Underground drip irrigation serves two purposes
Dispose of wastewater and irrigate trees.
Water is plentiful in the fruit-growing area along Lake Michigan’s eastern shore, so it’s not scarcity that’s an issue. The problem is with some water that’s been made slightly dirty but is perfectly useful if handled right.
That’s led some fruit growers and fruit processors to make double use of wastewater through subsurface trickle irrigation systems installed in fruit orchards. The system uses water that would otherwise be wasted, to irrigate.
As Beau Shacklette tells it, a fruit-processing company approached the company he works for, Trickl-Eez Company in St. Joseph, Michigan, wanting an onsite system for disposal of wastewater from their processing plant. Trickl-Eez, working with an environmental engineering company, developed the Agricultural Wastewater Dispersal System that Trickl-Eez now sells and installs.
Shacklette, the regional sales manager for Trickl-Eez in Traverse City, Michigan, has installed systems at four fruit-processing companies and for a few growers since getting state Department of Natural Resources approval for the system four years ago.
The fruit-processing companies need to get rid of wastewater they have used to cool, wash, or handle fruit or vegetables, Shacklette said. The water contains low levels of soluble solids and nutrients. The companies are located away from municipal sewage disposal systems and needed either to install their own waste treatment plants or come up with methods acceptable to the state.
On-land disposal of such water through irrigation is legal, but in northwest Michigan there is a long winter season when the land is frozen and won’t accept surface-applied water. Putting the water into the ground below the frost layer solves that problem.
The orchardists, mostly growers of tart cherries, use cold well water to cool fruit during harvest in July. While this water is not considered a waste requiring treatment, there is a lot of it leaving cooling pads and trying to find its way somewhere. “Growers know it’s just a matter of time until they have to contain and dispose of the water that runs off their cooling pads,” Shacklette said.
Trickle irrigation is growing as a practice, especially in young cherry orchards, so the water has a use.
The system Trickl-Eez developed is a grid of underground drip irrigation tubing that runs down the rows and alleys of fruit orchards. Some of the processing companies are growers themselves, so they have their own orchards, or there are orchards close by they can access. In some cases, they’ve installed the systems in open fields devoted to production of hay.
“One important requirement was that the disposal system be able to operate year round,” Shacklette said. “A subsurface drip irrigation system was chosen as the best delivery system to move lagoon discharge water to adjacent fruit orchards where the trees can benefit from the nutrients in the water as well as receiving beneficial irrigation water.”
Allen Steimel, the plant general manager for Leelanau Fruit Company near Suttons Bay, about 20 miles north of Traverse City, said his company installed a four-acre system a year ago as an expansion for their on-land sprinkler irrigation disposal system.
“We process brined cherries for maraschinos,” he said, “so we work year around using stored cherries. We needed a way to dispose of water during the winter time.”
The water is only marginally dirty since it’s used to move cherries that contain some residual brine solution. The actual spent brine is disposed of by injection into deep wells.
In the summer, water used in the pitting operation contains more nutrients, and that is spray irrigated since frozen ground is not an issue.
The company needs to dispose of about 22 million gallons of water a year, and most of that is sprinkler irrigated onto land that grows hay for horses, Steimel said.
Other systems Shacklette has installed vary in size from 5 to 16 acres. When installed in existing orchards, he said, usually three lines are run down each alley. Lines run on both sides of a tree row, about 30 inches from the trees, and one down the center of the alley.
In the fruit area in northwest Michigan, soil is often sandy to gravelly, and trees, especially young trees, benefit greatly from irrigation, and many growers use trickle irrigation in young orchards.
To make the drip irrigation disposal system work, water has to be relatively free from solids or the emitters will clog. In the processing plant systems he designs, Shacklette likes to have two lagoons, linked in series, that serve as settling ponds that remove much of the organic matter. Then the water is pumped through filters before getting into the drip lines. Water from cooling pads does not contain enough solids to require filtration.
Shacklette, who originally came to Michigan from Colorado and is experienced in irrigation systems, thinks this system will work well for food processing plants in any environment anywhere.
“The Agricultural Wastewater Dispersal System can be expanded to many other sites,” he said. “It provides a very practical, affordable, and common-sense solution to the previously very difficult problem of how to manage agricultural wastewater and put it to a beneficial use rather than create an environmental problem.”
There is also a food safety aspect to drip irrigation. Since no effluent water is sprayed onto foliage or fruit, there are no contamination issues, Shacklette said.
Unlike sprinkler application, where water slams the ground, compacting it and causing surface runoff, subsurface irrigation lets the soil act as a huge absorption system and biofilter, he said. Growing plants and trees can benefit from the water and the nutrients it contains.
The loading rate needs to be designed to fit the soil type, and the system is computer controlled to dispense the correct amount of water, Shacklette said. Trees must be able to absorb the nutrients in the water or they can leach down below the root zone.
The dispersal system includes several components.
First are the pretreatment lagoons, where oxygen is added to provide aerobic, odor-free conditions for breakdown of solids in the wastewater.
Next are the computer controls and pumps that move the water in a controlled dosing cycle.
Filters are very important, Shacklette said, to keep the drip tubes from plugging.
The drip system in the field or orchards is divided into zones, to which water entry is controlled by valves.
The final part is the underground drip lines that are buried from one to two feet deep. The lines contain pressure-compensating emitters.
“One of the biggest advantages to the subsurface drip system is the ability to provide the dose and rest cycles that facilitate wastewater infiltration into the soil,” Shacklette said. “Timed doses allow for the even distribution of the liquid waste throughout the day or night.”