A closed-loop manure treatment system expected to produce potable water is being tested in North Carolina with support from a three-way coalition involving the state attorney general; Smithfield Foods’; Save Our State Foundation, an environmental organization; and Frontline Farmers, an organization of pork producers in eastern North Carolina.

The state Department of Environment and Natural Resources will test the process on a Greene County hog farm. The system will treat effluent from a 3,600-head, feeder-to-finish operation that utilizes an under-slat flush system. No lagoons will be involved. Initial investment is less than $125,000, which is far less than many of the 18 technologies that are being tested as possible replacements for the lagoon-sprayfield method. It is expected to require 3.5 hours per day to operate. Cost of electricity and chemicals is estimated at $1.50 per pig for those weighing 50 pounds to market.

The technology is being used successfully in municipal waste-treatment plants in California and Illinois to produce drinking water for human consumption.

Simply put, the process starts with mechanical separation of solids, then a four-step water treatment:

1 The affluent passes through two, 2,500-gallon settling tanks.

2 Then it goes into a 300-gallon dosing tank where chemical disinfectant is added and blended.

3 It then moves to another 300-gallon dosing tank where a polymer is added for flocculation, nitrification and denitrification.

4 Finally, water is recycled back to the three finishing hog houses.

Solids will be hauled away from the site and either composted or applied to land.

Odor, pathogens and nitrogen emissions also will be checked. The Research Triangle Institute will conduct economic analyses on the process and North Carolina State agricultural economists will weigh costs and benefits.