Tag Archives: UV disinfection

Sulfaquinoxaline Transformation by Chorine and UV

Nassar R, Mokh S, Rifai A, Chamas F, Hoteit M, Al Iskandarani M. Transformation of sulfaquinoxaline by chlorine and UV light in water: kinetics and by-product identification. Environ Sci Pollut Res Int. 2017 Dec 1. doi: 10.1007/s11356-017-0814-4.

Sulfaquinoxaline (SQX) is an antimicrobial of the sulfonamide class, frequently detected at low levels in drinking and surface water as organic micropollutant. The main goal of the present study is the evaluation of SQX reactivity during chlorination and UV irradiations which are two processes mainly used in water treatment plants. The SQX transformation by chlorination and UV lights (254 nm) was investigated in purified water at common conditions used for water disinfection (pH = 7.2, temperature = 25 °C, [chlorine] = 3 mg L-1). The result shows a slow degradation of SQX during photolysis compared with chlorination process. Kinetic studies that fitted a fluence-based first-order kinetic model were used to determine the kinetic constants of SQX degradation; they were equal to 0.7 × 10-4 and 0.7 × 10-2 s-1 corresponding to the half time lives of 162 and 1.64 min during photolysis and chlorination, respectively. In the second step, seven by-products were generated during a chlorination and photo-transformation of SQX and identified using liquid chromatography with electrospray ionization and tandem mass spectrometry (MS-MS). SO2 extrusion and direct decomposition were the common degradation pathway during photolysis and chlorination. Hydroxylation and isomerization were observed during photodegradation only while electrophilic substitution was observed during chlorination process.

Evaluation of a Handheld UV Disinfection Unit

Timmermann LF, Ritter K, Hillebrandt D, Küpper T. Drinking water treatment with ultraviolet light for travelers – Evaluation of a mobile lightweight systemTravel Medicine and Infectious Disease. 2015 Nov 6. pii: S1477-8939(15)00174-X. doi: 10.1016/j.tmaid.2015.10.005.

BACKGROUND: The SteriPEN® is a handheld device for disinfecting water with ultraviolet (UV) radiation. The manufacturer claims a reduction of at least 99.9% of bacteria, viruses, and protozoa. The present study intends to verify the general effectiveness of the device. Furthermore, the influence of bottle geometry and water movement is examined and the issue of user safety with regard to UV-C radiation is addressed.

METHODS: The device was applied on water containing a known number of microorganisms (Escherichia coli, Staphylococcus aureus, and the spore of Geobacillusstearothermophilus) and the survival rate was examined. Three different types of bottles commonly used among travelers served as test containers. All tests were conducted with and without agitating the water during irradiation. Furthermore, a spectral analysis was performed on the light of the device.

RESULTS: The SteriPEN® reached a mean reduction of more than 99.99% of bacteria and 99.57% of the spores when applied correctly. However, the results of the trials without agitating the water only yielded a 94.98% germ reduction. The device’s maximal radiation intensity lies at 254 nm which is the wavelength most efficient in inactivating bacteria. The UV-C fraction is filtered out completely by common bottle materials. However, when applied in larger containers a portion of the UV-C rays exits the water surface.

CONCLUSIONS: If applied according to the instructions the device manages a satisfactory inactivation of bacteria. However, it bears the danger of user errors relevant to health. Therefore, education on the risks of incorrect application should be included in the travel medical consultation. Also there are still aspects that need to be subject to further independent research.

UV Irradiation Effects Free Chlorine Consumption

Zhang TY, Lin YL, Xu B, Xia SJ, Tian FX, Gao NY. Effect of UV irradiation on the proportion of organic chloramines in total chlorine in subsequent chlorination. Chemosphere. 2015 Sep 29;144:940-947. doi: 10.1016/j.chemosphere.2015.09.074.

This study investigated the changes of chlorine species and proportion of organic chloramines during the chlorination process after UV irradiation pretreatment in drinking water. It was found that the UV pretreatment could enhance the percentage of organic chloramines by increasing free chlorine consumption in the chlorination of raw waters. The percentage of organic chloramines in total chlorine increased with UV intensity and irradiation time in raw waters. However, for the humic acid synthesized water, the percentage of organic chloramines increased first and then decreased with the increase of UV irradiation time. The value of SUVA declined in both raw and humic acid synthesized waters over the UV irradiation time, which indicated that the decomposition of aromatic organic matter by UV could be a contributor to the increase of free chlorine consumption and organic chloramine proportion. The percentage of organic chloramines during chlorination of raw waters after 30-min UV irradiation pretreatment varied from 20.2% to 41.8%. Total chlorine decreased obviously with the increase of nitrate concentration, but the percentage of organic chloramines increased and was linearly correlated to nitrate concentration.

UV Radiation and Aquatic Ecosystems: A Nice Story

This article makes some good points about the science of UV radiation. But extrapolating to generalized assertions about the future status and fate of natural aquatic systems from “climate change” goes a bit too far. But it’s a nice story.

We must remember, UV radiation was around and having its effects on aquatic ecosystems for many centuries before any of these researcher were born. What may be “new” discoveries to them (and us) are certainly not new for the ecosystem. To take such a limited knowledge base and extrapolate to the future (e.g., long term effects of warmer waters) is rather premature, if not silly. Especially in view of the extreme cold many natural aquatic systems are currently experiencing. Seems to me some warming would be a good thing….

Häder DP, Williamson CE, Wängberg SA, Rautio M, Rose KC, Gao K, Helbling EW, Sinha RP, Worrest R. Effects of UV radiation on aquatic ecosystems and interactions with other environmental factors. Photochemical and Photobiological Sciences. 2014 Nov 12.

UV reactions

Interactions between climate change and UV radiation are having strong effects on aquatic ecosystems due to feedback between temperature, UV radiation, and greenhouse gas concentration. Higher air temperatures and incoming solar radiation are increasing the surface water temperatures of lakes and oceans, with many large lakes warming at twice the rate of regional air temperatures. Warmer oceans are changing habitats and the species composition of many marine ecosystems. For some, such as corals, the temperatures may become too high. Temperature differences between surface and deep waters are becoming greater. This increase in thermal stratification makes the surface layers shallower and leads to stronger barriers to upward mixing of nutrients necessary for photosynthesis. This also results in exposure to higher levels of UV radiation of surface-dwelling organisms. In polar and alpine regions decreases in the duration and amount of snow and ice cover on lakes and oceans are also increasing exposure to UV radiation. In contrast, in lakes and coastal oceans the concentration and colour of UV-absorbing dissolved organic matter (DOM) from terrestrial ecosystems is increasing with greater runoff from higher precipitation and more frequent extreme storms. DOM thus creates a refuge from UV radiation that can enable UV-sensitive species to become established. At the same time, decreased UV radiation in such surface waters reduces the capacity of solar UV radiation to inactivate viruses and other pathogens and parasites, and increases the difficulty and price of purifying drinking water for municipal supplies. Solar UV radiation breaks down the DOM, making it more available for microbial processing, resulting in the release of greenhouse gases into the atmosphere. In addition to screening solar irradiance, DOM, when sunlit in surface water, can lead to the formation of reactive oxygen species (ROS). Increases in carbon dioxide are in turn acidifying the oceans and inhibiting the ability of many marine organisms to form UV-absorbing exoskeletons. Many aquatic organisms use adaptive strategies to mitigate the effects of solar UV-B radiation (280-315 nm), including vertical migration, crust formation, synthesis of UV-absorbing substances, and enzymatic and non-enzymatic quenching of ROS. Whether or not genetic adaptation to changes in the abiotic factors plays a role in mitigating stress and damage has not been determined. This assessment addresses how our knowledge of the interactive effects of UV radiation and climate change factors on aquatic ecosystems has advanced in the past four years.

Click here for paper (Open Access).

Endospores a surrogate for Cryptosporidium inactivation by UV

Garvey, M., Clifford, E., O’Reilly, E. and Rowan, N. Efficacy of Using Harmless Bacillus Endospores to Estimate the Inactivation of Cryptosporidium Parvum Oocysts in Water. Journal of Parasitology. 2012 Nov 12.

Abstract: The need to use complex in vitro cell culture, expensive equipment and highly-trained technicians that are available only to specialist laboratories has significantly limited studies assessing the potential of pulsed UV light (PUV) to inactivate the waterborne parasite Cryptosporidium parvum in drinking water. This constitutes the first study to report on the use of different non-pathogenic Bacillus endospores as potential surrogate organisms to indicate the PUV inactivation performance of C. parvum oocyst suspended in water. Findings showed that PUV effectively inactivated ca. 5 log10 CFU/ml B. megaterium and B. pumilus endospores suspended in water at a UV dose of 9.72 µJ/cm2 that also inactivated statistically similar levels of C. parvum oocysts (P <0.05) as determined by combined in vitro HCT-8 cell culture and qPCR. Specifically, this study demonstrated that Bacillus megaterium exhibited greater or similar PUV-inactivation kinetic data compared to that of similarly treated C. parvum over the UV dose range 6.4 to 12.9 µJ/cm2. Therefore, the former may be used as indicator organism for safely investigating the PUV-inactivation performance of this chlorine- resistant waterborne parasite at waste water treatment plant level. Findings presented will impact positively on future water quality studies and on public health.

New York City to start UV disinfection facility

The facility is the world’s largest, with 56 massive UV units to disinfect drinking  water from the city’s major sources—the Delaware County and Catskill watersheds…….up to 9 billion liters per day. Click here for more….

Solar water disinfection (SODIS) effectiveness

Kevin G. McGuigan, Ronán M. Conroy, Hans-Joachim Mosler, Martella du Preez, Eunice Ubomba-Jaswa, Pilar Fernandez-Ibañez. Solar water disinfection (SODIS): A review from bench-top to roof-top. Journal of Hazardous Materials. http://dx.doi.org/10.1016/j.jhazmat.2012.07.053

Solar water disinfection (SODIS) has been known for more than 30 years. The technique consists of placing water into transparent plastic or glass containers (normally 2 L PET beverage bottles) which are then exposed to the sun. Exposure times vary from 6 to 48 h depending on the intensity of sunlight and sensitivity of the pathogens. Its germicidal effect is based on the combined effect of thermal heating of solar light and UV radiation. It has been repeatedly shown to be effective for eliminating microbial pathogens and reduce diarrhoeal morbidity including cholera. Since 1980 much research has been carried out to investigate the mechanisms of solar radiation induced cell death in water and possible enhancement technologies to make it faster and safer. Since SODIS is simple to use and inexpensive, the method has spread throughout the developing world and is in daily use in more than 50 countries in Asia, Latin America, and Africa. More than 5 million people disinfect their drinking water with the solar disinfection (SODIS) technique. This review attempts to revise all relevant knowledge about solar disinfection from microbiological issues, laboratory research, solar testing, up to and including real application studies, limitations, factors influencing adoption of the technique and health impact.

Click here for full paper (fee).