2007 Annual Report 1a.Objectives (from AD-416) Development and evaluation of manure treatment systems. Specific objectives: define and determine engineering parameters of existing and proposed biological treatment systems for treatment of animal manures and agricultural wastewaters; determine optimal strategies for cultivating specific aquatic plants and/or algae, capturing manure nutrients, using farm labor and equipment efficiently; and characterize and compare costs and benefits of aquatic plant treatment systems with existing biological treatment processes and manure management practices. 1b.Approach (from AD-416) Results from laboratory-scale studies demonstrate the ability of algal systems to remove nutrients from dairy, swine and aquacultural wastewaters. Such systems offer a new approach for management and recycling of nutrients within agricultural facilities. However, further research is necessary to properly evaluate the costs and benefits of full scale versions of these systems for agricultural producers.In this research, engineering parameters for field-scale manure treatment systems using algae and aquatic plants will be developed and used to compare the costs and benefits of different treatment systems.Treatment efficiency, capital and operational costs, and biomass utilization strategies will be evaluated for each type of system. Small scale aquatic plant systems will be used to estimate water quality treatment and biomass production parameters where needed. Costs and benefits of different treatment strategies will be compared to existing manure management practices. 3.Progress Report This report documents research conducted under a specific cooperative agreement between ARS and the University of Maryland. Additional details can be found in the report for the parent project 1265-12000-028-00D, Biological treatment of manure to capture nutrients and transform contaminants. Completed experiments with pilot-scale algae-based dairy manure treatment system. Among agricultural sources of N and P, animal manures (poultry, dairy, beef, swine) are estimated to contribute 18% of the N and 25% of the P that enter the Chesapeake Bay (Chesapeake Bay Foundation, 2004). An alternative to the current practice of spraying dairy manure effluents on agricultural fields is to grow crops of algae using the effluents and thus convert manure N and P into potentially valuable algal biomass. The objective of this study was to determine values for productivity, nutrient content, and nutrient recovery using filamentous green algae grown in outdoor raceways at different loading rates of raw and anaerobically digested dairy manure effluent. Algal turf scrubber raceways (30 square meters each) were operated in central Maryland for approximately 270 days each year (roughly April 1 to Dec 31) from 2003 to 2006. Algal biomass was harvested every 4-12 days from the raceways after daily additions of manure effluent corresponding to loading rates of 0.3-2.5 g total N (TN) and 0.08–0.42 g total P (TP) per square meter per day. Mean algal productivity values increased from approximately 2.5 g dry weight per square meter per day at the lowest loading rate to 25 g dry weight per square meter per day at the highest loading rate. Mean N and P contents in the dried biomass increased 1.5 to 2.0 -fold with increasing loading rate up to maximums of 7% N and 1% P (dry weight basis). Although variable, algal N and P accounted for roughly 70-90% of input N and P at loading rates below 1 g TN, 0.15 g TP per square meter per day. N and P recovery rates decreased to 50-80 % at higher loading rates. There were no significant differences in algal productivity, algal N and P content, or N and P recovery values from raceways with carbon dioxide supplementation compared to values from raceways without added carbon dioxide. On an acre basis, these values are equivalent to a yearly productivity value of 12 tons of algal biomass per acre at a loading rate of 2400 lbs TN, 350 lbs TP per acre. Using these values, cost estimates for the yearly operational costs per cow, per lb N, per lb P, or per lb of dried biomass are $778, $4.90, $24.20, and $0.60, respectively. Within the context of reducing nutrient inputs in sensitive watersheds such as the Chesapeake Bay, these costs are still well below the estimates of $8.60 per lb N cited for upgrading existing water treatment plants. Sale of the dried algal biomass as an organic fertilizer could also provide a significant source of revenue. Widespread use of this material in lieu of inorganic fertilizers in urban/suburban areas could help reduce fertilizer-related nutrient losses from these areas. ADODR monitoring was accomplished by monthly meetings and by email.