A Study in Sand: How Dewatering Screens Can Provide Cleaner, Drier Bedding Sand

June 28, 2021
Dewatering Screens have been proven to remove up to 40% of the moisture and up to 80% of the organic matter from separated recycled sand bedding. Here's how.

Clean, dry bedding is critical for cow health and comfort, and key to the production of high-quality milk. When bedding is clean and dry, there is less chance for bacteria to grow and less chance for the cows’ udders to come into contact with harmful pathogens that can cause mastitis and higher somatic cell counts.

Bedding material can be organic (straw, sawdust, dried manure solids, etc.) or inorganic, such as sand. Sand is a popular type of freestall bedding material for several reasons. Being an inorganic material, it doesn’t promote the growth of bacteria. It is moisture-wicking and readily drains away any urine or dripped milk. It cushions the cow’s body and provides traction as she stands or lies down, reducing the risk of potential knee or hock injuries. Sand is also available worldwide.

A major benefit of sand bedding is that it can be recycled for reuse in the freestalls, potentially saving dairy producers thousands of dollars each year from buying new sand. 

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How to Recycle Sand Bedding

Bedding sand can be recycled with sand lanes or mechanical sand separation equipment, such as Sand-Manure Separators. The separation method selected may depend on whether or not the manure is diluted. 

Sand Lanes

Sand lanes are long concrete lanes that are sloped slightly. They are utilised where dilution is used to convey manure. When the sand-laden manure stream is flushed into the lane, ideally the sand settles out on the concrete lane while the manure fibers remain suspended in the water and continue flowing down the lane.

The sand needs to be removed from the sand lane daily or even multiple times per day in order for this separation method to be most effective. This is because as soon as sand starts to settle, the channeling begins to occur and settling dynamics change.

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A McLanahan Sand Lane System (shown at right) accepts sand from a sand lane (shown at left) and dewaters it for less stockpiling time and quicker reuse. 

Sand-Manure Separators

Sand-Manure Separators take the sand-laden manure stream — either diluted or undiluted — and separate it via mechanical means. The sand-laden manure enters the pool area of the Sand-Manure Separator, where the heavy sand particles settle to the bottom of the machine. A rotating screw conveys the settled sand out of the pool area and up the incline, allowing water to drain from the sand. A spray bar provides a final rinse of the sand as it travels up the incline toward the discharge end.

Mechanical Sand Separation Systems provide higher and more consistent sand recovery and better moisture removal than sand lanes. This means higher recovery of cleaner sand. When used together with the addition of an Agricultural Hydrocyclone, Sand-Manure Separators and sand lanes can recover up to 95% of sand from the manure stream. This allows for the potential of sand-bedded dairies to make use of anaerobic digestion or biogas systems. 

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McLanahan Sand-Manure Separators separate the sand from the manure stream, discharging a clean, stackable bedding sand suitable for reuse in the freestalls. 

What is the Ideal Moisture Content for Recycled Sand Bedding?

The ideal moisture content for sand is 0%. Practically speaking, new bedding sand ranges in moisture content from 5-10%, depending on how it was processed and stored. The lower the moisture content, the lower the chance bacteria will grow and thrive. This goes back to clean, dry bedding being the key to cow comfort, cow health and milk production.

When recycling sand bedding, producers should try to get the moisture content as low as possible before reuse.

Sand removed from a sand lane is often too wet and dirty to be reused right away. It is typically stacked on sloped concrete pads to allow the water to drain or piled into windrows and turned over and over. In either case, it can take weeks or months for the sand to be dry enough to be put back into the freestalls. Stockpiling sand requires space and sand inventory to account for the piles of being moved and allowed to drain.

Agricultural Sand Dewatering Screens are standard with Sand-Manure Separation Systems and can be used as a stand-alone to improve sand lane quality. With each system the goal is to remove excess moisture from the sand for quicker reuse, cutting down on conditioning time, decreasing inventory requirements and freeing up valuable land space.

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McLanahan Agricultural Sand Dewatering Screens remove up to 40% of the moisture in separated recycled sand bedding. 

Dewatering Screens for Sand Bedding

Dewatering Screens have been used successfully to remove excess moisture from aggregate sands, industrial sands and mineral sands for decades. They feature an inclined deck onto which separated recycled sand is fed. The motion of two counter-rotating vibratory motors throws the material upward and forward toward the discharge end, allowing the water to detach from the sand and drain through openings in the screen media.

The first Dewatering Screen used to dewater separated recycled sand bedding was tested extensively. The results were as follows:

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The tests also revealed another benefit of the Dewatering Screen. As water detaches from the sand particles and drains through the screen media, it takes with it some of the small organic fibers that remain in the sand. 

Since then, Dewatering Screens have been reducing the moisture content of separated recycled sand bedding on dairy farms around the world. 

Dewatering Screen Benefits for Dairies Recycling Sand Bedding

In addition to removing excess moisture and reducing organic matter to produce cleaner, drier bedding sand, Dewatering Screens allow dairy producers to decrease sand inventory and free up land space, as dewatered sand can be reused in one week or less.

Dewatering Screens are used as standard equipment immediately following Sand-Manure Separators to provide a recycled sand product with a moisture content as low as 12%. They can also be used as part of a Sand Lane System to remove up to 50% of the water from sand recovered from a sand lane.

In either setup, a Dewatering Screen will provide a drip-free, stackable sand product that requires less stockpiling and conditioning time before reuse. The separated recycled sand is proven to be cleaner and drier than sand not processed through a Dewatering Screen, which makes for happier, healthier cows and increased milk production.

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Tags: Bedding Management, Dairy, Agriculture, Manure Management, Dewatering, Sand Bedding