In our last blog post, we discussed the main causes of emitter clogging in irrigation systems: physical, biological and chemical.
We also presented information on the types of clogging expected from the use of different irrigation water sources.
Emitter clogging can cause a lot of damage to your irrigation system and significantly impact your bottom line. For this reason, a well-designed irrigation system should include preventative measures to avoid emitter clogging.
Water quality analysis
Prior to designing an irrigation system, it’s important to understand the quality of the irrigation water source by sampling the water and performing a water quality analysis. This analysis can be done at a water testing laboratory and the test protocol should be specific to irrigation water so that the results include typical contaminants that can cause emitter clogging.
For example, the water analysis should include testing for hardness or mineral content [presence of calcium (Ca) and magnesium (Mg)], as mineral precipitation from water sources with high mineral content can produce suspended solids that clog emitters. Water quality testing can also provide information on total suspended solids (TSS) and particle size distribution, which will enable you to evaluate the expected quantity and size of organic and inorganic solids in the water that could potentially clog emitters.
Clogging prevention solutions
When selecting clogging prevention solutions for your irrigation system, you should consider the following factors:
- Operating conditions
- Water source and quality
- Clogging factors in the water
- Emitter characteristics, such as the opening size
As these factors vary greatly from site to site, there is no standard recommendation to cover all conditions. In general, irrigation system design aimed at preventing emitter clogging should include the following:
- Chemical treatment (chlorination and/or acid injection)
- Flushing allowances for irrigation lines
A well-designed filtration system can prevent the physical clogging of irrigation system emitters. The size and type of filter is determined by the quality of the irrigation water, the maximum particle size that can be passed through the emitter opening and the volume of irrigation water that can flow through the filter before the filter needs to be cleaned.
You can usually get information about the maximum allowable particle size from the emitter manufacturer. If this information isn’t available, use a conservative rule of thumb that any particle larger than one-tenth the diameter of the smallest opening of the emitter should be removed. This also prevents bridging, which occurs when small particles aggregate and clog an emitter by forming a bridge across the opening.
If the water contains a large amount of sand, a sand separator can be installed to separate sand and other heavy particles from the water using centrifugal action. In addition, if the water source contains a large amount of silt, or is a fast-moving stream, a settling basin can be used to remove the solids.
Screen, media or disc filter solutions can be used to remove inorganic or organic clogging hazards such as slimes, algae, moss, snail and/or plant residues from irrigation water.
These filter solutions can either be manual, requiring an operator to manually remove the filter element(s) and wash or replace them, or automatically self-cleaning.
Chlorination and disinfection procedures are key to controlling the biological clogging of irrigation systems. However, if the pH of the water is high (above 7.5), chlorination becomes relatively ineffective for bacterial control. For this reason, acid injection may be required to lower the pH level and increase the biocidal action of the chlorine.
Injecting acids, such as sulfuric, hydrochloric or phosphoric acid, into irrigation water to reduce pH levels will also decrease the possibility of mineral precipitation in hard water which also helps prevent emitter clogging.
Naturally occurring dissolved iron in irrigation source water can be oxidized by aeration during pumping or chemically oxidized by acid injection to form precipitates that then clog emitters. If an irrigation water source is found to contain high levels of iron, treatment will be required. One solution is to pump the water to a tank or reservoir and aerate the water or add a chemical oxidant (such as chlorine) so that the ferrous iron is oxidized and can be settled or filtered out of the water before delivery to the irrigation system.
Note that acid and chlorine injection points should be at least 2 to 3 feet apart and should never be combined in the same container as dangerous chlorine gas is released.
When adding fertilizers to source water (fertigation), it is recommended that you perform tests to determine if the specific combination of fertilizers and other chemicals in the irrigation water interact and result in mineral precipitation that could cause emitter clogging.
Regular flushing of irrigation systems is recommended to minimize the buildup of sediment and organic residues. The irrigation system should be designed so that the sizes of the main line, laterals and valves facilitate sufficient flushing velocity.
By including a regular maintenance program that includes inspection and flushing of your irrigation system, you will be able to significantly reduce the amount of emitter clogging occurring.
Proactively prevent your emitters from clogging
In order to protect your investment in an effective irrigation system and make sure your crops are irrigated in the most uniform manner, it’s important to define a proactive strategy to prevent emitter clogging.