THE ISSUE OF MICROALGAE IN FILTRATION SYSTEMS

THE ISSUE OF MICROALGAE IN FILTRATION SYSTEMS

During the hottest months of July and August in the European summer, the high temperatures and the growth phase of crops increase the need for irrigation in most agricultural plantations. However, it is common to experience problems in irrigation systems during this period, which has become a constant challenge.

The root of this problem lies in the proliferation of microalgae. These unicellular microorganisms contain chlorophyll and other photosynthetic pigments, allowing them to perform oxygenic photosynthesis without differentiation into root, stem, and leaf structures. They are highly efficient at fixing CO2 and converting solar energy into biomass. Their metabolism can be autotrophic (using only CO2 and sunlight) or heterotrophic (requiring external sources of organic compounds as an energy source).

The most common groups of microalgae in continental waters are:

  • Cyanobacteria
  • Chlorophytes
  • Cryptomonads
  • Glaucophytes
  • Euglenoids

 

During the aforementioned period, rivers experience low water levels (low flow) exacerbated by the current drought. Despite this, the load of organic compounds in the rivers remains constant due to the regular discharges from upstream water treatment plants. Additionally, the optimal temperatures for microalgae growth range between 16 and 24 degrees Celsius. The water from these rivers is used for direct irrigation or channeled through irrigation systems, either by capturing it directly or storing it in reservoirs.

These conditions provide an ideal environment for the exponential growth of microalgae:

  • Sunlight hours
  • Increased concentration of nutrients in the watercourses
  • High temperatures

 

This massive growth of microalgae causes problems throughout the irrigation network, excluding only groundwater sources.

The first symptoms of this problem manifest in the filtration system. The filters begin to require more frequent cleaning until they become clogged and cease to function. Physical and chemical cleaning of the filters is necessary, but the problem reappears shortly after they are restarted. The most concerning aspect is that some microalgae manage to pass through these filtration systems and proliferate in the drip emitters, further aggravating the magnitude of the problem.

What is the most recommended filtration system?

At Lama Filtration Systems, as manufacturers of the three major families of physical filtration systems: screen, media, and disc, we believe that the most effective solution to prevent these situations is media filtration.

Based on experience, we always recommend to our clients to opt for this system as it is the only one that filters in depth. The microalgae, which can even be dissolved in the water, adhere to the sand (or the filtering element contained within the filter) and therefore do not pass into the filtered water.

Additionally, during the passage of solids through the media, processes of sedimentation (a kind of decantation), centrifugal forces, physical adsorption phenomena (Van der Waals forces and electrokinetic) and electrostatic interaction are generated.

Although screen and disc filtration is efficient and more economical for water from canals and irrigation ponds, it is not the best solution during the critical months of microalgae growth.

Therefore, at Lama Filtration Systems, we propose that for long-term intensive crops, sand filters should be implemented followed by automatic screen or disc filtration as safety filters.

 

Our Recommendations

Anticipation and planning guarantee the highest water quality by foreseeing the possible appearance of microalgae. Although the initial investment may be slightly higher, it is crucial to consider that the filtration system represents only between 7 and 9% of the total investment in the irrigation installation. Thus, the additional initial cost of sand filtration is not significant in the overall investment and, above all, prevents production reduction and drip emitter clogging, which negatively impacts the operation.

Once the hottest months have passed and the growing season ends with the temperature decrease, the microalgae usually disappear, and the problem is forgotten until the next summer.

At Lama Filtration Systems, especially in new stations, we advise learning about this issue in nearby operations and taking preventive measures by installing sand filtration systems. In addition to ensuring better water quality, this will prevent the recurrence of microalgae-related problems each year.

We have been solving and advising on this problem for over 75 years, being a technological ally for our clients.