Water Efficiency Practices for Aquaculture

Aquaculture is the practice of raising fish in hatcheries and farms for food, sport, or release to the wild. Aquaculture operations generally use large quantities of water to maintain water levels in production tanks and raceways. The various requirements associated with different fish species and ages affects water reuse throughout the rearing system. For example, adult fish can better survive somewhat degraded water quality conditions than young fish, so recycling is more feasible in tanks containing older fish.

Since large volumes of water are required to maintain aquaculture systems, water efficiency practices are important to reduce the demands on source water. The water efficiency practices in this fact sheet involve active monitoring and control of source water supplies and the application of these practices throughout the facility. A comprehensive audit can be performed to assess the facility’s water system and identify loca-tions where these practices can be employed to conserve water. Please see fact sheet WD-DWGB-26-16, “Performing a Business or Industry Water Use and Conservation Audit.”

• Determine minimum flow rates needed to maintain required tank/raceway conditions such as tem-perature, dissolved oxygen, and dissolved solids concentrations. Maintain these rates and regularly monitor specific tank conditions.
  
  
• Maintain or install accurate mechanisms to control flows throughout the aquaculture system. De-vices include sealed weir boards and pipe valves.
  
  
• Install flow meters or sharp crested weirs for proper flow measurements. This allows for more ac-curate control of tank flow rates and water conditions.
  
  
• Minimize water use for tank and facility washing. Use pressurized culture water along with physi-cal scrubbing, rather than clean source water, for cleaning.
  
  
• Routinely check for leaks in all areas of the facility, including domestic. Regularly repair leaking pipes, tanks and channels. Retrofit old channeled systems with valved pipes.
  
  
• Establish a routine maintenance program.
  
  
• Upgrade older infrastructure with newer tanks and piping as the old ones wear out.
  
  
• Circulate water from hatchery or early stage tanks to later fingerling or yearling tanks.
  
  
• Utilize state-of-the-art recirculation technology wherever possible. These systems often employ a technique called a swirl separator, comprised of a cone-shaped tank and whirlpool, to remove fish wastes and are used in conjunction with treatment and aeration.



• Implement efficient alternative processes for culturing fish. Processes may include installing aera-tion systems to control dissolved oxygen levels and minimizing the flow required to maintain satu-rated conditions.
  
  
• Employ a pumping and treatment system to recycle water. Aquaculture treatment methods are de-signed to remove dissolved solids and reduce nitrate, nitrite and ammonia. Temperature and trace contaminants are also factors that must be considered when assessing the feasibility of a recycling system. The following is a list of treatment methods used in aquaculture.
  
  
  • Nitrogen/sulfide gas strippers
  • Screens and particulate filters, e.g., cartridge, sock filters, remove large particles that could po-tentially damage pumps and plug pipes and valves.
  • Bio-filters, comprised of an appropriate media-filled container, remove nitrate, nitrite and am-monia.
  • Rapid sand filters remove nitrate, nitrite, ammonia and particulates.
  • Activated carbon filters/ion exchange systems remove nitrate, nitrite, ammonia and other cations.
  • Membrane filters, e.g., reverse osmosis, micro-, nano-, ultra-filtration, remove nitrate, nitrite, ammonia, salts and metals.
  • Ultra-violet radiation or ozone systems for pathogen loads in source water.
    
    
• Sweep or shovel floors, drives, parking lots, and walkways rather than hosing down.
• Wash fleet vehicles less often. Consider using spent culture water for washing purposes.
• Use hose nozzle shutoff devices.
• Use low-flow plumbing and equipment in bathrooms and other domestic areas.
• Minimize high water use landscaping. Utilize natural plantings. Most native plants are drought-resistant and hardy, requiring no additional water application. See fact sheet WD-DWGB-26-4, “Fundamentals of Xeriscaping and Water Wise Landscaping.”

For Additional Information
Please contact the Drinking Water and Groundwater Bureau at (603) 271-2513 or dwgbinfo@des.nh.gov or visit our website at www.des.nh.gov/dwgb. All of the bureau’s fact sheets are on-line at www.des.nh.gov/dwg.htm.

NHDES Water Conservation Program, www.des.nh.gov/h2o_conservation.htm

Aquaculture News, Useful links to recirculation and reuse technology.
www.theaquaculturenews.com

Reference:
_____, MRI Water Conservation Technical Bulletin # 3, Water Conservation Best Management Practices for Aquaculture; New England Interstate Water Pollution Control Commission, Wilmington, MA; 1996.

Note: This fact sheet is accurate as of October 2007. Statutory or regulatory changes, or the availability of additional information after this date may render this information inaccurate or incomplete.