Group Title: Lake Alfred AREC research report
Title: Estimating chlorine requirements
Full Citation
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 Material Information
Title: Estimating chlorine requirements
Series Title: Lake Alfred AREC research report - Lake Alfred AREC ; HWF-100
Physical Description: 2 p. : ; 28 cm.
Language: English
Creator: Ford, Harry W., 1922-
Agricultural Research and Education Center (Lake Alfred, Fla.)
Donor: unknown ( endowment )
Publisher: University of Florida, IFAS, Agricultural Research and Education Center
Place of Publication: Lake Alfred, Fla.
Publication Date: November 15, 1980
Copyright Date: 1980
Subject: Water -- Purification -- Chlorination -- Florida   ( lcsh )
Irrigation water -- Quality -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: Harry W. Ford.
General Note: Caption title.
General Note: "11/15/80-HWF-100."
 Record Information
Bibliographic ID: UF00094252
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 406531930

Full Text

(/E-> Lake Alfred AREC Research Report-CS80-1
MAR 26 1981
Harry W. Ford
University of Florida, I4S o
Agricultural Research and Educa b-leaterUniv. Of Florida
Lake Alfred, Florida 338

Liquid sodium hypochlorite (NaOCl), commonly called household
or swimming pool bleach, is the.only bactericide that has a
24(c) approved EPA label for use in low volume irrigation systems
in Florida. Chlorine gas and HTH (calcium hypochlorite) do not
have a label.

Chlorine requirements must be known in order to utilize any type of water source. In
the majority of wells and water sources tested, 65 to 81% of the chlorine reacted or was
adsorbed by inorganic compounds and organic substances in the water. The hypochlorous
acid required to satisfy such requirements is of no value as a slimicide. The free
chlorine (the excess hypochlorous acid) is the active slimicide and should be established
before injection.

Prepare a standard sodium hypochlorite solution (NaOCl). Mix 16 ml of fresh 5.25% (b)
wt) NaOCI with 50 ml deionized water. Place in 60 ml amber glass dropping bottle
containing a straight pipette medicine dropper and store at < 75F. Determine the exact
chlorine concentration in the standard by adding 1 drop (with the medicine dropper) to a
300 to 500 ml bottle of deionized water. This becomes your calibration bottle. The exact
volume of the bottle selected must then be used throughout the procedure. Shake for 10
sec and read for total chlorine with an N,N-diethyl-p-phenylenediamine (DPD) portable
chlorine test kit. The test kit must also be able to read free chlorine. Total chlorine
should be between 0.5 and 3.0 ppm and.should be recorded. Concentration of the standard
should be rechecked each week, or when used. A new standard should be prepared when the
concentration (as tested in deionized water) drops below 1.0 ppm. Label the standard as-
"1 drop equals ppm in ml calibrated bottle."

Collect a water sample in the calibrated bottle from the irrigation system that is to
be treated with chlorine. If the water contains sulfides, then it will require 9 ppm of
chlorine for each ppm'of sulfides. If the water contains iron, it will require about 1
ppm of chlorine for each 0.7 ppm of iron. Usually 0.5 to 1.0 ppm NaOCl is required for
organic matter (surface water will be higher).

Add sufficient drops of NaOCl standard solution to the bottle of irrigation water to
obtain 0.2 to 3 ppm of free chlorine. Mix the sample for about 15 sec, read for free
chlorine. If there is no red color in the test vial, collect another water sample and add
more drops of the standard NaOCl solution. If more than 3 ppm of free chlorine (that is
the upper limit of the test kit) is present, start over by using fewer drops of standard
chlorine solution. If free chlorine can be read on the test kit color disc (even a very
low value of 0.2 ppm), then run the test for total chlorine on the same water in the
calibration bottle. It may be necessary to dilute the total chlorine reading if above 3
ppm, the highest value on the test kit scale.
Calculations of chlorine requirements. The difference between the amount of chlorine
added to the sample and the total chlorine residual (total chlorine reading after adding
drops of the standard) represents the chlorine that will be lost to chemical reactions
such as hydrogen sulfide, iron or, other inorganic metals. The difference between the


total chlorine residual in the sample and the free chlorine in the sample represents the
chlorine that will be reacting with organic matter and nitrogenous substances such as
ammonia. Lets assume that 1 drop of NaOCl standard equaled 3 ppm. Lets further assume
that 3 drops of 3 ppm NaOCI standard when added to the sample in the calibration bottle
yielded 2.5 ppm free chlorine. In this example, the free chlorine residual is in the
desired range of 2 to 3 ppm. Thus, the initial rate for injection of NaOCl into the drip
irrigation system would be 9 ppm (3 drops x 3 ppm standard). In the example, if the free
chlorine residual reading had been only 1 ppm, 'then it would be necessary to inject 10.5
ppm of NaOCl to obtain a 2.5 ppm free chlorine residual (3 drops x 3 ppm standard + 1.5).
Conversely, if the free residual chlorine level read 2.5 ppm on the test kit and one
desired only 1.0 free residual after adding 3 drops of 3 ppm standard, the amount of NaOCI
to be injected would be 7.5 ppm (3 drops x 3 ppm standard 1.5). The concentration of
chlorine can be adjusted up or down during actual injection depending on chlorine test
readings taken from emitters along the line and at the end of the system.

Formulas can be used to calculate the gal per hr (gph) of NaOCl solution that must be
injected to obtain a desired ppm of chlorine in the irrigation water. The gal per min
(gpm) pumping rate must be known.

Formula for gph of 10% NaOCl 0.0006 x (ppm of desired chlorine)
x (gpm pumping rate)

Formula for gph of 5.25% NaOCl 0.00114 x (ppm of desired chlorine)
x (gpm pumping rate)

Formula for Ibs per hr of gas Cl 0.000998 x (ppm desired chlorine)
x (gpm pumping rate)

* 4

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