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Constructed Wetland Turns Swine Waste into Odorless, Reusable Water
AUBURN, Ala. - The disposal and treatment of waste from swine and other livestock operations has been a concern of many people recently, and Auburn University researchers may have found an economical and effective answer to that problem. At the Alabama Agricultural Experiment Station's Sand Mountain Substation in Crossville, the wastewater from a full scale swine operation is being treated and made reusable, entirely by a constructed wetlands system, according to Tom McCaskey, professor of animal and dairy sciences in the College of Agriculture.
"It's a natural system. This is nature's way of treating wastewater," he said.
The 500-pig-per-year farrow-to-finish operation consists of three barns -- the farrowing barn, nursery and finishing house. Water flushes the waste from pens in these barns into two primary lagoons which flow into a secondary lagoon and then into a shallow pond. The lagoons act as temporary wastewater storage structures which help to settle out some of the solids in the wastewater.
In the next step, the wetlands do their work. The water flows from the shallow pond into the first set of five "cells," or manmade swamps. After about nine days, the water flows into the second set of cells to be treated for another nine days. These 10 cells total only one acre, but they are enough to turn the swine waste into odorless, reusable water. The one acre wetland treats about 7,700 gallons of wastewater daily.
The wetlands are planted with aquatic plants like cattails, bulrush and giant cutgrass, which which help treat the wastewater through a process called phytoremediation. "These plants and the microorganisms associated with the wetlands transform raw sewage into pond water," McCaskey said.
From the wetlands, the clean water is pumped into a holding pond and flows by gravity back through the barns, restarting the whole process.
McCaskey said that studies have shown that bacteria such as E. coli and Salmonella die out during the treatment of wastewater. "This system helps to eliminate these bacteria, so if you recycle the treated wastewater, you don't risk spreading enteric infection," he said.
This project had two objectives when it was started seven years ago.
The first was to find out if the wetland wastewater treatment concept would work for livestock operations. The idea was originally developed to be used for small communities that could not afford expensive sewage treatment plants. Researchers found that the idea not only works for livestock wastewater, which is much more concentrated in pollutants than city sewage, but that it is efficient, economical and low maintenance.
"It has worked for seven years and it is just as efficient as it was seven years ago," McCaskey said.
The second objective was to determine the maximum wastewater loading rate for the wetlands that would result in high wastewater treatment efficiency over a period of several years.
"There is a maximum nutrient load limit at which these constructed wetlands will efficiently treat wastewater. We didn't want to overload the system causing it to fail," McCaskey said.
McCaskey feels that one of the most significant outcomes of this project is that the treated water from this constructed wetland meets the requirements for discharge water from constructed wetlands treating municipal sewage.
"Even though this wastewater we are treating has a higher nutrient load than municipal sewage, we can meet the same wetland treatment criteria as municipalities," he said.
Constructed wetlands treating municipal sewage can be permitted to discharge the treated water to a stream, but the wetland system used to treat swine lagoon wastewater is not discharged, but is instead reused.
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News from:
Office of Ag Communications & Marketing
Auburn University College of Agriculture
Alabama Agricultural Experiment Station
3 Comer Hall, Auburn University
Auburn, AL 36849
334-844-4877 (PHONE) 334-844-5892 (FAX)
Contact Jamie Creamer, 334-844-2783 or jcreamer@auburn.edu
by Anna M. Lee
December 16, 1997
