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Algae advances as alternative for improving water


May 12, 2010
By USDA-ARS

May 10, 2010 — Algae –
already being eyed for biofuel production – could be put to use right away to
remove nitrogen and phosphorus in livestock manure runoff, according to an
Agricultural Research Service (ARS) scientist.



May 10, 2010 — Algae –
already being eyed for biofuel production – could be put to use right away to
remove nitrogen and phosphorus in livestock manure runoff, according to an
Agricultural Research Service (ARS) scientist.

That could give resource
managers a new eco-friendly option for reducing the level of agricultural
pollutants that contaminate water quality in the Chesapeake Bay.

Microbiologist Walter
Mulbry works at the ARS Environmental Management and Byproduct Utilization
Research Unit
in Beltsville, Md., which is located in the Chesapeake Bay
watershed. In 2003, Mulbry set up four algal turf scrubber (ATS) raceways
outside dairy barns in Beltsville. The shallow 100-foot raceways were covered
with nylon netting that created a scaffold where the algae could grow.

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For the next three years,
from April until December, a submerged water pump at one end of the raceways
circulated a mix of fresh water and raw or anaerobically digested dairy manure
effluent over the algae. Within two to three weeks after the ATS system was
started up every spring, the raceways supported thriving colonies of green
filamentous algae.

Algae productivity was
highest in the spring and declined during the summer, in part because of higher
water temperatures and also because the raceways provided snails and midge
larvae ample opportunity to graze on the algae.

Mulbry and his partners
harvested wet algae every four to 12 days, dried it, and then analyzed the
dried biomass for nitrogen and phosphorus levels. His results indicate that the
ATS system recovered 60 to 90 percent of the nitrogen and 70 to 100 percent of
the phosphorus from the manure effluents. They also calculated that the cost
for this capture was comparable to other manure management practices – around $5
to $6 for each pound of nitrogen that was recovered and around $25 for each
pound of phosphorus that was recovered.

Results from this research
were published in Bioresource Technology.

Read more about this
research in the May/June 2010 issue of Agricultural Research magazine,
available online at: http://www.ars.usda.gov/is/AR/archive/may10/algae0510.htm.


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