tory requirements by orders of magnitude (see
Treated water and final effluent results).
Membrane bioreactor technology
The MBR in Cold Spring has the capacity to
treat 1. 7 million gallons of wastewater per day. It
vacuums wastewater through 0.04 micron openings in hollow membrane ;bers. The automated
system runs 24 hours a day, seven days a week.
“The membrane bioreactor technology, which
incorporates biological phosphorus and ammonia removal, better prepares the plant for current
and future limits,” said Clay Watson, environmental services manager.
TREATED WATER AND FINAL EFFLUENT RESULTS, MONTHLY AVERAGE
GNP Company chicken processing plant, Cold Spring, Minn.
Oil and grease
Biological oxygen demand (B.O.D.)
Total suspended solids (T.S.S.)
NTU = Nephelometric turbidity units
The St. Cloud facility’s wastewater discharge is now cleaner than the regulatory
requirements by orders of magnitude.
Wastewater treatment technology
The Cold Spring facility is a showcase of
wastewater treatment technology:
;The wastewater treatment facility employs membrane bioreactor technology, ultraviolet disinfecting and sand ;ltration.
;The blower system, which is the most energy ef-;cient available, runs between 30,000 and 35,000
RPM and produces up to 2,800 cubic feet per
;Variable frequency drives in the blower system control energy use according to the facility’s needs.
;400,000 to 500,000 gallons daily are reused in non-
bird contact tasks, such as cleaning ;oors, screen-
ing, bird module washing, vacuum pumps, com-
pressors and cooling towers and lawn sprinkling
Water usage is based on the plant’s production of
190,000 birds per day, 6. 6 gallons of water per bird,
or 28. 8 million gallons per month, and 8. 9 million
gallons per month of reconditioned water.
Wastewater treatment by the numbers
Cold Spring is the ;rst poultry processing plant
to use MBR technology for wastewater treatment
and is currently one of the largest MBR facilities in
Minnesota (and in the world in terms of gallons processed per day). System volumes are as follows:
; 1. 4 million gallons of wastewater are processed
How MBR works
The hollow membrane ;bers are at the heart of
the MBR system. Unlike in other ;ltration systems,
the wastewater ;ows outside-in as a vacuum is pulled
through 0.4 micron openings in the ;bers. Pumps periodically reverse pulse to change the direction of the ;ow
to keep the ;ber media clean and free of particulates.