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Managing recycled sand for low bacteria counts

John K. Bernard and Joseph G. ‘Jake’ Martin for Progressive Dairyman Published on 01 March 2018
Sand separator

Sand is considered the gold standard for bedding dairy freestalls. It is commonly used to bed freestalls because it does not support significant bacterial growth, has a low water-holding capacity and shifts with the cow to provide a comfortable surface on which to lay.

However, cows drag several kilograms of sand out of the freestall each time they exit (as much as 20 to 23 kilograms per cow per day).

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This sand should be separated from the waste stream so it doesn’t fill the waste storage pond, reduce wastewater storage capacity, accumulate in drainage pipes and shorten the lives of wastewater pumps.

Properly managed recycled sand can be used for freestall bedding, thereby reducing the need to purchase additional sand, which reduces operating costs.

Evolution of sand settling and recovery lanes

In the Southeast and other areas of the U.S., most flush-cleaned dairies use a sand settling/recovery lane to separate sand from the manure solids during flushing.

The design of sand settling/recovery lanes has changed over time to improve the efficiency of sand collection and to produce a cleaner product.

The sand settling/recovery lane at the University of Georgia Dairy Research Center was built in 1998, a time when little was known about sand bedding handling and recovery.

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The four-row freestall has a 3 percent slope and is flushed four times each day. The flush water enters the 130-foot travel lane which enters the sand settling area. The sand settling area is 20 feet long and 30 feet wide with a 0.01 percent slope.

There are some areas where water velocity slows and organic matter accumulates. Approximately 55 to 65 percent of the sand flushed from the barn is captured and available for recycling.

The rest of the sand is captured in a gravity manure solids separator and disposed of with the manure solids. We have learned how to clean the sand in our system over time by flushing the lanes closest to the sand lane and working our way across the barn to maximize cleaning of the sand.

The settling/recovery lane is cleaned twice daily. Additional flush water from the milking parlour that has lower solids content also washes the sand to provide additional cleaning.

A skid loader is used to remove sand that accumulates in the travel lanes at the end of the barn weekly. This is typically very clean sand. Our sand is piled and left to dry for a minimum of one month.

Typically, the organic matter of this material runs less than 1 percent when it is put back into the freestalls. In our operation, fresh sand is added as needed to balance supply; typically, we run a 50-50 mix but will use 100 percent fresh sand if we are running low. Freestalls are bedded once each week.

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Current sand separation and recovery lane systems

Regardless of the size of the dairy farm, newer sand lanes are typically around 300 feet long, providing greater distance for separating, cleaning and storing the sand.

This increases the amount of sand recovered, with some producers achieving greater than 95 percent recovery. Newer sand lanes are designed to reduce the velocity to 1 to 1.5 feet per second.

If the velocity is too fast, more sand moves downstream with the flush water. If the velocity is too slow, additional manure solids settle with the sand.

General recommendations for new sand separation/recovery lanes are:

  • 12 feet wide (pump-flush systems) or 20 feet wide (tank-flush systems)

  • Minimum of 12-inch lane curbs

  • 0.2 percent floor slope

  • At least 300 feet long

Also, the cleanliness of the flush water affects the quality of the recycled sand, so dirty water will result in dirty sand.

Some points to consider:

  • When removing sand from the sand lane, leave any sand contaminated with manure solids in the lane. Some producers use a skid loader to work the sand during flushing to get it cleaner.

  • When piling the sand, put it in a place where it can drain. Newer sand lane designs offer a concrete de-watering area adjacent to the sand lane as a place to allow for an initial de-watering of the sand.

    From here, the sand is normally relocated to another location on the farm to complete de-watering of the material.

  • It has been recommended that the sand be left for one month before reusing to allow for drying and degradation of any remaining manure solids.

Frequency of lane cleanout is affected by size of the dairy. More freestalls contributing sand to the lane will result in sand accumulating in the lane faster. Sand should be removed from the lane on a regular basis so the sand itself does not interfere with the flow of water in the basin.

Assuming a 23-kilograms per-cow-per-day sand accumulation in the lane and 50 kilograms of sand per cubic foot, about 0.45 cubic feet of sand will accumulate in the lane for each cow.

Therefore, a 100-cow dairy will accumulate 45 cubic feet of sand per day whereas a 300-cow dairy will accumulate 135 cubic feet of sand. If the sand lane is 20 feet wide and 300 feet long, and the sand is an average of 2 inches deep, then the 100-cow dairy will accumulate about 13 linear feet of sand per day while the 300-cow dairy will accumulate 40 linear feet of sand in the lane.

Therefore, larger farms, with herd numbers in the thousands will need to clean out these lanes multiple times each day.

The recycled sand should be sampled and evaluated periodically. Some labs offer bacterial analysis which identifies the types of bacteria present as well as their concentrations.

Total bacteria concentrations less than 300,000 colony-forming units per gram are considered to be minimal-risk, and concentrations greater than 1 million colony-forming units per gram as high-risk.

When compared with bulk tank sample analysis, sand analysis provides another tool to evaluate the source of mastitis organisms that are problematic in the herd.

Another option is to test the sand for organic matter (100 - ash). As organic matter increases, there are more nutrients available to support bacteria growth. The goal is to keep the organic matter less than 1.5 percent.

Keep the area around the sand lane clean. Wet sand that has manure solids provides an attractive area for flies to breed. Also, manage sand piles to keep weeds from growing.

Unless the plant material is removed from the sand at loading, you are adding organic matter to the bedding. Weeds also provide a place for flies to get out of the sun during the heat of the day.

We are seeing more dairymen cover their older sand piles with plastic to reduce the addition of moisture to the sand in the last few weeks before reuse. In areas of significant rainfall, this method can result in drier sand being placed into freestalls.

Other points to consider:

  • It is important to keep the area around the sand piles and alleys clean of gravel to prevent it from getting into the recycled sand and causing foot injuries.

  • Do not use recycled sand in calving pens or for bedding newborn calves because Johne’s or other disease organisms may be in the sand and could be transferred to the calf.

  • Many producers will relocate sand from these areas to the sand lane for washing and reuse as freestall bedding in the milking herd.  end mark

PHOTO: Sand can be separated from the waste stream using sand separation and recovery lane systems, then recycled and reused as freestall bedding. Be sure to sample the recycled sand regularly to check for bacterial loads that could cause issues with milk quality. Photo by Karen Lee.

Joseph G. “Jake” Martin, P.E., M.S., is with JGMIII Inc., consulting agricultural engineers, Gainesville, Florida.

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