Streamline - Spring 2014 - (Page 15)

What's New in UV? BY DONNA LAWSON, WASTEWATER OPERATIONS SPECIALIST Many of the early UV systems were adapted from pressured vessels that were used for disinfecting drinking water. RIGHT. UV banks at Marion, Va. BELOW. Brass fittings, new and worn. IN 1877, TWO English scientists, Thomas Blunt and Arthur Downes, found that direct sunlight had a fatal effect on bacteria and other organisms. They also discovered that the blue, violet and ultraviolet rays of sunlight had the greatest bactericidal effect. Ultraviolet light was discovered to be electromagnetic radiation that has a shorter wave length than visible light with a range of 400 nm to 10 nm. Other scientists during the late 1800s built upon their work and determined that the most effective wavelength for sterilizing bacteria is around 250 nm. Overexposure to ultraviolet light (UV) can be harmful resulting in sunburn, premature aging and skin cancer and a small amount is necessary to help produce Vitamin D. As early as 1906, UV was used to disinfect drinking water. The city of Marseille, France, began using UV for their water supply in 1910. Chlorination gained popularity in the United States for both water and wastewater and UV was never adopted as the conventional disinfectant agent as in Europe. Conventional UV lamps rely on an electrode to ignite gas in a quartz tube. The gas is an argon and mercury mix and the quartz tube has electrodes on one end. Introduce a high-voltage current and electricity passes between the electrodes exciting the mercury on the way thus producing ultraviolet light from the energized mercury photons. For the next 25 years, lamp ignition was a trial and error process. In 1938, Westinghouse Electric demonstrated the first fluorescent gas discharge lamp. Lamps and ballasts were improved in the 1940s, which enabled the development of UV companies. Increased awareness of chlorine disinfection byproducts and the environmental movement of the 1960s led to the EPA to discourage the use of chlorine for disinfecting wastewater and provided research money and construction grants for UV disinfection in the 1970s. During this time, EPA established the Innovative and Alternative (I&A) Technology program, which made possible the installation of several full-scale UV systems throughout the country. One of the first wastewater plants to use UV disinfection on a large scale was NW Bergen in Waldwick, New Jersey. Many of the early UV systems were adapted from pressured vessels that were used for disinfecting drinking water. Companies developed systems with higher UV transmittance specifically for wastewater treatment. The rapid development of these initial systems brought attention to UV disinfection, but it also highlighted the design flaws, such as: * replacement of lamps, quartz sleeves and ballasts required the entire UV system to be shut down, * inadequate cleaning systems, * poor hydraulics causing short circuiting and poor treatment, www.vrwa.org 15 http://www.vrwa.org

Table of Contents for the Digital Edition of Streamline - Spring 2014

From the President
From the Executive Director
The Importance of an Immediate Response
What’s New in UV?
Proper Disposal of Pharmacy Products
Source Water Protection Notes
Faces
Ergs, Joules and Other Stuff
Establishing a Water Distribution System Flushing Program
Wastewater Math
Curtis Water Wins Big in D.C.
Throwing My Loop: Friends to Keep You Warm
eLearning Benefits
Membership Application
Do You Know What Your VRWA Benefits Are?
VRWA Mailbag
Welcome New Members
Training Calendar
Board of Directors
VRWA Committees
Index to Advertisers/Ad.com

Streamline - Spring 2014

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