1. If sludge turns white during operation
Cause of occurrence:

Lack of nutrition, excessive proliferation of filamentous or fixed ciliates, and poor growth of bacterial colonies;

High or low pH values can cause a large number of filamentous bacteria to grow, resulting in loose sludge and larger volume.

Solution:

Adjust the influent load according to the nutritional ratio, add ammonia nitrogen dropwise, and maintain the sludge color for several days to recover;

Adjust the pH value of the influent and maintain the pH value of the aeration tank between 6 and 8. Maintaining the pH value range for a long time can effectively prevent sludge expansion.

2. If black sludge is found during operation

Cause of occurrence:

The dissolved oxygen in the aeration tank is too low, and the anaerobic decomposition of organic matter releases H2S, which reacts with Fe to generate FeS

Solution:

By increasing the oxygen supply or reflux sludge, as long as the dissolved oxygen in the aeration tank is increased, the sludge will gradually return to normal after more than 10 hours.

3. Difficulty in sludge filtration or increased effluent chromaticity during the laboratory process

Cause of occurrence:

Lack of nutrition or low water temperature, poor sludge growth, and a large amount of sludge deflocculation

Solution:

Increase load balancing nutrition, increase water temperature, and improve the growth environment of sludge.

4. A large number of bubbles are generated in the aeration tank

Cause of occurrence:

The high inflow load and high impact load cause some sludge to decompose and adhere to bubbles, making them sticky and not easily broken, resulting in the accumulation of a large number of bubbles on the water surface.

Solution:

Reduce the inflow and slightly increase the amount of returned sludge. After stabilizing for a period of time, the bubble reduction system gradually returns to normal.

5. The aeration tank produces tawny or gray foam

Cause of occurrence:

The sludge is aged and the sludge age is too high, and the sludge after flocculating is attached to the foam.

Solution:

Increase sludge discharge and gradually update the newly generated sludge in the system. The sludge renewal process needs to last for several days, during which the operating environment should be well controlled to ensure that the newly generated sludge has strong activity (ensuring a stable level of dissolved oxygen between 1.0 and 3.0, a balanced proportion of nutrients, and appropriate addition of nutrients).

6. There are large pieces of black sludge floating up in the sedimentation tank

Cause of occurrence:

The sedimentation tank has dead corners and local sludge accumulation is anaerobic, producing CH4 and CO2. Bubbles attach to the sludge particles, causing them to float upwards. The effluent ammonia nitrogen is often high;

The reflux ratio is too small, and the sludge reflux is not timely, causing anaerobic conditions.

Solution:

If there are dead corners in the sedimentation tank, the problem of maintaining the system in a high dissolved oxygen state can be alleviated. The fundamental solution requires structural modifications to the dead corners to achieve;

Increase the reflux ratio to prevent sludge from staying in the sedimentation tank for too long.

7. The mud level in the sedimentation tank is too high, and the suspended solids in the effluent increase

Cause of occurrence:

Excessive load and incomplete decomposition of organic matter affect the sedimentation performance of sludge, resulting in poorer sedimentation efficiency;

The load is too low, the sludge lacks nutrients, and the flocculation performance deteriorates due to the increase of low nutrient tolerant bacteria;

The sludge age is relatively long, the sludge concentration in the system is too high, and the sludge structure is loose and not easy to settle;

Excessive water temperature leads to an increase in small molecule organic matter, and bacterial micelles adsorb too much organic matter, resulting in sludge flocculation.

Solution:

Reduce the load to reduce the total amount of influent COD, increase dissolved oxygen to gradually restore sludge performance;

Increase the water intake and control it within an appropriate range, maintain a high dissolved oxygen state for a period of time, and inhibit the further increase of low nutrient bacteria;

Increase the discharge of excess sludge and control the sludge concentration in the system within a reasonable range;

Reduce the water temperature in the aeration tank, control the dissolved oxygen level well, and after a period of time, the sludge can return to normal.

8. Sludge bulking

In activated sludge systems, sometimes the settling performance of sludge deteriorates, the specific gravity decreases, and the volume increases, making it difficult for sludge to settle in the sedimentation tank. In severe cases, sludge overflows and loses, resulting in a sharp decrease in treatment efficiency. This phenomenon is called sludge bulking. Sludge bulking is the most difficult problem to solve in activated sludge systems, and there is still no good solution.