Frequently Asked Questions and Troubleshooting in Activated Sludge Process (Part 2)
Q: I ran into a problem. In the past few days, we found that the sludge was floating in lumps in the secondary sedimentation tank, which was very loose. It may be due to swelling of the sludge, which is not serious. But I am very surprised that the MLVSS of the biochemical tank is about 2000mg/l, the sludge age is relatively short, the sludge is not aging, and it is within the control range. The dissolved oxygen at the end of the biochemical tank is between 2-4, which is good. (We use the siphon to absorb the returned sludge. According to my observation, the return system of the second settling tank is normal, and the sludge sedimentation in the second settling tank is basically returned). The COD of the inlet water is not very high. The COD of the secondary effluent is below 60mg/l (should be very good), and the entire biochemical system is very normal. In this case, why does sludge bulking occur? There is also the three secondary settling tanks we are using. Why is sludge floating and loosening occurred in only one, while the other two are normal?
1. First of all, it should be confirmed whether there is filamentous bacteria expansion in the activated sludge, and how is the degree of expansion.
2. Usually the following methods can be judged: a, SV30 detection. b. SVI detection. c. Microscopic examination. But it seems that these three parameters are not in the information you gave me.
3. My experience is that the swelling of filamentous bacteria is related to the single composition of wastewater, insufficient dissolved oxygen, and low dietary ratio. Other reasons such as pH and temperature will not caused it, but at best they play a supporting role.
4. The wastewater component is single, the growth of normal bacterial micelles is easily inhibited, and some wastewater components are beneficial to the proliferation of filamentous bacteria.
5. Insufficient dissolved oxygen, aeration has a dead zone, which is also conducive to the proliferation of filamentous bacteria, which is mainly reflected in the huge surface area of the filamentous bacteria pen and the low oxygen environment is more conducive to its proliferation.
6. The reasons for the proliferation of filamentous bacteria that are too low are basically the same as for insufficient dissolved oxygen.
7. The environment in which normal micelles and filamentous bacteria are located determines whether filamentous bacteria will swell.
8. Determine whether filamentous swelling occurs through diagnostic means.
9. If it is filamentous bacteria swelling, your three secondary sedimentation tanks will swell at the same time. It is impossible for only one to swell, so please also confirm whether filamentous bacteria swells.
Q: What problems should be paid attention to when debugging a new sewage plant? What are the main steps? Where should I find relevant information? (Anaerobic UASB + high-load biological filter method/solid contact method).
1. Commissioning issues I think you should consult the design and construction unit of your environmental protection facilities! Generally speaking, the construction unit is responsible for commissioning and staff training.
2. Sludge inoculation and load adjustment are the most important tasks.
Q: How is the effluent compliance rate of the sewage plant calculated? Is there a weekly average, and how to calculate? Is there any mandatory requirement for the effluent compliance rate?
As far as I know, it seems that there is no hard and fast rule, and the internal management of the enterprise can have this term. The cycles can be set by yourself.
Q: When beer wastewater is treated by contact oxidation, a large amount of foam will be produced, and the COD of the effluent is unstable. Why this happened?
1. Beer wastewater is sewage with a high B/C ratio, which is easily degraded by biological systems. Therefore, the biological activity is higher. When the impact load is large and the food-micrometer ratio is too high, a large amount of foam (white) is especially prone to be produced. Generally, the foam generation can be alleviated by increasing the concentration of activated sludge.
2. Because beer wastewater is affected by the production process, the water volume and concentration of each time period of the day vary greatly. When the adjustment tank does not have a large adjustment capacity, it is especially easy to produce shock loads. As a result, it's possible that foam generation and effluent indicators are unstable.
3. Of course, the ph of beer wastewater changes greatly and should be adjusted properly to ensure that the ph of the wastewater entering the biochemical tank is adjusted in place, otherwise foam may also be generated, but this mostly occurs during accidental operation.
Q: Drainage of multiple printing and dyeing enterprises wastewater gather for centralized treatment. The main process is physicochemical-anaerobic-aerobic, and the aerobic process is activated sludge process. The current situation is that the aerobic influent COD is about 600mg/l and the sulfur is about 100mg/l. , The COD of the effluent of the aerobic tank is about 100mg/l, the sludge concentration (MLSS) is about 800mg/l, the F/M is about 0.35, and the dissolved oxygen at the end of the aerobic tank is about 2mg/l. The tricky problem is that the sedimentation performance of the sludge in the secondary sedimentation tank is very poor, mostly in a suspended state, and the effluent loss is serious. The sludge concentration at the bottom of the secondary sedimentation tank is very low, not much higher than that in the aeration tank. The loss of sludge leads to the quality of the effluent exceeded. There is a small amount of filamentous bacteria in the sludge microscopic examination. I suspect that the reason for the suspension of the sludge is the expansion of the combined water sludge, but I cannot tell because I know less about it. I want to know your opinion, any good countermeasures? And whether S2- that is too high in the water will cause sludge poisoning? And what are the consequences to the sludge?
1. The COD removal rate is 83%, which should be ok, because the source water you are dealing with is difficult to treat.
2. The indicators are also well controlled.
3. Regarding the floating mud phenomenon in the effluent, I think it is related to the quality of the source water you are treating. I don't know how the SV30 settles, so it is not easy to judge, but I think there are two manifestations of activated sludge suspension: a. The activated sludge is suspended after flocculation. b. Activated sludge does not flocculate and suspend. A is formed by activated sludge enveloping bubbles, and B is caused by sludge expansion.
4. Generally, the source water contains a large amount of sulfide, which easily leads to the reproduction of filamentous bacteria containing sulphur particles and causes the sludge to produce floating mud. At the same time, if the sulfide content is too high, the sludge will easily reduce its activity, leading to bleaching mud. Therefore, it should be attributed to the fact that the sulfide content is too high and the bleaching mud is caused.
5. I think it can alleviate the phenomenon of floating sludge to increase the concentration of sludge appropriately. At the same time, with the operation of the system, activated sludge should be domesticated to adapt to the water quality like this.