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Hello everyone! Today, we’re going to discuss an important but often overlooked topic in wastewater treatment—alkalinity supplementation in aerobic tanks. Alkalinity plays a key role in the nitrification process, directly affecting the growth and efficiency of microorganisms.Today, we will briefly introduce: Why do aerobic pools need to be supplemented with alkalinity? And how to choose the right base to supplement the alkalinity.
Why do aerobic tank need to be supplemented with alkalinity?
During wastewater treatment, especially in nitrification reactions, nitrifying bacteria convert ammonia nitrogen in water into nitrates and nitrites. This process consumes a lot of alkalinity. In the denitrification process, although the denitrifying bacteria will produce some alkalinity, it is far from enough to make up for the consumption of the nitrification reaction. Therefore, if the alkalinity is not replenished in time, the pH value in the tank will decrease, which will affect the growth of nitrifying bacteria, and thus reduce the treatment efficiency.
Especially when the pH value of the water source itself is low (less than 6.5), the pH value will further decrease after biochemical treatment. If not controlled, this will affect the smooth progress of the nitrification reaction, and even lead to a serious slowing down of the reaction rate.
How to Supplement Alkalinity?
So, how to supplement the alkalinity in the aerobic tank? There are many kinds of alkaline agents commonly used on the market, such as: soda ash, tablet soda, liquid soda, sodium hydroxide and sodium bicarbonate. The alkalinity of each base is different, and the application is also different.
Comparison of Different Alkalis
- Sodium Carbonate (Soda Ash) – The Most Common Choice
Soda ash is the most commonly used agent to supplement alkalinity. Its alkalinity is relatively mild, it is safer to operate, and it is not easy to cause excessive pH fluctuations. Although a larger dosage is required, soda ash is very common in the aerobic tank because it is relatively easy to control.
- Sodium Hydroxide (Caustic Soda) – Strong but Risky
Both solid (caustic soda flakes) and liquid sodium hydroxide have high alkalinity and are mainly used for rapid pH neutralization.Because of their strong alkalinity and relatively small dosage, they are not suitable for alkalinity supplementation in aerobic tank.
If the pH exceeds 8.5, ammonia nitrogen may volatilize, further affecting microbial activity. For this reason, caustic soda is not recommended for alkalinity control in aerobic tanks.
- Sodium Bicarbonate (Baking Soda) – Mild but Inefficient
This alkalinity is small and the dosage is large. Although it can supplement alkalinity, excessive use may cause gas release, foam production, and affect the normal operation of the reaction tank. Therefore, in general, the use of sodium bicarbonate is not as widespread as soda ash.
Maintaining proper alkalinity is crucial for stable nitrification in aerobic tanks. Due to its mild properties, soda ash has become the most commonly used alkaline agent, which can effectively regulate the pH value while avoiding adverse effects on microorganisms due to high pH value. Relatively speaking, tablet soda, liquid soda, etc., are more used for acid-base neutralization, so it is not recommended for alkalinity supplementation in aerobic tank.
Understanding these basic knowledge can help you better carry out sewage treatment, ensure the smooth progress of the reaction, and improve the effect of water treatment.
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