Alternative Disinfection Technologies Research Articles

Formation of halonitromethanes from benzylamine during UV/chlorination: Impact factors, toxicity alteration, and pathways.

Halonitromethanes (HNMs), a representative nitrogen-containing disinfection byproduct, have gained significant concerns due to their higher cytotoxicity and genotoxicity. UV/chlorination is considered a promising alternative disinfection technology for chlorination. This study aimed to investigate the HNMs formation from benzylamine (BZA) during UV/chlorination. The experimental results revealed that the yields of HNMs initially raised to a peak then dropped over time. Higher chlorine dosage and BZA concentration promoted the formation of HNMs, whereas alkaline pH inhibited their formation. The presence of bromine ion (Br-) not only converted chlorinated-HNMs (Cl-HNMs) to brominated (chlorinated)-HNMs Br (Cl)-HNMs) and brominated-HNMs (Br-HNMs) but also enhanced the total concentration of HNMs. Besides, the calculated cytotoxicity index (CTI) and genotoxicity index (GTI) of HNMs were elevated by 68.97% and 60.66% as Br- concentration raised from 2 to 6µM. The possible formation pathways of HNMs from BZA were proposed based on the intermediates identified by a gas chromatography/mass spectrometry (GC/MS). In addition, the formation rules of HNMs in actual water verified the results in deionized water during UV/chlorination. The results of this study provide basic data and a theoretical basis for the formation and control of HNMs, which is conducive to applying UV/chlorination.

Formation of halonitromethanes from glycine during LED-UV265/chlorine disinfection

LED-UV265/chlorine is a promising alternative disinfection technology that emits mono-wavelength light for high germicidal efficiency. Halonitromethanes (HNMs) are highly cytotoxic and genotoxic disinfection byproducts that can be formed during LED-UV265/chlorine disinfection. Thus, this work aimed to investigate the HNMs formation from glycine (Gly) during LED-UV265/chlorine disinfection. The results indicated that the concentrations of chlorinated-HNMs (Cl-HNMs) increased first and then decreased as the reaction proceeded. Besides, the effects of operating parameters (UV intensity, free chlorine dosage, and pH) and coexisting ions (Cu2+ and Br−) on HNMs formation were investigated. It was found that the formation concentrations of Cl-HNMs increased with the increase of LED-UV265 intensity and free chlorine dosage but decreased with increased pH. The presence of Cu2+ promoted the formation of Cl-HNMs. The total concentration of HNMs (at 3 min) with adding 1.5 mg/L Cu2+ was 30.90% higher than that without Cu2+. Notably, nine species of HNMs were detected after adding Br−, and the total concentrations of HNMs were enhanced. Moreover, Cl-HNMs were gradually transformed into brominated (chlorinated)-HNMs and brominated-HNMs as Br− concentration increased. According to the findings, the possible formation mechanism of HNMs from Gly during LED-UV265/chlorine disinfection was deduced. Finally, it was demonstrated that the formation laws of HNMs from Gly in real water samples were basically consistent with those in simulated water. Insights obtained in this study help to comprehend the HNMs formation from Gly and provide strategies for controlling the production of HNMs during LED-UV265/chlorine disinfection.

How do material characteristics and antimicrobial mechanisms affect microbial control and water disinfection performance of metal nanoparticles?

Abstract Nanotechnology has been rapidly developing in the past decade, and metal nanomaterials have shown promising improvement in microbial control. Metal nanoparticles have been applied in medical settings for adequate disease spread control and to overcome the challenges of multidrug-resistant microorganisms. Recently, the demand for safe water supply has increased, requiring higher sanitation of the water treatment technology as well as being environmentally sustainable. However, the employed water disinfection technologies cannot meet the elevated demand due to limitations including chemical byproducts, immobility, energy consumption, etc. Metal nanomaterials are considered to be an alternative disinfection technology considering their high efficiency, mobility, and stability. A significant amount of research has been carried out on enhancing the antimicrobial efficiency of metal nanomaterials and determining the underlying antimicrobial mechanisms. This paper provides an overview of emerging metal nanomaterials development, including the synthesis method, material characteristics, disinfection performance, environmental factors, potential mechanism, limitations, and future opportunities in the water disinfection process.

Cu(II) assisted peroxymonosulfate for antibiotic resistant bacteria inactivation: A potential disinfection technology in swimming pool

Alternative disinfection technology to chlorination is required to control the risk of antibiotic resistance in swimming pools. In this study, copper ions (Cu(II)), which often exist in swimming pools as algicides, were used to activate peroxymonosulfate (PMS) for the inactivation of ampicillin-resistant E. coli. Cu(II) and PMS showed synergistic effects on E. coli inactivation in weak alkaline conditions, obtaining 3.4 log inactivation in 20 min with 10 μM Cu(II) and 100 μM PMS at pH 8.0. Quenching experiments indicated that radicals (i.e., OH and SO4−) were not the main disinfectors for E. coli inactivation. Based on the structure of Cu(II) and density functional theory calculations, the Cu(II)-PMS complex (Cu(H2O)5SO5) was recommended as the active species for E. coli inactivation. Under the experimental conditions, the PMS concentration had a greater influence on E. coli inactivation than the Cu(II) concentration, possibly because increasing PMS concentration accelerates ligand exchange reaction and facilitates active species generation. By forming hypohalous acids, halogen ions could improve the disinfection efficiency of Cu(II)/PMS. The addition of HCO3− concentration (from 0 to 1.0 mM) and humic acid (0.5 and 1.5 mg/l) did not significantly inhibit the E. coli inactivation. The feasibility of adding PMS to waters containing Cu(II) for the inactivation of antibiotic-resistant bacteria was validated in actual swimming pool waters, where 4.7 log inactivation of E. coli was achieved in 60 min.

Efficient wastewater disinfection by raised 1O2 yield through enhanced electron transfer and intersystem crossing via photocatalysis of peroxymonosulfate with CuS quantum dots modified MIL-101(Fe)

Peroxymonosulfate (PMS)-based photocatalysis is a promising alternative approach for wastewater disinfection. Singlet oxygen (1O2) is sensitive and efficient for bacterial inactivation. This study developed a 1O2-predominated PMS disinfection technique under visible light with CuS quantum dots (QDs) modified MIL-101(Fe) (CSQDs@MF). CuS QDs modification greatly enhanced the 1O2 quantum yield by 80% than that of MIL-101(Fe). Photoelectricity and photoluminescence tests demonstrated that both the enhanced electron transfer and energy transfer were responsible for improved 1O2 generation in Vis/PMS/CSQDs@MF system. The system took 60 min to inactivate 7.5-log E. coli, and it could be applied in a broad pH and dissolve oxygen range. Bacterial inactivation mechanism suggested that 1O2 attacked cell membrane first, then induced oxidative stress, up-regulated intracellular ROS level, eventually broke DNA strand. The system showed good disinfection performance on Gram-positive B. subtilis and fecal coliforms in practical wastewater, implying it is a promising alternative disinfection technology for wastewater treatment.

Degradation of organics and formation of DBPs in the combined LED-UV and chlorine processes: Effects of water matrix and fluorescence analysis

Combined processes of light-emitting diodes ultraviolet (LED UV) and chlorination (Cl2) are alternative disinfection technologies in drinking water, while the formation of disinfection by-products (DBPs) needs to be evaluated. This study investigated the impacts of critical water matrix factors on the DBP formation in the combined processes. Moreover, the correlation between the degraded natural organic matter (NOM) and the formed DBP was studied. Simultaneous UV/Cl2 outperformed single Cl2 and sequential combined processes in degrading humic acids (HA) and resulted in the highest DBP yield. Iodide at 5–20 μg/L and bromide at 0.05–0.2 mg/L slightly affected the degradation of organics, while increased the formation of brominated DBPs up to 36.6 μg/L. pH 6 was regarded as the optimum pH, achieving high efficiency of HA degradation and a lower level of total DBP formation than pH 7 and 8 by 11 % and 24 %, respectively. Compared to HA samples (46.8–103.9 μg/L per mg/L DOC), NOM in canal water were less aromatic and yielded fewer DBPs (19.6 and 21.2 μg/L per mg/L DOC). However, the extremely high bromide in site 1 samples (18.6 mg/L) shifted the chlorinated DBPs to their brominated analogues, posting around 1 order of magnitude higher levels of toxicities than HA samples. The reduction of absorbance at 254 nm (UV254) correlated with all DBP categories in HA samples, while the correlation coefficients were compromised when included in the canal samples. For the first time, this study found that parallel factor analysis (PARAFAC) would neglect the fluorescence change caused by iodide/bromide in UV/Cl2, while the changes could be captured by self-organising map (SOM) trained with full fluorescence spectra. Fluorescence Ex/Em pairs were proposed to predict DBP formation, suggesting a potential method to develop an online monitoring system for DBPs.

A critical review over the electrochemical disinfection of bacteria in synthetic and real wastewaters using a boron-doped diamond anode

Inadequate access to clean water and sanitation are the most relevant problems afflicting developing and industrialized nations. Global water scarcity is expected to grow worse in the coming decades and this has motivated the scientific community to identify new, safe, and robust water disinfection technologies at lower cost and with less energy, diminishing the use of chemicals and impact on the environment. Usually, conventional methods of water treatment can solve this problem satisfactorily, such as chlorination, but, sometimes, they can be chemically, energetically, and operationally intensive. Therefore, the science and technology has encouraged the development of other alternative disinfection technologies. In this frame, electrochemical disinfection or electrodisinfection is currently experiencing a renaissance due to the tremendous contributions of novel electrocatalytic materials as well as the use of electric current as an inexpensive and suitable reagent to drive the inactivation of waterborne pathogens, avoiding conventional chemical oxidizers or reducing agents. Electrodisinfection has a significant technical impact, because it can be easily scaled up or design small–portable devices, benefiting from advantages such as versatility, environmental compatibility, automation, inherent safety, and potential cost effectiveness among others. Diamond films emerge as a novel and sustainable solution to electrogenerate powerful oxidants for effectively controlling waterborne pathogens in drinking water. The overarching goal of this critical review is to evidence the importance of diamond electrochemical methods as alternative for the eradication of waterborne infectious agents from public and drinking waters. The mechanisms of bacteria inactivation, and the fundamentals and applications of electrochemical oxidation with diamond to disinfect synthetic and real waters and wastewaters are exhaustively discussed. The use of hybrid and sequential processes involving electrochemical oxidation with other techniques, as well as endodontic and food control applications, are also analyzed. A section remarking the future challenges of electrodisinfection with diamond is finally presented.

Application of UVOX Redox® for swimming pool water treatment: Microbial inactivation, disinfection byproduct formation and micropollutant removal

Alternative disinfection technologies may overcome some of the limitations of conventional treatment applied in swimming pools: chlorine-resistant pathogens (e.g. Cryptosporidium oocysts and Giardia cysts) and the formation of chlorinated disinfection byproducts. In this paper, results of full scale validation of an alternative disinfection technology UVOX Redox® (hereinafter referred to as UVOX) that combines ozonation and UV irradiation are presented. The performance was assessed in terms of microbial inactivation, disinfection byproduct formation and micropollutant removal. UVOX was able to achieve 1.4–2.7 log inactivation of Bacillus subtilis spores at water flows between 20 and 76 m³/h. Lower formation of trichloromethane and dichloroacetic acid was observed with UVOX followed by chlorination when compared to chlorination alone. However, due to the use of ozone and the presence of bromide in the pool water, the formation of trihalomethanes and haloacetic acids shifted to more brominated byproducts. Chlorine alone was able to remove the target micropollutants: acetaminophen, atenolol, caffeine, carbamazepine, estrone, estradiol, and venlafaxine (>97% removal) after 24 h, with the exception of ibuprofen (60% removal). The application of UVOX in chlorinated water enhanced the removal of ibuprofen. The application of UVOX could lower the usage of chlorine to the level that provides an adequate residual disinfection effect.

Virucidal effect of high power ultrasound combined with a chemical sanitizer containing peroxyacetic acid for water reconditioning in the fresh-cut industry

The use of chlorine-based sanitizers is widespread throughout the fresh produce industry in the process water to maintain microbial safety of produce, avoid cross-contamination and recycle water. In this study, alternative disinfection technologies were investigated due to the negative reports showing chlorine instability in the presence of organic matter and the undesirable by-product residues. Tsunami® (15.2% peroxyacetic acid and 11.2% hydrogen peroxide) and high-power ultrasound (HPU, 0.56 kW/l, 20 kHz), alone or in combination, were evaluated in lettuce process water analyzing their ability to reduce MNV during either produce washing or water recycling. PAA concentrations of 6.4, 12.8 and 16 mg/l as well as HPU were insufficient for application in the produce washing tank where a rapid MNV inactivation is required. In contrast, a complete rapid inactivation of MNV (7.4 log TCID50) was recorded when 80 mg/l of PAA was used. For recycled water reconditioning, HPU was applied and no virus reduction was observed. Two PAA concentrations (6.4 and 12.8 mg/l) that can be found in the recycled water were also tested. The MNV inactivation was faster at 12.8 mg/l than at 6.4 mg/l of PAA with 2.6 and 2 log reductions after 20 min contact. One additional log reduction was achieved 20 and 40 min later, respectively. MNV inactivation fitted the Bipashic model well. A contact time of 95 and 115 min would be required to obtain the complete elimination of MNV (4.4 log TCID50) by 6.4 and 12.8 mg/l of PAA. PAA efficacy was not enhanced by the combination with HPU in contrast to the inactivation of pathogenic bacteria tested in other studies. This indicates that viruses are more resistant to this hurdle technology than pathogenic bacteria such as Escherichia coli O157:H7, Salmonella and other HPU conditions such as higher frequencies and combination of HPU with other physical treatments need to be explored.

Efficacy of Pulsed UV-Light Treatment on Wastewater Effluent Disinfection and Suspended Solid Reduction

AbstractDisinfection of municipal wastewater effluents is a critical component of water pollution control. To achieve this, novel alternative disinfection technologies have been getting attention recently such as pulsed ultraviolet (UV) light, which can be used to inactivate microorganisms in a short time. Therefore, the research reported in this paper was undertaken to determine the efficacy of pulsed UV light for inactivation of Escherichia coli and Bacillus subtilis spores, in synthetic and real municipal wastewater effluent. The results with synthetic municipal wastewater effluent demonstrated that complete inactivation was obtained with an 8-cm sample distance, 30-mL sample volume, and 15-s time combination for E. coli [8.53log10 colony-forming units (CFUs)/mL reduction], whereas a 15-mL sample volume (with the same sample distance and treatment time) was required for B. subtilis (7.57log10CFU/mL reduction) at total energy dose of 10.9 J/cm2. A response surface model was developed to predict the ina...

Peracetic acid as an alternative disinfection technology for wet weather flows.

Rain-induced wet weather flows (WWFs) consist of combined sewer overflows, sanitary sewer overflows, and stormwater, all of which introduce pathogens to surface waters when discharged. When people come into contact with the contaminated surface water, these pathogens can be transmitted resulting in severe health problems. As such, WWFs should be disinfected. Traditional disinfection technologies are typically cost-prohibitive, can yield toxic byproducts, and space for facilities is often limited, if available. More cost-effective alternative technologies, requiring less space and producing less harmful byproducts are currently being explored. Peracetic acid (PAA) was investigated as one such alternative and this research has confirmed the feasibility and applicability of using PAA as a disinfectant for WWFs. Peracetic acid doses ranging from 5 mg/L to 15 mg/L over contact times of 2 to 10 minutes were shown to be effective and directly applicable to WWF disinfection.

INVESTIGATION OF EFFECTS OF MEDIA IONS ON THE E.COLI DISINFECTION BY ULTRASOUND

Diminishing water sources and their contamination by pathogenic microorganisms in pariculat set forth the neccessity of application of disinfection processes. Chlorine which has been used for disinfection purposes and disinfection by-products generated bu the reaction of chlorine with organic compounds are known to have adverse effects on human health, therefore the research on alternative disinfection techniques has brought into question. Ultrasound disinfection is among major alternative disinfection technologies. In this study the removal of Eschericia coli that is a major indicator microorganism which is a fecal contamination factor that can be found in water media, was performed in ultrasound reactor. Various frequencies were studied in ultrasound reactor and effects of various media ions (HCO 3 - , NO 3 - , SO 4 -2 ) and hydrogen peroxide and nitrogen gas fed to the system at various flow rates were examined. Optimum microorganism inactivation was attained when the operation frequency of the reactor is 28kHz. The increased concentration of SO 4 -2 and HCO 3 - ions added to the system favored the microorganism inactivation, however the presence of NO 3 - didn't change the inactivation yield of the ultrasound system

Chlorine Gas vs. Sodium Hypochlorite: What's the Best Option?

This article discusses a study by the city of Lakeville, Minnesota, to evaluate alternative disinfection technologies that was driven by U.S. Department of Homeland Security concerns about risks associated with handling, storing, and using toxic chlorine gas. The study evaluated alternative disinfection systems for the city's water treatment plant, considering the plant's existing system, safety, security, cost‐efficiency, and finished water quality. The Lakeville study did not evaluate ultraviolet, ozone, chloramine, or chlorine dioxide systems because of site and cost constraints. The study focused on sodium hypochlorite (NaOCl), that provides residual protection but is safer than chlorine gas and less expensive than other alternative disinfection systems. Installing a NaOCl system would require the city of Lakeville to make few modifications to its existing system, and finished water quality would be similar to what is presently produced. The article discusses the advantages and limitations of using sodium hypochlorite, and provides comparisons of capital costs and annual O&M costs of chlorine gas, commercial sodium hypochlorite, and on‐site sodium hypochlorite generation. The article includes a total present worth analysis for a 20‐mgd sodium hypochlorite disinfection system.

Electrochemical Alternatives for Drinking Water Disinfection

Chlorination is the most common method worldwide for the disinfection of drinking water. However, the identification of potentially toxic products from this method has encouraged the development of alternative disinfection technologies. Among them, electrochemical disinfection has emerged as one of the more feasible alternatives to chlorination. This article reviews electrochemical systems that can contribute to drinking water disinfection and underscores the efficiency of recently developed diamond films in chlorine-free electrochemical systems.

Photoreactivation of Escherichia coli following medium-pressure ultraviolet disinfection and its control using chloramination

Ultraviolet (UV) disinfection is becoming increasingly popular as an alternative disinfection technology to chlorination in recent years. In this study, we investigated the photoreactivation of Escherichia coli following medium-pressure (MP) UV disinfection of synthetic water by a bench-scale collimated beam apparatus. The UV doses ranged from 1.6 -19.7 mWs/cm2 and photoreactivation was investigated for 6 hours under fluorescent light. In addition, chloramination was applied after UV disinfection to investigate its ability to control photoreactivation. It was found that photoreactivation occurred for all UV doses tested and the increase in bacteria numbers ranged from 0.04 to 1.35 log10. However, the degree of photoreactivation decreased with increased UV doses. Chloramination experiments revealed that the addition of 0.5 mg/l of monochloramine resulted in suppression of photoreactivation for 1 hour only. An increased monochloramine dose of 1 mg/l was found to prevent photoreactivation for the entire duration of the experiment. The results of this study have shown that photoreactivation occurs even after MP UV disinfection, although it is of a lesser extent at higher UV doses. This study has also established that secondary chloramination can effectively suppress and eliminate photoreactivation with a chloramine dose of 1 mg/l.

A methodology for the evaluation of disinfection technologies

There are several concerns associated with the use of chlorine for potable water disinfection. These are the resistance of certain pathogens, the formation of toxic disinfection by-products and the adverse effects on aesthetic water quality. Owing to these concerns the water industry is continually reviewing alternative disinfection technologies. A methodology has been devised that will aid the water industry in evaluating the potential of these technologies. The methodology uses seven criteria to evaluate the technologies, these are: inactivation efficiency, disinfection byproduct (DBP) formation, toxicity, aesthetic water quality, cost, scalability and residual maintenance. Each criterion is assessed by associated questions in order of importance in accordance with a protocol. The criteria are evaluated using UK water quality regulations as standards. Ultraviolet (UV) disinfection was used as an example to demonstrate the methodology. UV was shown to meet all the criteria apart from the provision of a residual disinfectant. Several other disinfection technologies were evaluated using the methodology. Direct electrochemical disinfection and mixed oxidant generators were identified as having the most potential for replacing chlorination.

Electrochemical disinfection, an environmentally acceptable method of drinking water disinfection?

In general, chlorination is the method of drinking water disinfection most favoured by the water industry. Occasional outbreaks of water transmitted disease, the identification of chlorine as a source of potentially harmful disinfection by-products, and the emergence of recalcitrant pathogens has led to heightened regulation for the removal of microbial pathogens and disinfection by-products from drinking water. As a result, research and development of alternative disinfection technologies has intensified. Electrochemical disinfection has emerged as one of the more feasible alternatives to chlorination. Research using a range of cell configurations has shown electrochemical disinfection to be effective against a range of pathogens. However, in many of the systems, disinfection efficacy appears to be related to the generation of chlorine species. The apparent prevalence of chlorine as the mechanism of disinfection begs the question as to whether electrochemical disinfection has an advantage over chlorination in terms of its inactivation efficacy and potential to form disinfection by-products. This paper reports on a series of experiments evaluating the disinfection efficacy of an electrochemical disinfection technology against Escherichia coli and bacteriophage MS2. The results of these experiments conclude that electrochemical disinfection can be effective without the generation of chlorine species.

Different frames, different fears: communicating about chlorinated drinking water and cancer in the Canadian media

Risk issues become complicated when scientific evidence concerning a potential environmental exposure is equivocal; particularly when many argue that the public health benefits of a policy action outweigh any potential negative health effects. Chlorinated drinking water, and chlorinated disinfection byproducts (CDBPs) that are formed during the disinfection process, represent a useful case-study for examining these complications. We conduct a media analysis of chlorinated drinking water stories in the Canadian print media from 1977 to 2000. We examine media presentations of science compared to framings by scientists, regulators, the chlorine industry, water utility representatives, and non-governmental organizations of the CDBP issue based on key informant interviews. We argue that there are two main framings of the debate, each of which are powerful in constructing risk perceptions. On the one hand, many frame the debate as a ‘voluntary’ risk: we choose chlorine disinfection to protect against microbial risks with a possible adverse consequence of that protection. On the other hand, others frame the issue as an ‘involuntary’ risk: chlorine disinfection was a ‘choice’ imposed by public health and water utility officials; a choice that carries a potential cancer risk, and alternative disinfection technologies are advocated. We demonstrate these different frames by examining metaphorical constructs of water, chlorine and cancer contained within them.