Learn About Aquaculture
HERE YOU CAN LEARN ABOUT ALL ASPECTS OF AQUACULTURE
Efficiency versus Type ...
Select the right type of aerator for the application.
An aerator's standard aeration efficiency (SAE) is an important consideration when comparing one aerator with another.
The SAE can be calculated by measuring the aerator’s oxygen transfer and the amount of energy used per horsepower, per hour, under standard conditions. An SAE of 2.1, for example, means that 2.1 pounds of oxygen per horsepower, per hour, are transferred to the water under standard conditions. The higher the SAE, the higher the oxygen transfer, the higher the efficiency.
However, SAE numbers are a fair comparison only when comparing aeration equipment of the same exact type. You cannot use the SAE as your only tool in the selection of an aeration system. Before looking at the SAE numbers, choose the right type aerator or oxygenator for the job.
Here are some examples (analyze the differences):
- A surface aerator like our Kasco 3/4-hp (with an SAE rating of 2.9) may be a good choice where the volume of water is small and the stocking density is high, such as in a culture tank or small pond. It may be a poor choice, however, if cold water temperatures are required when air temperatures are warm (summer trout culture), because both the motor and the airborne water droplets will add unwanted heat.
- A surface aerator would be a poor choice for a large or deep pond. Without moving water away from the aerator, it will continue to pump the same water over and over again, adding no oxygen where it is needed.
- A surface aerator may be excellent in emergencies because it quickly raises the oxygen level in a small area. If trained, the fish will move to that location. Again, it will not be a good choice for full-time aeration because it will not disperse oxygen throughout the pond.
- A diffused air system (with an SAE rating of 2.7) may be the best choice for multiple tanks and ponds because the energy source (blower) can be centralized and just the right amount of energy (compressed air) can be easily directed where it is needed. What appears to be lower SAE efficiency (2.7) is more than offset by comparative application efficiency.
- Water-moving aeration devices like the AIRE-02® Series II aerator and paddle wheel type aerators are excellent choices for medium and large ponds where movement of oxygenated water away from the aerator is most important.
- If destratification alone will solve a bottom oxygen problem, only a few air diffusers may be needed to accomplish this. For instance, a 10-acre lake, 15' deep, may need only 3/4 hp (see Lake Aeration). Only 1 cfm of air may be needed to aerate a 1/20-acre pool when raising tropical fish (see FAT CAT™ aerators), compared to 6 cfm per pool using airlifts.
- A destratification system, such as our Great Lakes® aeration system, should not be used as an emergency aerator because it very quickly mixes the water. Its rate of oxygen transfer is excellent; however, it cannot raise the oxygen level of such a large volume quickly enough to avoid a fishkill. It can actually aggravate the problem.
- Even noise is a consideration above and below the water surface. Pentair AES diffused air systems are preferred over agitators in bait stores, improving conditions for both the fish and the employees. As more of our research is conducted under water, we are increasingly aware of underwater noise produced by devices such as paddle wheels, agitators, airlifts and drilled pipe spargers (our Sweetwater® air diffusers have a barely audible hiss). Some fish breeders have reported that diffused air is the only aeration method they can use that will not disrupt breeding. The situations and considerations are virtually endless, so take some time to research the best aeration method for your particular application. For the price of a phone call, you can discuss your application with a Pentair technician and get an expert opinion (877-347-4788).
Standard aeration efficiency tests conducted at Auburn University showed that the Pentair AES Sweetwater® diffuser and 1-hp blower combination yielded a 2.71 SAE. Prior to rating our diffusers, Auburn gave air diffusers in general an SAE rating of only 1.6. That 70 percent increase illustrates how much efficiency can change when the right combination is used.
You know how you can tell what people know by the questions they ask? Well, we know that most people don’t know about watts. They ask, "How many amps does this motor use?" instead of, "How many watts does this motor use?" Watts are what you pay for, not amps (amps are used to size breakers, etc.).
The direct current formula we all learned (volts x amps = watts) is correct for incandescent light bulbs and electric heaters, but it is not correct for motors. When dealing with power loads that involve inductance magnetic devices such as motor windings, solenoids, transformers, lamp ballasts, etc., the formula for single-phase loads is volts x amps x power factor = watts.
In many cases, especially with linear air compressors and mag drive pumps, the actual watts used are significantly less than what is calculated by multiplying volts x amps. The only way to determine the watt consumption of a motor is to test it using a wattmeter (such as our KW4). In the Pentair AES catalog, we have published the actual watts for most of our motor-driven devices as tested in our RDTE shop with our wattmeter.
Sweetwater® models AQ3, AQ5, AQ7, AQ73, AQ9 & AQ93
DO NOT REMOVE THE ROTOR OR LOOSEN ANY OF THE ELECTRIC MOTOR-THROUGH BOLTS.
We recommend carbon vane replacement at nine-month intervals to ensure trouble-free operation of your compressor. The following tools are required: 3/8" or 7/16" socket/wrench, small hammer and antiseize compound.
- Remove the two end caps from the front of the muffler box (if applicable) and the five muffler box bolts, being careful not to damage the gasket. If the gasket is torn, scrape it off with a sharp knife and replace.
- Tap the box with a small hammer to loosen it. Do not pry with a screwdriver.
- Remove the six bolts holding the end plate to the body. Remove the end plate. Do not remove the rotor or loosen any of the electric motor through bolts.
- Check that vanes are moving freely in and out of vane slots. Replace any vane if more than 50% extends past the vane slot. Top clearance (between rotor and body) may be adjusted by loosening body bolts and lightly tapping on the compressor body while turning the rotor. About .004 inch—the thickness of a sheet of paper—works well.
- Remove vanes and clean both sides with fine emery cloth. Clean the end plate with fine emery cloth.
- Flush vanes, body, rotor and end plate with solvent (part no. AQ255), and remove all solvent from each part.
- Check the body, rotor and end plate for scoring. If each part is clean and shows no signs of scoring, reinstall parts. If scoring is present, replace with new part(s) or contact Pentair Aquatic Eco-Systems for service.
- Insert new vanes.
Reassemble by reversing the previous directions. We always recommend using an antiseize lubricant on each bolt to ensure its easy removal for the next vane replacement. Bolts should be reinstalled and tightened in a similar manner to replacing the lug nuts on a vehicle wheel. Start with one bolt and move to the right, skipping one and tightening the next.
When reinstalling the muffler box (if applicable), be certain to install the center bolt first to ensure proper gasket alignment. Before replacing the muffler box, plug your compressor in for a quick sound check of the valve rotation. If an unusual sound or stopping of the rotor takes place, disconnect and recheck the vane replacement.
If you have any problems, contact Pentair Aquatic Eco-Systems at 877-347-4788 for assistance.
Cost is one of the biggest considerations. This generalized chart should help to quantify the difference between using an air blower with diffusers and using pure oxygen with a water pump and oxygen saturator (oxygen cone). Also see "Oxygen or Aeration" Tech Talk.
THIS GENERALIZED CHART IS BASED ON:
- Electric Cost of 8¢ per KWH,
- Sweetwater® Standard Diffusers at 40" H2O,
- Water Temperature 80°F (27°C) Sea Level,
- Fresh Water @ 24 lb/day Oxygen Concentrator,
- 40 gpm Pump Using 5 Amps @ 115V.
This cost comparison illustrates that blowers are more efficient at lower D.O. saturation values and pure oxygen is more efficient at higher D.O. saturation values. Note that the cost of adding pure oxygen remains almost the same until reaching higher super saturation levels, then pumping pressures and, therefore, cost goes up.