Attention: Lakeshore cottage committees, neighbours of retention ponds, and more:
Dissolved Oxygen (DO) is the most important thing you need to know if you want to love your waterbody again.
Did you know the dissolved oxygen (DO) concentration in your favourite waterbody is the most important thing you need to know? That is, if you want to enjoy your waterbody again or continue to for years to come.
That’s right! Low DO in your favourite waterbody will lead to the death of fish and invertebrates, such as frogs and crayfish. Low DO will also dramatically reduce the beneficial bacteria that consume nutrients in the water. Now this is where this problem escalates because excessive nutrients in your waterbody will increase the muck depth on the shoreline and lake floor. More muck creates a perfect bed for aquatic weeds thereby further increasing the organic matter and nutrient levels in the water. As the water gets cloudier from muddy bottoms, you will see the formation of green algae on the surface of your once beautiful waterbody.
In summary, more nutrients in the water is not a good thing. That’s why wastewater from lagoons or run-off from agricultural fields are known pollutants of freshwater bodies. You may be surprised to learn that many homeowners or cabin owners like yourself pollute their own waterbody by dumping their grass clippings, autumn leaves, and even their fire pit residue directly into the water. When it comes to keeping your favourite waterbody beautiful, you should know that adding organic matter to your lake or pond will release more nutrients. So find another place for your leaves, lawn clippings, and fire pit residue!
How To Keep DO Levels Up In Your Favourite Waterbody?
Simple answer… water aeration. Water aeration is the process of adding diffused oxygen to water. Water aeration benefits waterbodies that are anoxic. Anoxia is a fancy term for “the oxygen level is too low.”
How Can You Aerate Your Own Waterbody?
Water aeration is most effective when the oxygen-rich air is supplied directly to the bottom of your lake or retention pond. By doing so, air is applied directly to the oxygen-loving bacteria that love to eat the muck off the bottom of the lake or pond. In stagnant waterbodies a thermocline develops towards the bottom (see infographic above). Water below the thermocline is colder and anoxic in comparison to the water above the thermocline. By applying oxygen to the bottom of the pond, you remove the thermocline and activate the bacteria you want working for you. Simultaneously, you also remove the anaerobic loving organisms from the lake that produce nasty things like blue-green algae.
2 Significant Methods for Providing Subsurface Aeration Are:
- Coarse Bubble Aeration
- Fine Bubble Aeration
|Coarse Bubble||Fine Bubble|
|Bubble Size||10 mm||.02 mm|
|Ability to add DO to anoxic water||1.5-2.0lb/ hp-hr
Or 6-8% efficiency
Or 22-32% efficiency
|Ability to break up a thermocline||Yes||Yes|
|Size of compressor||7-15 hp – 2-4 operates large diffuser||1.5 HP operates 3 diffusers. Modular design can add more diffusers as required.|
|Cost of system||$45,000||$25,000|
|Cost to operate||$1,500-$2,000/month||$65/month|
|Noise of compressor||Require earplugs and insulated building to dull the noise||Quieter than a central air conditioner 75 decibels|
|Ease of repair||Difficult and usually expensive||Can be done on-site|
|Compressor housing||Building with ventilation||Comes with weatherproof cabinet or can be placed indoors|
|Compressor system and maintenance||Filter and oil changes required||Filter changes and maintenance kit every 24 months|
|Airline||PVC pipe needs to be weighed down||Self-weighted lead free|
|Diffuser Plates||Large auger type bubbler weighted down with concrete blocks. Requires a commercial diver to install.||Self weighted PTFE coated to prevent clogging. Designed to entrain water from the bottom.|
|Automatic restart after power failure||No, system must be manually restarted each time.||Yes, system has a built in restart proving peace of mind.|
Several communities have come to the conclusion they need to replace their course bubble aeration system for fine bubble. The cost to run, as well as the noise reduction, have been identified as the drivers for switching. The communities who have made the switch have not seen any decrease in the DO levels of their waterbodies.
This is a compressor for fine bubble aeration which is many times quieter than coarse bubble aeration.