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Hello everyone, today we will discuss a common and important issue in aerobic tanks—activated sludge turning white. Normally, the activated sludge in the aerobic tank should be brownish-yellow. When color changes, especially turning white, it may indicate potential problems in the system.
The whitening of activated sludge not only affects the system’s stability but may also lead to a decrease in wastewater treatment effectiveness. Therefore, understanding the causes and taking timely actions are key to ensuring the system runs efficiently.
Why Does Activated Sludge Turn White in the Aeration Tank?
- Unbalanced Carbon, Nitrogen, and Phosphorus If there is not enough carbon or nitrogen in the water, microorganisms cannot grow well. This can cause the sludge to become loose and turn white.When there is a lack of nitrogen or phosphorus, microorganisms will preferentially utilize other available nutrients for growth, leading to loose sludge structure and resulting in sludge whitening.
- Too Much Aeration Excessive aeration is another common cause of sludge whitening. Excessive fan power or aeration rate, especially during the “explosion” phase when activated, may lead to excessive dissolved oxygen.Excessive oxygen supply can accelerate the oxidation reaction of microorganisms, destroy the structure of microbial flocs, and cause changes in the characteristics of sludge, resulting in whitening phenomenon. Long term over aeration may also lead to the formation of small white flocs, further affecting sludge settling and treatment efficiency.
- High load impact or low dissolved oxygen When the COD concentration in the inflow suddenly increases, the system will encounter high load impact. The sudden increase in oxygen demand by microorganisms leads to a rapid decrease in dissolved oxygen, resulting in sludge swelling and whitening. At the same time, when the dissolved oxygen is too low, microorganisms are unable to effectively decompose organic matter, which in turn affects the flocculation of sludge and leads to a whiter appearance of the sludge.
- Low pH in the Water If the water has a very low pH (below 6), it can harm the microorganisms in aerobic tank. In acidic conditions,In acidic environments, filamentous bacteria are prone to growth and occupy a dominant position in the system. The rapid proliferation of filamentous bacteria can cause sludge bulking and affect the formation of bacterial flocs, ultimately leading to the whitening of sludge.nd cause the sludge to become loose and white.
Solutions to White Activated Sludge
Based on the above causes, we can take the following measures to solve the white sludge problem and ensure stable operation of the aeration tank:
- Adjust the Carbon, Nitrogen, and Phosphorus Ratio Make sure the carbon, nitrogen, and phosphorus in the water are balanced. Add enough carbon, nitrogen, and phosphorus sources to help microorganisms grow. Especially during long periods of low load, provide enough nutrients to prevent bulking and whitening.
- Control Aeration Amount Avoid over-aeration. Keep the air supply and dissolved oxygen at the right level. Regularly check the aeration system and equipment to make sure they are working well, and prevent too much oxygen from affecting microbial activity.
- Optimize System Load Control the influent flow and COD concentration to avoid high load shocks. If COD levels fluctuate a lot, consider adjusting the system’s operating conditions to keep the sludge in the best state and avoid whitening due to lack of oxygen.
- Adjust Influent pH Adjust the pH level to keep the water’s acidity in the right range for microbial growth. Avoid too low pH, as it can cause excessive growth of filamentous bacteria, which affects sludge flocculation and makes the sludge look white.
Summary: Keeping the Aeration Tank Sludge Healthy
White activated sludge is a common issue in aeration tanks, usually caused by imbalances in carbon, nitrogen, and phosphorus, over-aeration, high load shocks, and low pH. By understanding these causes, we can take the right actions to keep the wastewater treatment system running smoothly and ensure the treated water meets the standards.
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