With the increasing water struggles facing growers these days, it is no wonder we see a rise in the demand for water reclamation, treatment, and reuse. Traditional growing practices include drip irrigation, flood irrigation, and overhead sprinkler irrigation for crops planted directly in the soil. The drain water from these irrigation events is often unseen as it leaches through the soil profile back into the underground water source. Regulatory pressure will eventually demand that this drain water is limited, tested, and proven safe for reentry into the water supply. This opens the eyes to many growers to alternative growing practices such as outdoor soilless substrate farms, greenhouse growing, and indoor vertical farms.
With these alternative growing practices, the drain water is more visible and calculable. We can determine precise drain amounts via sensors, calculations and timing, and advanced cultural techniques. However, this drain water must now be collected and disposed of in some manner. Nitrate removal systems are now available to allow growers the potential for a safe discharge. Some urban indoor farms are even paying trucking services to remove water from their facilities. But the obvious question is, why can’t we reuse this water?
Irrigation drain water from soilless farms has the potential for bacterial growth and other potentially harmful organisms that we would not want to introduce into the system. However, the water is nutrient-rich and can provide benefits to the crops and the fertilizer budget for many growers. The solution for these challenges is not easy and is one of the most significant objections we find when providing drain water treatment solutions. But for many growers this will be a must-have addition.
Chemical treatment options using hydrogen peroxide, peracetic acid, and others are very popular and familiar to many growers who often use these chemicals in other aspects of the farm. However, with any chemical treatment, the dangers of chemicals, and the added cost, the systems are relatively simple and cost-effective.
Ultra-Filtration is where water is pumped through a membrane, and suspended solids, pathogens, parasites, and fungi cannot pass, leaving clean, permeate water behind. These are popular in indoor cannabis farms and greenhouses. They are new to the agriculture space and require discharge water from the filtration process that is chemically treated. However, they show promise for indoor and smaller farms.
Reverse Osmosis also uses a pressurized system through prefilters and membranes to completely rid the water of sediment and dissolved solids. The concentrate must be dealt with, and all the nutrients are removed from the water, but the process can be very effective. Several companies offer these types of systems, and they can be scaled to large farming operations.
Ultraviolet or UV sterilization systems use UV-C light to destroy pathogens like fungi, bacteria, and viruses. These systems have a fine filtration requirement to ensure that pathogens cannot “hide” behind any solids and require a pre-chemical treatment. These are highly effective systems and scalable to large farms.
With all these system types, and these are just a few of many, growers have options for the treatment of irrigation drain water for reuse and blending. We have even seen a combination of several of these systems and others used together for water treatment. The availability and regulation of water use forces growers to think outside the standard toolbox regarding their irrigation systems. The importance of staying ahead of the curve is more evident now than ever.