Removing & Controlling Biofilm in Agricultural Water Irrigation Systems

August 28, 2019

Growers know biofilm builds up in pipes, tubes and irrigation trenches, but don't realize that eradicating biofilm can improve crop quality and yields.

Most growers are more or less aware of the slippery scum that builds up in pipes, tubes, irrigation trenches, and other means of transporting water. But many fail to recognize the serious negative impact of biofilm buildup on growing conditions for indoor and outdoor applications.

But by taking steps to eliminate biofilm and control its future proliferation, growers can improve their crop quality and yields, and reduce the cost of maintaining their water systems.

What is biofilm?

Biofilm deposits are colonies of a various types of single-celled bacteria, fungi, and algae. The formation of biofilms begins with one or more species of microorganisms latching onto the side of a pipe or other means of carrying water. These first arrivals in turn serve as a colonization point for other lifeforms that might otherwise not be able to bond to a smooth, uncontaminated surface.

These initial colonies can then attract the attention of other microorganisms, as well as viruses, nematode and insect larvae, and other lifeforms. The result is a complex ecosystem of living single- and multi-celled organisms, as well as the decaying matter left over by past generations of dead organisms. As these biofilm formation sites mature, pieces break off and are deposited elsewhere in the water system, with the result being widespread contamination.

Many of the bacteria and other organisms within a biofilm do not present any direct health threat. However, biofilms can capture and serve as a spawning point for viruses, E. coli and other harmful bacteria, Cryptosporidium, and water molds (fungi) which can be harmful to plants).

If the water flowing through a water system contaminated with biofilm is used for human consumption, people drinking the water may be sickened by the bacteria, viruses, and parasites spawned from the biofilm.

Biofilms can harm plants exposed to contaminated water through fungal infection, as well as oxygen deprivation.

While human health is always a concern, water used strictly for agricultural purposes can still cause serious harm to plants if its contaminated by biofilm. Growers may fight stubborn, repeated fungal infections in their plants, not realizing that the water used to sustain their crops is the source of the infection.

This is especially the case for indoor growers cultivating plants in hot houses and greenhouses. The warm environments found indoors provide the perfect growing environment for fungal spores introduced via contaminated water systems. In recent years, cannabis growers have been plagued with infestations of the fungus Fusarium, as well as so-called ‘water molds’ like Pythium and Phytophthora. These pathogens are readily transported through contaminated water, and thrive in the warm, moist growing conditions often found in indoor growing operations.

But bacterial, fungal, and viral infections are only the beginning of the problem. Many of the algae, fungi and bacteria species bound up in biofilm are aerobic, meaning they need oxygen to survive. They source this needed oxygen from the water passing by. The result is that water passing through a biofilm-infested water system becomes seriously deoxygenated.

Low oxygen levels in water present a couple problems in agricultural contexts. First, plant roots need oxygen to survive. Secondly, most harmful bacteria, including those which infect plants, are anaerobic. Thus, low oxygen levels in the water in turn contributes to low oxygen levels in the soil (or whatever growth medium is being used), encouraging the growth of harmful anaerobic bacteria.

The deoxygenated, anaerobic water conditions resulting from biofilm infestations can cause harm to water systems, as well as plants.

As biofilms grow and develop, and dissolved oxygen levels drop, anaerobic sulfur-reducing bacteria often find a happy home. These bacteria are notorious for the sulfurous, rotten-egg flavor and smell they give water. This is the result of hydrogen sulfide they give off as a metabolic byproduct.

While the gross taste and smell produced by these bacteria usually doesn’t present a health issue, the real issue is that dissolved hydrogen sulfide is extremely corrosive, eating through pipes and fittings made from iron, steel, and copper.

In addition, biofilms often harbor iron-reducing bacteria. These bacteria survive by absorbing extremely small quantities of dissolved iron (or manganese) and combining them with oxygen. This process lowers already low dissolved oxygen levels. But a more serious consequence is that it creates slimy deposits in water systems—perfect for growing and spreading biofilm.

You can see how biofilms produce and thrive in a vicious cycle that is difficult to break.

A hardy microorganism colonizes a rough spot in the wall of a pipe or the ridge of a pipe fitting. Other microorganisms glom on. The growing biofilm begins to deoxygenate the water, encouraging the growth of sulfur- and iron-reducing bacteria. These produce slimy deposits and cause damage that produces more latching points for new biofilms, and so on.

There is no one-time fix for biofilms. No water source is pure and clean. Preventing the growth of biofilm requires a continuous intervention. So, how do you eliminate existing biofilm deposits, and prevent their future formation?

Ozone-based water treatment significantly increases dissolved oxygen levels, oxidizing and killing biofilms and preventing their growth.

Biofilms are very difficult to break down, due to the slimy, greasy coatings they form that protect the microorganisms underneath. This is why many traditional approaches to biofilm elimination involve injecting oxidizers such as chlorine dioxide or sodium hypochlorite into water systems.

While this is a suitable approach for agricultural applications, it does present problems. For one, such treatments tend to be costly, and must be repeated to keep water systems clear. But the real problem is that both chlorine dioxide and sodium hypochlorite are strongly corrosive,  eating through iron and nickel-based alloys. This causes holes in pipes and threaded fittings, as well as the formation of oxide deposits that can obstruct water flow. This means that with each additional use of a traditional oxidizer, you damage your water system. And the resulting corrosion and metal deposits make your water system ever more hospitable to biofilm.

Recognizing these issues with traditional approaches, Watson Well has developed an ozone-based water treatment system. The levels of dissolved oxidation produced by through the use of ozone—an extremely powerful but short-lived oxidizer—in our systems are sufficient to break down biofilms and prevent their future formation. But because the dissolved ozone breaks down rapidly—in a matter of minutes—we avoid the damage to water systems inflicted by traditional approaches to biofilm treatment.

We invite you to learn more about our water treatment systems, or to contact us directly to learn more about how an ozone-based water treatment system can remedy your biofilm problem, and improve the overall productiveness and profitability of your agricultural business.

California Groundwater Association
National Groundwater Association