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Common problems of sludge treatment- MLSS abnormal

Source:Jiangsu Envset     Time:26 October 2020

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Mixed liquor suspended solids (MLSS) refers to the content of mixed suspended solids at the end of the aeration tank, expressed by MLSS, which is an indicator reflecting the number of microorganisms in the aeration tank. Next, we will briefly introduce the causes of abnormal mixed liquor suspended solids.


(1) The relationship with sludge age. Sludge age is an operable means to reach the sludge age index by removing activated sludge. Therefore, controlling the age of the sludge also results in a suitable sludge concentration range.
(2) The relationship with temperature. For the normal activated sludge flora, the microbial activity in it will double when the temperature drops by 10°C. Therefore, during operation, we only need to reduce the system sludge concentration when the temperature is high, and increase the system sludge concentration when the temperature is low to achieve the purpose of stabilizing the treatment efficiency.
(3) The relationship with the settlement ratio. The higher the concentration of activated sludge, the greater the final result of the sedimentation ratio, and vice versa. It should be noted that during operation, the settlement ratio increased due to the high concentration of activated sludge, and the observed settlement sludge is compressed and compacted; the increase in settlement ratio caused by the increase in the concentration of non-activated sludge is mostly inferior to compactness and dull color. The sedimentation ratio caused by low mixed liquor suspended solids is too low, and the observed sedimentation sludge has a dull color, poor compressibility, and sparse sedimentation of activated sludge.

Generally, it is difficult to increase the concentration of activated sludge in the following two situations:
1. When the sludge does not meet the various control indicators, it is difficult to upgrade, that is, it is mainly for SV30, micro-food ratio and MLSS in the activated sludge control indicators. According to the traditional activated sludge method, SV3015% is usually controlled, the MLSS value is 1100-2500mg/L, and the F/M value is above 0.08. If there is no control reference value that can reach the index, it can be considered that it has the ability to adjust and improve, and it is necessary to increase the concentration;
2. If the sludge meets the requirements of the process reference value, if the sludge meets the requirements of the process reference value, if the sludge concentration is difficult to increase, it is necessary to focus on analyzing whether it is necessary to upgrade.

Reasons for difficulties in upgrading and how to deal with them:
1. Excessive aeration and too high dissolved oxygen control: The effect of over-aeration on the increase of mixed liquor suspended solids is mainly manifested in the fact that the free bacteria produced during the process of activated sludge upgrading are easily oxidized by excessive aeration, making the concentration unable to go further Promote
2. Insufficient nutrient dosage: it is more effective to ensure that the nutrient is added in a reasonable amount, and it is more effective to judge whether the nutrient dosage is sufficient by detecting the residual nutrient of the effluent water quality;
3. The influent substrate concentration is too low;
4. Influent water contains excessive toxic or inhibitory substances.

Jiangsu Envset provides customers with a variety of high-quality wastewater treatment solutions. Our company sells professional sewage treatment equipment. If you have any questions about the abnormal concentration of activated sludge, please contact us.

Tag: Mixed liquor suspended solids, MLSS abnormal