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

BMPs forAquaculture Production

Lori Marsh, Associate Professor, Biological Systems Engineering,

Virginia TechSeptember 19, 2005

Aquatic Animal Production(CAAP/AAP) Systems:

• Flow-through

• Recirculating

• Net pen and cages

• Ponds

• Lobster pounds, Crawfish, Shellfish, Aquariums, and Alligators

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.

Recirculating Systems

• Highly intensive culture

• Actively filter and reuse water

• Water treatment including– Ammonia removal– Solids removal– Oxygenation– Temperature control….

• Capital intensive at startup

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

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)

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.

BMP for Removal of Solids in a Flow-through System

• 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.

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

Solids Disposal

• Dewatering – Natural evaporation– Mechanical assistance

• Filtration• Squeezing• Capillary action• Vacuum withdrawal• Centrifugal

– Chemicals are often added to assist with the dewatering process

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

Vermicomposting of solids

Vermicomposting uses earthworms to transform organic wastes and results in two

saleable products: vermicompost and worms.

VERMICOMPOST WORMS

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

After settling, the contents were run

through a hydroclone.

HYDROCLONE

The bins in operation

WORM BINS

Material from beds was run through a

trommel screen resulting in

screened material, unscreened

compost, and worms.

WORM SEPARATOR

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.

CONCLUSIONS

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.

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.

Mortality Management

• Avoid disease outbreaks

• Inspect daily, remove mortality promptly

• Proper disposal—composting, rendering

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.

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.)

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.