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Aeration Technical Information
TECHNICAL DETAILS OF AERATION

When the intended goal(s) of an aeration system are to tie up and/or remove nutrients which fuel algae growth certain parameters must be met:

  1. The physical movement of water, turnover, and/or roll rate becomes very important. This changes algae's preferred growing environment. 1960's data suggested turnover rates of every 30 days+-. Today often times our goals are to turn most lakes and pond over every 3 1/2-30 hours. Today with the improvements in air technology this can often times be accomplished with substantially less horsepower than what was used in the past to obtain a 30 day roll rate.
  2. Dissolved oxygen (D.O.) must be maintained at the lake bottom sediment layer on a continuous basis. When a lake goes anoxic nutrients will again be released from the bottom sediment (If the lake remains stratified throughout the summer this may not be an issue).
  3. Adequate oxygen will precipitate phosphorus from the water and release hydrogen sulfide, methane, ammonia, and carbon dioxide gases. Again these are all fuel for nuisance algae.
  4. D.O., total phosphorus, and pH peaks and lows should be identified, among other parameters.
Recognize these conditions when custom designing an aeration system. D.O. is the single most important water quality parameter. - Especially D.O. at the bottom.
  1. Identify the purpose of the aeration system.
  2. Determine lake volume in acre feet.
  3. Identify inflows and discharge rates (This should be added to lake volume).
  4. Maximum depth location(s) should be identified - Use contour map if available.
  5. Consider these water requirements:
    • 5 lbs. oxygen oxidizes 1 lb. nitrogen
    • 3 lbs. oxygen oxidizes 1 lb. carbon
    • 1-1.5 lbs. oxygen oxidizes 1 lb. B.O.D.
    • .04 lbs. oxygen/hour is required for 100 lbs of fish
    • 1 lb. oxygen oxidizes 1 lb. hydrogen sulfide
    • .67 lb. oxygen oxidizes 1 lb. manganese
    • .4 lb. oxygen oxidizes 1 lb. iron
  6. Will the system remain operating year around?
  7. When locating power locations and voltage options acknowledge equipment noise tolerance levels.
  8. Investigate permit requirements - Especially if open water will exist during the winter months.
  9. Smaller acreage generally requires greater air discharge locations.
  10. Deep water lakes may not require de-stratification if enough D.O. and water movement occurs in the epolimnetic water.
  11. Inadequate or undersized aeration can cause many concerns.
  12. Shallow water may benefit more from circulation and agitation.
  13. Recognize water temperature requirements if a two story fishery exists. Consider hypolimnetic air or injecting pure oxygen when partially aerating deep water.
Additional ways to improve aeration efficiency:
  1. The smaller the air bubble produced (50-1000 microns) the better the oxygen transfer. Smaller bubbles provide more surface area for oxygen absorption and float to the surface much slower. It is easy to obtain 10 times the oxygen absorption efficiency simply by reducing bubble size from 1/8" bubbles to 50-500 micron bubbles.
  2. Excess PSI wastes horsepower, energy costs, and adds substantially to operating expenses (27" or 2.31' water = 1 PSI). Delivering economical and the correct amounts of CFM to specific depths further determines aeration efficiency.
  3. Flow interference, SCFM/unit delivery, linear lift, and active diffuser surface area all increase aeration efficiency.
  4. Using appropriate air hose I.D. (inside diameter) dramatically reduces PSI (pounds per square inch) pressure loss. Example: @ 4 CFM 1/2" I.D. in 1000' air hose requires 11.6 PSI; 3/4" I.D in 1000' air hose requires 1.3 PSI
  5. Sizing the right compressor(s)(PSI and CFM) for the job. - Excesss horsepower wastes energy.
  6. Consider solar aeration as an option.

 

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