Water disinfection: Innovations in chemistry and light

2010

Disinfection is the most essential and final treatment given to drinking water to render the water free from harmful pathogens. The most conventional and common form of disinfection involves the use of strong oxidants that have the potential to produce undesirable disinfection by-products (DBP). Therefore, many researchers have been trying to find alternative disinfection methods to reduce the adverse effects of conventional techniques. Hence, in this paper, these methods will be critically reviewed along with their advantages, disadvantages, and potential applications in specific circumstances. The most common methods that will be discussed in this paper are (i) chemical, (ii) thermal (iii) electrical and (iv) non-conventional technologies. The second part of this paper will focus on using ultrasound technology as a practical application of nonconventional technologies for disruption of the cell of microorganisms in water. The main objective of this paper is to illustrate the current non-conventional methods for water disinfection that captured the interest of research field.

Catalysts

The search for alternative water sources is pushing to the reuse of treated water coming from municipal wastewater treatment plants. However, this requires that tightened standards be fulfilled. Among them is the microbiological safety of reused water. Although chlorination is the mostly applied disinfection system, it presents several disadvantages, such as the high doses required and the possibility of formation of dangerous by-products. Moreover, the threat of antibiotic resistance genes (ARGs) spread throughout poorly treated water is requiring the implementation of more efficient disinfection systems. Ozone and photo assisted disinfection technologies are being given special attention to reach treated water with higher quality. Still, much must be done to optimize the processes so that cost-effective systems may be obtained. This review paper gives a critical overview on the application of ozone and photo-based disinfection systems, bearing in mind their advantages and disadvan...

Emerging contaminants is a rather diverse and heterogeneous group of chemicals consisting of pharmaceuticals and personal care products, steroids and hormones, drugs, fragnances, surfactants, flame retardants, perfluorinated compounds, complexing agents, etc. Among these, endocrine disrupting chemicals (EDCs), pharmaceuticals (Phs) and benzotriazoles (BTs) are compounds which present significant scientific interest due to their toxicological and chemical characteristics and their persistent detection in the aquatic environment. Wastewater treatment plants are a well known source and one of the most significant pathways for the transfer of such chemicals to the environment. It is well evidenced that most of these chemicals are only partially removed through biological treatment and therefore being detected in secondary effluents. Disinfection is most often the last stage of treatment before wastewater being disposed to the aquatic environment. The primary goal of disinfection is to reduce the pathogenic content of wastewater and its effectiveness on the removal of such chemicals is not well studied. The objectives of this study were to assess the effectiveness of chlorination and UV disinfection to remove selected EDCs, Phs and BTs from secondary treated wastewater and to further investigate the role of crucial operating parameters such as chlorination contact time and UV dose, wastewater pH and total suspended solids content on process performance. Several chlorination batch tests have been performed with secondary treated wastewater samples, which were spiked with the target compounds and chlorine. A collimated UV source consisting of one low pressure lamp, was employed to assess dose response curves for each sample tested. UV dose (Ct) was calculated as the product of the UV intensity and the contact time. For the determination of the target compounds, wastewater samples before and after disinfection were analyzed. According to the results chlorination leads to an appreciable removal of EDCs and Phs even at the first minutes of chlorination. In contrast, the removal of BTs even at high chlorine doses of 245 mgCl2/lt ×min were very low. Regarding the effect of pH on chlorination efficiency, it seems that the removal of EDCs and Phs increases at pH values around 7. On the other hand, BTs removal is not significantly affected by the pH and TSS content of wastewater during chlorination. Furthermore UV disinfection at UV doses in the order of 40-150 mWs/cm 2 is not effective to remove Phs. From the target compounds tested, only ketoprofen and diclofenac exhibited appreciable removal only at higher UV doses.

Comptes Rendus Chimie, 2008

This article is aimed at presenting (i) a fundamental research on the efficiency of photocatalysis in water disinfection and (ii) the efficiency of a photocatalytic prototype, developed by Buxair firm, to remove avian influenza virus in air. In water disinfection, two model strains of Escherichia coli (K12 PHL849 and K12 PHL1273) were selected and a comparison of the efficiencies of TiO 2 Degussa P-25 versus TiO 2 Millennium PC500 were estimated. A more important inactivation of E. coli PHL1273 was obtained on TiO 2 Millennium PC500, in line with its better adherence on this solid. An experimental study was performed using a dialysis membrane to investigate the impact of the contact between the microorganisms and the photocatalyst and to determine the role of H 2 O 2 generated in situ. In air disinfection, a total inactivation of virus A/H5N2, close to avian influenza virus A/H5N2, was obtained in a single pass in the Buxair Ò gas phase dynamic photoreactor using a contaminated air flow rate of 40 m 3 /h. To cite this article: C. Guillard et al., C. R. Chimie X 15 (2007). Ó 2007 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved.

Applied Engineering, 2019

Chlorination is the most used technique of killing microorganisms' in water through the potable water industry. Some outbreaks of water born disease, the definition of chlorine as a source of greatly toxic disinfection by-products (DBPs), and the appearance of recalcitrant microbes have conducted to revised regulation for the elimination of microorganisms and DBPs from potable water. Therefore, researching new disinfection techniques has been developed. Electrochemical disinfection or electrodisinfection (ED) has appeared as one of the more valuable alternatives to chlorination. Research employing a range of cell designs has illustrated ED to be efficient towards an interval of microbes. Nevertheless, in several cases, killing pathogens' performance seems to be linked to the production of chlorine species. The obvious dominance of chlorine in the form of the pathway of killing microbes' emerges the interrogation if ED is really more beneficial than chlorination in a matter of its demobilization performance and risk to generate DBPs. Convenient ED devices must be designed and monitored sophistically since the present state of non-monitored use of ED devices is not favorable in terms of hygienic and health risks considerations. Great works remain to be performed.

OALib, 2020

The most frequently utilized technique for demobilizing pathogens remains disinfection. This is a fundamental stage in drinking water treatment as it removes the hazards related to water-borne diseases like typhoid and cholera. Therefore, disinfecting water employing chemical oxidants such as chlorine has been one of the main public health progresses through the previous century. During the time that this preserves the residual concentrations of disinfectant for the control of microbes, it may greatly elevate the generation of disinfection by-products (DBPs). Lately, Chaukura et al. [1] published an excellent review of the presence of organic matter (OM) in water sources and assessed its impact on the generation of DBPs. Especially, they discussed the production of DBPs, examined the contribution of OM on DBPs generation, and estimated and recommended techniques for eliminating DBPs. This work focuses on the main findings obtained by Chaukura et al. [1] and explores the authors' experience in dealing with disinfection processes and their DBPs generation issues as well as the techniques to remove them from water. Enhanced coagulation and membrane processes are efficacious in eliminating OM. An efficacious and economically usable procedure to dominate the production of DBPs in water treatment plants is to eliminate the precursors before they interact with chemical disinfectants, which should be avoided or at least reduced.

http://ijshr.com/IJSHR_Vol.2_Issue.1_Jan2017/IJSHR001.pdf, 2017

The water consumption in chemical, pharmaceutical and construction activities constitutes sizeable amount out of total water consumption. The reuse and recycle of industrial wastewater needs to be effectively carried out. Disinfection of water used for domestic and potable purposes is still a challenge for developing and under developed countries. Disinfection of water can be done physical, chemical and biological methods. Recycle and reuse of wastewater can be carried out by treating the wastewater and further using advanced treatment methods like membrane separation, electro-dialysis and pervaporation. Maintaining water quality in water distribution system is one of the major problems in developing countries.

International Journal of Environmental Health Engineering, 2013

The Science of the total environment, 2015

Disinfection by-product (DBP) formation may be a concern when applying ultraviolet light and free chlorine (UV/chlorine) as an advanced oxidation process (AOP) for drinking water treatment, due to typically large chlorine doses (e.g. 5-10mgL(-1) as free chlorine). A potential mitigating factor is the low chlorine contact times for this AOP treatment (e.g. seconds). Full-scale and pilot-scale test results showed minimal trihalomethane (THM) and haloacetic acid (HAA) formation during UV/chlorine treatment, while dichloroacetonitrile (DCAN) and bromochloroacetonitrile (BCAN) were produced rapidly. Adsorbable organic halide (AOX) formation was significant when applying the UV/chlorine process in water that had not been previously chlorinated, while little additional formation was observed in prechlorinated water. Chlorine photolysis led to chlorate and bromate formation, equivalent to approximately 2-17% and 0.01-0.05% of the photolyzed chlorine, respectively. No perchlorate or chlorite...

This review paper deals with the formation of disinfection by-products (DBPs). Water basin remains a wonderful chemical reactor that allows the occurrence of intricate secondary disinfection chemical reactions, forming several hundreds of DBPs at the same time with microorganisms killing. The kinetics of DBPs formation is tightly dependent on water physicochemical characteristics such as temperature, hydrophobic/hydrophilic fractions in natural organic matter (NOM), pH, and pretreatment. Reducing DBPs levels in drinking water is not a relevant measure as the newly-developed analytical techniques and the health-related research reveal that the tolerable DBPs' levels must be further decreased and would be detected at ng L-1 instead of μg L-1 scale. Furthermore, because of the fact that man is being exposed to DBPs concentrations in drinking water in his lifetime, there will be a cumulative effect of these toxic chemical products even at their more reduced concentrations. Hence, the removal of these chemical products is sought for and is considered a real challenge and the main objective of water treatment technology for mankind survival.