Use of Algae Reactors to Remediate Eutrophication in the Mississippi River Delta Brendan Scott Joseph Vassios BZ 572 November 9, 2010

Mississippi River Basin 1.5 Million Square Miles

Ecology of Hypoxia

Introduction – Mississippi River  Increased fertilization and leaching of top soil has increased nitrogen concentrations in the Mississippi River and consequently the Gulf of Mexico  Increased concentrations of nitrogen has led to seasonal eutrophication of the Gulf of Mexico

Nitrogen  Nitrogen is used by plants for:  Nucleic acid (DNA & RNA)  Amino acids  Pigments  Eutrophication as a result of increased nitrogen can lead to:  Detrimental algae blooms  Reduced dissolved oxygen (hypoxia)  Fish kills

Nitrogen’s Role in Eutrophication

Current Regulation of Nitrogen  EPA limits for nitrogen in drinking water:  Nitrate – 10 ppm  Nitrite – 1 ppm  Ammonia – Varies  Total N – 11 ppm  Leaching from agricultural soils is currently unregulated

USGS, 2010

Nitrogen Levels Directly Proportional to Amount of Tile Farming USGS, 2010

Current Remediation Strategies  Current strategies incorporate mitigation by altering farming processes  Reduce nitrogen inputs  Crop rotation  Modified cultural practices  Previous research using algae for wastewater remediation (phytoaccumulation):  Algae turf scrubber  Algae biofilm

Algae Turf Scrubber

Algae Biofilm Qun et al., 2008

Algae Biofilm Qun et al., 2008

Potential Algae Species Anabaena cylindricaSpirogyra sp. obacteriaslides.shtml b20a.htm

Algae is also intentionally cultivated, supporting a multimillion dollar international industry

Design Criteria For Algae Reactor  Simple  Passive  Relatively efficient  Movable  Exploit a natural ecosystem  Turn a waste stream into energy

Palate sized for ease of transport with a footprint of 11 square feet Ergonomically accessible for reach with a height of 5 feet Effective surface area of 1320 square feet created by 120 trays spaced one ½ inch apart

Cheap durable construction materials Plexi glass for reactor housing Removable screens as scaffolding for algae

Hybridization of Existing Technologies

Wastewater Treatment Calculations Monod Growth Kinetics With variables of Influent Nitrogen Concentration Reactor Effluent Substrate Concentration Specific Growth Rate Hydraulic Retention Time S=K[(1+bθ)/(θ(Yq-b)-1)] Yielded reactor surface areas smaller than “Dead Zone”

Optimal Residence Time of 8 Days

Calculation Based on Equal Areas Area of “Dead Zone” 8000 square miles at peak Effective surface area of reactor 1320 Square feet Number of units required for total removal 169 million, Equivalent to 67 square miles of reactors 0.004% of farm land in Mississippi River basin

Moving Forward  Create working prototype  Trials with various algae species, light conditions, residence times  Test influent and effluent conditions over long time span  Test reactor algae as fertilizer or product stream  Determine economic viability of reactors  Conduct risk assessment and feasibility studies

Questions?

References  Size-Dependent Nitrogen Uptake in Micro and Macroalgae, M. Hein, Marine Ecology Press Series Vol. 118, 1995  Sources and Transportation of Nitrogen in the Mississippi River Basin, D. Goolsby, USGS  Phytoremediation as a Management Option for Contaminated Sediments in Tidal Marshes, V. Bert, Environmental Science Vol. 16, 2009  Nutrient Uptake in Streams Draining Agricultural Catchments of the Midwestern United States, M. Bernot, Fresh Water Biology Vol. 51, 2006  Nutrient Removal Potential of Selected Aquatic Macrophytes, K. Reddy, Journal of Environmental Quality Vol. 14, 1985  Nitrogen and Phosphorus Removal from Urban Wastewater by the Microalga Scendesmus obliquus, M. Martinez, Bioresource Technology, Vol. 73, 2000

 Nitrogen and Phosphorus in the Upper Mississippi River: Transport, Processing, and effects on the river ecosystem, J. Houser, Hydrobilogia Vol. 640, 2010  Nutrient Content of Seagrass and Epiphytes in the Northern Gulf of Mexico: Evidence of Phosphorus and Nitrogen Limitation, M. Johnson, Aquatic Botany Vol. 85, 2006  Reducing Hypoxia in the Gulf of Mexico: Advise from Three Models, D. Scavia, Estuaries Vol. 27, 2004  Limnology, Third Edition, R. Wetzel, Academic Press

 Ecological Stoichiometery in Freshwater Benthic Systems: Recent Progress and Perspectives, W. Cross, Freshwater Biology Vol. 50, 2009  Postaudit of Upper Mississippi River BOD/DO Model, W. Lung, ASCE  Environmental Biotechnology: Principals and Applications, P. McCarty, McGraw-Hill, 2001  An economic assessment of algal turf scrubber technology for treatment of dairy manure effluent, C. Pizarro, Biological Engineering Vol. 26, pg , 2006  Removing nitrogen and phosphorus from simulated wastewater using algal biofilm technique, W.E.I. Qun, Front. Environ. Sci. Engin. Vol. 2, pg , 2008  Nutrients in the Nation’s Streams and Groundwater, , Circular 1350, N. Dubrovsky, USGS, Accessed at: