Recycling Rainwater

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Lucas Greenhouses’ water treatment system includes the grey ozone contact tank, six pre-filters and four posy filters.

Water recycling is not a new idea for greenhouse growers; many have done it for ages. But some growers are taking water recycling to a new level with 5-micron filter technology, ozonation and rainwater harvesting. These methods ensure that the water these growers use is the cleanest, most pure water available, allowing them to reduce pesticide and fungicide use, improve plant health and realize cost savings. And they’re also showing that thanks to rainwater catchment systems, it’s possible to be completely independent of city and ground water.

Metrolina Greenhouses’ Quest To Improve Water Quality

“Clean water is our number one chemical,” says Abe Van Wingerden of Metrolina Greenhouses in Huntersville, N.C. “Many growers miss that. They test their water quality and use chemicals to mitigate those problems. We do the opposite to reduce chemical usage.”

Indeed, the Van Wingerdens have been on a quest to improve their water quality over the past two years. With a unique blend of harvesting rainwater, reclaiming used irrigation water and implementation of two filtering systems featuring 5-micron technology, they have invested significant time and money to provide crops with the best quality of water.

Metrolina has been collecting, recycling and testing water for more than 30 years. They built the operation’s first retention pond in 1976, and today, Metrolina has three ponds on its property that can hold up to 250 million gallons of water. The 162-acre greenhouse operation gets 98 percent of its water from the ponds, which store harvested rainwater exclusively. Metrolina has never used city water and only uses well water in a few specific cases, relying on rain to supply the more than 1.5 million gallons of water it uses daily.

Glossary Of Water Terms

Micron rating: The average size of the openings between pieces of the filter media are represented in microns. A 50-micron filter has larger openings than a 5-micron filter, so the 50-micron filter will let larger particles pass through the filter than the 5-micron element. Bacteria typically range in size from 2 to 10 microns.

Copper ionization: Copper ions have the ability to pierce the protective outer membrane of a cell and disrupt enzyme balance, thereby killing algae. Lethal to bacteria and algae, copper ions purify water and provide beneficial nutrients, while eliminating the need for chemicals like chlorine.

Ozone: Sometimes called “activated oxygen,” ozone contains three atoms of oxygen rather than the two atoms we breathe. Ozone is the second most powerful sterilant in the world and can be used to destroy bacteria, viruses and odor. The third oxygen atom makes ozone extremely reactive, and it readily attaches itself to other molecules, attacking compounds until they are destroyed in a process called oxidation. Ozone reverts back to oxygen after it is used, making it very environmentally friendly.

Collection And Filtration

According to Director of Research Mark Yelanich, Metrolina’s rainwater catchment system yields 5 million gallons of water from one inch of rainfall. Water is collected from barn roofs, greenhouse roofs, flood floors, the adjacent parking lot, which is constructed with pervious concrete, and drains in the yard. All harvested water drains through a series of connecting pipes to the retention ponds. From there, it is filtered through a complex system and cleaned before it touches the crops.

In 2010, the Van Wingerdens were unsatisfied with their water quality and decided to look around at other greenhouse operations for a fix. They met Charlie Hayes, an agricultural water specialist with Advanced Treatment Technologies, who analyzed Metrolina’s water source, retention ponds, filtration systems, greenhouse flood floor systems and water disinfecting process.

As a result, the Van Wingerdens implemented the next generation of filtering technology, installing Dramm 5-micron filter systems in two of its greenhouse ranges. Water from the retention ponds now filters through a 50-micron filter to catch large particles and sediment. Then, it goes through the 5-micron filters, which prevent disease pathogens like Phytophthora, Pythium and Rhizoctonia from entering the water supply. From there, water is disinfected through a copper ionization process and pumped into one of three holding tanks, measuring 600,000 gallons, 500,000 gallons and 300,000 gallons.

Water for the irrigation booms is pumped directly from the holding tank to the crops, while flood irrigation water runs through the fertilizer feed before being pumped into the greenhouse to flood floors. It takes 30 to 40 minutes to the flood floors, using between 30,000 and 40,000 gallons per bay. It takes an equal amount of time for unused water to come back and refilter into the 600,000 gallon tank, where the water feed level is checked and quality is tested. If the water is too dirty to be reused, it goes back to the retention pond and through the filtering process.

Filtration Reduces Disease, Aids System Maintenance

Since implementing the new filter systems, Metrolina’s growers have noticed a marked reduction in disease and insect pests, thus reducing chemical inputs, Van Wingerden says. Boom filters and nozzles are also cleaner; before using 5-micron technology, they had to be cleaned daily. Now they are cleaned every week, saving labor on irrigation system maintenance.

Most recently, large-diameter units were installed in January to increase flow from 500 gallons per minute to 1,000 gallons per minute, with the capacity to accommodate 2,000 gallons per minute. The operation’s next steps, Art says, are to install a third 5-micron filtering system and improve aeration in the retention ponds to keep water from stagnating.

Saving Money + Helping The Environment = A Win For Everyone

Because Metrolina catches and reuses all irrigation water, the operation is exempt from a local tax on water runoff. Zoned under farm status, permits for adding irrigation infrastructure have not been necessary. When building its retention ponds, Metrolina followed the Environmental Protection Agency’s Best Management Practices, and the ponds are inspected annually for compliance.

Thus far, Metrolina has invested nearly $600,000 for the two systems, piping and pumps, and the operation will continue to invest in improving water quality. Abe recommends fellow growers invest in clean water, as well, to stay ahead of potential mandates.

“We do the right thing environmentally by reclaiming and recycling water, but we also need the water, and we have realized cost savings on many fronts,” he says. “Know your local laws, do your research and put a full system in place for the best quality water. In the end, you’re better off getting ahead of the law than waiting for someone to come to your operation in a van with a siren to tell you what you need to do.”

Lucas Greenhouses Closes The Loop

Complete containment: it’s a goal George Lucas and his staff at Lucas Greenhouses in Monroeville, N.J., have been working toward since the 55-acre operation began recycling water in 2002, and they attained it in July.

“We just switched on the new system last week,” Lucas said at press time. “We’ve only used it one time to run samples and check to see what was coming through. We have $750,000 tied up in this system. Once it’s proven to be working, we will be 100-percent contained, and we can safely reuse water without fear of it being contaminated.”

Lucas Greenhouses’ journey toward building a safe, closed-loop irrigation system began with installation of flood floors in 2002. When the operation began recycling water, Lucas worried about the amount of chemicals in the water.

“I need my water to be clean,” he says. “If there is a fungicide or insecticide leaching through, I’m afraid my plants will build immunities to those chemicals.”

At a Young Plant Research Group meeting in Florida, Lucas met Hayes, who was selling ozone water treatment systems. He hired Hayes to install an ozone and filtration system to treat two 17,500-gallon water tanks for flood floor irrigation. The system was installed in 2006, with great success. Lucas says he was impressed with the crops’ response to the extra oxygen in the water, but it still didn’t solve the problem of extra chemicals.

Ozone, UV And Filtration Clear Water Of Chemicals And Pathogens

Prior to installing the ozone system, Lucas had purchased an ultraviolet (UV) treatment system but never used it because he didn’t have proper filtration. So when he asked Hayes to build a new closed loop system, Hayes suggested using ozone, the UV system and filter technology to solve the chemical problem.

Water used for the flood system comes from the retention pond and is filtered several times down to 5-microns. Then it is pumped into a 28,000-gallon tank where it is treated overnight with ozone, which kills pathogens like Rhizoctonia and Pythium. It is then UV-treated, put through a bio-filter and pumped onto the greenhouse flood floor. When it gets to a certain level, it goes through a paper filter and back into the holding tank for re-ozoning. The process continues all day through the irrigation system and the water is cleaned again overnight.

For propagation material, which represents 20 percent of Lucas Greenhouses’ crop, water comes from a well and is pumped through a fertilizer injector, then onto crops via overhead booms. Excess water is collected into a separate tank next to the flood water tank, goes through the ozone system and back into the tank, so it can be reused for flood water.

While ozone kills pathogens and oxidizes water to improve plant health, it does have its challenges. If water pH is too high, ozone is harsh on elements like iron and manganese. It can also burn plant roots if oxygen levels get too high, so sensors will automatically shut the system down if this occurs.

Since using the ozone and filtration irrigation systems, Lucas says root growth is healthier, thanks to the extra oxygen in the water, and the operation uses less fungicide and insecticide. He says he thinks ozone and filter technology will catch on once growers see it can be done.

“As soon as someone has it working well, it will be attractive to growers who want to reduce chemicals and improve water quality,” Lucas says. “It’s very expensive and always a trial-and-error-process, but the cost is all up front, so once it’s in, there are no additional expenses. With this system, we can show growers you can be environmentally friendly and still grow healthy crops.”

Laura Drotleff is editor of Greenhouse Grower.
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