Climate change means more rain, and that rain washes more organic stuff into our surface waters. This makes it harder for sunlight to kill off bad germs with UV radiation. It’s a real threat to drinking water safety for millions, including the 10+ million people who get their water from Lake Michigan.<\/p>\n
Solar ultraviolet radiation, UV-A and UV-B, is nature’s own free disinfectant. When water is clear and shallow, UV light damages the DNA and RNA in bacteria, viruses, and protozoa. This stops nasty pathogens like Cryptosporidium<\/em>, Giardia<\/em>, and norovirus from multiplying. Water utilities and regulators have always seen this natural die-off as an extra layer of protection between source water and treatment plants.<\/p>\n The problem Williamson et al. (2017) pointed out is simple: dissolved organic matter (DOM) \u2014 that brown, tannin-rich stuff from soil and decaying plants \u2014 soaks up UV wavelengths before they can reach pathogens deeper in the water. As rain gets heavier and permafrost thaws, DOM is building up in rivers and lakes worldwide. We call this “browning.” Many northern lakes have already seen a 10\u201330% drop in UV transparency over the last two decades.<\/p>\n Water treatment engineers need to deal with this trend. They must increase the UV dose in treatment systems<\/strong>, add other disinfection methods, and keep an eye on turbidity and DOM concentration in real time. For cities that get their water from surface sources, this research really highlights why we need multiple barriers for treatment. Think coagulation, filtration, UV disinfection, and chlorination. You can’t just rely on one step.<\/p>\n Reverse osmosis (RO) systems remove dissolved organic matter at the membrane stage. This means less chlorine is needed and fewer disinfection by-products (DBPs) form later on. If you pair RO pre-treatment with UV disinfection, you get water that’s both pathogen-free and low in DOM. That tackles both the direct contamination risk and the browning problem this study describes.<\/p>\n Author Full Names: Williamson, Craig E.; Madronich, Sasha; Lal, Aparna; Zepp, Richard G.; Lucas, Robyn M.; Overholt, Erin P.; Rose, Kevin C.; Schladow, S. Geoffrey; Lee-Taylor, Julia Abstract: Climate change is accelerating the release of dissolved organic matter (DOM) to inland and coastal waters through increases in precipitation, thawing of permafrost, and changes in vegetation. Our modeling approach suggests that the selective absorption of ultraviolet radiation (UV) by DOM decreases the valuable ecosystem service wherein sunlight inactivates waterborne pathogens. Here we highlight the sensitivity of waterborne pathogens of humans and wildlife to solar UV, and use the DNA action spectrum to model how differences in water transparency and incident sunlight alter the ability of UV to inactivate waterborne pathogens. A case study demonstrates how heavy precipitation events can reduce the solar inactivation potential in Lake Michigan, which provides drinking water to over 10 million people. These data suggest that widespread increases in DOM and consequent browning of surface waters reduce the potential for solar UV inactivation of pathogens, and increase exposure to infectious diseases in humans and wildlife.<\/p>\n The post Climate change-induced increases in precipitation are reducing the potential for solar ultraviolet radiation to inactivate pathogens in surface waters<\/a> appeared first on Facts About Water<\/a>.<\/p>\n Source: Water Feed<\/p>\n","protected":false},"excerpt":{"rendered":" Climate change is accelerating the release of dissolved organic matter (DOM) to inland and coastal waters through increases in precipitation, thawing of permafrost, and changes in 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\nSource: SCIENTIFIC REPORTS, 7 10.1038\/s41598-017-13392-2OCT 12 2017<\/a>
\nLanguage: English<\/p>\n