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Test system keeps dairies cleaner

A UNIVERSITY of Arkansas graduate student is finding ways to reduce waste solids and phosphorus in water used to clean “loafing areas” and milking parlors on dairy farms.

“The right additives can help remove 80 percent of solids and 75 to 85 percent of phosphorus from flush water,” said Gabe Timby of Leslie, Ark., who is working on a master's degree in crop soil and environmental sciences.

“The result is that a much cleaner filtrate goes into the wastewater lagoon and can be recycled more often and more times.”

Flush systems are waste management systems used on larger dairy farms, said Tommy Daniel, soil chemist for the Arkansas Agricultural Experiment Station and Timby's thesis advisor. A filter is used to separate solids from the flush water, but most get through and settle out of the water in a lagoon.

In a series of tests, Timby used eight organic polymers alone and in combinations with aluminum chloride. The polymers bind solids into larger, more solid clumps and aluminum chloride binds phosphorus. These clumps are easier to filter out of the water.

“By removing most of the solids and phosphorus, the waste water is a lot cleaner going into the lagoon,” Timby said. “The water can be recycled for flushing loafing areas many more times than before.”

Eventually, the water will have to be applied to land, he said.

The phosphorus it contains is a nutrient that helps fertilize pastures, but if phosphorus levels exceed what the grass can utilize and what the soil can hold, it may run off into streams, lakes or ponds with rain. Reducing phosphorus and solids means dairy producers can recycle the water longer, reducing water use and land applications.

“These techniques will extend sustainability of dairy operations by reducing phosphorus levels in the soil and turning solids into a product that can be hauled away and used for compost,” Daniel said.

For example, he said, Texas dairy producers in Erath County send the solid extracted from wastewater to a community composter and the state highway department uses it to fertilize roadside grasses that stabilize highway embankments.

Fred Miller is Science Editor for the Arkansas Agricultural Experiment Station. e-mail:

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