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United States Department of Agriculture

Agricultural Research Service

Title: Development of Algal Turf Scrubbers to Treat Dairy Manure

Authors
item Westhead, Elizabeth
item Pizarro, Carolina
item Mulbry, Walter
item Wilkie, Ann - UNIV FL, SOIL & WATER

Submitted to: BARC Poster Day
Publication Type: Abstract Only
Publication Acceptance Date: March 15, 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 primary objective of this research was to evaluate and develop algal turf scrubber (ATS) technology to remove N, P and soluble carbon from dairy manure. Laboratory-scale ATS units were operated in batch mode by continuously recycling wastewater. ATS units were seeded with algal consortia from nearby streams. The algal turfs were established at 25 C using a 16 hour photoperiod with 400 watt metal halide lights, a flow rate of 111 Lpm, and grown using dairy manure from two different dairy farms. The pH of the systems was maintained at pH 7-7.5 to minimize ammonia volatilization. After the turfs were established, daily additions of manure were increased each week until the amounts reached 0.6-0.96 g TN/day. Each week, algal biomass was harvested and approximately one-third of the ATS wastewater was replaced with distilled water. Algal biomass was dried prior to analysis for total nitrogen (TKN), total phosphorus (TKP), and inorganic constituents. Wastewater samples were collected 3-4 times a week and stored at 4 C prior to analysis for TKN, TKP, ammonia, nitrate, nitrite, orthophosphate, conductivity, and COD. The dried algae contained approximately 1.2% P and 6.7% N. Algal nitrogen accounted for 50-75% of TKN added. Algal phosphorus accounted for >95% of TKP added.

Last Modified: 8/27/2014
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