Recently, many friends have encountered the problem of activated sludge loss while working in sewage treatment plants, which is a headache to deal with. Activated sludge is like the 'capable worker' of a sewage treatment plant, without it, the sewage cannot be treated completely. Today we will break and crush it, and talk about what is the loss of activated sludge and how to solve it!
The loss of activated sludge, these reasons are 'ridiculous'
There is a problem with aeration
The aeration process is like providing oxygen to activated sludge. If the supply is not appropriate, the sludge is prone to malfunction. First of all, excessive aeration is like constantly making you gasp for breath, which you can't take for a long time. Excessive aeration can lead to excessive metabolism of microorganisms in activated sludge, causing the sludge structure to be disrupted and become loose, making it easy for it to escape with the water flow. There is also insufficient aeration, at which point microorganisms are like fish lacking oxygen, with decreased vitality, poorer settling performance, and ultimately leading to sludge loss. For example, in some sewage treatment plants, due to fan failure, aeration suddenly becomes insufficient, and within a few days, it is found that the sludge in the sedimentation tank has significantly decreased.
The water quality fluctuates too violently
The quality of the sewage we treat can vary greatly. If a large amount of toxic and harmful substances, such as heavy metals and high concentration acidic and alkaline wastewater, suddenly rush into activated sludge, it is similar to "poisoning". These substances can inhibit the growth of microorganisms, and even directly "poison" them. When microorganisms die, the sludge structure disperses and is lost. It's also not feasible to have too much variation in the organic load of the incoming water. For example, in food processing plants, the production volume during holidays is large, and the organic matter in the discharged sewage suddenly increases. Microorganisms cannot digest it, and the sludge becomes unstable, resulting in loss.
Sludge aging
Activated sludge also has a lifespan. If the age of the sludge is too long and microorganisms continue to "die and not interact with each other", it will lead to the aging of the sludge. The color of aged sludge becomes darker, the structure becomes loose, and the settling performance deteriorates, making it easily lost with the effluent. Like vegetables that have been stored at home for a long time, wilting and lacking their original resilience. Some sewage treatment plants, due to improper management, fail to discharge sludge in a timely manner, and the age of the sludge exceeds the normal range by several times, resulting in severe sludge aging and increasingly serious loss problems.
The 'enemies' of microorganisms are causing trouble
In addition to the above, there are also some microbial "enemies" that can cause sludge loss. For example, excessive proliferation of filamentous bacteria, like messy hair, can entangle activated sludge, making it loose and easily lost under the action of aeration and water flow. There are also some post protozoa, such as rotifers and nematodes, which, if in large numbers, will ingest a large number of microorganisms in activated sludge, destroy the sludge structure, and lead to sludge loss.
Secondary sedimentation tank "not awesome"
The secondary sedimentation tank is a crucial location for sludge sedimentation and separation. If the hydraulic load of the secondary sedimentation tank is too high and the water flow speed is too fast, like a turbulent river, the settled sludge will be washed away by the water flow before it can stand firm. The design of the secondary sedimentation tank is also unreasonable, such as poor tank type and abnormal operation of the scraper, which can affect the sedimentation and reflux of sludge, leading to sludge loss. Some sewage treatment plants have malfunctions in the secondary sedimentation tank scraper, which cannot timely remove the sludge. The sludge accumulates and ferments at the bottom of the tank, and eventually flows away with the water flow.
Don't panic! These measures are extremely effective
Adjust the aeration system
If excessive aeration is found, quickly reduce the aeration rate. The aeration rate can be controlled by adjusting the speed of the fan and the opening of the valve. At the same time, install an online dissolved oxygen monitor to monitor the dissolved oxygen content in water in real time, and control the dissolved oxygen within an appropriate range. Generally, the dissolved oxygen in aerobic tanks is controlled at 2-4mg/L. If there is insufficient aeration, promptly inspect the aeration equipment such as fans to see if there is a malfunction, repair what needs to be repaired, and replace what needs to be replaced. You can also increase the number of aeration devices or adjust the layout of aeration heads to make aeration more uniform.
Stable water quality
In the face of water quality fluctuations, we need to take precautions in advance. Before the sewage enters the treatment system, a regulating tank is set up to mix the sewage of different time periods and water qualities evenly, making the water quality more stable. For wastewater containing toxic and harmful substances, pre-treatment must be carried out, such as removing heavy metals and acid-base substances through neutralization, precipitation, and other methods. Water quality monitoring equipment can also be installed at the inlet. Once abnormal water quality is detected, the treatment process can be adjusted in a timely manner, or the sewage can be directed to the accident pool to avoid impacting the activated sludge.
Control the age of sludge
Regularly monitor the sludge age and control it reasonably based on the treatment process and water quality. Generally speaking, different processing techniques have different suitable ranges of mud age. For example, in the ordinary activated sludge process, the sludge age is controlled at 3-5 days; The biofilm method can extend the mud age by 10-30 days. When signs of aging are found in the sludge, increase the discharge volume in a timely manner, discharge the aged sludge, and allow new sludge to be replenished to maintain the activity of the sludge. At the same time, do a good job in the treatment and disposal of sludge to avoid secondary pollution.
Dealing with Microbial 'Enemies'
If filamentous bacteria overgrow, the first step is to adjust the nutrient ratio of the incoming water. Many times, the proliferation of filamentous bacteria is due to the imbalance of carbon to nitrogen ratio in wastewater. Increasing nitrogen and phosphorus sources appropriately can balance microbial nutrition and inhibit the growth of filamentous bacteria. Chemical agents can also be added, such as sodium hypochlorite, hydrogen peroxide, etc. These agents can kill some filamentous bacteria, but attention should be paid to controlling the dosage to avoid harm to other microorganisms. For cases where there is an excessive number of metazoa, it is possible to increase the sludge reflux rate, dilute the concentration of metazoa, or add some drugs that have inhibitory effects on metazoa.
Optimize the operation of the secondary sedimentation tank
If the hydraulic load of the secondary sedimentation tank is too high, the inflow should be appropriately reduced, or the secondary sedimentation tank should be modified to increase its volume and reduce the hydraulic load. Check the operation of equipment such as mud scraper, conduct regular maintenance and upkeep to ensure the normal operation of the equipment. It is also possible to adjust the operating parameters of the secondary sedimentation tank, such as adjusting the sludge return ratio, to facilitate better sedimentation and return of sludge. At the same time, strengthen the inspection of the secondary sedimentation tank, promptly identify problems, and handle them in a timely manner.
Although the loss of activated sludge is a common problem in the sewage treatment process, as long as we understand the cause, prescribe the right medicine, and take appropriate treatment measures, we can definitely solve this problem. I hope the content shared today can help everyone and ensure the smooth operation of the sewage treatment plant!
