Drainage Management Systems
By Trudy Kelly Forsythe
Finding solutions in a closed-loop nutrient system.
By Trudy Kelly Forsythe
What do you get when you put a Michigan dairy farmer and a conservationist in a car for several hours? If the dairy farmer is Blaine Baker, co-owner of Bakerlads Farm in Clayton, and the conservationist is Thomas Van Wagner, technical co-ordinator for the Lenawee Conservation District Center for Excellence Program, you get the initial designs of a livestock reservoir wetland sub-irrigation system.
“Tom got the idea from systems in Ohio they are using for irrigation of crops and thought maybe we could put it together for irrigation of wastewater for dairy,” Baker says. “We designed it on the trip out and back to the conference.”
Baker and his brother Kim are the fifth generation to farm the 130-year-old dairy farm, currently milking 500 cows on 2,200 acres. They were looking for a simple way to remove a lot of water without doing it physically, and they wanted to do it environmentally since milk-house wastewater used for washing and sanitizing equipment and livestock can potentially pollute surface and groundwater systems.
Due to state regulation requirements, Bakerlads Farm collects some rainwater along with the water it uses to clean a bulk tank and pipelines each day. The bulk tank takes 500 to 600 gallons, while the lines require more than 1,000 gallons each day, considering they milk three times a day with each wash going through three different cycles. Over a year, the system moves approximately 2.2 million gallons of wastewater.
Designed to collect and store wastewater generated from the dairy farm for crop irrigation the following growing season, the livestock reservoir wetland sub-irrigation system is a closed-loop nutrient system where wastewater is treated in a designed wetland, then circulated through a subsurface tile system. It is stored and used, if needed, for irrigating growing crops or, if unused, circulated back into the wetland or storage pond.
“Most people collect rainwater, wastewater and manure and it all goes into one big pit,” says Baker, explaining this results in a manure slurry to dispose of. “We have two pits, one for manure and the other for parlour wash water and bunker stormwater. So, while we still deal with four to five million gallons, it’s two and a half to three million gallons of manure, and two million gallons of water to utilize, but that’s easy to do.”
To help do that, Baker brought in Dave Dunne of Dave’s Drainage to take care of the sub-irrigation, and Paul Andre of Andre Land Forming to dig the storage lagoon and build a three-section wetland the size of a football field.
“All of the sections are about three feet deep with wastewater going in the south end and pumping out the north end,” Baker says. “The first section has cattails and other vegetative plants. The second section is filled with pea stones for the water to flow through. The third chamber is open water that sees some UV action from the sun.”
The wetland is designed to manage the surface and subsurface flow and is able to treat it all during a four- to seven-day period at peak flow rates. Its objective is to reduce or remove the biological oxygen demand, suspended solids, pathogenic bacteria, total phosphorus, ammonium and nitrates from the water before it enters the sub-irrigation system.
There are some technical considerations to keep in mind when designing and installing this closed-loop nutrient system. One is elevation, since gravity helps move the water through the system without reliance on pumps.
“The field tile outlet needs to go back into the system to make it a closed loop,” Dunne says. “It requires a pump, but you want it to flow from the top to the bottom.”
While a minimum of three pumps is needed to transport water to the sub-irrigated cropland and a fourth to return excess water to the wetland, the farm actually has five pumping plants based on the volume of water, distance and elevations of its site. Each is powered by a single-phase, 110-volt electrical motor and is in a sealed concrete manhole with a slide gate on the outlet to the ditch.
Contractors also need to quantify the amount of wastewater they are dealing with including rainwater, lot and driveway run-off, silage leachate and milking centre wastewater. And the drainage system has to be sized to provide adequate irrigation capabilities. “The tile spacing is closer for subsurface irrigation than for drainage. This project used 30-foot spacing instead of the 40-foot tile spacing normally used for drainage.”
Putting the system in did not require a lot of additional expenses upfront, and Baker says the pump needed to move the water is economical to operate. Plus there are savings by not needing equipment to physically move the wastewater. Dunne adds, “Handling all the wastewater with a simple 110-volt electric pump means no equipment to compact the fields.”
Baker appreciates the simplicity of monitoring a small pump versus driving a manure tanker since the simple 110-volt pump does the job of a lot of diesel fuel, man-hours and equipment.
Comparing water samples taken one year prior to the system’s installation and then during a three-year period during operation revealed reduced levels of sulfate, nitrogen and nitrates as well.
While irrigation was not a primary goal for this system for Bakerlads Farm, which only sub-irrigates about 20 acres of the 1,200 acres of crops it grows, it does offer some benefits in this area as well.
“We’re on clay soil so sub-irrigation is minimal and we only do it on low acreage, but a secondary benefit is an increase in yield, depending on the weather,” says Baker. He explains that they do a corn-soybean rotation with 50 per cent of each growing on 950 acres and alfalfa on an additional 250 acres. “In 2012, we saw a 50 bushel increase in a sub-irrigated corn crop yield.”
But in the end, Baker concludes, “It’s a very economical way to get rid of a lot of water.”