Page Banner

United States Department of Agriculture

Agricultural Research Service

Title: Use of Algal Turf Scrubbers to Treat Dairy Manure

Authors
item MULBRY, WALTER
item Wilkie, Ann - UNIV OF FL AT GAINESVILLE

Submitted to: Journal of Phycology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 27, 2001
Publication Date: N/A

Interpretive Summary: An alternative to land spreading of manures is to grow crops of algae on the nitrogen and phosphorus present in the manure. Compared to terrestrial plants, filamentous algae have exceedingly high growth and nutrient uptake rates. Moreover, they are capable of year-round growth in temperate climates, can be harvested on adapted farm-scale equipment, and yield a biomass that should be valuable as an animal feed supplement. The primary objective of this research was to evaluate and develop one method of growing filamentous algae (an algal turf scrubber (ATS)) to remove nitrogen, phosphorus and soluble carbon from dairy manure. Laboratory scale experiments were conducted using natural mixtures of algae that were fed diluted dairy manure. Results from nutrient balance results show that most of the manure nitrogen, and nearly all of the manure phosphorus, was taken up by the algae. Results from these experiments are important because they show for the first time that dairy manure contains all of the necessary nutrients needed for algae growth in this type of system. In addition, the nutrient balance results show that manure nitrogen and phosphorus are effectively captured in this system. The resulting algae have a high nitrogen content and may therefore find use as a protein supplement to animal feed.

Technical Abstract: An alternative to land spreading of manures is to grow crops of algae on the nitrogen and phosphorus present in the manure. Compared to terrestrial plants, filamentous algae have exceedingly high growth and nutrient uptake rates. Moreover, they are capable of year-round growth in temperate climates, can be harvested on adapted farm-scale equipment, and yield a biomass that should be valuable as an animal feed supplement. The objective of this research was to evaluate algal turf scrubber (ATS) technology to remove N, P and soluble carbon from raw and anaerobically digested dairy manure. Laboratory-scale ATS units were operated in batch mode by continuously recycling wastewater. ATS units were seeded with algal consortia from a nearby stream and grown using dairy manures from two different dairy farms. Algal biomass was harvested weekly and dried prior to analysis for TKN, total phosphorus, and inorganic constituents. Wastewater samples analyzed for TKN, ammonia, nitrate, orthophosphate, conductivity, and COD. Using a typical manure input containing 0.5 g NH4-N per day, the dried algal yield was approximately 5 g/m2-day. The dried algae contained approximately 1.5-2% P and 5-7% N. When grown on either of the two digested manures, algal nitrogen accounted for 18-75% of NH4-N (13- 54% of TKN) added and 33-100% of total soluble P added.

Last Modified: 7/25/2014
Footer Content Back to Top of Page