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.