BMPs for Aquaculture Production

1. BMPs forAquaculture Production Lori Marsh, Associate Professor, Biological Systems Engineering, Virginia Tech September 19, 2005

2. Aquatic Animal Production(CAAP/AAP) Systems: • Flow-through • Recirculating • Net pen and cages • Ponds • Lobster pounds, Crawfish, Shellfish, Aquariums, and Alligators

3. Flow-through Systems • Constantly flowing culture water • Commonly use raceways or tanks • Found throughout US • Require consistent volume of water • Most use well, spring or stream water as source • Primary method to grow salmonid species such as rainbow trout.

4. Recirculating Systems • Highly intensive culture • Actively filter and reuse water • Water treatment including • Ammonia removal • Solids removal • Oxygenation • Temperature control…. • Capital intensive at startup

8. Net Pens and Cages • Suspended or floating holding systems • Located along a shoreline or pier or anchored off shore • Rely on natural water movement to assure water exchange/quality for fish

9. What’s the Problem with CAAPs? • 4,200 commercial facilities (1998 USDA census) • Water quality concerns include • Suspended solids, P, NH3, BOD • Drugs (e.g. oxytetracycline or formalin) • Chemicals (e.g. copper-containing pesticides) • Pathogens (primarily a concern for native biota)

10. BMPs for Feed Management • Applicable to all systems • Avoid overfeeding • Match feeding to feed requirements • Direct feed to fish • Use quality feed, and store to reserve nutrient quality • Handle feed to minimize fines • Active feed monitoring (net pens): detects when feed pellets are passing below fish.

11. Quiescent Zones typically constructed with wire mesh to exclude fish from last 10% of raceway. Designed to insure that overflow rate is smaller than particle settling velocity. Solids typically removed by suction through a vacuum head. BMP for Removal of Solids in a Flow-through System

12. Other BMPs for Solids Removal • Sedimentation basins • Off-line settling (OLS) basins receive water and solids slurry from Quiescent Zone (QZ). • Note: QZ + OLS are most common settling system for flow-through systems. • Full-flow settling (FFS) systems stand alone and collect water flow from entire facility (need 2 operating in parallel for solids removal). • Secondary Settling • Microscreens • Vegetated ditches • Constructed wetlands

13. Solids Disposal • Dewatering • Natural evaporation • Mechanical assistance • Filtration • Squeezing • Capillary action • Vacuum withdrawal • Centrifugal • Chemicals are often added to assist with the dewatering process

14. Solids Composting • Dewatered sludge mixed with bulking agent to add carbon, reduce moisture, increase aeration • Must be aerated (turned or by adding air) • Often screened to remove bulking agent • Advantages: reduces volume, stabilizes material, heating destroys pathogens, value added product

15. Vermicomposting of solids Vermicomposting uses earthworms to transform organic wastes and results in two saleable products: vermicompost and worms. WORMS VERMICOMPOST

16. WHY CONSIDER VERMICOMPOSTING? • Two saleable products • Possibility of worms as fish feed • Worm composting faster than microbial • Worms turn the material so machines/people don’t have to • Vermicomposting suitable for high- moisture waste

17. After settling, the contents were run through a hydroclone. HYDROCLONE

18. WORM BINS The bins in operation

19. Material from beds was run through a trommel screen resulting in screened material, unscreened compost, and worms. WORM SEPARATOR

20. CONCLUSIONS • Processing rate very slow during extreme temperature conditions >29 C or < 10 C; therefore an unconditioned greenhouse does not appear suitable for this process. • During more optimum temperature conditions, worms processed 2.3 kg dry sludge/m2-week. • For the estimated sludge production at BRA, a 30.5 m x 91.5 m (100’x300’) structure would be required to house sufficient worm beds.

21. Land Application of Solids • Can land apply without dewatering • Hydraulic limitations not nutrient • Need provisions for times of frozen ground • BMPs for land application of animal wastes would apply, e.g. site conditions, weather, crop nutrient uptake, application rates, land availability, setbacks, slopes, neighbors, etc.

22. Waste Treatment Options for Effluent • POTW • Lagoons: BMPs for lagoons apply, e.g. site selection, design, start up, maintenance, record keeping, clean water diversion, etc.

23. Mortality Management • Avoid disease outbreaks • Inspect daily, remove mortality promptly • Proper disposal—composting, rendering

24. BMPs for Ponds • Avoid discharges e.g. seine harvest rather than draining; maintain freeboard for storm volume, drain from top when necessary. • Implement erosion control for pond ( protection from waves, aerators, vehicles, etc.) and watershed. • Manage rainwater: divert excess runoff, • Maintain good vegetation and avoid livestock production in watershed. • Use drugs and chemicals only as needed, use only FDA- and EPA-approved water quality enhancers and follow label directions carefully.

25. Constituents of concern • Nutrients • Bacteria (?) • Carr, O.J. and R. Goulder. 1993. Directly counted bacteria in a trout farm and its effluent. Aquacult. Fish. Manage. Vol 24, no. 1, pp. 19-27. • Pharmaceuticals (?) • Halling-Sorensen, B. et al. 1998. Occurrence, fate and effects of pharmaceutical substances in the environment—A review. Chemosphere. Vol 36, no.2, pp. 357-393. Jan. (Nice abstract. Unfortunately, article is in German.)

26. References • Claude E. Boyd. Guidelines for aquaculture effluent management at the farm-level. Aquaculture. Vol 226 Issues 1-4, Oct. 2003. pp 101-112. • USEPA. BMPs for CAAP Facilities. www.epa.gov/guide/aquaculture.