Flush-Flume Simplicity

January 27, 2011 08:17 AM
 
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Effective Means of Handling Sand-Laden Dairy Manure

Simple is good. That’s the basic concept driving the flush-flume sand separation system at 3-D Dairy, a 1,350-cow operation in Malone in east central Wisconsin.

The facility, built by brothers John, Joe and Bill Diederich, began as a 600-cow operation on shavings-bedded mattresses in 2000. Two hundred cows were added in 2005 and an additional 550-cow barn was built in 2009.

"In 2009, we had to decide whether to stay with sawdust or switch to sand," says John Diederich. "Shavings were hard to get and were expensive. And sand offered better cow comfort and traction. All the studies say there is nothing better than sand."

Cow footing was one of the driving forces in the switch. "Alley floors can get slippery with shavings, especially in the fall," Diederich says. "We always had some injured and downer cows, though we couldn’t pin it to the floor surface. But since we’ve switched to sand, the number of injuries has drastically changed."

Sand brings its own set of problems: what to do with it after it gets kicked out of the stalls and mixes with manure. The layout and topography of 3-D Dairy lent itself to a flush-flume system.

The third stage of 3-D Dairy’s lagoon system lies 40' to 50' below the three freestall barns and one heifer barn. Every time a pen is emptied of cows for milking, workers switch on a 60-hp pump that pushes 1,300 to 1,400 gal. of water/sand/manure per minute to a cross-barn flume. The pump runs for a preset 20 minutes, which is enough time for workers to scrape pen alleys.

Workers in the barns then scrape manure into the flume. (They only scrape when the flush water is running.) The flume, some 500' long, crosses all three freestall barns, where it flushes sand into the sand separation building.

The sand is deposited into a sand separation lane, 72' long, 4' wide and 3' deep. The water/manure/sand mixture slows down to 1' per second and the sand simply settles out. A 12" auger at the bottom of the pit moves the sand to the center, where it is dropped into an 18" inclined McLanahan auger for "dewatering."

Clean, fresh water is used for this dewatering. It floats out additional manure solids and augers out the reclaimed sand. The process uses just 600 to 800 gal. of clean, new water per day, or roughly ½ gal. per cow per day.

"When we’re using new sand, we reclaim about 75%," Diederich says. The fines get flushed along with manure solids into the 1.1-million-gal., concrete-lined Stage 1 lagoon. From there, the sand/manure can be land-applied.

"When we’re using reclaimed sand, we’ll reclaim 90% to 95%," Diedrich says. This sand is then stockpiled with a payloader or backhoe onto an outside 120'x120' concrete-floored stacking slab. The Diederichs like to let the sand drain for six weeks or so before re-using it.

Sand can also be stockpiled in the 55'x90' sand separation building. The facility has in-floor heat and insulated, 20' sidewalls.

"We try to keep the building above freezing in winter for both the sand separation process and to keep sand thawed for bedding," Diedrich says. In the depth of winter, the Diedrichs will sometimes bring sand from the stacking slab back into the building to thaw before re-use.

From the Stage 1 lagoon, the liquid, virtually sand-free, low-solid manure flows into Stage 2, which is a 9-million-gallon, clay-lined lagoon. From Stage 2, water containing about 2% solids flows into Stage 3, a 14-million-gallon, clay-lined lagoon. It is from here that water is pumped back through the system for flushing.

In 2010, when the Diederichs were using all new sand, the Stage 1 lagoon was full of sand after five months. "But then we started using reclaimed sand. When we emptied Stage 1 in the fall, it was not nearly as full," Diedrich says.

Liquid manure is pumped from Stage 2, which can be emptied in about 10 days. Stage 3 is the flush-water lagoon, so it is not pumped down.

 

The one disadvantage of the system is that it produces slightly more odor than the shavings. "It’s the one thing I don’t like about the system," Diedrich says. "We had been a low-odor farm."

With the old system, the shavings flowed directly into the lagoon, would crust over and not be agitated until pump-out. The flush-flume system is constantly in motion. "We’re always stirring it up when we recycle the water through the flume," Diedrich says. As that water leaves, water is drawn from Stage 2 into 3 and from Stage 1 into 2.

The biggest odor issues occur at pump-out, when Stage 2 is agitated. "The odors aren’t the real obnoxious ones, but there is a manure odor," Diedrich says. "If we get a north wind, people
driving by can get a whiff."

The benefits of the system include cow comfort, bedding cost savings and reduced hauling costs. The Diederichs pay about $8 per ton for the sand they’re using. "It’s the coarsest sand we could find with rounder stones and no sharp edges," Diedrich says.

They top off and re-bed stalls three times per week, using about 10 yd. per 123-stall pen. That works out to roughly 50 lb. of sand per stall per day. "We go through a fair amount of sand simply because we now have it available," Diedrich says.

The jury is still out on milk quality. With shavings, 3-D’s somatic cell counts were below 200,000 cells/ml in winter and slightly above that in summer. With sand, SCCs spiked to 300,000 cells/ml last summer, which was unusually wet and humid.

"As fall got here, they dropped back to 180,000 to 190,000," Diedrich says. "We’d like to see them even lower because a lot of sand-bedded barns get below 150,000."

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