| Material Information
||The use of chlorine in low volume systems where bacterial slimes are a problem
||Lake Alfred AREC reseach report
||2 p. : ; 28 cm.
||Ford, Harry W., 1922-
Agricultural Research and Education Center (Lake Alfred, Fla.)
||University of Florida, IFAS, Agricultural Research and Education Center
||Place of Publication:
||Lake Alfred FL
||Irrigation -- Research -- Florida ( lcsh )
Irrigation -- Equipment and supplies -- Maintenance and repair -- Florida ( lcsh )
||government publication (state, provincial, terriorial, dependent) ( marcgt )
non-fiction ( marcgt )
||Statement of Responsibility:
||Harry W. Ford.
||"5/15/75 (Revised 11/15/80)-HWF-100."
| Record Information
||University of Florida
||All rights reserved by the source institution and holding location.
||oclc - 76883402
Lake Alfred AREC Research Report-CS75-5
5/15/75 (Revised 11/15/80)-HWF-100
THE USE OF CHLORINE IN LOW VOLUME SYSTEMS WHERE BACTERIAL SLIMES ARE A PROBLEM
Harry W. Ford
University of Florida, IFAS
Agricultural Research and Education Center
Lake Alfred, Florida 33850
Liquid sodium hypochlorite (NaOCI), 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.
There has been considerable interest in chlorine for controlling all types of
bacterial slimes and algae. Chlorine is not a "shotgun" type solution to all problems.
Its most promising use is in the area of preventive maintenance and it must be monitored
carefully. This report is an attempt to clarify the present status of chlorine, based on
research, for use in low volume systems in Florida.
Limitations with Chlorine. Chlorine used correctly can control several problems. It
is excellent for preventive maintenance. It is a waste of time and money to inject
chlorine into a system that is already clogged from sulfur slimes or iron deposits.
Chlorine above 100 ppm will dissolve elemental sulfur globules but will not remove the
bacterial cells of the matrix. Chlorine precipitates soluble iron in water. It will not
dissolve iron present in the emitters and microsprinklers.
Characteristics of Chlorine. Chlorine dissolved in water is an active oxidizing agent
and has for many years been recognized and used as an efficient agent for destroying
microorganisms. It has been the primary ingredient for use in potable drinking water and
has become the most widely used disinfectant. Chlorine gas (C12), sodium hypochlorite
(NaOC1), and calcium hypochlorite [Ca(OC12)] dissolved in water will hydrolize to form
hypochlorous acid (HOC1), a powerful oxidizing agent that is a stronger disinfectant than
C12 alone. The germ killing action of HOC1 is either by oxidizing the organism or by
preventing the cells from oxidizing glucose, an essential ingredient for life. The
killing action works best below pH 7.5 since HOC1 is a weak acid.
Chlorine as a bactericide exists as several compounds. It should not be confused with
the chloride ion (C1-) which is a basic ingredient in liquid and dry fertilizers.
Chlorides have no oxidizing or biocidal properties. Chlorine gas is the most common and
cheapest source of chlorine, but it does not dissolve readily in water by simple bubbling
procedures so that expensive injection equipment kept in good operating condition must be
utilized. Chlorine is considered a problem gas that can clog and corrode injection
Liquid sodium hypochlorite (NaOCI) is the easiest form of chlorine to handle since
amounts required can be measured rather accurately. There is no residue to clog injection
lines. Powdered calcium hypochlorite [Ca(OC12)], also called High Test Hypochlorite
(H.T.H.) chlorine, can be used but with certain disadvantages. H.T.H. calcium
hypochlorite, when mixed in concentrated injection solutions, forms a milky suspension
containing calcium oxalate, calcium carbonate, and calcium hydroxide which clog injection
lines. A balance for weighing the powder is also necessary.
The Chemistry of Chlorine. When chlorine is added to well water, some of it will
combine with organic substances that may be present in the water. This is called combined
chlorine. Chlorine will also react with ammonium ions. The compounds formed are called
chloroamines. "Some of the chlorine will also react with certain inorganic compounds such
as hydrogen sulfide (H2S) and iron (Fe) and be completely changed to a chloride.
Chlorine that has not reacted with anything and is therefore still in excess is called
free chlorine. It is the free available chlorine that can kill sludge forming bacteria.
It is the hypochlorous acid molecule (which exists below pH 7.8) that is responsible for
most of the killing action. The pH of the water should be less than 7.5 otherwise the
free chlorine level must be increased by a factor of 2 to 3 times to be effective.
In order to use chlorine effectively, one must have a chlorine test kit that will
measure the free chlorine. Several types of kits have been evaluated for use with low
volume irrigation systems. The best is a relatively new method designed to use the
chemical N,N-diethyl-p-phenylenediamine (DPD). The DPD kits for measuring free chlorine
can be purchased from a number of swimming pool supply outlets and several low volume
irrigation companies in Florida.
Chlorine as a biocide kills by having a free chlorine contact time of at least 30
minutes. Dumping large quantities of chlorine into the irrigation system without careful
monitoring, will not kill organism populations faster (because of the contact tire) but
may injure the roots of young trees if the level is above 30 ppm free chlorine. Anyone
who monitors his chlorine levels will never have concentrations approaching 30 ppm (parts
Since sodium hypochlorite (NaOC1) is the only chlorine compound approved for use in
Florida, it is necessary to use injection equipment that will permit control of the amy.ount
of chlorine solution being used. There are injection pumps on the market that can be used
on both the suction and pressure side of irrigation pumps. The chlorine injection pumps
should be adjustable so that the injection rates can be changed. The easiest method for
determining the amount of chlorine required is to gradually increase the injection rate
until a free chlorine level is detected by using the chlorine test kit. SEE ALSO: AREC
Research Report "Using a DPD test kit." The amount of chlorine required will
change-sometimes daily. It there are slimes already in the system, chlorine requirements
will be high. Chlorine levels probably can be reduced as the system becomes free of
The best concentrations and contact times for chlorine are reported in other research
reports such as "The use of surface waters for low volume irrigation," "Slimes of sulfur
in low volume irrigation" and "Iron in low volume irrigation."