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The Chlorine Dilemma
... Both direct and indirect sewage effluents will ultimately wind up in lakes and rivers, posing a threat to aquatic ecosystems and wildlife. Increased chlorine disinfectant levels can cause direct damage to organisms by disintegrating cell walls or oxidizing proteins (Sedlak and von Gunten 2011). ...
... Disinfection chemicals can create hazardous secondary byproducts such as trihalomethanes or halo acetic acids when they interact with other materials (Sedlak and von Gunten 2011). Aquatic creatures are found to be extremely harmful to these by-products (Liu and Zhang 2014). ...
... Chlorine disinfectants damage marine plants and animals in two respects. Firstly, by damaging their cell walls or oxidizing their proteins, chlorine can directly kill organisms (Sedlak and von Gunten 2011). Second, to form damaging compounds, the disinfectants contain chemicals that may bind with other materials. ...
Coronavirus refers to a group of widespread viruses. The name refers to the specific morphology of these viruses because their spikes look like a crown under an electron microscope. The outbreak of coronavirus disease 2019 (COVID-19) that has been reported in Wuhan, China, in December 2019, was proclaimed an international public health emergency (PHEIC) on 30 January 2020, and on 11 March 2020, it was declared as a pandemic (World Health Organization 2020). The official name of the virus was declared by the WHO as “COVID-19 virus”, formerly known as “2019-nCoV”, or “Wuhan Coronavirus”. The International Committee on Virus Taxonomy’s Coronavirus Research Group has identified that this virus is a form of coronavirus that caused a severe outbreak of acute respiratory syndrome in 2002–2003 (SARS). As a result, the latest severe acute respiratory syndrome has been classified as a corona virus 2 (SARS-CoV-2) pathogen by this committee. This disease spread quickly across the country and the world within the first 3 months of the outbreak and became a global pandemic. To stop COVID-19 from spreading, the governing agencies used various chemicals to disinfect different commercial spaces, streets and highways. However, people used it aggressively because of panic conditions, anxiety and unconsciousness, which can have a detrimental impact on human health and the environment. Our water bodies, soil and air have been polluted by disinfectants, forming secondary products that can be poisonous and mutagenic. In the prevention and spread of COVID-19, disinfection is crucial, but disinfection should be carried out with sufficient precautions to minimize exposure to harmful by-products. In addition, to prevent inhalation, adequate personal protective equipment should be worn and chemical usage, concentrations, ventilation in the room and application techniques should be carefully considered. In the USA, 60% of respondents said they cleaned or disinfected their homes more often than they had in the previous months. In addition to the robust use of disinfection approaches to combat COVID-19, we will explore safe preventative solutions here.
... 162 These disinfectants get into the infected area's sewage system through runoff and domestic effluents, which in turn, end up in freshwater bodies. 163 Due to the irritating and corrosive effects of disinfectants (e.g., chlorine) on the mucous membranes of the respiratory and gastrointestinal tracts, 164 excessive use of large amounts of these chemicals in urban environments could directly or indirectly pose a significant threat to urban wildlife. 162 Chlorine-based disinfectants impact aquatic life by releasing chlorine that destroys living cells' walls and oxidizes proteins. ...
... 162 Chlorine-based disinfectants impact aquatic life by releasing chlorine that destroys living cells' walls and oxidizes proteins. 163 Chlorine can also react with other chemicals in the aquatic environment, forming harmful compounds such as disinfection byproducts. For instance, chlorine can react with dissolved organic matter, something which widely occurs in freshwater bodies, 165 forming hazardous disinfection byproducts To protect the rights of the author(s) and publisher we inform you that this PDF is an uncorrected proof for internal business use only by the author(s), editor(s), reviewer(s), Elsevier and typesetter TNQ Books and Journals Pvt Ltd. ...
... such as trihalomethanes. 163,166 Chlorine also reacts with nitrogen in aquatic environments, forming carcinogenic agents such as chloramine or N-nitrosodimethylamine. 167,168 p0385 As COVID-19 spreads worldwide, the consumption of disinfectants will increase, this having the potential to result in a global environmental disaster. As such, aquatic ecological integrity assessments must be conducted, during and after the pandemic, on a global scale, to control or minimize the environmental impacts of such disinfectants. ...
The World Health Organization (WHO) has recently pronounced severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) as a serious pandemic. It is, therefore, mandatory for public health authorities to have an environmental health management plan against COVID-19. This chapter summarizes articles and official reports related to environmental health management and prevention policies against COVID-19. Because medical sectors require comprehensive guidelines to follow in such pandemic situations, this chapter highlights the significant factors of COVID-19 transmission in our environment (e.g., air), waste management for COVID-19, and protection and disinfection policies against COVID-19. At present, scientists are still discovering more about COVID-19 and its effect on the environment and the health sector. As such, further research is required to increase knowledge about the structural and pathogenic features of COVID-19 and to find effective treatments to dominate this epidemic.
... 162 These disinfectants get into the infected area's sewage system through runoff and domestic effluents, which in turn, end up in freshwater bodies. 163 Due to the irritating and corrosive effects of disinfectants (e.g., chlorine) on the mucous membranes of the respiratory and gastrointestinal tracts, 164 excessive use of large amounts of these chemicals in urban environments could directly or indirectly pose a significant threat to urban wildlife. 162 Chlorine-based disinfectants impact aquatic life by releasing chlorine that destroys living cells' walls and oxidizes proteins. ...
... 162 Chlorine-based disinfectants impact aquatic life by releasing chlorine that destroys living cells' walls and oxidizes proteins. 163 Chlorine can also react with other chemicals in the aquatic environment, forming harmful compounds such as disinfection byproducts. For instance, chlorine can react with dissolved organic matter, something which widely occurs in freshwater bodies, 165 forming hazardous disinfection byproducts such as trihalomethanes. ...
... For instance, chlorine can react with dissolved organic matter, something which widely occurs in freshwater bodies, 165 forming hazardous disinfection byproducts such as trihalomethanes. 163,166 Chlorine also reacts with nitrogen in aquatic environments, forming carcinogenic agents such as chloramine or N-nitrosodimethylamine. 167,168 As COVID-19 spreads worldwide, the consumption of disinfectants will increase, this having the potential to result in a global environmental disaster. As such, aquatic ecological integrity assessments must be conducted, during and after the pandemic, on a global scale, to control or minimize the environmental impacts of such disinfectants. ...
The World Health Organization (WHO) has recently pronounced severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) as a serious pandemic. It is therefore mandatory for public health authorities to have an environmental health management plan against COVID-19. We summarise articles and official reports related to environmental health management and prevention policies against COVID-19.
... Forte oxidante, é empregado também para remoção de odor, cor e oxidação de ferro e manganês nas águas de abastecimento, bem como para remoção de amônia, melhoria na remoção de gordura, controle de bulking em lodos ativados e oxidação de enxofre nas águas residuárias (SNOEYINK; JENKINS, 1980;DONNERMAIR;BLATCHELEY III, 2003;WHITE, 2010). Por causa do alto poder de oxidação, reage com inúmeros compostos -orgânicos e inorgânicos -, o que pode acarretar a formação de subprodutos, como tri-halometanos, ácidos haloacéticos, halocetonas, entre outros (WEF, 1996;HUA;RECKHOW, 2008;SEDLAK;VON GUNTEN, 2011). ...
... Forte oxidante, é empregado também para remoção de odor, cor e oxidação de ferro e manganês nas águas de abastecimento, bem como para remoção de amônia, melhoria na remoção de gordura, controle de bulking em lodos ativados e oxidação de enxofre nas águas residuárias (SNOEYINK; JENKINS, 1980;DONNERMAIR;BLATCHELEY III, 2003;WHITE, 2010). Por causa do alto poder de oxidação, reage com inúmeros compostos -orgânicos e inorgânicos -, o que pode acarretar a formação de subprodutos, como tri-halometanos, ácidos haloacéticos, halocetonas, entre outros (WEF, 1996;HUA;RECKHOW, 2008;SEDLAK;VON GUNTEN, 2011). ...
... A dose de cloro, suas espécies em equilíbrio na água e o cloro residual, que diferem com o tempo de contato, são variáveis críticas para a desinfecção (JOL-LEY; JOHNSON, 1990;CHENG, 2003). A cloração representa, também, um eficiente processo de remoção ou transformação de micropoluentes inorgânicos (DEBORDE; VON GUNTEN, 2008;SEDLAK;VON GUNTEN, 2011). Segundo White (2010), amônia, aminoácidos, proteínas, material carbonáceo, nitritos, ferro, manganês, cianetos, entre outros, possuem efeitos diretos nas reações químicas com o cloro. ...
Neste estudo, foram monitoradas as variações de cloro residual livre e combinado após aplicação de cloro em diferentes dosagens e tempos de contato em esgoto advindo de tratamento preliminar. Em alguns casos, para um mesmo tempo de contato, houve maiores concentrações de cloro residual livre quando aplicadas menores dosagens de cloro. Em um segundo momento, no mesmo efluente, foram investigados parâmetros para servir de indicadores de breakpoint, o qual só ocorreu com aplicação de 80 mg.L-1 de cloro. O pH e o potencial redox (pε) mostraram-se correlacionados à curva de cloro residual total e, analisados em conjunto com a condutividade elétrica, foram capazes de apontar o breakpoint da cloração.
... To circumvent external contamination and control naturally present microbial (re)growth, residual disinfectants such as free chlorine and chloramine are commonly added before distribution. Those approaches are being challenged as the use of free chlorine may induce the formation of by-products that can be a toxic nuisance to humans 23 , and the use of chloramine may promote the development of nitrifying bacteria 5 . The latter oxidize the ammonia to nitrite and subsequently to nitrate. ...
... The latter oxidize the ammonia to nitrite and subsequently to nitrate. However, both compounds can become toxic for humans 23 . In addition, some byproducts can also cause a deviating odor and taste (e.g., trichloroanisoles) 24 . ...
Anthropogenic activities and climate change can deteriorate the freshwater quality and stress its availability. This stress can, in turn, have an impact on the biostability of drinking water. Up to now, the microbiological quality of drinking water has been maintained through the selection of high-quality water sources allied to the use of disinfectants and the removal of organic carbon. But as freshwater becomes richer in other nutrients, strategies used so far may not suffice to keep a steady and high-quality supply of drinking water in the future. This article readdresses the discussion on drinking water biostability. We need to reframe the concept as a dynamic equilibrium that considers the available nutrients and energy sources (potential for growth) relative to the abundance and composition of the bacterial community (potential to consume the available resources). npj Clean Water (2021) 4:28 ; https://doi.
... The wide uses of disinfection for drinking water in treatment plants not only guarantee the water quality of finished water, but also maintain disinfectant residuals in DWDSs to prevent the microbial recontamination of the finished water as it moves through the DWDSs [2][3][4]. Traditionally, chlorine has been used to disinfect drinking water due to its relatively low cost and high availability [5]. However, the formation of disinfection byproducts (DBPs) is a side effect of chlorination, since many DBPs can significantly affect human health [2]. ...
... According to these results, the pH-dependency of the apparent second-order rate for FLE chlorination could be described by equation (5). ...
Fleroxacin (FLE) is an emerging third-generation fluoroquinolone antibacterial agent (FQs) that has been frequently detected in aqueous environments. However, there is a lack of sufficient knowledge regarding the transformation mechanisms of FLE within drinking water distribution systems (DWDSs) when residual chlorine and ClO2 are present. To address this gap, this study makes the first attempt to explore the kinetics, transformation byproducts and toxicity variations during fleroxacin (FLE, an emergent pollutant) degradation by chlorine and ClO2 in a pilot-scale DWDSs. The obtained results show that (i) the FLE degradation rate by chlorine was higher than by ClO2 at pH 7.4 in the pilot-scale DWDSs; (ii) the degradation efficiency of FLE was significantly affected by pH, with FLE degradation by chlorine possessing the highest rate at neutral pH, and the degradation rate was positively correlated with pH (from 6.5 to 9) during the ClO2 disinfection process; (iii) pipe materials can appreciably affect the relative performance of the FLE degradation efficiency by chlorine and ClO2; (iv) seven and eight intermediates are identified during chlorination and ClO2 oxidation, respectively, and the cleavage of the piperazine group was the committed step and the main oxidation reaction, and (v) the toxicity assessment demonstrates that the toxicity of FLE chlorination and ClO2 are both higher than the blank experiment, and ClO2 disinfection can reduce the potential risk compared to the chlorine disinfection.
... 3 The most popular disinfection method is chlorination attributed not only to its low cost and high primary disinfection efficiency, but also to its capability of providing a secondary disinfection effect via the remaining free chlorine and/or chloramines. 4 Nevertheless, chlorination and chloramination inevitably generate carcinogenic disinfection by-products that threaten human health. 4,5 This problem can be solved by using nonchlorine-based techniques such as ultraviolet (UV) or membrane filtration. ...
... 4 Nevertheless, chlorination and chloramination inevitably generate carcinogenic disinfection by-products that threaten human health. 4,5 This problem can be solved by using nonchlorine-based techniques such as ultraviolet (UV) or membrane filtration. 6,7 With the accumulation of technology development and industrial experience, these alternative techniques have become more robust and cost-effective, showing great potential for substituting chlorination in centralized water facilities. ...
Locally enhanced electric field treatment (LEEFT) has been considered as a novel and promising technology for efficient microorganism inactivation in recent years. Previous studies were primarily conducted on bacteria and viruses. Here, polydopamine-protected copper-oxide-nanowire-modified copper mesh (PDA-CuONW-Cu) electrodes were fabricated and utilized in a flow-through LEEFT device to treat two microalgae species, Chlorella vulgaris and Microcystis aeruginosa. The results showed that the LEEFT achieved efficient microalgae inactivation and growth control. The inhibition of Fv/Fm were 46.7% and 34.3% for C. vulgaris and M. aeruginosa, respectively, after five LEEFT cycles at a flow rate of 1.2 mL/min and a 10 V alternating voltage with a frequency of 10⁴ Hz. The fluorescence staining and the flow cytometer measurement verified the inactivation of microalgae cells, with dead cell ratios increasing to 61.3% and 56.5% for C. vulgaris and M. aeruginosa, respectively. Both species could still grow after removing the electric field, indicating that the LEEFT is a physical treatment process without residual anti-microbial effects. Nevertheless, with five LEEFT cycles, the 96 h-growth inhibition reached 60.1% and 66.2% for C. vulgaris and M. aeruginosa, respectively. The LEEFT can still be a promising control method for microalgae blooms when the LEEFT electrodes are durable enough for long-term circular treatment.
... Infectious diarrheal diseases attributed to inadequate water are estimated to cause 502 thousands deaths a year, with the majority being children under age five (Prüss-Ustün et al. 2014). Conventional disinfectants for water treatments such as chlorine, chlorine derivatives, and ozonation can form harmful disinfection by-products which may provide an unintended health hazard (Sedlak and Gunten 2011;Jamil et al. 2015). UV irradiation as an alternative disinfectant method is safer, but it has non-residual effect and requires high energy (Darby et al. 1995). ...
... Chlorine and chlorine derivatives are still the most widely used as water disinfection overall the world. While they are effective against most pathogenic microorganisms, economical, and easy to use, but, one of their drawbacks is that chlorine interacts readily with natural organic matter (NOM) present in all source surface waters to generate numerous disinfection by-products (DBPs) (Sedlak and Gunten 2011). In biological applications, silver (Ag) ions gained the significant attention due to their unique electrical and optical properties. ...
One-pot synthesis of a new magnetic disinfectant was achieved through the polymerization of thiourea and formaldehyde in the presence of magnetite nanoparticles (MTUF). The obtained magnetic chelating resin was loaded with Ag(I) ions. This material was tested as a disinfectant for water pathogenic microorganism’s deactivation. The toxicity of MTUF before and after Ag(I) loading was estimated. The antimicrobial activity tests of MTUF-Ag were carried out against Escherichia coli, Salmonella Typhimurium, and Pseudomonas aeruginosa as examples of Gram-negative bacteria; Listeria monocytogenes, Staphylococcus aureus, Enterococcus faecalis, and Bacillus subtilis as examples of Gram-positive bacteria; and Candida albicans as representative for fungi. The results showed that the minimum inhibitory dosage (MID) of MTF-Ag against Escherichia coli, Salmonella Typhimurium, Listeria monocytogenes, Staphylococcus aureus, and mixed culture were 1.5, 2.0, 1.0, 1.5, and 1.5 mg/mL, respectively, after 40 min of contact time. While C. albicans was more resistant to the magnetic disinfectant, only three log reductions were done at 2.5 mg/mL. The studied MTUF-Ag was successfully tested for water and wastewater pathogenic microorganism’s deactivation. It can be concluded that MTUF-Ag could be a good candidate for water disinfection.
... . Among those disinfectants, chlorination is a widespread disinfection technique applied in treatment plants and distribution systems in order to control microbial contamination. Chlorine is relatively inexpensive and easily available, making it a popular choice for utilities [6]. However, drinking water chlorination produces potentially carcinogenic disinfection byproducts (DBPs) [7,8]. ...
... Because of regulatory limitations of certain DBPs, alternate disinfectants have been sought to minimize the formation of DBPs while maintaining the sufficient inactivation of pathogens in the water supply system [6]. Chloramines are often used as an alternate drinking water disinfectant. ...
Chloramination of bisphenol A (BPA) in a pilot-scale water distribution system (WDS) was investigated to assess factors that influence degradation rate and degradation products. In deionized water (DW) and in the WDS, complete degradation of BPA after chloramination required > 9 hours. At Cl/N mass ratios of 3, 4 or 6, the degradation rate was appreciably greater in the WDS than in the DW. In both the DW and WDS, the bromide ion concentration had little influence on BPA degradation. The BPA degradation rate was greatly affected by pH and temperature in both the DW and in the WDS. The rate of BPA degradation by chloramination increased with increasing flow velocity, but the increase was limited. The BPA degradation rate in different pipes followed the order: ductile iron pipe > polyethylene (PE) pipe > stainless steel pipe. Twelve specific degradation products of BPA that were produced following chloramination were tentatively identified, with 2-chloro-BPA as the main byproduct. One nitrogenous byproduct produced following chloramination was detected for the first time, and appeared at 15 min, indicating that nitrogen from the chloramine participated in the BPA degradation reaction at the beginning of the experiment. In the presence of chloramines and BPA, the formation of trihalomethanes (THMs), haloacetic acids (HAAs) and halogenated nitromethane (HNMs) occurred primarily in the initial 3 h. The intermediates of BPA that were formed during chloramination had relatively little influence on THM, HAA and HNM formation. The degradation pathways for BPA during chloramination in the WDS are proposed.
... Conventional disinfection treatments, namely chlorination or ozonation, have significant drawbacks such as the formation of disinfection by-products (DBPs) or the lack of residual effect [1][2][3]. For this reason, in recent years Advanced Oxidation Processes (AOPs) have emerged as an alternative series, although not all the AOPs ensure the non-formation of DBPs [4,5]. These processes can achieve the simultaneous removal of different types of contamination, simplifying the wastewater reclamation process and potentially reducing the time and cost of the process [6]. ...
... For example, people have extensively applied chlorine disinfectants to prevent coronavirus progression. Although there are benefits to the use of disinfectants and hand sanitizers against COVID-19, these germicidal agents penetrate porous media and pollute water resources directly and indirectly (Ghafoor et al., 2021;Bandala et al., 2021;Kumar et al., 2021b), which poses even more severe risks to aquatic ecosystems (Sedlak and von Gunten, 2011;Ghafoor et al., 2021;Bhattacharya et al., 2021). The continued release of these pollutants into the environment could potentially have catastrophic effects on aquatic ecosystems worldwide . ...
Although the World Health Organization (WHO) announcement released in early March 2020 stated there is no proven evidence that the COVID-19 virus can survive in drinking water or sewage, there has been some recent evidence that coronaviruses can survive in low-temperature environments and in groundwater for more than a week. Some studies have also found SARS-CoV-2 genetic materials in raw municipal wastewater, which highlights a potential avenue for viral spread. A lack of information about the presence and spread of COVID-19 in the environment may lead to decisions based on local concerns and prevent the integration of the prevalence of SARS-CoV-2 into the global water cycle. Several studies have optimistically assumed that coronavirus has not yet affected water ecosystems, but this assumption may increase the possibility of subsequent global water issues. More studies are needed to provide a comprehensive picture of COVID-19 occurrence and outbreak in aquatic environments and more specifically in water resources. As scientific efforts to report reliable news, conduct rapid and precise research on COVID-19, and advocate for scientists worldwide to overcome this crisis increase, more information is required to assess the extent of the effects of the COVID-19 pandemic on the environment. The goals of this study are to estimate the extent of the environmental effects of the pandemic, as well as identify related knowledge gaps and avenues for future research.
... Ferrate (Fe(VI)) has been considered as an alternative oxidant that can lead to efficient micropollutant abatement in wastewaters (Lee et al., 2005a, as a preoxidant to mitigate DBP formation in drinking water (Rougé et al., 2020b;Yang et al., 2013), and/or as a coagulant (Jiang et al., 2001). In addition, Fe(VI) does not produce known harmful byproducts such as chlorinated organic compounds (from chlorine use), chlorite (from ClO 2 use), or any significant levels of bromate (from O 3 use in bromide-containing waters) (Gan et al., 2019;Jiang et al., 2016;Sedlak and von Gunten 2011). However, limited information is available on the reaction between Fe(VI) and primary amines. ...
Ferrate (Fe(VI)), a promising water treatment oxidant, can be used for micropollutant abatement or disinfection byproduct mitigation. However, knowledge gaps remain concerning the interaction between Fe(VI) and dissolved organic matter structures, notably primary amines. This study investigated degradation kinetics and products of several aliphatic primary amines by Fe(VI). Primary amines showed appreciable reactivity toward Fe(VI) (2.7−68 M⁻¹s⁻¹ at pH 7−9), ranking as follows: benzylamine > phenethylamine > phenylpropylamine > methylamine ≈ propylamine. Nitriles were the main oxidation products of the primary amines, with molar yields of 61−103%. Minor products included aldehydes, carboxylic acids, nitroalkanes, nitrite, nitrate, and ammonia. The buffering conditions were important. Compared to phosphate, borate enhanced the reactivity of the amines and shifted the products from nitriles to carbonyls. An evaluation of the effect potency of some cyano-compounds by an in vitro bioassay for oxidative stress response and cytotoxicity suggested that non-halogenated nitriles are unlikely to pose a significant threat because they were only toxic at high concentrations, acted as baseline toxicants and did not cause oxidative stress, unlike halonitroalkanes or halonitriles. The formation of non-halogenated nitriles is preferable to the formation of nitroalkanes arising from the ozonation of primary amines (other than amino acid N-terminals) because, during chlorination, nitriles remain unreactive while nitroalkanes lead to potent halonitroalkanes.
... The formation of disinfection by-products (DBPs) caused by chlorination disinfection has attracted continuous attention (Richardson et al., 2000;Sedlak and von Gunten, 2011). More than 700 DBPs have been identified by 2020 (Richardson and Kimura, 2020), and more emerging DBPs are constantly being discovered. ...
Hypobromous acid (HOBr), a highly reactive active species, can be formed and impact reaction processes with organic pollutants in source water during chlorination disinfection of the water containing bromide (Brˉ). In this study, we investigated the transformation kinetics of 10 parent polycyclic aromatic hydrocarbons (PAHs) and formation mechanisms of transformation products in the presence of Brˉ during chlorination. The results indicated that HOBr can accelerate the processes of electrophilic substitution (ES) and single electron transfer (ET) reactions in PAHs, and the second-order rate constants of HOBr are 10²-10³ times higher than those of hypochlorous acid (HOCl) with PAHs. HOBr was more conductive to induce ES reactions than HOCl. In water containing Brˉ, HOBr and HOCl dominate the reaction processes with PAHs, although other active bromine species may still affect reaction processes. In terms of transformation products, higher reactivity of HOBr results from faster formation of oxygenated PAHs (OPAHs) and halogenated PAHs (HPAHs) than HOCl. As an example of 3 model PAHs, anthracene transforms faster to its oxygenated products at a higher concentration, while pyrene and fluorene transform faster to halogenated products. These fundamental results were essential to understanding the transformation kinetics of PAHs and the formation of toxic disinfection by-products in the presence of Brˉ.
... The physicochemical treatment process for wastewater for instance reverse osmosis (RO), nanofiltration, advanced oxidation, or activated carbon, are facing big challenges by require for enormously energy and expensive particularly in application at large scale treatment plants (Subba Rao and Venkatarangaiah, 2014;Ezugbe and Rathilal, 2020). Although conventional disinfectants such as: ozone, chlorine and chlorine derivatives are effective for water treatment but they form dangerous by-products to human health such as trihalomethane compounds in highly polluted water (Sedlak and Gunten, 2011;Beltrán et al., 2021). Although ultraviolet (UV) radiation is considered safer and act as an alternative disinfectant method but it needs high energy and has not any residual effect (Collivignarelli et al., 2018). ...
Herein, green and non-toxic bismuth [email protected] carbon nitride (Bi2S3@g-C3N4) nanosheets (NCs) were firstly synthesized by ultrasonicated-assisted method and characterized with different tool. Bi2S3@g-C3N4 NCs antimicrobial activity tested against three types of microbes. As well the heterostructured Bi2S3@g-C3N4 NCs was investigated for removing dye and hexavalent chromium under visible light and showed high efficiency of photocatalytic oxidation/reduction higher than g-C3N4 alone, attributing to lower recombination photogenerated electron-hole pairs. Bi2S3@g-C3N4 NCs showed high antimicrobial efficiencies against Staphylococcus aureus (S. aureus) as a Gram positive bacterium, Escherichia coli (E. Coli)as a Gram negative bacterium and Candida albicans (C. albicans) and that the disinfection rates are 99.97%, 99.98% and 99.92%, respectively. The core mechanism is that the bacterial membrane could be destroyed by reactive oxygen species. The Bi2S3@g-C3N4 NCs is promising for environmental disinfection including water and public facilities disinfection and solar photocatalytic depollution. Turnover number (TON) and Turnover frequency (TOF) are used as concise assessment indicator for photocatalytic efficiency.
... A particular problem in drinking water supply is the dilemma of chlorine disinfection. While disinfection of drinking water greatly reduced pathogen risks and associated incidences of waterborne disease and is recognized as one of the major public health accomplishments of the 20th century, the high reactivity of HClO and ClO − in chlorine disinfection with natural organic matter also induces formation of a variety of toxic disinfection by-products such as Cl − /Br − /I − trihalomethanes (THMs), including chloroform (CHCl 3 ), which could be harmful to human and aquatic life [2]. Water authorities around the world have set safe limits for THMs, with some countries using total THMs and others providing standards for each individual THMs. ...
Chlorination is a widely adopted disinfection method in water and wastewater treatment for the protectionof public health, as it greatly reduces pathogen risks and associated incidence of waterborne diseases. Chlo-rination, however, also creates disinfection by-products (DBPs) such as trihalomethanes, which, epidemiolog-ically, have been associated with a higher incidence of some forms of cancer. Therefore, developing sensorsfor monitoring the chlorine dosage and DBPs concentrations in real-time and in-line is of critical importanceto public health. Carbon dots (CDs) are an emergent class offluorescent nanomaterial offering highly-sensitive sensing functionalities towards a diverse range of chemical/biochemical contaminants, owing totheir tuneablefluorescence, rich surface functionalities, low to non-toxicity and ease of synthesis. In thisstudy, we demonstrate that 1) highlyfluorescent CDs (quantum yield 38%) can be produced from simplethermal treatment from biowastes such as human hairs without employing any solvents; 2) thefluorescencespectra and intensity of the synthesized CDs responds to the presence and quantity of chloroform with highsensitivity, with a limit of detection of 3 ppb; and 3) through a pair-wise comparative study on autoclave-synthesized CDs (OCDs) and microwave-synthesized counterpart, we discovered that the pyridinic N oxidethat is unique to OCDs imparts sensitive and selective sensing functionality towards chloroform; 4) thePL-based sensing functionality is not solely determined by the binding affinity between the analyte andthe carbon dots, but also the electronic structures of the interacting entities. This study provides an in-depth study on how to utilize the diverse features of biowastes and impart unique functionalities to CDsfor developing advanced functional materials.
... To this end, the values recommended by the literature are used. Calculations related to this section are presented in Equation 1 [15][16][17][18]. ...
Nowadays, water supplies face critical conditions in terms of quality and quantity. Furthermore, growth in population along with their needs require an increasing
level of water-related resources. Consequently, the potential application of purifi ed wastewater supplies can be considered in agriculture, industry, and irrigation of green
spaces. Hence the necessity of disinfection and reduction of microbial load in the outlet sewage of water treatment plants are so clear for all designers and operators.
Chlorine contact reactors are one of the major pillars of any wastewater treatment plant, whether urban or industrial. A new method is presented in this study based on the
optimization of the dispersion amount in a Chlorine Contact Plug Flow Reactor (CCPFR) using single-objective Genetic Algorithm (GA) and nonlinear condition functions,
Simulated Annealing Algorithm (SAA) and Pattern Search Algorithm (PSA). Then, it is attempted to assess the hydraulic behavior of the reactor and the microbial load
removal performance using statistical, probabilistic and experimental practices. This research was done in a case study of Mashhad city’s wastewater treatment plant.
The results of presented study illustrate that GA model has the best outcomes for designing CCPFR and the desired reactor with a depth of 2.45m, width of 1.23m,
length of 24.8m, a number of 15 channels, and a retention time of 87 minutes is able to reduce a population of 300000 microorganisms (MPN/100 ml) at the entry to 274
(MPN/100 ml) at the exit. As per this method, investment cost of CCPFR is reduced around 30 percentages in comparison of traditional computation system.
... Due to the production of many poisonous by-products of chlorination and the potential to enhance EPS production (Sedlak and von Gunten, 2011), chloramine-related reagents (chloramine and chlorine dioxide) are used as alternative disinfectants. Chloramines mainly refer to derivatives of ammonia with N-H bonds replaced by N-Cl bonds. ...
Microbial extracellular polymeric substances (EPS) have a profound role in various wastewater treatment and reclamation processes, in which a variety of technologies are used for disinfection and microbial growth inhibition. These treatment processes can induce significant changes in the quantity and properties of EPS, and altered EPS could further adversely affect the wastewater treatment and reclamation system, including membrane filtration, disinfection, and water distribution. To clarify the effects of microbial inactivation approaches on EPS, these effects were classified into four categories: (1) chemical reactions, (2) cell lysis, (3) changing EPS-producing metabolic processes, and (4) altering microbial community. Across these different effects, treatments with free chlorine, methylisothiazolone, TiO2, and UV irradiation typically enhance EPS production. Among the residual microorganisms in EPS matrices after various microbial inactivation treatments, one of the most prominent is Mycobacterium. With respect to EPS properties, proteins and humic acids in EPS are usually more susceptible to treatment processes than polysaccharides. The affected EPS properties include changes in molecular weight, hydrophobicity, and adhesion ability. All of these changes can undermine wastewater treatment and reclamation processes. Therefore, effects on EPS quantity and properties should be considered during the application of microbial inactivation and growth inhibition techniques.
... Second, the bonding of chlorine to dissolved organic matter can produce hazardous byproducts including, trihalomethanes or haloacetic acids. Besides, the carcinogenic formation as a result of the chemical reaction of chlorine with nitrogen is inherently dangerous Sedlak and Von Gunten, 2011;Liu and Zhang, 2014;Bei et al., 2016). All things together, it is strongly suggested that countries conduct an environmental impact assessment to study how much the environment is affected by COVID-19 pandemic. ...
The global crisis caused by SARS-CoV-2 (COVID-19) affected economics, social affairs, and the environment, not to mention public health. It is estimated that near 82% of the SARS-CoV-2 genome is similar to the severe acute respiratory syndrome. The purpose of the review is to highlight how the virus is impacted by the environment and how the virus has impacted the environment. This review was based on an electronic search of the literature in the Scopus, Science Direct, and PubMed database published from December 2019 to July 2020 using combinations of the following keywords: SARS-CoV-2 transmission, COVID-19 transmission, coronavirus transmission, waterborne, wastewater, airborne, fomites, and fecal-oral transmission. Studies suggest the thermal properties of ambient air, as well as relative humidity, may affect the transmissibility and viability of the virus. Samples taken from the wastewater collection network were detected contaminated with the novel coronavirus; consequently, there is a concern of its transmission via an urban sewer system. There are concerns about the efficacy of the wastewater treatment plant disinfection process as the last chance to inactivate the virus. Handling solid waste also requires an utmost caution as it may contain infectious masks, etc. Following the PRISMA approach, among all reviewed studies, more than 36% of them were directly or indirectly related to the indoor and outdoor environment, 16% to meteorological factors, 11% to wastewater, 14% to fomites, 8% to water, 9% to solid waste, and 6% to the secondary environment. The still growing body of literature on COVID-19 and air, suggests the importance of SARS-CoV-2 transmission via air and indoor air quality, especially during lockdown interventions. Environmental conditions are found to be a factor in transmitting the virus beyond geographical borders. Accordingly, countries need to pay extra attention to sustainable development themes and goals.
... DBPs are formed from the reactions of disinfectants such as chlorine, chloramines, ozone, and chlorine dioxide with compounds in water and wastewater such as natural organic matter (NOM) and ammonium, bromide and iodide (Sedlak and von Gunten, 2011). Recent research also reports the formation of DBPs through the transformation of micropollutants such as pharmaceuticals and personal care products (PPCPs) and endocrine disrupting chemicals (EDCs) (Benotti et al., 2009;Dodd and Huang, 2004;Hu et al., 2017;Richardson, 2011;Westerhoff et al., 2005). ...
This review focuses on the degradation kinetics and mechanisms of disinfection byproducts (DBPs) under UV and solar irradiation and in UV-based advanced oxidation processes (AOPs). A total of 59 such compounds are discussed. The processes evaluated are low pressure, medium pressure and vacuum UV irradiation, solar irradiation together with UV/hydrogen peroxide, UV/persulfate and UV/chlorine AOPs. Under UV and solar irradiation, the photodegradation rates of N-nitrosamines are much higher than those of halogenated DBPs. Among halogenated DBPs, those containing iodine are photodegraded more rapidly than those containing bromine or chlorine. This is due to differences in their bond energies (EN−N < EC−I < EC−Br < EC−Cl). Molar absorption coefficients at 254 nm and energy gaps can be used to predict the photodegradation rates of DBPs under low pressure UV irradiation. But many DBPs of interest cannot be degraded to half their original concentration with less than a 500 mJ cm⁻² dose of low pressure UV light. HO• generally contributes to less than 30% of the degradation of DBPs except iodo-DBPs in UV/H2O2 AOPs. Reaction mechanisms under UV irradiation and in HO•-mediated oxidation are also summarized. N−N bond cleavage initiates their direct UV photolysis of N-nitrosamines as C−X cleavage does among halogenated compounds. HO• generally initiates degradation via single electron transfer, addition and hydrogen abstraction pathways. Information on the reaction rate constants of SO4•− and halogen radicals with DBPs is rather limited, and little information is available about their reaction pathways. Overall, this review provides improved understanding of UV, solar and AOPs.
... Consecutively, they have been used for the transformation/abatement of inorganic and/or organic micropollutants detected in water ( von Gunten, 2018 ). However, undesirable dis-infection by-products (DBPs) or harmful transformation products can be generated from the reactions of oxidants with water matrix components and micropollutants under certain conditions ( Boorman, 1999 ;Gallard and von Gunten, 2002a , b;Richardson et al., 2007 ;Sedlak and von Gunten, 2011 ). ...
Hypochlorous acid (HOCl) is typically assumed to be the primary reactive species in free available chlorine (FAC) solutions. Lately, it has been shown that less abundant chlorine species such as chlorine monoxide (Cl2O) and chlorine (Cl2) can also influence the kinetics of the abatement of certain organic compounds during chlorination. In this study, the chlorination as well as bromination kinetics and mechanisms of 12 olefins (including 3 aliphatic and 9 aromatic olefins) with different structures were explored. HOCl shows a low reactivity towards the selected olefins with species-specific second-order rate constants <1.0 M-1s-1, about 4-6 orders of magnitude lower than those of Cl2O and Cl2. HOCl is the dominant chlorine species during chlorination of olefins under typical drinking water conditions, while Cl2O and Cl2 are likely to play important roles at high FAC concentration near circum-neutral pH (for Cl2O) or at high Cl- concentration under acidic conditions (for Cl2). Bromination of the 12 olefins suggests that HOBr and Br2O are the major reactive species at pH 7.5 with species-specific second-order rate constants of Br2O nearly 3-4 orders of magnitude higher than of HOBr (ranging from <0.01 to >103 M-1s-1). The reactivities of chlorine and bromine species towards olefins follow the order of HOCl < HOBr < Br2O < Cl2O ≈ Cl2. Generally, electron-donating groups (e.g., CH2OH- and CH3-) enhances the reactivities of olefins towards chlorine and bromine species by a factor of 3-102, while electron-withdrawing groups (e.g., Cl-, Br-, NO2-, COOH-, CHO-, -COOR, and CN-) reduce the reactivities by a factor of 3-104. A reasonable linear free energy relationship (LFER) between the species-specific second-order rate constants of Br2O or Cl2O reactions with aromatic olefins and their Hammett σ+ was established with a more negative ρ value for Br2O than for Cl2O, indicating that Br2O is more sensitive to substitution effects. Chlorinated products including HOCl-adducts and decarboxylated Cl-adduct were identified during chlorination of cinnamic acid by high-performance liquid chromatography/high resolution mass spectrometry (HPLC/HRMS).
... Chlorine-based disinfectants threaten human health, agricultural production, environmental quality and aquatic ecosystem health in a variety of ways by (1) reaction with Natural Organic Matter (NOM) or bromide in raw-water leads to the formation of DBPs such as Trihalomethanes (THMs), bromates, effl uent and other chemical compounds which poses acute toxicity to human health, aquatic ecosystem and other consumers [13][14][15][16][17]. (2) The direct toxic effect of chlorinebased chemicals on the aquatic organisms including vegetative bacteria, mycobacteria, viruses, and fungi by destroying their cell membranes, the cell hydrophobicity, as well as total Adenosine Triphosphate (ATP) [18,19]. (3) Formation of carcinogenic nitrosamines and chloramine from chlorine have been observed in drinking water and human blood in Washington, DC, and other cities [20]. ...
Because of the current situation regarding the Covid-19 pandemic in more than 200 countries and territories, an early discussion is proposed on the use of chlorinebased disinfectants as an important precautionary measure to disinfect the surfaces and kill the Covid-19. However, the excessive use of chlorine-based disinfectants will
surely make the highest residual concentrations in the water, soil, and other environmental components by various means such as surface runoff and leaching, etc. Crossing
the permissible limits in water and soil system and in other environmental components will pose risks to human health in the form of skin, eyes, cancer, and other associated
diseases. Similarly, it may also decline the agricultural production by excessive salt (Cl-
) accumulations (salinization) and will also threaten the aquatic and wild ecosystems.
Therein, the ecological integrity assessments regarding the use of chlorine-based disinfectants in the current situation are very much important. Meanwhile, this will open a
new area of interest for the researcher and would be of great importance to investigate its critical levels in the environmental components and its potentially toxic effects.
... Moreover, it can solubilise the surface of lead pipes, which does not happen in the presence of a chlorine residual, due to the latter's stronger oxidising capacity. 21 Therefore, changes of this type need a cautious and balanced investigation on a site by site basis. ...
Guest editors Tom Bond, Wenhai Chu, Urs von Gunten and Maria José Farré introduce the Environmental Science: Water Research & Technology themed issue on drinking water oxidation and disinfection processes.
... To prevent microbial growth in the distribution systems, water treatment plants often use chemical disinfectants such as chlorine, ozone, chlorine dioxide, and chloramines. The use of disinfectants, however, leads to the formation of harmful disinfectants byproducts (Li and Mitch, 2018;Sedlak and von Gunten, 2011) and selection for antibiotic resistant bacteria (Shi et al., 2013;Zhang et al., 2019). In some European countries (e.g., the Netherlands, Denmark, and Switzerland), biofiltration (e.g., rapid (RSF) or slow (SSF) sand filtration, granular activated carbon filters) are widely applied methods for the removal of the contaminants without the use of disinfectants (Bertelli et al., 2018). ...
Elevated concentrations of ammonium and methane in groundwater are often associated with microbiological, chemical and sanitary problems during drinking water production and distribution. To avoid their accumulation, raw water in the Netherlands and many other countries is purified by sand filtration. These drinking water filtration systems select for microbial communities that mediate the biodegradation of organic and inorganic compounds. In this study, the top layers and wall biofilm of a Dutch drinking water treatment plant (DWTP) were sampled from the filtration units of the plant over three years. We used high-throughput sequencing in combination with differential coverage and sequence composition-based binning to recover 56 near-complete metagenome-assembled genomes (MAGs) with an estimated completion of ≥70% and with ≤10% redundancy. These MAGs were used to characterize the microbial communities involved in the conversion of ammonia and methane. The methanotrophic microbial communities colonizing the wall biofilm (WB) and the granular material of the primary rapid sand filter (P-RSF) were dominated by members of the Methylococcaceae and Methylophilaceae. The abundance of these bacteria drastically decreased in the secondary rapid sand filter (S-RSF) samples. In all samples, complete ammonia-oxidizing (comammox) Nitrospira were the most abundant nitrifying guild. Clade A comammox Nitrospira dominated the P-RSF, while clade B was most abundant in WB and S-RSF, where ammonium concentrations were much lower. In conclusion, the knowledge obtained in this study contributes to understanding the role of microorganisms in the removal of carbon and nitrogen compounds during drinking water production. We furthermore found that drinking water treatment plants represent valuable model systems to study microbial community function and interaction.
... Disinfection has been widely applied in drinking water, swimming pool water, and reclaimed water treatment processes (Sun et al. 2019). However, an unintentional consequence is that disinfectants (chlorine, chloramine, chlorine dioxide, and ozone) react with natural organic matter (NOM) and other pollutants to generate disinfection byproducts (DBPs) (Sedlak and von Gunten 2011). More than 2000 DBPs form during various disinfection processes, and most of them are semi-volatile or volatile, but a few are soluble polar compounds. ...
Disinfection byproducts (DBPs) have attracted extensive attention due to their adverse health effects such as genotoxicity, mutagenicity, and carcinogenicity. With higher formation potential and occurrence in all disinfection processes, trihalomethanes (THMs) are one of the most significant DBPs. Since ions are universally existent by natural or anthropogenic input to groundwater or surface water, the effects of ions (Ca2+, Mg2+, NH+4, As3+, Fe3+, Al3+, Cu2+, and F−) on THM formation during chlorination in bromide-containing water were investigated in the present study. The results showed that THM formation and speciation were substantially influenced by the ions, but the degree and mechanisms of effects were critically dependent on the ion species. THM formation was inhibited by Ca2+, Mg2+, As3+, and NH+4 significantly, and was enhanced by Fe3+, Cu2+, and Al3+. The mechanisms of influence of the above ions were interpreted for complexation, consumption, and catalysis. Furthermore, due to the higher Br− concentration, CHBr3 was the dominant species in THMs.
... Also, accompanied with the decomposition of ozone in aqueous environment, hydroxyl radical (HO % ) could be generated in ozone system and thus acts as a secondary and less-selective oxidant to react with various contaminants at near diffusion-controlled rates (von Gunten, 2003a;Hoigne and Bader, 1975). Hypochlorite is one of the most commonly used disinfectants in drinking water treatment (Sedlak and von Gunten, 2011), and its potential for TrOCs abatement has also been extensively studied in recent decades (Dodd and Huang, 2004;Duirk and Collette, 2006). It was found that hypochlorite could degrade contaminants via oxidation, addition, or electrophilic substitution pathways despite its high reactivity may be limited to particular functional groups (mainly amines, reduced sulfur moieties or activated aromatics) (Deborde and von Gunten, 2008;Lei and Snyder, 2007). ...
Bisulfite-activated permanganate (PM/BS) process has proven to be a promising method for trace organic contaminants (TrOCs) abatement. However, to our knowledge, most previous studies on PM/BS process were limited in synthetic water at lab-scale. Hence, the performance of TrOCs abatement by PM/BS process was investigated in real waters in this study, and for the first time, its feasibility as a pretreatment process was evaluated at pilot-scale. The lab-scale results indicated that almost all tested TrOCs could be completely removed from pure water, while their removal efficiencies varied widely from ∼20% to ∼90% in real waters. Correlation analysis suggested that TrOCs abatement decreased linearly with increasing concentration of dissolved organic matter (DOM) and halide ions in real waters. The TrOCs with electron-donating groups were more likely to be decomposed in PM/BS process. The PM/BS pretreatment produced MnO2 and decreased the aromatic signal of the DOM, which enhanced the removal of DOM during subsequent coagulation-sedimentation processes. Comparing with ozonation, chlorination, and permanganate processes, PM/BS process showed some advantages in terms of TrOCs abatement and operating costs. Furthermore, the pilot-scale experiment confirmed that PM/BS process combined with traditional water treatment processes could achieve excellent TrOCs abatement (greater than 84%).
... With the wide application of disinfection technologies based on chlorine, a large group of Halogenated Organic Compounds (HOCs) can be generated as disinfection by-products (DBPs) (Richardson et al., 2007). Due to the enrichment in bodies through the food chain, HOCs are harmful to both human and wildlife (Butt and Stapleton, 2013;Sedlak and von Gunten, 2011;Teuten et al., 2005). Besides the common DBPs, such as trihalomethanes (THMs) and haloacetic acids (HAAs) (Richardson et al., 2007), a new series of halogenated DBPs, chlorophenols (CPs), which are highly toxic, mutagenic and carcinogenic (Pera-Titus et al., 2004), have been detected during the chlorination of organic matter in large-scale disinfection of drinking water (Ge et al., 2006;Xiao et al., 2012). ...
In this study, efficient simultaneous degradation and dechlorination of the photo-recalcitrant emerging disinfection byproduct, 2-chlorophenol (2-CP), was achieved by vacuum-ultraviolet (VUV) system for the first time. Different from the conventional UV system, the combined action of direct photolysis and OH oxidation in VUV system led to a significantly higher removal efficiency for 2-CP. In UV system, 2-CP degradation rate constants was independent of the initial 2-CP concentration, and was increased with enhancing pH. To the contrary, in VUV system, higher initial concentration of 2-CP resulted in lower rate constant, and the degradation rates of 2-CP under both acidic and alkaline conditions were higher than that at the neutral pH. Moreover, humic acid could inhibit 2-CP degradation more prominently in VUV system than in UV system, owing to the scavenging effect of OH by it. The degradation pathways of 2-CP were proposed based on the identified main degradation products by GC–MS/MS. Furthermore, degradation of the other seven typical halogenated phenols by VUV irradiation in tap water, ultrafiltrated water and Mill-Q water were investigated to verify the feasibility of the system. Based on the systematic economic analysis, VUV process is economically feasible for the advanced treatment of tap water to remove halogenated phenols.
... Chlorination is a low-cost disinfection process of drinking water; this method has been used for a long time to inactivate waterborne pathogens and control microbial growth [1]. However, pollutants that originally exist in source water result in numerous disinfection byproducts during this process [2]. ...
The chlorination of parent polycyclic aromatic hydrocarbons (PAHs) has become a recognized fact during chlorination disinfection. However, bromide ion (Br⁻), which exists in natural water, may fundamentally affect the reaction mechanism. This study investigated the transformation mechanism of PAHs and the formation trend of halogenated PAHs (HPAHs) in the presence of Br⁻ during chlorination. Twelve PAHs were divided into two groups, active and inactive, containing only hypochlorous acid (HOCl). However, the presence of Br⁻ accelerated the reaction process of active PAHs. At high a Br⁻ concentration, inactive PAHs transformed to become “false active”. Two reaction types, including electrophilic substitution and single electron transfer reactions, occurred in PAHs during chlorination. We screened the transformation products using comprehensive two-dimensional gas chromatography-time of flight-mass spectrometry (GC × GC-TOF MS) and identified the occurrence of two reaction types. The presence of Br⁻ affected the species of transformation products. In general, the number of species of chlorinated PAHs decreased and those of brominated PAHs increased with an increase in the Br⁻ concentration. In addition, we first observed the occurrence of 2 types of brominated and chlorinated acenaphthenes, predicted the formation pathways, and inferred the most probable structure using a quantum chemical computation method. Therefore, the formation mechanism of HPAHs in drinking water during the chlorination treatment process was evaluated. The presence of HPAHs in drinking water requires more attention.
... Strategies to reduce chlorinated DBP levels in drinking water include switching from chlorination to other disinfection methods, removing DBPs after formation, and removing NOM. Replacing chlorine with chloramines can reduce THM and HAA formation, but chloramines can increase the formation of nitrosamines, toxic, unregulated DBPs that can cause leaching of lead pipes (46). DBPs can be removed from water by air stripping using countercurrent packed columns, diffused and sprayed aeration, and hollow fiber membranes, but these methods apply only to volatile DBPs. ...
Alongside the rising global water demand, continued stress on current water supplies has sparked interest in using nontraditional source waters for energy, agriculture, industry, and domestic needs. Membrane technologies have emerged as one of the most promising approaches to achieve water security, but implementation of membrane processes for increasingly complex waters remains a challenge. The technical feasibility of membrane processes replacing conventional treatment of alternative water supplies (e.g., wastewater, seawater, and produced water) is considered in the context of typical and emerging water quality goals. This review considers the effectiveness of current technologies (both conventional and membrane based), as well as the potential for recent advancements in membrane research to achieve these water quality goals. We envision the future of water treatment to integrate advanced membranes (e.g., mixed-matrix membranes, block copolymers) into smart treatment trains that achieve several goals, including fit-for-purpose water generation, resource recovery, and energy conservation.
Expected final online publication date for the Annual Review of Chemical and Biomolecular Engineering, Volume 11 is June 8, 2020. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
... While disinfectant residuals are effective in managing microbial growth in the DWDS, there are some key issues associated with them. These include esthetic and corrosion related problems [25,27,28] but more importantly the formation of harmful disinfection byproducts (DBPs) [29][30][31], which are also regulated. Further, there is an increasing recognition that the disinfectant residuals may be associated with selection of some opportunistic pathogens [16,32] and antibiotic resistance genes (ARGs) in drinking water [33][34][35]. ...
Limiting microbial growth during drinking water distribution is achieved either by maintaining a disinfectant residual or through nutrient limitation without using a disinfectant. The impact of these contrasting approaches on the drinking water microbiome is not systematically understood. We use genome-resolved metagenomics to compare the structure, metabolic traits, and population genomes of drinking water microbiome samples from bulk drinking water across multiple full-scale disinfected and non-disinfected drinking water systems. Microbial communities cluster at the structural- and functional potential-level based on the presence/absence of a disinfectant residual. Disinfectant residual alone explained 17 and 6.5% of the variance in structure and functional potential of the drinking water microbiome, respectively, despite including multiple drinking water systems with variable source waters and source water communities and treatment strategies. The drinking water microbiome is structurally and functionally less diverse and variable across disinfected compared to non-disinfected systems. While bacteria were the most abundant domain, archaea and eukaryota were more abundant in non-disinfected and disinfected systems, respectively. Community-level differences in functional potential were driven by enrichment of genes associated with carbon and nitrogen fixation in non-disinfected systems and γ-aminobutyrate metabolism in disinfected systems likely associated with the recycling of amino acids. Genome-level analyses for a subset of phylogenetically-related microorganisms suggests that disinfection selects for microorganisms capable of using fatty acids, presumably from microbial decay products, via the glyoxylate cycle. Overall, we find that disinfection exhibits systematic selective pressures on the drinking water microbiome and may select for microorganisms able to utilize microbial decay products originating from disinfection-inactivated microorganisms.
... There was a statistically significant increase in short gestational duration and low birth weight and especially in short body length and very small head circumference in areas using sodium hypochlorite as a disinfectant [6]. In addition to inactivating water-borne pathogens, Cl reacts with natural organic matter to produce a variety of toxic disinfection by-products (DBPs) when Cl disinfection is applied to drinking water [7]. Among men, exposure to chlorinated surface water enhanced the risk of bladder cancer [8,9]. ...
The detection sensitivity of chlorine (Cl) and sulfur (S) elements is poor using direct laser-induced breakdown spectroscopy (LIBS) because of the high ionization energy of Cl and S. Therefore, a new technique, namely indirect laser-induced breakdown spectroscopy (ID-LIBS), was proposed to improve the detection sensitivity of Cl and S elements. The method detected Cl in water by indirectly detecting the excess silver (Ag) after the precipitation reaction of Ag and chloride. Similarly, the method indirectly detected S in water by detecting the excess barium (Ba) after the precipitation reaction of Ba and sulfate, due to Ag and Ba with low ionization energy and easy excitation. The lines of Ag I 546.5 nm and Ba I 553.5 nm were detected. The R² values of 0.999 and 0.997 were obtained for Cl and S, respectively. The limit of quantitation (LoQ) was 2 mg/L for Cl and 5 mg/L for S. The detection sensitivity was improved by about three orders of magnitude compared to using Cl I 822.17 nm and S I 921.28 nm. The results showed that the technique of indirect LIBS can achieve the sensitive detection of Cl and S in water indicating that the technique has tremendous potential for element analysis of water.
... Despite its critical importance for public health, 1 disinfection of drinking water has raised concerns because of the formation of disinfection by-products (DBPs). 2,3 DBPs are formed by the reactions between disinfectants (commonly chlorine or chloramine) and natural organic matter (NOM) as well as inorganic precursors (e.g., bromide). 2 Epidemiological studies suggested an increased risk of bladder cancer after life-long ingestion of chlorinated drinking water pointing toward adverse health effects of DBPs. ...
Disinfection by-products (DBPs) in drinking water have been associated with increased cancer risk but single DBPs cannot explain epidemiological cancer occurrences. To test if combined effects of DBPs are plausible to explain epidemiological evidence for adverse health effects, we assessed if mixture effects of DBPs can be predicted using the concentration addition (CA) model. We prepared 12 mixtures of DBPs (trihalomethanes, halonitromethanes, haloacetonitriles, haloketones, haloacetic acids, chloral hydrate, haloacetamides, 3-chloro-4-(dichloromethyl)-5-hydroxy-5H-furan-2-one) in equipotent concentration ratios. We determined effect concentrations with three reporter gene bioassays (AREc32, ARE-bla, and p53-bla) based on human cell lines and one bacterial assay (Microtox). The experimental effect concentrations agreed well with the effect concentrations predicted with the CA model, which suggests that the CA model is applicable for reactive DBPs despite different molecular mechanisms because the reporter gene assays are only detecting one mechanism each. Modelling of mixture effects of DBPs in ratios detected in drinking water revealed that haloacetonitriles, haloketones, and mono-haloacetic acids contributed the most to the total effect indicating a higher health relevance of these DBP groups. In drinking water samples the sum of the detected DBPs explained <6% of effect in most cases. The CA model could be applied to prioritize DBPs for further risk assessments to potentially close the gap between toxicological cancer risk predictions and epidemiological findings.
... Disinfection of marine culture water is essential in RAS to prevent disease outbreak and pathogen contamination [4]. Chlorine, chlorine dioxide, chloramines, and sodium hypochlorite (NaClO) are chlorination disinfectants used frequently in marine culture [5]. The disinfectants inactivate any residual pathogenic microorganisms, meanwhile, they can also react with the organic matter and inorganic ions (e.g., bromide ions and iodine ions) in source water to generate unintended halogenated disinfection byproducts (DBPs) such as trihalomethanes (THMs) and haloacetic acids (HAAs). ...
The effects of water matrices on the reaction kinetics and transformation products of roxithromycin (ROX) with sodium hypochlorite (NaClO) were investigated. It was found that the removal efficiency of ROX was dependent on the type of disinfected water. For simulated fresh water, marine culture water and seawater, the reaction rate constant was 0.0521 min⁻¹, 0.0757 min⁻¹ and 0.106 min⁻¹, respectively. The bromide ions in seawater and marine culture water not only promoted the reaction of ROX with NaClO but also caused the generation of brominated DBPs (Br-DBPs). Four DBPs including one chlorinated DBP (Cl-DBP) and three Br-DBPs were identified. The cladinose moiety and C14 atom were the main reaction centers which were easily attacked by disinfectant in fresh water. The desosamine moiety was also broken away from the parent compound ROX in the simulated marine culture water and seawater. Adsorbable organic halogen (AOX) analysis demonstrated that the Br-DBPs in water samples containing bromide ions were generally more carcinogenic than the Cl-DBPs formed in fresh water.
... Chlorine has been the most widely used disinfectant for many decades, and it has been able to control microbial contaminants in order to improve drinking water quality and thus protect public health [1]. However, disinfection of water using chlorine results in the formation of disinfection byproducts (DBPs), which are a profound concern [2][3][4][5][6]. ...
Global production of engineered nanoparticles (ENPs) continues to increase due to the demand of enabling properties in consumer products and industrial applications. Release of individual or aggregates of ENPs have been shown to interact with one another subsequently resulting in adverse biological effects. This review focuses on silver nanoparticles (AgNPs), which are currently used in numerous applications, including but not limited to antibacterial action. Consequently, the release of AgNPs into the aquatic environment, the dissociation into ions, the binding to organic matter, reactions with other metal-based materials, and disruption of normal biological and ecological processes at the cellular level are all potential negative effects of AgNPs usage. The potential sources of AgNPs includes leaching of intact particles from consumer products, disposal of waste from industrial processes, intentional release into contaminated waters, and the natural formation of AgNPs in surface and ground water. Formation of natural AgNPs is greatly influenced by different chemical parameters including: pH, oxygen levels, and the presence of organic matter, which results in AgNPs that are stable for several months. Both engineered and natural AgNPs can interact with metal and metal oxide particles/nanoparticles. However, information on the chemical and toxicological interactions between AgNPs and other nanoparticles is limited. We have presented current knowledge on the interactions of AgNPs with gold nanoparticles (AuNPs) and titanium dioxide nanoparticles (TiO2 NPs). The interaction between AgNPs and AuNPs result in stable bimetallic Ag-Au alloy NPs. Whereas the interaction of AgNPs with TiO2 NPs under dark and light conditions results in the release of Ag⁺ ions, which may be subsequently converted back into AgNPs and adsorb on TiO2 NPs. The potential chemical mechanisms and toxic effects of AgNPs with AuNPs and TiO2 NPs are discussed within this review and show that further investigation is warranted.
... Epidemiological studies have shown that consumption of chlorinated drinking water with halogenated DBPs is related to increased spontaneous abortions, stillbirth, birth defects, and bladder and colorectal cancers [1][2][3]. To control DBPs, efforts have been devoted to minimizing the formation of DBPs by removing the major DBP precursor, NOM, or by adopting alternative disinfectants [4,5]. Notably, the precursor removal may not be very effective and the application of alternative disinfectants may generate their own sets of DBPs. ...
... Because chloramine species have a moderate oxidizing power and thus react less with dissolved organic matter, they form fewer organochlorinated by-products. As such, chloramines are increasingly used as an alternative to conventional chlorination and serve as microbial disinfectants for nearly half the population of the USA [116,[123][124][125][126][127][128]. Consequently, residual chloramines in drinking water are not a health concern, and in fact may be desirable. ...
Nitrate contamination in surface and ground waters is one of this century's major engineering challenges due to negative environmental impacts and the risk to human health in drinking water. Electrochemical reduction is a promising water treatment technology to manage nitrate in drinking water. This critical review describes the fundamental principles necessary to understand electrochemical reduction technologies and how to apply them. The focus is on electrochemical nitrate reduction mechanisms and pathways that form undesirable products (nitrite, ammonium) or the more desirable product (dinitrogen). Factors influencing the conversion rates and selectivity of electrochemical nitrate reduction, such as electrode material and operating parameters, are also described. Finally, the applicability for treating drinking water matrices using electrochemical processes is analyzed, including existing implementation of commercial treatment systems. Overall, this critical review contributes to the understanding of the potential applications and constraints of electrochemical reduction to manage nitrate in drinking waters and highlights directions for future research required for implementation.
... Chlorine has been the most widely used disinfectant for many decades, and it has been able to control microbial contaminants in order to improve drinking water quality and thus protect public health [1]. However, disinfection of water using chlorine results in the formation of disinfection byproducts (DBPs), which are a profound concern [2][3][4][5][6]. ...
Disinfection of drinking water is important to prevent microbial infection and disease. However, chlorine as a disinfectant is capable of reacting with inorganic and organic constituents of water to produce hazardous chlorinated disinfection byproducts (Cl-DBPs). Brominated and iodinated DBPs (Br-DBPs and I-DBPs), which are more genotoxic and cytotoxic than their chlorinated analogs, may also be formed in the presence of bromide (Br⁻) and iodide (I⁻) in water. This paper first reviews the formation of Cl-DBPs and Br-DBPs by considering the rates of the reactions of chlorine with natural organic matter (NOM) and its model compounds. The reactions of chlorine with Br⁻ and I⁻ yield acids (HOBr/OBr⁻ and HOI/OI⁻, respectively), which subsequently either disproportionate or react with NOM to form Br-DBPs and iodate/I-DBPs, respectively. The mechanisms of the formation of DBPs in the presence of metal ions and metal oxides (which already exist in water and are released from pipes) and nanoparticles (NPs) (input from the use of consumer products) are then reviewed. Water parameters (pH, cationic and anionic constituents, and types and concentration of NOM) also influence the production of DBPs. Plausible mechanisms of the influence of metal ions on the formation of bromate involve complexation of metal ions with moieties of NOM. Metal oxides catalyze the reactions accountable for the formation of Br-DBPs. Only a few studies have been conducted on the effect of NPs on DBP production during chlorination. More research is needed to understand the variation in NP chemistry under environmental conditions (pH, dissolution, and light), and whether NPs influence DBP formation during chlorination.
... Chlorine is extensively used as a disinfectant in municipal sewage treatment plants due to its effectiveness, low cost and ease of application (Lee and von Gunten, 2010;Drinan and Spellman, 2012;Shannon et al., 2008). In addition to inactivating pathogenic microorganisms, chlorine reacts with effluent organic matter present in sewage effluents to generate unintended disinfection byproducts (DBPs) (Rebhun et al., 1997;Shon et al., 2006;Krasner et al., 2009;Sedlak and von Gunten, 2011;Tang et al., 2012;Hatt et al., 2013;Huang et al., 2016;Cai et al., 2016). ...
Chlorination is extensively applied for disinfecting sewage effluents, but it unintentionally generates disinfection byproducts (DBPs). Using seawater for toilet flushing introduces a high level of bromide into domestic sewage. Chlorination of sewage effluent rich in bromide causes the formation of brominated DBPs. The objectives of achieving a disinfection goal, reducing disinfectant consumption and operational costs, as well as diminishing adverse effects to aquatic organisms in receiving water body remain a challenge in sewage treatment. In this study, we have demonstrated that, with the same total chlorine dosage, a three-step chlorination (dosing chlorine by splitting it into three equal portions with a 5-min time interval for each portion) was significantly more efficient in disinfecting a primary saline sewage effluent than a one-step chlorination (dosing chlorine at one time). Compared to one-step chlorination, three-step chlorination enhanced the disinfection efficiency by up to 0.73-log reduction of Escherichia coli. The overall DBP formation resulting from one-step and three-step chlorination was quantified by total organic halogen measurement. Compared to one-step chlorination, the DBP formation in three-step chlorination was decreased by up to 23.4%. The comparative toxicity of one-step and three-step chlorination was evaluated in terms of the development of embryo-larva of a marine polychaete Platynereis dumerilii. The results revealed that the primary sewage effluent with three-step chlorination was less toxic than that with one-step chlorination, indicating that three-step chlorination could reduce the potential adverse effects of disinfected sewage effluents to aquatic organisms in the receiving marine water.
... Chlorine is one of the most frequently used disinfectants in drinking water and wastewater because of its effective reactivity against bacteria and viruses (Tawk et al. 2015). In recent years, there has been an increasing concern about the fate of organic micropollutants during water chlorination (Deborde and von Gunten 2008;Sedlak and von Gunten 2011). However, many studies found that the pollutants were not mineralized effectively during the chlorination process, but the pollutants were transformed (Soufan et al. 2012). ...
The reactivity and fate of parabens during chlorination were investigated in this work. Chlorination kinetics of methylparaben (MeP), ethylparaben (EtP), propylparaben (PrP), and butylparaben (BuP) were studied in the pH range of 4.0 to 11.0 at 25 ± 1 °C. Apparent rate constants (k app) of 9.65 × 10(-3) M(-0.614)·s(-1), 1.77 × 10(-2) M(-1.019)·s(-1), 2.98 × 10(-2) M(-0.851)·s(-1), and 1.76 × 10(-2) M(-0.860)·s(-1) for MeP, EtP, PrP, and BuP, respectively, were obtained at pH 7.0. The rate constants depended on the solution pH, temperature, and NH4 (+) concentration. The maximum k app was obtained at pH 8.0, and the minimum value was obtained at pH 11.0. The reaction rate constants increased with increasing temperature. When NH4 (+) was added to the solution, the reaction of parabens was inhibited due to the rapid formation of chloramines. Two main transformation products, 3-chloro-parabens and 3,5-dichloro-parabens, were identified by GC-MS and LCMS-IT-TOF, and a reaction pathway was proposed. Dichlorinated parabens accumulated in solution, which is a threat to human health and the aqueous environment.
... Currently, the most common method of disinfection is chlorination, presenting as inconvenient the need for transportation and storage of hazardous reagents, careful and judicious application of established dosage and compliance with the safety requirements with the consequent increase in operating costs (Rajab et al. 2015). Furthermore, this method can promote the formation of by-products, which have adverse effects on human health, such as trihalomethanes and chloramines (Sedlak and Von Gunten 2011). In addition to these inconvenience, studies have shown that chlorination, as well as the Responsible editor: Angeles Blanco UV method using low pressure lamp, are not completely effective in the treatment of water, since some pathogens have reactivation capability, such as Escherichia coli and Campylobacter jejuni, the rotavirus and astrovirus viruses, Cryptosporidium parvum and Giardia lamblia parasites, and the fungi Microsporidia (Szewzyk et al. 2000;Gusmão et al. 2010). ...
The yeast Saccharomyces cerevisiae, a microorganism with cell walls resistant to many types of treatments, was chosen as a model to study electrochemical disinfection process using dimensionally stable anodes (DSA). DSA electrodes with nominal composition of Ti/RuO2TiO2 and Ti/RuO2TiO2IrO2 were evaluated in 0.05 mol L−1 Na2SO4 containing yeast. The results showed inactivation about of 100 % of the microorganisms at Ti/RuO2TiO2 by applying 20 and 60 mA cm−2 after 120 min of electrolysis, while a complete inactivation at Ti/RuO2IrO2TiO2 electrode was achieved after 180 min at 60 mA cm−2. When chloride ions were added in the electrolyte solution, 100 % of the yeast was inactivated at 20 mA cm−2 after 120 min of electrolysis, independent of the anode used. In the absence of chloride, the energy consumption (EC) was of 34.80 kWh m−3, at 20 mA cm−2 by using Ti/RuO2TiO2 anode. Meanwhile, in the presence of chloride, EC was reduced, requiring 30.24 and 30.99 kWh m−3 at 20 mA cm−2, for Ti/RuO2TiO2 and Ti/RuO2IrO2TiO2 electrodes, respectively, The best performance for cell lysis was obtained in the presence of chloride with EC of 88.80 kWh m−3 (Ti/RuO2TiO2) and 91.85 kWh m−3 (Ti/RuO2IrO2TiO2) to remove, respectively, 92 and 95 % of density yeast. The results clearly showed that yeast, as a model adopted, was efficiently inactivated and lysed by electrolysis disinfection using DSA-type electrodes.
... The main reason is that almost none of these disinfectants fulfils each of the three most important requirements of a disinfectant: effectiveness, relatively low cost and the ability to provide a residual in the distribution system to prevent regrowth of microorganisms (Tibbetts, 1995). The only exception of that is chloramine, which has though been linked to the formation of toxic nitrogen-containing DBPs (N-DBPs) (Sedlak and Von Gunten, 2011). Although the concentrations of N-DBPs are normally lower than that of common halogenated DBPs (Krasner et al., 2006), e.g. ...
... The reactivity towards metals may also prevent lead leaching from pipes. This was observed after substitution of chlorination by chloramination, which led to increased levels of dissolved lead in the distribution system and human blood [25]. ...
... DBPs are primarily formed from the reactions between disinfectants (e.g., chlorine) and certain organic matters or inorganic species (e.g., bromide and iodide) [1]. Over the past four decades, a few hundreds of DBPs have been identified [2,3]. Among them, nitrogen-containing DBPs (N-DBPs) have gradually become a new focus, because they are generally more toxic than carbonaceous DBPs (C-DBPs) such as trihalomethanes (THMs), which are well studied and regulated in many countries [4][5][6]. ...
Free amino acids (AAs) can form trihalomethanes (THMs) and haloacetonitriles (HANs) during chlorination in drinking water treatment plants, but they account for a small fraction of dissolved organic nitrogen (DON) pool in natural waters. In contrast, combined AAs contribute to a greater identifiable DON portion, but the information on the formation and control of THMs and HANs from them is limited. Ultraviolet/hydrogen peroxide (UV/H2O2) and ultraviolet/persulfate (UV/PS), two typical UV-based advanced oxidation processes (UV-AOPs), are both promising drinking water technologies for the reduction of trace organic contaminants. The objective of this study is to examine the effects of the two UV-AOP pre-treatments on the formation of carbonaceous and nitrogenous disinfection by-products (C- and N-DBPs), which were indicated by THMs and HANs, respectively, during post-chlorination and chloramination of tyrosine (Tyr) in free and combined forms. Results showed that direct UV photolysis, PS pre-oxidation alone or H2O2 pre-oxidation alone did not significantly impact the THM and HAN formation during subsequent chlorination. However, the two UV-AOP pre-treatments could somewhat alter the DBP formation. In general, under the identical doses (UV irradiation dose and molar oxidant dose), UV/PS pre-treatment better controlled the HANs than UV/H2O2 during AA post-chlorination, though UV/PS might slightly promote the formation of chloroform. In contrast, the two UV-AOP pre-treatments did not obviously affect the THM and HAN formation when post-chloramination was applied. In addition, a marked difference was observed in the speciation of DBPs formed from free AAs and short oligopeptides in the presence of bromide. For free Tyr, more brominated THMs were formed than brominated HANs; but for short oligopeptides, more bromine was incorporated into HANs than THMs.
Porphyrins are differentiated π-conjugated compounds with unique photochemical and redox properties. The tetrapyrrole macrocycle core of porphyrins is extremely favorable for the complexation of metal ions, resulting in hybrid metal–organic molecules with good photocatalytic properties. Over the years, porphyrins have been extensively tested as photocatalysts in advanced oxidative processes for the degradation of various organic contaminants in water. Recently, the use of porphyrins supported on solid materials is viewed as one of the most effective strategies to obtain photocatalytic systems with superior properties and applicability. Supported porphyrins can form highly organized hybrid materials, with high electron conductivity and great photoreaction properties. Here we review concepts, development, and application of supported porphyrins/metalloporphyrins. The first sections present an overview of the water contamination problem, the fundamentals of the photocatalytic treatment of water, and the main properties of porphyrins. The following sections focus on the application of supported porphyrins in the photodegradation of common organic contaminants in water. The last two sections discuss the main mechanisms and limitations.
The present emphasis on environmental preservation and human health is resulting in an increased use of chlorine for disinfection and waste water treatment. Increased use of chlorine and present study of chlorine toxicity in aquatic organisms have emphasized the need for close scrutiny of present disinfection procedures. Breathing rate of Oreohromis niloticus in control was found to be stable and the average value in a minute was 123. It was noted that as the dosage concentration of chlorine increases the rate of gill movement decreases gradually. A significant negative correlation was noted between dosage concentration and gill movement. The average gill movement varied from 123 in the control to 64 in 20 ppt. It was found that as the concentration of chlorine increases the amount of oxygen consumption is also increases. Average value showed a clear trend of increased rate of oxygen consumption with that of increased level of chorine in the medium. The oxygen consumption was varied between 0.0117 mg/ml/gm body weight in control to 0.01975 mg/ml/gm body weight in 20 ppt of Chlorine.
Nitrogenous disinfection by-product (N-DBPs) has always been one of the most concerned disinfection by-products (DBPs) in recent years. The toxicity of regulated DBPs is generally less than that of N-DBPs, which have been widely detected in finished drinking water. Despite the fact that N-DBPs are highly toxic, there are currently no N-DBPS species officially regulated by governments around the world. This paper provides a review of the formation mechanism and precursors of nitrogen-containing disinfection by-products in drinking water treatment. Also, the spcieces and inducing factors of N-DBPs were summarized. The data were mainly collected from 2000-2002 and 2006-2007 US Survey in effluents of US WTPs. Because nitrogen source is a prerequisite for the formation of nitrogen-DBP in drinking water, the occurrence of N-DBPS may increase due to the influence of sewage and algae blooms on water sources. Chloramine disinfection are used in most of developed countries for preferred secondary disinfection to reduce the formation of chlorine-related by-products, but this increases the formation potential of N-DBPs. Furthermore, the safety control of N-DBPs and suggestions for the further exploration of for efficient drinking water are discussed. Coagulation and filtration are not very effective in removing precursors (such as amino acids) of N-DBPs and the precursors need to be removed before disinfection.
Exposure to pathogenic microorganisms, especially viruses, can lead to various diseases, allergies, and hospital infections. The application of sampling procedure is still a challenge to sample viruses from different environments such as air, water, wastewater, etc. However, there are many procedures such as filtration, impactor, impinger, cyclone, electrostatic separator, and MD-8 airscan that are applied for sampling and measuring viruses from air. Among conventional filters, the gelatin type can be readily dissolved in a liquid for molecular counting or cell culture without significant changes in virus tissue. Liquid impingers are the most frequent devices that are applied for the collection of viral aerosols. Also, many methods including precipitation, ultracentrifugation, electronegative membrane, and ultrafiltration have been used to prepare samples of food, wastewater, feces, urine, and surfaces. In many studies, the aforementioned methods have been employed to sample the coronaviruses such as SARS-CoV-2 in various environments. Also, various PCR procedures have been commonly used to identify the virus from the environmental samples.
The growth of undesired bacteria can cause numerous problems. Seeking effective and sustainable bacteria inactivation approaches is an everlasting effort. Here, we show that nano-enhanced electric field treatment (NEEFT) can cause rapid bacteria inactivation with a lower applied voltage than bulk EFT. A lab-on-a-chip with nanowedge-modified electrodes is developed, and the bacteria inactivation in NEEFT is visualized and studied in real-time at a single-cell level. Rapid bacteria inactivation (~ 1 ms) occurs specifically at nanowedge tips where the electric field is enhanced due to the lightning-rod effect. Nanowedges with a high aspect ratio are critical for bacteria inactivation. NEEFT works for both immobilized and free-moving cells, where the free-moving cells will be first attracted to the nanowedge tips followed by rapid inactivation. The mechanism study shows that the bacteria inactivation is caused by electroporation induced by the nano-enhanced electric field. The bacteria inactivation performance depends on the strength of the enhanced electric field instead of the applied voltage. Quick pore closure and membrane recovery under moderate NEEFT indicate that electroporation is the predominant mechanism. NEEFT only requires facile treatment to achieve bacteria inactivation, which is safe for treating delicate samples and energy-efficient for large scale applications. It is also expected to find applications for targeted cell inactivation.
El objetivo del presente trabajo fue evaluar tres procesos para la remoción de materia orgánica e inactivación de Salmonella spp re inoculada en agua proveniente de granjas porcícolas. Se hicieron muestreos puntuales del agua para realizar la caracterización física, química y microbiológica. A continuación, se seleccionaron las condiciones de operación que favorecieran el proceso de fotólisis a través de un diseño factorial 2x2. Finalmente se realizaron cinéticas de inactivación/remoción valorando fotólisis UV254 nm, fotólisis UV254 nm con peróxido de hidrógeno H2O2 a 15 ppm y peróxido de hidrógeno H2O2 a 15 ppm. La inactivación de Salmonella spp se favoreció al emplear una aireación de 1 L/min y con una concentración de Salmonella spp de 1x104 UFCmL-1 obteniendo una inactivación de 97.3±1.9% a los 10 minutos de tratamiento. Por otro lado, para las cinéticas de inactivación se estableció que los mejores tratamientos fueron fotólisis y fotólisis/H2O2, sin que hubiera diferencias significativas. A los 30 segundos de exposición la inactivación de Salmonella fue del 99.9±2.4% en T1, con una remoción de la demanda química de oxígeno (DQO), NO3 y NO2 del 30±2, 27±3, 83±4, 41±1,0 y 99±5% para T1 y T2 respectivamente. La bacteria se recuperó en T2 y T3 y los tratamientos no tuvieron efecto residual, determinando que las poblaciones finales fueran de 8 UFC/ml y 3x103 UFC/ml, respectivamente.
Transformation of atenolol (ATN), a micropollutant containing a secondary (2o) amine moiety, can be significantly enhanced in water treatment with sequential and combined use of chlorine and UV (chlorine/UV) through photolysis of the N-Cl bond. This study investigated the transformation kinetics, products, and mechanisms of the amine moiety of ATN in chlorine/UV (254nm). The fluence-based, photolysis rate constant for N-Cl ATN was 2.0×10⁻³ cm²/mJ. Transformation products (TPs) with primary (1o) amines were mainly produced, but TPs with 2o and 3o amines were also formed, based on liquid chromatography (LC)/quadrupole-time-of-flight/mass spectrometry and LC/UV analyses. The amine-containing TPs could be further transformed in chlorine/UV (with residual chlorine in post UV) via formation and photolysis of new N-Cl bonds. Photolysis of N-Cl 1o amine TPs produced ammonia as a major product. These data could be explained by a reaction mechanism in which the N-Cl bond was cleaved by UV, forming aminyl radicals that were transformed via 1,2-hydrogen shift, β-scission, intramolecular addition, and 1,2-alkyl shift. Among these, the 1,2-alkyl shift is newly discovered in this study. Despite enhanced transformation, only partial mineralization of the ATN’s amine moiety was expected, even under UV/chlorine advanced oxidation process conditions. Overall, the kinetic and mechanistic information from this study can be useful for predicting the transformation of amine moieties by chlorine/UV water treatment.
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