The use of surface water for low pressure irrigation systems

Material Information

The use of surface water for low pressure irrigation systems
Series Title:
Lake Alfred AREC research report
Ford, Harry W., 1922-
Agricultural Research and Education Center (Lake Alfred, Fla.)
Place of Publication:
Lake Alfred FL
University of Florida, IFAS, Agricultural Research and Education Center
Publication Date:
Rev. ed.
Physical Description:
6 p. : ill. ; 28 cm.


Subjects / Keywords:
Irrigation -- Florida ( lcsh )
Water resources development -- Florida ( lcsh )
Crops -- Water requirements -- Florida ( lcsh )
Chlorine ( jstor )
Irrigation systems ( jstor )
Surface water ( jstor )
government publication (state, provincial, terriorial, dependent) ( marcgt )
non-fiction ( marcgt )


General Note:
Caption title.
General Note:
"4/18/75 (Revised 5/10/79)-HWF-100."
Statement of Responsibility:
Harry W. Ford.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
76804776 ( OCLC )


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Full Text

F r Lake Al ed.AREC Research
3 4/18/75 (Revised 5/10/79)


Harry W. Ford

University of Florida, IFAS
Agricultural Research and Education Center
Lake Alfred, Florida 33850


of no.


The major clogging problems with surface waters occur f omrdgco e ition
residues of filamentous green algae and completed iron. Most surac ers
must be filtered and the best filtration is probably a manual or automatic
backflush-type sand filter. Without chemical treatment, .EIh. A miveianaroida
of algae will develop throughout the sand tank. Organit residues uf algne,
including diatoms, can pass through the sand. Green filamentous algae
have also been found growing in the thin white translucent PVC pipe which
is often used above ground as suction and transport lines. It is essential
that all pipes and containers located above ground either be painted to
prevent light penetration or use a type of PVC pipe that does not permit
light penetration.

Residues of decomposing algae can accumulate in lines, emitters, and
microsprinklers. Algae transported into the black polyethylene pipe of
the irrigation system will not continue to grow. The algal residue
consists of ruptured cells which form a soft gelatinous organic slime.
The soft non-sticky deposit can accumulate iron and support growths of
iron bacteria and many other filamentous and slime forming bacteria. In
low pressure irrigation systems with algal problems, iron has been found
in emitters and at the ends of lines. Iron, detected in concentrations as
low as 0.1 ppm in canal water, will become concentrated in the algal
organic slime that may accumulate in the irrigation lines.

It should be assumed that all surface
at some time during the irrigation season.
because of many different factors. One of
increases occurs during an algal bloom.

waters will contain algae
The level of algae fluctuates
the major and rather sudden

Surface water can be used for low pressure irrigation if treated
with liquid chlorine (sodium hypochlorite). The liquid chlorine should
be injected into the suction line between the inlet and the centrifugal
pump. The chlorine solution should be injected for 40 minutes either
when starting up the irrigation system or any time during the day but
no later than 2 hours before stopping the system. The treatment should
be repeated every 6 to 12 hours of total irrigation time. The best time
to make the injection is just after backflushing the filter. It is
essential that the chlorine pass through the filter in order to prevent

Liquid sodium hypochlorite (NaOCl), commonly called
bleach, is the only bactericide that has a 24(c)
approved EPA label for use in low pressure irrigation
systems in Florida. No other chlorine form has been
approved. HUME L
----rI-rn- HllU.MEL


The Use of Surface Water for
Low Pressure Irrigation Systems -2-

bacterial growths from occurring in the filter. Treating immediately
after backflushing reduces the amount of chlorine required. It also
minimizes sticking action of the slimes as they are trapped in the
filter so that backflush characteristics are improved.

Chlorine can be injected through calibrated orifices as a suction
system or by use of a motor driven liquid chlorine injection pump.
The entire system can be automated when a chlorine injection pump is
used. All that is required is a timer that can be set to inject chlorine
for 45 minutes every 6 to 12 hours. The timer is attached to the circuit
controlling the centrifugal pump. The timer will run only during the
period that the irrigation system is "on". Consequently, the timer
accumulates total irrigation time from 6 to 12 hours.

The injection system can not be automated if a suction system
through microorifices is used. Orifices should be constructed from
teflon or other materials that are not damaged by chlorine. SEE: Table 1,
Fig. 1. Brass and all metals should be avoided. PVC and PE
(polyethylene) type materials are satisfactory. Orifice type systems
should be confined to operations in which the pumping capacity is greater
than 100 gpm. The orifice must be large enough to pass small particles.
We have found that orifices used on systems less than 100 ppm may clog
from particles in the chlorine solution.

It is essential that a DPD type chlorine test kit be purchased and
used to read total chlorine and free chlorine residual. Keep the test kit
in a cool place. Total chlorine includes all chlorine that is absorbed on
organic matter plus extra chlorine for killing the bacteria. Free chlorine
is the excess chlorine over and above all chemical reactions and other type
reactions in the system. It is the type of chlorine that kills bacteria
and algae. Chlorine should be injected to obtain a minimum of 1.0 ppm
[mg/1] free residual chlorine assuming the pH of the water is below 7.5.
This reading should be obtained at the last emitter or microsprinkler on
the irrigation system. Such an "end of line" measurement is often
inconvenient since one cannot be certain when the chlorine will reach the
last emitter. A more convenient method is to take a reading close to the
pump. This reading should be at least 2 ppm of free residual chlorine.
The best method is to read both locations initially and adjust the pump
reading according to the reading at the last emitter. Initially, the
amount of chlorine required will be very high because of contamination
in the system. With treatments over a period of time, the amount of
chlorine probably can be reduced. If there is insufficient free residual
chlorine, all of the chlorine injected is wasted and may actually cause
additional problems.

Surface water systems, that do not contain iron, will encounter little
or no difficulty with the chlorine treatment if the pH is below 7.0. Higher
pH values for surface water may result in certain organic precipitation
reactions for which we have no control at this time.

The Use of Surface Water for
Low Pressure Irrigation Systems -3-

Surface waters containing iron can be treated with chlorine for
40 minutes every 6 hours providing the pH is less than 6.5. Above
pH 6.5 certain organic precipitation reactions combined with completed
iron may gradually clog the irrigation system.

A survey of lakes and ditches has indicated that total chlorine
requirements may vary from 3 to 10 ppm. This could require the use of
7 gallons of 10% sodium hypochloride in 45 minutes for a pumping system
of 800 gpm.

The cost of the chlorine treatment is considerably less than labor
to clean and maintain a partially clogged irrigation system.

The Use of Surface Water for
Low Pressure Irrigation Systems

Table 1. Polyethylene orificez for pump suction (or psi differential)
and gph NaOCI to be injected.

gph of NaOCl at specified Hg vacuum
Diam of (or psi differential)
Drill orifice 5 inches 10 inches 15 inches 20 inches
size (inch) (2.5 psi) (5.1 psi) (7.6 psi) (10.1 psi)

-- 0.022x 1.00 2.10 2.90 3.30
68 0.031 1.50 2.30 3.10 4.30
58 0.042 2.00 4.00 5.40 6.507
53 0.070 3.30 6.20 --
43 0.089 3.70 -- -

Zorifices constructed from the tethered exit plug sections of Spot
Systems vortex emitters--some with the addition of 0.015 inch and
0.023 inch tubing.

YThe max flow rate with optional fritted filter and other resistance
to flow factors.

XStandard Spot emitter orifice without drilling.

The Use of Surface Water for
Low Pressure Irrigation Systems

Figure 1.

A vacuum type chlorinator to permit automatic operation on wells
that have non-leaking foot valves. The injection point is
between the foot valve and the pump.

The use of a plastic check valve, without spring, permits the back
surge of pressure (when the pump is stopped) to close the check valve
and automatically stop the flow of chlorine solution. Flow will not
start again until the next irrigation. The only attention required is
servicing the orifice (I) and the filter (H). The basic design has been
tested for one season under field conditions. SEE: Fig. 1 for lettering

The check valve used was Model C-395-6 of Blue White Industries.
Other brands of the same design should work.

- Plostic Tee

Plastic Check Valve

SSpring Removed
From Check Valve

NoOCI Line
into Well

-To Pump

II Suction

Foot Valve

EPA approved 24 (c) label for slimes in irrigation systems.



(EPA Reg. No. 148-628)



It is a violation of Federal law to use this product
in a manner inconsistent with its labeling.

Crop/Site: WelL" water and surface water sources used for irrigating fruits,
vegetdAle, and ornamental crops in Florida.
.. arget Pest/Problem: Bacterial slimes that clog the emitters in drip/trickle
and low pressure irrigation systems.
Dosage: 0.5-1.0 ppm free residual chlorine as measured at the last emitter
in the irrigation system.
Dilution or Application Rate: Do not dilute the.chlorine solution.
Method of Application: Adjustable proportioning suction type or pressure type
liquid chlorine injection pumps.
Frequency/Timing of Applications: Continuous injection or intermittent injections
of a duration to fill the irrigation system at the end of each irrigation
cycle if slimes are controlled.
Field Reentry Safety Interval: None.
Preharvest Interval: None.
Other Requirements: Free chlorine residual levels must be monitored with DPD
(N,N diethyl-p-phenylenediamine) test kits.
All applicable directions, restrictions, and precautions on the EPA-registered
label are to beffollowed.


24(c) Registrant:

P.O. BOX 2383, [KANSAS CITY, KA ~N ISAS 66110

EPA SLN FL 770046