Procedure To Clean Your Aeration Diffusers Regularly

Article written by: Jason Danaher Ph.D. 

A fish farmer operating a recirculating aquaculture system will need to maintain efficient oxygen transfer rates to ensure their fish continue to grow and extend the life of the low pressure aeration system (i.e. regenerative blower). Traditionally, silica-based diffusers are utilized in the aquaculture industry to maintain oxygen concentrations in fish tanks and biofilters (Figure 1). The diffusers create a medium-sized air bubble with a surface area to volume ratio appropriate for high oxygen transfer rates. 

Figure 1. Aeration manifold used in aquaculture with glass silica-based diffusers.

Over time fouling of the diffuser will occur. The surface of the diffuser along with the internal void spaces will become colonized with bacterial films naturally present in the system water. Also, dissolved calcium in the system water reacts with carbon dioxide (CO2) generated as a byproduct of fish and microorganism respiration to form calcium carbonate (CaCO3). The deposition of calcium carbonate and other compounds, like calcium phosphate [Ca3(PO4)2], on the diffuser surface is known as “scaling” in the aquaculture industry. Biofilms and scaling can lead to significant decreases in the volume of air emitted by diffusers and significantly increase the back pressure on the regenerative blower because the volume of air generated cannot quickly escape through the diffuser and into the water. 

If you have visually noticed a decrease in the volume of bubbles released by a diffuser, certain diffusers on the same distribution line releasing more air volume than others, or oxygen concentration has consistently been less than historical concentrations, it is time to inspect the diffusers and perform simple maintenance to return them to working order. The maintenance routine described below using muriatic acid will remove biofouling and mineral deposits and allow the diffuser to once again emit the intended volume of oxygen to maintain fish growth and health. In addition, unwanted back pressure on your regenerative blower will be reduced; thus, increasing its longevity and saving you money on the monthly utility bill. 

Muriatic acid is a diluted form of hydrochloric acid (HCl) and is easy to find in home improvement or swimming pool supply stores. Prior to cleaning the diffusers there are safety precautions to follow when handling muriatic acid:

• Read the product Safety Data Sheet (SDS) and always wear appropriate personal protective еquipmеnt (PPE) including glovеs, gogglеs, and protеctivе clothing to shiеld your skin and еyеs from potеntial еxposurе to muriatic acid or solutions containing it. 

• When using muriatic acid, it is еssеntial to dilutе it with watеr according to thе instructions provided. ALWAYS add thе acid to watеr slowly and carefully to prevent splashing or chеmical reactions. 

• NEVER add water directly to the acid.

• Work in a wеll-vеntilatеd arеa or usе propеr rеspiratory protеction to avoid inhaling thе fumеs gеnеratеd by muriatic acid. Adеquatе vеntilation hеlps rеducе thе concеntration of acid vapors in thе air and cleaning diffusers outdoors is the best option.

• Avoid mixing muriatic acid with othеr clеaning products, еspеcially chlorinе blеach. Combining thеsе substancеs can produce toxic chlorinе gas, which poses a severe health risk. 

• Propеr disposal of muriatic acid is crucial to prеvеnt еnvironmеntal damagе. Refer to the SDS or contact your local wastеwatеr trеatmеnt plant or hazardous wastе collеction cеntеr for guidancе on safе disposal mеthods.

Diffuser Cleaning Procedure:

1. Remove the dirty diffuser(s) from the aquatic system. 

2. Using a hand brush, give the diffuser(s) surface a quick scrub to remove surficial biological growth and then rinse with freshwater. 

3. Next, make sure you are wearing the proper PPE and then mix a 1:1 solution of muriatic acid and water (based on volume) together in a plastic container large enough and deep enough to contain the diffuser(s) and ensure each diffuser remains submerged. 

4. Soak the diffuser(s) for 20 to 30 minutes in the 1:1 solution of muricatic acid and water.

5. Then, making sure you are wearing the proper PPE again, carefully remove the diffuser(s) from the solution and rinse it with freshwater. Be careful as even the weakened acid during the rinse process can still damage your skin. 

6. Reinstall the clean diffuser(s) and repeat process for any additional diffuser(s).

7. Finally, properly dispose of the cleaning solution when all diffusers are cleaned.

Figure 2. Diffuser manifold system showing a diffuser experiencing biofouling (left) and a recently cleaned diffuser (right) using muriatic acid. 

Photo credit: Jennifer Holdsworth.

Remember that regular maintenance and cleaning prevent clogging and biofouling from negatively affecting the health of your fish. By identifying and addressing common diffuser problems, like biofouling and scaling, you can improve your oxygen transfer efficiency, reduce energy costs, and extend the life of your aeration system. Feel free to call Aquatic Equipment & Design, Inc. staff at 407-995-6490 or email info@aquaticed.com for additional information and tips on maintaining your diffusers and low pressure aeration system.