Classification

Inorganic Suspended Matter

• Phytoplankton (Algae and Bacteria)

• Bacteria
• Algae
• Phytoplankton
• Zooplankton

• Aerobic + Anaerobic
• Sludge formation
Courtesy of
Nu3

• There is a cyclic seasonal pattern in the development of algae. In winter, when there is little light and low temperatures, the growth of algae is minimal. In spring when temperatures rise and there is an increase in radiation as well as in the availability of nutrients, Blossoming occurs.

• Water source (River, lake)
• Water tanks (Settling pool, Reservoirs)
• On dripline surface.

• Zooplankton
• Phytoplankton

• The size of zooplankton varies within the range of
0.2-30 mm.

• Carbonates
• Iron
• Fertilizers
• Silt

Others

Water + Carbon dioxide + Calcium carbonate c
Calcium Hydrogen carbonate
H
2
O + CO
2
+ CaCO
3
[
Ca(HCO
3
)
2(aq)
םומיח

1.5
1
0.5
0
-0.5
0
-1
Langelier Index vs Temperature
Scale begin
3 8 12 16 19 24 29
Temperature (C)
34 41

16 Cº
20 Cº
45 Cº
28 Cº

• White tubing
• Subsurface installation
• Shading

• Wrong mixtures
• Phosphorous – Calcium
• Sulfate – Calcium
• Phosphorous – Iron
• High pH
• Dirt

Dissolution ( gr/L ) of some fertilizers
Dissolution ( gr/L ) of some fertilizers c c c
Temp C c c c
Urea
Ammonium Sulfate
Potassium Nitrate
Potassium Sulfate
Potassium
Chloride
MAP

Soluble Ion
CaNo
3
Soluble Ion
H
3
PO
4
D.C.P

• Calcium – Phosphorous
• Calcium – Sulfate
• Magnesium + “
• Wrong dilution of P acid in hard water.

Ca Nitrate + MAP

• Accumulation on surface

• It can generally be stated that clogging problems due to the occurrence of impurities in irrigation water become more acute if the water has a high content of:
• Suspended particles of organic or inorganic matter.
• Precipitate-forming elements.
• Bacteria that secrete slime.

• The turbidity of a water sample is a measure of the ability of its suspended and colloidal materials to diminish the penetration of light through the sample.
• Turbidity is measured by means of a turbidimeter

• Particle-size Distribution
- This test is performed by counting the particles and establishing their size distribution.
• Hydrogen Sulfide (H
2
S) - Water from deep wells may require H
2
S determination.
Portable test-kits are available for rapid field testing.

Water Quality Criteria
A water classification system for indicating clogging hazard in trickle systems (Bucks and Nakayama -
1980)

Classification of Drip Irrigation Water
Quality

Natural Water Quality Classification

Evaluation of Carbonate Sedimentation

Evaluation of Carbonate Sedimentation

Chlorination is based on the injection of various chlorine compounds into the irrigation water.

• It creates an environment in which algae can no longer develop.
• It acts as an oxidizing agent, causing the decomposition of organic matter.
• It prevents the agglomeration and sedimentation of organic suspended matter.
• Its oxidizes substances such as iron and manganese, producing insoluble compounds that can then be removed.
• Eliminating sulfur bacteria.

Reactions of Chlorine with Water
• Hydrolysis:
H
2
0+CL
2
= HOCL + H
• Ionization:
HOCL = H + + OCL -
+ + CL -
• Effective chlorination is influenced by the following factors:
• Available chlorine (concentration and type).
• pH
• Contact time
• Temperature

Distribution of HOCL and OCL in Water at indicated pH levels

Comparison Between Different Forms of Chlorine

Safety Precautions
Active chlorine preparations are strong oxidation agents and as such are toxic to human beings and livestock . Read the manufacturer safety instructions on the label of the package before applying the treatment and act accordingly.
Direct contact with chlorine may cause burns, blindness and may even be fatal. Therefore, protective glasses, gloves, shoes and suitable clothing must be used when handling chlorine to prevent contact with exposed parts of the body.
Solid chlorine tablets are dangerous when they comes in contact with fertilizer concentrates and may cause an explosion.
Keep hypochlorite in an opaque container, sealed against light and air, since they cause decomposition of the material and reduce its concentration.

Do not mix chlorine and fertilizer concentrates, Inject these materials by separate injector pumps or inject them one after the other.
Chlorine is not effective for prevention of scale formation or its decomposition.

• Continuous injection of chlorine at low, uniform concentration (normally 1-10 ppm), throughout the entire irrigation cycle.
• Intermittent injection at higher concentration
(normally over 10 ppm) once or several times during the irrigation cycle (for a duration of up to approximately 20 minutes per day).
• Super chlorination at a concentration of 50 ppm, for a duration of 5 minutes during the irrigation cycle

Recommended method: Application of the chlorine by injection for one hour during each irrigation cycle, together with injection of acid for pH reduction.

Methods of Chlorination

Methods of Chlorination

When calculating the desired chlorine concentration, the following factors should be considered

• The availability of chlorine depends on its form:
• Chlorine gas: 100% availability.
• Calcium hypochlorite: 65 - 70% availability
• Sodium hypochlorite: 5 - 15% availability

Chlorine concentration
Application of high doses of chlorine may cause a much too rapid decomposition of the organic sediments and result in the clogging of the drippers.
It should be borne in mind that the chlorine concentration in the system weakens in time, depending on the distance from the point of injection.
Chlorine concentration at the end of the system is, therefore, generally lower. This should be taken into account when calculating the required chlorine dose, so as to ensure the required residual level at the distal points of the system.

Recommended Concentration of Free
Chlorine in Water (ppm) for various purposes

Chlorination Control

The chlorination process
• It is recommended applying chlorination treatment as near as possible to the drip lines to ensure that the sediments do not migrate from the main pipe system, or sub-mains, to the drip lines.
• Check the sensitivity of the crop to chlorine.
• Do not use nitrogen fertilizers containing ammonium when injecting chlorine. It causes the formation of compounds which dissolve with difficulty.
•Chlorine should not be injected into the system when the dissolved iron concentration in the water exceeds
0.4 ppm.

The injection process a . Select the required chlorine concentration according to the table b . Calculate the required flow rate of the chlorine into the system c . Select a suitable injector pump or mix the chlorine and water to obtain a volume suitable for the injector pump.
d . Flush the system thoroughly, including the main pipe line, the sub-mains and the drip lines.
e . Inject the chlorine into the system.
f . Check the residual chlorine concentration at the terminal point of the system.

g . Verify that the quantity of chlorine meets the requirements. If it is insufficient, add more chlorine.
h . Continue injecting the chlorine for the required period according to the application type (continuous or intermittent).
i . Thoroughly flush the pipe system and the drip lines at the end of the treatment.
j . It may be necessary to repeat the chlorine application more then once.

Special Problems of Chlorination
• Loss of chlorine in storage tank

Special Problems of Chlorination
• Decrease in free residual chlorine concentration in the system

Special Problems of Chlorination
• Reaction of chlorine with water containing fertilizers

Special Problems of Chlorination
• Use of injection pumps

• Copper sulfate can be used effectively to control algae in reservoirs

Diesel oil floats on the water surface,
Following treatment with diesel oil, concentration of suspended matter decreases.

Treatment with Acid

Treatment with acid is based on the injection of one of the variety of types of acid into the irrigation water
Functions
• Prevents precipitation of dissolved solids.
• Dissolves existing precipitates.
• Improves efficiency of chlorination when applied in conjunction with chlorine.

Types of acids used for injection into drip systems
The three acids most commonly used for injection into drip irrigation systems are as follows:
Hydrochloric acid (HCl) – a highly corrosive material, but widely used in Israel owing to its low cost.
Phosphoric acid (H
3
PO
4
): This material, apart from its intended cleaning effect, acts as a source of phosphorous nutrient.
Sulfuric acid (H
2
SO4): This acid attacks most metals and is extremely hazardous for human beings .

Safety precautions
Acids are toxic to human beings and animals. Read the safety instructions given by the manufacturer on the label of the package before applying the treatment and act accordingly.
When dissolving the acid in water, add the acid to the water prepared previously in a suitable vessel. Do not add water to acid . Adding water to the acid is liable to generate considerable heat.
Take measures to prevent the irrigation water treated with the acid from penetrating a water supply system upstream of the point of injection .

This acid should not be injected into water containing dissolved iron. The treatment should be applied so as to reduce the pH level of the water to less than 6.5, in order to prevent formation of phosphate sediments.
The acid does not react in a dangerous or toxic manner with other salts or chemicals found in the irrigation water.

Treatment Doses and
Frequencies
In general, the more frequent the acid treatments, the lesser the risk of dripper clogging. The frequency of treatment should be adjusted according to the treatment purpose.
The treatment purposes are as follows: a . Prevention of sedimentation – preventative treatment: continuous injection of acid at a low dosage prevents the settlement of carbonates. The acids should be injected to the system continuously at a concentration which will reduce the pH of the water to
6-6.5.

b . Dissolution of sediments – Aggressive treatment.
This treatment is applied when clogged drippers are located and/or when there is accumulation of salts on the walls of the drip line.
In addition, acids should be applied once or twice during the season according to the appearance of the accumulated sediments. At times additional treatments may be needed.
Apart from the treatments during the season, it is recommended injecting acid into the system at the end of each irrigation season.
A pH level of 2 should be reached in the water.
c . Improving the effectiveness of chlorination.

Application those components of the irrigation system which are sensitive to acids.
Special points to be noted
One treatment may not give optimum results. In which case the treatment should be repeated.
The acid should be injected to the system by means of a fertilizer injection pump. All parts of the pump must first be checked to ensure that they are resistant to acids.
The acid should be applied at the nearest point to the drip lines so as not to dissolve sediments in the main pipe system since these sediments might them migrate to the injected for 10 to 12 minutes.

Instructions for application of acids
Simple calibration enables verification of the quantity of acid required for the specified treatment.
a . Prepare a vessel with 1 liter of irrigation water.
b . Fill a medical syringe with the acid.
c . Gradually drip the acid into the water while stirring. For each drop of water, add 1 cc of acid.
d . Measure the pH level of the water until reaching the required level with pH meter or with litmus paper.
e. The quantity of dissolved acid in cc per liter of water = the quantity of acid in liters required per cubic meter of irrigation water.

f. Prepare the items required for the treatment: the injector pump, a vessel resistant to the acid, and the acid.
g. Prepare the acid solution to be injected.
h. Open the water and flush the components of the system well, including the main pipe, the sub-mains, the flush-out lines and the drip lines.
i. Inject the acid solution into the system.
j. Check that the acid has reached the end of the most distant drip lines. The acid can be identified by sampling the pH of the water.
k. Add water to the vessel and thoroughly flush the injection pump from the acid residues.

l. Continue to irrigate after completing the injection for an additional 30 minutes or so.
m. Flush the irrigation system once again with clean water free of dissolved sediments.

Improving efficiency of chlorination

Treatment with Sedimentation Retarders
Sedimentation retarders are chemicals of high molecular weight. They are soluble in water and contain various functional groups that retard the crystallization and sedimentation of carbonates and sulfates.

A wide range of sedimentation retarders is available, such as:
• Calgon (polymetaposphate).
• Polyacrilates.
• Phosphonates.
• E.D.T.A based materials.

• The most prevalent coagulant used is alum
(aluminum sulfate), which appears in either dry or liquid form.
• Alum is fed at doses up to 200 mg/l with
10-40 mg/l doses being common.

• The primary purpose for adding coagulants to water is to destabilize colloidal dispersions of small discrete particles, which would not be removed by sedimentation and filtration. The coagulant assists in forming a floc, which can sink in a tank or filter and then be removed.

Occurrence of Iron

Oxidation treatments can be carried out by means of various procedures, such as chlorination, aeration, potassium permanganate, etc.

Can be used to control iron deposition if the pH is below 6.5 and the iron concentration is less than 3.5 ppm, If the pH is above 6.5 , the iron concentration must be below 1.5 ppm.

Aeration causes the oxygen and water to react with the iron, as follows :
2Fe(HCO
3
)
2
+ 0.5O
2
+ 2H
2
O= 2Fe(OH)
3
+4CO
2

Occurrence of Iron
Prevention
• Sedimentation (settling) and filtration.
• Reclamation.

Criteria for Selecting Chemical
Treatment
• When the biological load is high
- chlorine should be applied to prevent algae development and to decompose organic matter.
• When suspended matter is high and biological mass is present - chlorine should be applied to prevent agglomeration.

Criteria for Selecting Chemical
Treatment
• When residual iron, sulfur or manganese
(above 0.5 ppm) is present - chlorine should be applied to oxidize these compounds and settle them in the filtration system.
• When the water source is a reservoir
- water should be treated by means of copper sulfate, diesel oil or fish.

Criteria for Selecting Chemical
Treatment
• When dissolved solids and pH are high
acid treatment is beneficial.
• When chemical and biological factors are high - both acid treatment and bacteria control be considered.

• If water is pumped directly from the bottom of the reservoir, then sand, silt and clay will be dragged into the irrigation system.
• If water is pumped from the surface of the reservoir,Then the contents of the upper water layer (branches, leaves, algae) will also be dragged into the irrigation system.
• The optimum pumping depth should be between 1.2-1.9 meters below water surface

• The pumping system (inlet pipe) should be protected against the infiltration of large bodies into the irrigation system.
• Before locating the pumping station, the main wind direction should be considered, in order to prevent floating material from drifting toward the pumping inlet.

• In reservoirs in which there is automatic primary filtration, backflushing water should be kept away from the pumping inlet.
• In reservoirs in which fish are grown, the pumping station should not be located near the feeding points.