port of the suction device and the surface of the filter were significantly lower in Group A than in Group B(P=0.000 and P=0.000,respectively).CONCLUSION Graphene nanocomposites can effectively sterilize the air in dental clinics by exerting their antimicrobial effects and may be used to reduce secondary pollution.

Effect of Different Disinfection Methods on Calluses of Amorphophallus albus P.Y.Liu&J.F.Chen

This study aimed to examine the effect of different disinfection methods on the callus of Amorphophallus albus in the tissue culture and rapid propagation system.The calluses induced from buds of A.albus were disinfected with benzalkonium bromide,mercury bichloride,sodium hypochlorite,and ethanol,respectively,for different time periods.The growth of calluses was compared between different treatments and observed in detail by dissection.The results showed that the disinfection with 0.1% mercury bichloride for 5 min and 75% ethanol for 5 s had mild effect on the callus,with the lowest browning rates of 16.32% and 15.46% and the lowest vitrification rates of 3.24% and 9.72%,respectively,after 20 d.The disinfection with benzalkonium bromide and sodium hypochlorite had strong effect on the callus cells,with the lowest browning rate of 50.69% and 25.12% and the lowest vitrification rates of 28.47% and 28.43%,respectively.The cytological observation result showed that the calluses disinfected with ethanol and mercury bichloride showcased compact structures,while those disinfected with sodium hypochlorite and benzalkonium bromide exhibited loose structures.To sum up,it is recommended that 75% ethanol or 0.1% mercury bichloride can be used for disinfection in the tissue culture and rapid propagation of A.albus,while the use of benzalkonium bromide and sodium hypochlorite should be avoided as much as possible.

Evaluation of the Impact of Refined Quality Control Management Model on the Qualified Rate of Disinfection and Sterilization of Surgical Instruments in the Sterilization Supply Center

Objective:To evaluate the application value of a refined quality control management model for a sterilization supply center.Methods:A retrospective analysis was conducted on the work situation of the sterilization supply center from January 2021 to January 2023.The work situation before January 31,2022,was classified as the control group;a routine quality control management model was implemented,and the work situation after January 31,2022,was classified as the observation group.The quality of medical device management and department satisfaction between the two groups were compared.Results:The timely recovery and supply rate,classification and cleaning pass rate,disinfection pass rate,packaging pass rate,sterilization pass rate,and department satisfaction score in the observation group were all higher than those of the control group(P<0.05).Conclusion:Implementing a refined quality control management model in the sterilization supply center can improve the quality management level of medical devices and department satisfaction and is worthy of promotion.

Double enzyme mimetic activities of multifunctional Ag nanoparticle-decorated Co_(3)V_(2)O_(8)hollow hexagonal prismatic pencils for application in colorimetric sensors and disinfection

Since the catalytic activity of most nanozymes is still far lower than the corresponding natural enzymes,there is urgent need to discover novel highly efficient enzyme-like materials.In this work,Co_(3)V_(2)O_(8)with hollow hexagonal prismatic pencil structures were prepared as novel artificial enzyme mimics.They were then decorated by photo-depositing Ag nanoparticles(Ag NPs)on the surface to further improve its catalytic activities.The Ag NPs decorated Co_(3)V_(2)O_(8)(ACVPs)showed both excellent oxidase-and peroxidase-like catalytic activities.They can oxidize the colorless 3,3’,5,5’-tetramethylbenzidine rapidly to induce a blue change.The enhanced enzyme mimetic activities can be attributed to the surface plasma resonance(SPR)effect of Ag NPs as well as the synergistic catalytic effect between Ag NPs and Co_(3)V_(2)O_(8),accelerating electron transfer and promoting the catalytic process.ACVPs were applied in constructing a colorimetric sensor,validating the occurrence of the Fenton reaction,and disinfection,presenting favorable catalytic performance.The enzyme-like catalytic mechanism was studied,indicating the chief role of⋅O_(2)-radicals in the catalytic process.This work not only discovers a novel functional material with double enzyme mimetic activity but also provides a new insight into exploiting artificial enzyme mimics with highly efficient catalytic ability.

Curative effect of hydrogen peroxide combined with silver ion disinfection on pelvic floor dysfunction

BACKGROUND Pelvic floor dysfunction(PFD)is related to muscle fiber tearing during childbirth,negatively impacting postpartum quality of life of parturient.Appropriate and effective intervention is necessary to promote PFD recovery.AIM To analyze the use of hydrogen peroxide and silver ion disinfection for vaginal electrodes in conjunction with comprehensive rehabilitation therapy for postpartum women with PFD.METHODS A total of 59 women with PFD who were admitted to the hospital from May 2019 to July 2022 were divided into two groups:Control group(n=27)received comprehensive rehabilitation therapy and observation group(n=32)received intervention with pelvic floor biostimulation feedback instrument in addition to comprehensive rehabilitation therapy.The vaginal electrodes were disinfected with hydrogen peroxide and silver ion before treatment.Intervention for both groups was started 6 weeks postpartum,and rehabilitation lasted for 3 months.Pelvic floor muscle voltage,pelvic floor muscle strength,vaginal muscle voltage,vaginal muscle tone,pelvic floor function,quality of life,and incidence of postpartum PFD were compared between the two groups.RESULTS Before comprehensive rehabilitation treatment,basic data and pelvic floor function were not significantly different between the two groups.After treatment,the observation group showed significant improvements in the maximum voltage and average voltage of pelvic floor muscles,contraction time of type I and type II fibers,pelvic floor muscle strength,vaginal muscle tone,vaginal muscle voltage,and quality of life(GQOLI-74 reports),compared with the control group.The observation group had lower scores on the pelvic floor distress inventory(PFDI-20)and a lower incidence of postpartum PFD,indicating the effectiveness of the pelvic floor biostimulation feedback instrument in promoting the recovery of maternal pelvic floor function.CONCLUSION The combination of the pelvic floor biostimulation feedback instrument and comprehensive rehabilitation nursing can improve pelvic floor muscle strength,promote the recovery of vaginal muscle tone,and improve pelvic floor function and quality of life.The use of hydrogen peroxide and silver ion disinfectant demonstrated favorable antibacterial efficacy and is worthy of clinical application.

Performance Parameters:Demobilization Antibiotic Resistant Bacteria(ARB)and Carrying Genes(ARG)in Wastewater Disinfection

The UV irradiation is used for removing Antibiotic Resistant Bacteria(ARB)and Antibiotic Resistance Genes(ARG)from wastewater treatment.Bacteriophages are viruses that infect within bacteria,are recognized for bacterial control.The influence of some parameters in quantification and performance influencing of pathogen demobilization could be considered in disinfection of wastewater.The comparison of Polyvalent phage(NE1)versus Coliphage(NE4)in suppressing a bacterium Escherichia coli(NDM-1:b-lactam-resistant)with UV irradiation was observed the efficacy in reduction of cells in the disinfection and parameter process.The results with the effect of UV-C irradiation on NDM-1 infected with 1%of NE4 showed a decrease of cells from 8×10^(6)to 2×10^(5)in 60 min with UV-C dose.The NDM1(E.coli)was infected with 1%of NE4(Polyvalent Phage)under magnetic stirring for 1 h,the cells count was 8×10^(6).After 1 h in UV-C e×posure,the cells number reached 3×10^(5).The NDM1 that was e×posed in 1 h of UV-C irradiation and then was infected with 1%of NE4.Cells counting were done 24 h after this procedure.These cells were e×posed in UV-C and showed a reduction in the number of cells from 1×10^(8)to 4×10^(5)after 60 min.The results indicate that bacteriophages can mitigate bacteria species,and combined the conventional water disinfection technologies that can support the microbial safety control strategies.

Progress in Analytical Methods of Halogenated Disinfection By-Products

Ensuring the health and safety of drinking water is crucial for both nations and their citizens.Since the 20th century,the disinfection of drinking water,effectively controlling pathogens in water sources,has become one of the significant advances in public health.However,the disinfectants used in the process,such as chlorine and chlorine dioxide,react with natural organic matter in the water to produce disinfection by-products(DBPs).Most of these DBPs contain chlorine,and if the source water contains bromine or iodine,brominated or iodinated DBPs,collectively referred to as Halogenated disinfection byproducts(X-DBPs),are formed.Numerous studies have found that X-DBPs pose potential risks to human health and the environment,leading to widespread concern.Mass spectrometry has become an important means of discovering new types of X-DBPs.This paper focuses on the study of methods for analyzing X-DBPs in drinking water using mass spectrometry.

Effect of Disinfection Time on Microbial Content and Quality of Cold Fresh Chicken

[Objective] The aim was to provide reference for the production technolo- gy of cold fresh chicken. [Method] Lactic acid was used as the disinfectant in cooling water, so as to study the effect of disinfection time on the microbial content and quality of cold fresh chicken. [Result] With disinfection of 20 min, the removal rates of the total colonies, coliforms and moulds reached over 95%. As the disinfec- tion time was further extended, it had no significant effect on the removal effects of the microbial content and could affect the tenderness and color of cold fresh chick- en. [Cendusion] The study provides references for the design and optimization of the production process of cold fresh chicken.

Characterization of dissolved organic matter fractions and its relationship with the disinfection by-product formation

Dissolved organic matter （DOM） has been identified as precursor for disinfection by-products （DBPs） formation during chlorination. Recently, it has been demonstrated that the characteristics of DOM influence the DBPs formation mechanism. A study was, therefore, initiated to investigate the effects of DOM fractions on DBPs formation mechanism. In the chlorination process, organic acids are dominant precursors of total thihalomethanes （TTHM） because of the vc-o and unsaturated structures. Furthermore, the TTHM formation of organic acids was affected by pH more greatly. Based on the fluorescence spectroscopy analysis, DOM fractions contained several fluorescence substances. During chlorination, humic acid-like substances were found to exhibit high chlorine reactivity and hydrophobic organics decomposed to smaller molecules faster than hydrophilic organics even at lower chlorine dosages. Unlike hydrophobic fractions, hydrophilic organics showed no toxicity following chlorination, suggesting that the toxic structures in hydrophihc organics showed high chlorine reactivity during chlorination.

Waste Water Disinfection During SARS Epidemic for Microbiological and Toxicological Control

Objective To evaluate the disinfection of wastewater in China. Methods During the SARS epidemic occurred in Beijing, a study of different disinfection methods used in the main local wastewater plants including means of chlorine, chlorine dioxide, ozone, and ultraviolet was carried out in our laboratory. The residual coliform, bacteria and trihalomethanes, haloacetic acids were determined after disinfection. Results Chlorine had fairly better efficiency on microorganism inactivation than chlorine dioxide with the same dosage. Formation of THMs and HAAs does not exceed the drinking water standard. UV irradiation had good efficiency on microorganism inactivation and good future of application in China. Organic material and ammonia nitrogen was found to be significant on inactivation and DBPs formation. Conclusion Chlorine disinfection seems to be the best available technology for coliform and bacteria inactivation. And it is of fairly low toxicological hazard due to the transformation of monochloramine.

Simultaneous Control of Microorganisms and Disinfection By-products by Sequential Chlorination

Objective To introduce a new sequential chlorination disinfection process in which short-term free chlorine and chloramine are sequentially added. Methods Pilot tests of this sequential chlorination were carried out in a drinking water plant. Results The sequential chlorination disinfection process had the same or better efficiency on microbe （including virus） inactivation compared with the free chlorine disinfection process. There seemed to be some synergetic disinfection effect between free chlorine and monochloramine because they attacked different targets. The sequential chlorination disinfection process resulted in 35.7%-77.0% TTHM formation and 36.6%-54.8% THAA5 formation less than the free chlorination process. The poorer the water quality was, the more advantage the sequential chlorination disinfection had over the free chlorination. Conclusion This process takes advantages of free chlorine＇s quick inactivation of microorganisms and chloramine＇s low disinfection by-product （DBP） yield and long-term residual effect, allowing simultaneous control of microbes and DBPs in an effective and economic way.

Growth and Repair Potential of Three Species of Bacteria in Reclaimed Wastewater after UV Disinfection

Objective The growth and repair potential of three typical microorganisms in reclaimed water after UV disinfection was investigated to assess the effects of photo-reactivation and dark repair of microorganisms,and the microbial safety of reclaimed water following this procedure.Methods The growth and repair potential of Escherichia coli,a fecal coliform strain and Bacillus subtilis in the effluent of a biological wastewater treatment plant disinfected by a low-pressure UV lamp were investigated.Results Any increase in bacterial numbers in the effluent after UV disinfection was due to damage repair.Exposure to photo-reactivating light for 8-10 h after UV irradiation with a dose of 5 mJ/cm 2,the highest percentage of photo-reactivation observed for E.coli and the fecal coliform strain was 29% and 15% respectively.B.subtilis showed little photo-reactivation under these conditions.The percentage of photo-reactivation was related to the UV dose and the photo-reactivating time,and a function was developed to forecast the final concentrations of E.coli and the fecal coliform strain after UV disinfection with possible photo-reactivation.Conclusion Different species of bacteria displayed different responses to UV light and different repair potentials.The repair of indigenous bacteria in wastewater needs to be investigated in future work.

Formation potentials of typical disinfection byproducts and changes of genotoxicity for chlorinated tertiary effluent pretreated by ozone

The effects of ozonation on the formation potential of typical disinfection byproducts （DBPs） and the changes of genotoxicity during post chlorination of tertiary effluent from a sewage treatment plant were investigated. Ozonation enhanced the yields of all detected chlorine DBPs except CHCI3. At a chlorine dose of 5 mg/L, the three brominated THMs and five HAAs increased, while chloroform decreased with the increase of ozone dose from 0 to 10 mg/L （ozone dose in consumption base）. At a chlorine dose of 10 mg/L, the two mixed bromochloro species THMs and two dominant HAAs （DCAA and TCAA） increased firstly and then decreased with the increase of ozone dose, with the turning point approximately occurring at an ozone dose of 5 mg/L. The genotoxicity detected using umu test, on the other hand, was removed from 7 Ixg 4-NQO/L to a negligible level by ozonation under an ozone dose of 5 mg/L. Chlorination could further remove the genotoxicity to some extent. It was found that SUVA （UV absorbance divided by DOC concentration） might be used as an indicative parameter for monitoring the removal of genotoxicity during the oxidation.

pH effect on the formation of THM and HAA disinfection byproducts and potential control strategies for food processing

Chlorine-based sanitizers have seen wide spread use in food sanitation. The reaction of chlorine species with organic matter is a concern for two reasons. Available chlorine can be “used up” by organic compounds resulting in a lower amount of chlorine available for disinfection. Another concern is that some forms of chlorine can react with some organic compounds to form toxic halogenated disinfection byproducts（DBPs）. Many studies have been conducted to evaluate the role of hypochlorous acid（HOCl） and hypochlorite ion（OCl–） in the production of DBPs with a particular interest in the production of trihalomethanes（THMs） and haloacetic acids（HAAs）. Since most of the chlorine reactions are pH dependent, pH is found to have a significant effect on the formation of chlorine DBPs. In many cases, the concentration of THMs decreases and HAAs increases as pH decreases. pH also plays an important role in the determination of the type and amount of DBPs formed, with lower, more acidic, pHs resulting in the formation of less chloroform. This review summarizes the information from the literature on the role of chlorine-based sanitizers as affected by pH in the formation of different types of DBPs. Alternative novel strategies to minimize the formation of DBPs are also discussed.

High-level disinfection of gastrointestinal endoscope reprocessing

High level disinfection(HLD) of the gastrointestinal(GI)endoscope is not simply a slogan, but rather is a form of experimental monitoring-based medicine. By definition,GI endoscopy is a semicritical medical device. Hence,such medical devices require major quality assurance for disinfection. And because many of these items are temperature sensitive, low-temperature chemical methods, such as liquid chemical germicide, must be used rather than steam sterilization. In summarizing guidelines for infection prevention and control for GI endoscopy, there are three important steps that must be highlighted: manual washing, HLD with automated endoscope reprocessor, and drying. Strict adherence to current guidelines is required because compared to any other medical device, the GI endoscope is associated with more outbreaks linked to inadequate cleaning or disinfecting during HLD. Both experimental evaluation on the surveillance bacterial cultures and in-use clinical results have shown that, the monitoring of the stringent processes to prevent and control infection is an essential component of the broader strategy to ensure the delivery of safe endoscopy services, because endoscope reprocessing is a multistep procedure involving numerous factors that can interfere with its efficacy. Based on our years of experience in the surveillance of culture monitoring of endoscopic reprocessing, we aim in this study to carefully describe what details require attention in the GI endoscopy disinfection and to share our experience so that patients can be provided with high quality and safe medical practices. Quality management encompasses all aspects of pre- and postprocedural care including the efficiency of the endoscopy unit and reprocessing area, as well as the endoscopic procedure itself.

Prescreening teratogenic potential of chlorinated drinking water disinfection by-products by using Hydra regeneration assay

Practicability of method for the Hydra regeneration assay on the prescreening teratogenic potential of chlorinated drinking water disinfection by products was studied through both the assays of toxicity of adult Hydra (T) and inhibition of the growth of regeneration Hydra (I) by using chloroform, dichloromethane and chloroacetic acid. The results showed that T 50 / I 50 ratios of chloroform and chloroacetic acid were 2 77 and 6 16 respectively, with teratogenic potential. T 50 / I 50 ratio of dichloromethane was 1.69, with weaker teratogenic potential. These experimental results indicated preliminarily that the Hydra regeneration assay has certainly applied value as a prescreening assay for developmental toxicity.

Enhanced Disinfection Effect of a Compound Disinfectant against Bovine Herpes Virus Type 1 at Low Temperature

A compound disinfectant, which consisted of didecyldimethylammonium chloride (DDAC), ortho-dichlorobenzene (1,2-dichlorobenzene, ODB), and chlorocresol (4-chloro-3-methylphenol, CC), and its component chemicals were individually tested for effectiveness against bovine herpes virus type 1 (BHV-1). DDAC, DDAC+ODB, DDAC+CC, and DDAC+ODB+CC showed effectiveness against BHV-1 at room temperature. However, ODB, CC, and ODB+CC showed no virucidal effects. The effects of all disinfectants tested were decreased at low temperature. DDAC showed disinfectant effects at a dilution of 1/800 and DDAC+ODB, DDAC+CC, and DDAC+ODB+CC at dilutions of 1/800 and 1/1600 at low temperature in the presence of 2% fetal bovine serum (FBS) but ODB, CC, and ODB+CC showed no virucidal effects. At low temperature and in the presence of 10% FBS, DDAC, DDAC+ODB, and DDAC+CC showed disinfectant effects at dilutions of 1/800, whereas ODB, CC, and ODB+CC showed no virucidal effects. DDAC+ ODB+CC was more effective (at 1/800 and 1/1600) than the other disinfectants under these conditions. In conclusion, a combination of three disinfectant components (DDAC+ODB+CC), enhanced the disinfectant effects at low temperature and in organic matter contamination.

Electrocatalytic H_(2)O_(2)generation for disinfection

Epidemics are threatening public health and social development.Emerging as a green disinfectant,H_(2)O_(2)can prevent the breakout of epidemics in migration.Electrochemical H_(2)O_(2)production powered by renewable electricity provides a clean and decentralized solution for on-site disinfection.This review firstly discussed the efficacy of H_(2)O_(2)in disinfection.Then necessary fundamental principles are summarized to gain insight into electrochemical H_(2)O_(2)production.The focus is on exploring pathways to realize a highly efficient H_(2)O_(2)production.Progress in advanced electrocatalysts,typically single-atom catalysts for the two-electron oxygen reduction reaction(2e−ORR),are highlighted to provide high H_(2)O_(2)selectivity design strategies.Finally,a rational design of electrode and electrolytic cells is outlined to realize the on-site disinfection.Overall,this critical review contributes to exploiting the potentials and constraints of electrochemical H_(2)O_(2)generation in disinfection and pinpoints future research directions required for implementation.

Enhanced visible-light photocatalytic degradation and disinfection performance of oxidized nanoporous g-C3N4 via decoration with graphene oxide quantum dots

Oxidized nanoporous g-C3N4(PCNO)decorated with graphene oxide quantum dots(ox-GQDs)was successfully prepared by a facile self-assembly method.As co-catalysts,the ultrasmall zero-dimensional(0 D)ox-GQDs can achieve uniform dispersion on the surface/inner channels of PCNO,as well as intimate contact with PCNO through hydrogen bonding,π-π,and chemical bonding interactions.In contrast with PCNO,the ox-GQDs/PCNO composite photocatalysts possessed improved light-harvesting ability,higher charge-transfer efficiency,enhanced photooxidation capacity,and increased amounts of reactive species due to the upconversion properties,strong electron capturing ability,and peroxidase-like activity of the ox-GQDs.Therefore,the visible-light photocatalytic degradation and disinfection performances of the ox-GQDs/PCNO composite were significantly enhanced.Remarkably,the composite with a 0.2 wt.% deposited amount of ox-GQDs(ox-GQDs-0.2%/PCNO)exhibited optimum amaranth photodegradation activity,with a corresponding rate about 3.1 times as high as that of PCNO.In addition,ox-GQDs-0.2%/PCNO could inactivate about 99.6%of Escherichia coli(E.coli)cells after 4 h of visible light irradiation,whereas only^31.9% of E.coli cells were killed by PCNO.Furthermore,h+,·O2-,and·OH were determined to be the reactive species generated in the photocatalytic process of the ox-GQDs/PCNO system;these species can thoroughly mineralize azo dyes and effectively inactivate pathogenic bacteria.