A combination of sand and wood chips go after E. coli, coliform bacteria and maybe excess nitrogen

A project to test the feasibility of using natural filtration to treat runoff from areas where cattle are confined is showing promise as a low-cost, low-maintenance option for cow-calf producers who have wintering sites or calving grounds near waterways.

Alan Stewart, a soil-resource specialist, and Sharon Reedyk, a water-quality specialist, with Agriculture and Agri-Food Canada’s Agriculture and Agri-Environment Services Branch (AESB) at Edmonton, are the project leads. Anna Cole, water-quality engineer with AESB at Saskatoon, monitored and maintained the filtration system, which was constructed this past spring at the Western Beef Development Centre near Lanigan, Sask.

“We live with a heritage of cattle sites near watercourses, so we are really hoping to find a solution to a problem facing many producers,” Stewart says. When the West was settled, many people established their homes near watercourses for their water supply and shelter. It was logical to set up the cattle facilities near the homestead for the same reasons and to take advantage of rough land that couldn’t be cropped.

Nowadays there is more concern with the effect of runoff on watercourses, he explains. Moving wintering sites can be very costly and it’s not a practical option for many producers.

The system

The natural filtration system is modelled along the line of small-scale municipal waste treatment systems and replicates the action of Mother Nature’s water treatment medium –soil.

There are three design elements: a retention pond to capture runoff water and two cells that contain natural media to filter the contaminants.

The retention pond is a normal dugout-type structure where the large particles settle out after a runoff. Highrisk times for runoff to move nutrients from manure directly into nearby surface water are in the spring when the ground is still frozen and during periods of heavy rainfall.

The cells for the prototype system are 18 by 36 by 2.6 feet. They are lined with black polyethylene plastic and sloped a bit so that the treated water gathers in a collection basin along the lower edge. The first cell is situated at a slightly higher elevation than the second.

A layer of gravel to aid drainage is topped with sand in the first cell and wood chips in the second cell. The requirements for media were that they had to be low-cost and readily available anywhere, Stewart explains. Benchscale projects to test the effectiveness of various options were carried out first. Sand is a basic soil medium used in many municipal treatment systems. Wood chips are an organic material that may provide a second type of treatment action targeted to removing nitrogen.

Observations

The filter system is set on a timer to operate during the frost-free months

from May into September. Since it’s a biological filter, warmth is a key element in degrading the contaminants.

A solar pump moves the water from the retention pond through a system of distribution pipes above the sand bed. The pump is set on a timer to cut in four minutes every hour so that it drips about 100 gallons of water an hour across the surface of the filter.

The water trickles down through the sand where naturally occurring microorganisms cling to the particles in the water to begin breaking down the contaminants. The filtered water gathers in the collection basin where a float trips a second pump anchored in a drainage ditch between the two filter cells. This pump pushes the water through a second network of distribution pipes over the bed of wood chips. The filtered water runs freely from the bottom of the wood chip bed back into the retention pond. The drainage ditch also leads back to the retention pond to contain excess water in the event of a heavy rainfall.

Cole says an on-farm setup would be designed to discharge the filtered water into the watercourse or a draw where it could filter away naturally. Ideally, the filters would be constructed to take advantage of gravity to reduce the use of pumps. The system would be sized according to the needs of the operation based on the amount of snowfall expected and the size of the confinement area.

There was very little maintenance required throughout the course of the summer though she says it may be necessary to flush sludge from the distribution network once a year. Adjustments to the project in future years may include changing the drip system to a sprinkler application.

The results from the water samples taken at various points in the system during the summer will be fully analyzed this winter. Cole was already able to confidently state that the sand filter had done a spectacular job of removing E. coli and coliform bacteria. It was just as effective during dry spells as it was during wet periods.

The maintenance aspects and the economics of the filter system will also be evaluated to determine the practicality of implementing this type of management practice on the farm.

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