Mineralization Explained

We are constantly going on about how an aquaponics system is sustainable and operates under minimal water consumption. However, what if we could optimize the system to become a zero-waste system? We understand that solid waste has to be removed from the system. But is there a way that we can utilize this waste to be beneficial to our system?

The concentrated sludge (fish waste) collects in the mechanical filter. This sludge contains valuable nutrients that could be beneficial to the system. The latest studies have shown that treating the sludge on-site is a great way to minimize the environmental impact as well as increase the nutrient cycle potential of an aquaponics system. The ultimate goal is to fully optimize an aquaponic system to become a closed-loop system and mineralization of solid fish waste is a way of contributing to this goal.

We like to use aerobic treatments to treat the sludge as this assists with the breakdown of organic matter. The aerobic treatment involves an oxidation process by exposing the sludge to oxygen. This exposure agitates the sludge as well as lowers the pH and releases bound minerals trapped in the sludge.  It provides your plants with water enriched with additional nitrates and a nutrient mix of iron, potassium, calcium and magnesium.

The oxidation of the sludge is carried out by the respiration of bacteria with CO₂, water and energy being the end product of the chemical reaction.

C₆H₁₂O₆ + 6O₂ -> 6CO_{2 +} 6H₂O + energy

Aerobic mineralization lowers the pH due to the CO₂ released and how it interacts with the water in the tank. This results in the formation of carbonic acid which then dissociates causing the pH to drop.

CO_2(g) + 2H₂O -> H₃O⁺ + HCO₃^–

The solid waste produced from the fish also contains ammonia. Therefore, by going through the process of mineralization you are ultimately optimizing your nitrate potential. Once the sludge is in the mineralization tank the ammonia is converted to nitrate using the oxygen provided through aeration.

NH₄⁺ + 2O₂ -> NO₃^_  + 2H⁺ + H₂O + energy

So now that you understand some of the chemistry behind the aeration process in mineralization, let’s take a look at the process taken to achieve it.

1. Remove the sludge from the mechanical filter and add it to your mineralization tank.
2. Add some molasses to your mixture, this assists in providing the bacteria with a sugar source as extra food.
3. Aerate your mineralization tank and wait for the magic to happen.
4. Once a week, turn off your air and wait for everything to settle.
5. The solids will settle to the bottom of your tank and there will be nutrient-rich water lying on the surface of the tank.
6. This clear water can be syphoned off and dosed back into your aquaponics system. You can do this using your dosing bucket.
7. Yes, it’s that easy.

Due to the simplicity of this process, you could even look at automating the syphon using a valve to feed the nutrient-rich water back into your dosing bucket and then your grow beds. This is because the process of aerobic mineralization does not require any pre-or post-treatment of the sludge.

We love using mineralization in our systems because it requires little to no effort while reaping the most benefit. Plus, it contributes to the beautiful sustainable, nutrient-cycling process of aquaponics. If you are intrigued and want to know more about how aquaponics works, check out our blog for more information, or better yet, join us for our next course.