| Greensboro, NC: "With hogs comes waste,"
says Dr. M. R. Reddy. "That hasn't changed. What has changed is the
public's awareness of problems associated with swine waste."
Growing public concern over swine waste, especially in large pork producing
states like North Carolina, is what drives Reddy, a professor of soil science
with North Carolina A&T State University's Department of Natural Resources
and Environmental Design, and Richard Phillips, an adjunct professor in
A&T's Agricultural and Biosystems Engineering Program, in their waste
disposal research.
"Both the state's human population and swine population are increasing
rapidly," said Phillips. "This means that more people are living
closer to more hogs than ever before. The result is increased levels of
concern about such issues as water pollution and odor."
According to Reddy, problems associated with swine waste stem from odors
caused by gases produced by decomposing waste in swine production facilities
and their waste disposal systems; and from water pollution resulting from
nitrogen and other contaminants entering water supplies through seepage
into ground water, and runoff from lagoons and facilities into streams
and rivers.
To address these concerns, Reddy and Phillips are experimenting with different
ways to address the disposal of swine waste. The locale of most of their
research is A&T's swine unit located just southeast of Greensboro.
The swine unit is home to a 100 to 150 head "farrow-to-finish"
swine operation. Waste from the swine is directed to a system of lagoons
and wetland cells before being applied to cultivated land.
At the heart of the waste disposal system are six constructed "wetland"
cells, which use selected aquatic vegetation to absorb nitrogen, phosphorus
and ammonium from the wastewater, while water in the cells converts nitrogen
to nitrogen gas, which is released into the air.
Before reaching the wetland cells, wastewater flows through two 12-feet
deep lagoons. After treatment in the cells, wastewater is held in a storage
pond prior to land application.
According to Reddy, most swine waste disposal systems rely on lagoons to
remove contaminants from waste prior to land application. The use of wetland
cells represents an additional treatment to the wastewater.
The wetland cells use a "marsh-pond-marsh" type of construction
in which both ends of a 40-meter long cell are populated by plant life
such as cattails and bulrushes, and the middle is 30-inch deep open pond.
"The wetland cells are designed to simulate a typical wetland setting,"
said Reddy. "We built the cells this way so that our findings are
applicable to natural conditions."
Wetlands remove excess nitrogen and other waste from water through filtration,
plant uptake, sedimentation and other biological processes. Using soil
and plant resources that occur naturally in a wetland environment, wetlands
provide a natural buffer between waste and the valuable resource of clean
water.
To determine the effectiveness of this waste treatment system, researchers
measure the nitrogen concentration of water as it exits the second lagoon
and is pumped into a wetland cell, and as it exits a wetland cell and flows
to the holding pond.
Though only limited results have been obtained from the two-year-old system,
early tests reveal that nitrogen levels are reduced by over 90 percent
using the A&T system.
"The large reduction in nitrogen concentration is encouraging,"
said Phillips. "It indicates to us that, once the system is operating
at a steady state, it might prove a useful option for the state's swine
farmers."
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For more information, please contact Dr. M. R. Reddy or Richard Phillips,
NC A&T School of Agriculture, (336) 334-7779.
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