June 2011 Case Studies

CK Greenhouses Solves Irrigation and Pathogen Problem By Al Zylstra

After increasing pot crop production, Charlie Kurtz, owner of CK Greenhouses, Cheshire, Conn., wanted to reduce leaf wetting from irrigation and the resulting foliar disease, so this past winter he converted five greenhouses to flood bench irrigation.

CK Greenhouses provides rooted cuttings, prefinished pots and basket starters to other growers and high quality disease-free plants are critical but recycled flood irrigation can contain water-borne pathogens to spread to other benches in the system. Capturing and recycling water and fertilizer can save as much as 50 percent, because all water is captured and recycled. Unfortunately, algae, pathogens, and suspended solids also are recycled with that water and need to be dealt with.

Kurtz ordered the initial 320 flood benches to retrofit into 35,000 square feet of existing greenhouses, allowing time to decide how to resolve the disease risk. He wanted to maintain clean water to protect crops with a standalone, self-managing system. He did not want to rely on a person to monitor cleanliness of water and tank treatments.

Rather than recirculating water to all benches from a central tank, the benches were split into five zones each with two dedicated tanks. Each group of benches recirculates only through the tanks in that zone to avoid cross contamination between zones. This is a good strategy, but with 10 tanks, treatment is more complex and expensive.

Charlie contacted Al Zylstra, manager of DRAMMwater . They explored several ideas for a system design, including treating just the water in two or three zones in the beginning to keep initial costs down. Ultimately Charlie wasn’t comfortable with that risk. Al recommended a single treatment system to treat the water in multiple tanks in rotation. This past December the system was ordered to treat all 10 tanks in five zones with a single Clearadvantage Ozone Treatment system.

The system consists of deep media filtration with recycled crushed glass filter media; a Clearadvantage ozone system with a patented pressurized ozone reaction vessel; 10 tank control valves; a dedicated circulation pump for each tank; and a touch screen computer controller. The pump at each tank circulates water through the treatment system, continuously rotating from tank to tank. The water is pre-filtered to 5 microns; disinfected in the reaction vessel and charged with a residual level of ozone, then sent back to the tank it came from, clear and free of pathogens. The residual level of ozone keeps biofilm from forming in the pipes and the tanks, and kills pathogens remaining in the flood tanks.

The oxidation-reduction potential level is monitored continuously and when the level is high enough to assure that the water is clean, the controller moves to the next tank and repeats the process. The system requires very little power and no chemicals or other consumables — and it requires limited maintenance. The growers monitor each tank’s disinfection level at the controller, rather than having to test and treat each tank individually.

Two additional benefits of ozone disinfection are no phytotoxicity concerns, and, since ozone converts back to oxygen, increased dissolved oxygen levels to enhance root development and nutrient use.