Streamline - Spring 2014 - (Page 15)
What's New in UV?
BY DONNA LAWSON,
Many of the
were used for
RIGHT. UV banks at
Marion, Va. BELOW.
Brass fittings, new
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
* inadequate cleaning systems,
* poor hydraulics causing short circuiting and
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
Ergs, Joules and Other Stuff
Establishing a Water Distribution System Flushing Program
Curtis Water Wins Big in D.C.
Throwing My Loop: Friends to Keep You Warm
Do You Know What Your VRWA Benefits Are?
Welcome New Members
Board of Directors
Index to Advertisers/Ad.com
Streamline - Spring 2014