Page 653 - Fundamentals of Water Treatment Unit Processes : Physical, Chemical, and Biological

608 Fundamentals of Water Treatment Unit Processes: Physical, Chemical, and Biological

main flow. They confirmed that the bacterial reductions were
BOX 19.1 DISINFECTION DEFINITIONS comparable to that achieved by hypochlorite. After this inves-
tigation, Wallace and Tiernan proposed to install a chlorine
The term ‘‘disinfection’’ is used here to mean the
feed system at Jersey City for $150 with performance guar-
‘‘inactivation’’ of microorganisms. Two kinds of defin-
antees (he mentioned that this was without having designed
itions, mathematical and mechanistic, are given in order
the apparatus prior to the proposal and ignorant of the prop-
to clarify their repeated use in this chapter.
erties of compressed chlorine gas). This first apparatus used
Mathematical: A mathematical expression of inactiva- hard rubber parts and solder for joints of metal tubing. When
tion is ‘‘log removal,’’ that is, log R,defined, log subject to chlorine under pressure the apparatus literally
R ¼ log(C)=C o ), which is the same as used in filtration. blew up in our faces. And, after many tries, we produced a
Alternatively, inactivation may be expressed as ‘‘per- controlling mechanism, . . . Further, to effect the solution of
cent removal’’ or ‘‘percent inactivation’’ or ‘‘fraction the gas in the stream, we put an inverted trough across the
inactivation,’’ the latter being defined, fR¼ (C o C)=C o , stream bottom, weighing it down with stones, and introduced
in which, C o ¼ initial concentration of microorganism s the gas at one end of the trough. During inspection by the
at time t ¼ 0(#=mL), and C ¼ concentration of micro- New Jersey State Board of Health, when the gas was turned
organisms at any time t > 0(#=mL). If, for example, on a considerable part came to the surface, but a good strong
C o ¼ 10,000 =mL and C ¼ 1#=mL, log R ¼ log breeze diluted it so Randolph (the official) got just a very
4
[1=10,000] ¼ log(10 ) ¼ 4, by the same token, slight odor. During the night, the apparatus had sprung a leak
fraction inactivation ¼ (10,000 1)=10,000¼ 0.9999 and all the tools in the shop were coated with rust, and they
(99.99%). Both log R and fraction (or percent) removal, had promptly thrown the device out the window. We rede-
that is, inactivation, are used commonly. signed the apparatus and made diffusers out of small alundum
Inactivation: The term ‘‘inactivation’’ means here that the grinding wheels, cemented into the saucer of a flower pot.
microorganism is rendered not capable of reproduction, Silver tubing was later used and the installation was com-
that is, its DNA is damaged or other parts of the cell pleted on February 22, 1913. The meter was a volumetric
are damaged, to the extent that it cannot replicate itself inverted siphon type, which we are still using.
(Malley, 2002a, p. 12). Another definition is that an The second installation was at Ford’s Pond where they
inactivated microorganism cannot metabolize, that is, pro- raised the price to $200. For the Stamford Water Works,
cess nutrients; which may be due to damaged enzymes which was considering hypochlorite, the consultant wanted
(which goes back to Fair et al., 1948, p. 1056) and may be to feed the disinfectant at a rate proportional to the main flow.
associated with disinfectant penetration of the cell wall. Wallace and Tiernan offered to install a Venturi-operated
automatic chlorinator for $500 before we had even made
the design. As Tiernan had stated, This surely was the mark
Niagara Falls, New York. Chlorine was obtained from the of our confidence and ignorance. It was only a few days,
Niagara Alkali Co., which was making chloride-of-lime. however, until Wallace had figured out a way of handling the
Tiernan continued his account of how chlorine gas tech- problem. Three balanced diaphragms, functioning as two,
nology developed to give a colorful story describing also were operated by the differential pressure across the Venturi
the start of their company, Wallace and Tiernan. The follow- throat in the water main, to maintain a drop in pressure across
ing is an abstract of his 1948 article. The story describes the gas control valve in proportion to the drop across the
how they developed, by trial and error and other means, the Venturi throat. This would give a proportional flow of chlor-
technology for chlorine metering, control, dissolution, and ine to the water through a variable orifice (the control valve).
concentrate feed. A simple, low voltage dc toy motor that was operated by six
In 1909, Martin F. Tiernan and C.F. Wallace began their dry cells and costing some six or eight dollars was cut in and
association. Wallace was an electrical engineer and worked out by contact operated by connections to the diaphragms.
with the Gerard Ozone Process Co. where Martin F. Tiernan This motor operated the control valve in the gas line until the
had been hired as a chemist. The ozone business folded and in drop in pressure across the valve was proportioned to that
1911, they were also let go from their next job; with $1800 in across the Venturi throat. The installation was made at Stam-
savings they started their own business and in September ford on September 3, 1913, and functioned perfectly from the
1911 they were involved in installing hypochlorite for very beginning. Chlorine was introduced into the intake well
Torrington, Connecticut to respond to a typhoid outbreak. through a silver tube and a diffuser submerged to a depth of
After working with other hypochlorite delivery systems, Tier- 25 ft (p. 1048). Later that year we installed automatics at New
nan visited (in 1912) Dr. Carl Darnall, MD, U.S. Army Haven, Torrington and Hartford, Connecticut. The automatic
Medical Corps, who suggested chlorine gas in lieu of hypo- feature of these machines was modified to eliminate the
chlorite for the Jersey City Water Company. After visiting the electric motor. In June 1913 Herman Rosentretter of the
Electrochemical Bleaching Gas Co. to see if chlorine gas was Newark, New Jersey Water Dept., hearing of our installations
available, he also visited with George Ornstein, a German for Jersey City, gave us an order for a direct-feed manual-
chemist, who showed a method of making a chlorine solution control machine for the entire Newark supply. The installa-
from chlorine gas that was then fed through an orifice to the tion was made at the Macopin intake, using diffusers which