Questions of Aging Sludge
The aging of Activated Sludge is usually related to excessive aeration and low load, which will consume excessive energy.
Reasons for Activated Sludge Aging
1. The sewage treatment system is under low load for a long time
The concentration of organic pollutants in the influent water is too low, and it is maintained in the state of low organic pollutants for a long time, such as COD lower than 100mg/L. Theoretically, if the influent concentration and flow rate are too low, it is OK to reduce the concentration of activated sludge. However, do not ignore that if the influent concentration is too low, the chance of activated sludge colliding with each other is too low, which ultimately leads to the phenomenon that activated sludge cannot flocculate and settle.
2. Aging of activated sludge caused by excessive aeration
Excessive aeration will lead to the disintegration and oxidation of activated sludge. Oxygen in the air is an oxidant. Excessive aeration will naturally lead to the oxidation of some bacteria in the activated sludge and the disintegration of the biocolloids.
3. The activated sludge concentration is too high
The activated sludge concentration is too high and there is no support of the metal substrate concentration. In short, the proportion of C, N and P is seriously unreasonable. It will eventually lead to aging of activated sludge.
4. Sludge discharge is not timely
Sludge discharge is the most commonly used means to control the concentration of activated sludge. The untimely discharge of sludge has a considerable impact on the sludge. If the sludge is not discharged for a long time, the activated sludge will age at the fastest speed.
Judgments of Activated Sludge Aging
Judgment 1:The aged activated sludge is easy to disintegrate, so small bacteria will dissociate in the water. But the water between the bacteria in the free state is still very clear. The sewage will not be turbid, but it will be seriously disintegrated in the late aging period, which will lead to turbid effluent!
Judgment 2:The aeration tank begins to produce a mixture of foam and scum, which is generally a thin layer, does not accumulate, and is gray in color (judged according to the color of the system).
Judgment 3:The mycelia become thick, and the sludge color changes from light to yellow or appears very dark, gray black, without fresh luster.
Judgment 4:The foam produced by the sludge from the returned secondary sedimentation tank is between the surfactant and the biological foam, and it feels a little sticky.
Judgment 5:Microscopic examination showed that the sludge structure was loose, with less filamentous bacteria, more rotifers and fewer protozoa.
Solutions of Activated Sludge Aging
1. Requirements for activated sludge age control
In order to ensure that the activated sludge will not age due to untimely sludge discharge during the operation of the biochemical system, it is necessary to frequently confirm the relationship between the current sludge discharge flow and the activated sludge concentration, and indirectly guide the control of the activated sludge discharge flow through the confirmation of the food micro ratio. At the same time, the uniformity of sludge discharge flow must be achieved to avoid excessive gap and flow fluctuation.
2. Uniformity of aeration and prevention of over aeration
Effectively control the aeration volume to avoid over aeration, and control the DO concentration at the outlet of the aeration tank to about 2.5mg/L. At the same time, it can also reduce the excessive power consumption of aeration and reduce the treatment cost.
3. Avoidance of low load operation
Avoid the occurrence of low load operation state, so as to avoid the occurrence of activated sludge aging. In addition to improving the concentration and biodegradability of the substrate in the influent as much as possible, it is more important to reduce the concentration of activated sludge as much as possible to ensure that the food to micro ratio can be kept within a reasonable control value (about 0.15-0.25). If necessary, additional carbon sources can be added to ensure the normal operation and reproduction function of activated sludge, such as adding septic tank water and introducing domestic sewage.
4. Add MBR process
The MBR process replaces the secondary sedimentation tank to separate HRT from SRT. Its filtering effect solves the long-term serious sludge aging problem without too much impact on the effluent.
Aging of Activated Sludge is a common phenomenon in most aerobic biochemical systems currently in operation, and aging of activated sludge will not only lead to the increase of main pollution indicators of effluent, but also lead to energy waste.
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