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In order to comply with nutrient management requirements, Missouri dairy producers are interested in settling as a means of partitioning nutrients and recovering sand used for bedding. Separation of solids also results in easier management of liquid storage facilities. This paper summarizes management requirements and performance of a manure management system utilizing flushing, sand bedding and a porous-wall settling basin based on a study of the Echelmier Dairy near Fulton, Missouri.

Two types of bedding sand were studied. Classified sand contained a significant percentage of smaller sand and clay particles. Concrete sand was a coarser, graded material containing few fine particles. The coarser sand was more expensive ($5.25/ton vs. $4.25/ton), resulted in cleaner cows, was more difficult to flush, settled more readily, and harbored fewer bacteria colonies in limited bacteriological studies.

The flush system provides a flow velocity of 5.2 ft/s(1.6 m/s) in the widest alley, which results in acceptable sand removal. Records of sand purchased, and sand used to bed freestalls indicate that about 75% of the sand flushed from the freestall barn is recovered from the settling basin for re-use as bedding. The rate of sand use is estimated at about 65 lb(30 kg) sand/freestall-day.

The two-chambered settling basin provides about 45 days storage in each chamber for the sandladen flushed manure from 450 cows (1,400 lb(636 kg) Holstein cows). Settled solids accumulate in the basin at the calculated rate of 2.14 ft3(0.06 m3)/cow-day, and represent volume fractions of about 0.55 ft3(0.016 m3)/cow-day for sand, and about 1.6 ft3(0.045 m3)/cow-day for manure. Sand accounts for a significant fraction of basin volume, and should be considered in basin sizing.

Sand recovered from the settling basin is stockpiled for a conditioning period before re-use as bedding. Most ideal results were obtained by allowing sand to condition for one month, followed by a moving/mixing operation and an additional 1 week conditioning before re-use as bedding. Limited bacteriological studies indicated similar bacteria profiles in fresh and recycled sand when these procedures were followed.