1. Q: How to distinguish sludge poisoning from sludge aging in appearance?

A: Generally speaking, serious aging of sludge will have a development process, and sludge poisoning will quickly cause cell disintegration. The ESS of effluent will increase obviously when sludge is aged and poisoned, and experienced people can distinguish from each other apparently. When sludge aging, the suspended solid particles in effluent are relatively larger, mostly fragmented. The suspended solid particles in effluent are relatively small when sludge is poisoned. Sludge poisoning and sludge aging can also be distinguished from the change of DO value. The process of sludge poisoning is faster, which will cause DO to rise in a short time. Sludge aging has a gradual process, and the process of DO rising is also gradual.

2. Q: Debugging a slaughterhouse wastewater, the process is: septic tank (HRT > 2d) - regulating tank - hydrolysis tank (HRT = 5) - contact oxidation tank (HRT = 6) - secondary clarifier. Because the COD of the effluent from the former septic tank is 700 and the contact oxidation time is relatively short, the water contact tank is changed into an aeration tank, but the effect of a diving aerator added is generally less than 0.5 DO, and the DO of the original aeration tank is normal. The SV of the two tank can reach 20~30. Now the influent volume is 70% of the designed water. The water quality of the effluent is still very poor, and the SS is more. The original aeration tank has a certain foam and thicker. Is it caused by the aging of the sludge?

A: COD700 is very normal. The foam has nothing to do with ammonia nitrogen. To determine whether it is biological foam or chemical foam, such as chemical foam, it will gradually decrease under such concentration of sludge. It is not possible to use water spray to eliminate bubbles. It feels that your sludge activity is poor, probably due to better nutrition than uncontrolled, such as nitrogen and phosphorus.

3. Q: There is less and less sludge in the aeration tank. The COD of the influent is about 100-200 mg/L. It is difficult for the sludge to grow. There is more dead sludge in the unused tank. What can we do?

A: Intermittent aeration can be used to discharge some sludge in a proper amount, although the amount of sludge is very small, if not, it will be less.

4. Q: One of our projects has been running for one year. Recently, due to the deterioration of the water quality, the S content in the biochemical device has reached about 100. Now the S content in the biochemical device is about 10. It has five days to recover. The COD in the influent is about 600, the COD in the effluent is about 300. Under the 10x16 microscope, we can see some dendritic things and some very small things (needle tip size). I don't know what it is. Sludge concentration is almost zero. How to adjust it? Should the sludge be oxidized and the gas volume be reduced?

A: It shows that the sludge has been severely damaged and disintegrated. It needs to be re-cultured.

5. Q: The sewage treatment system has just been built and is ready to start operation. The process: regulating pool - hydrolysis pool - anaerobic pool - aerobic pool - sedimentation pool - sludge treatment system will start trial operation soon. It is proposed to use inoculation and domestication. What are the specific points for attention in driving and domestication?

A: Static culture should be adopted in the initial stage of bacterial culture. After the initial formation of sludge, attention should be paid to preventing excessive self-oxidation of sludge. Many factories have experienced this kind of situation. Sludge does not increase or even decrease for a long time. The reason is that the nutrition and aeration time are not well controlled. Sludge is growing while it is continuously oxidizing itself. In the later stage of activated sludge culture, although the sludge concentration is low, some sludge should be discharged properly, which will be conducive to the further growth and reproduction of microorganisms.

6. Q: Anaerobic sludge culture method and matters needing attention in debugging process.

A: There are many ways to cultivate anaerobic sludge. It is suggested to adopt the step-by-step cultivation method. The general process is as follows: the excess sludge (anaerobic) of the aerobic system is put into the anaerobic reactor through the concentrator, and the dosage is about 20-30% of the reactor capacity. Then, heating (if heating is needed), gradually increasing the temperature to 1 C per hour, when the temperature rises to the required temperature for digestion (according to the design temperature). ) Maintain temperature. Nutrients should be gradually increased with the increase of microbial biomass, and should not be rushed. When the organic matter is hydrolyzed and liquefied (it takes one or two months), the sludge matures and produces biogas, the composition of biogas is analyzed, the ignition test is carried out normally, and then the biogas is used for daily operation. Initial start-up general control has lower organic load. When CODcr removal rate reaches 80%, the organic load can be increased gradually. Acetic acid concentration should be controlled below 1000mg/L when starting. The above is only a general requirement. It's better to ask experienced people for guidance.

7. Q: In some forums, we often see such a statement as "too much aeration, too high DO, bacterial self-oxidation, too low load, microbial self-oxidation, leading to flocculation". In ASM1, ASM2, ASM3 The growth coefficient of microorganisms is closely related to the concentration of matrix, which is a variable. When the organic load is low and oxygen supply is sufficient, microorganisms will quickly consume BOD in water, stop the growth and only attenuate, resulting in a net increase of 0, or even negative, and make the biomass increase and decrease. Therefore, it is appropriate to say that self-oxidation occurs at any time, not at low load and high DO.

A: It is true in theory, but sludge ageing is not limited to such understanding in actual operation. Although sludge ageing is mainly caused by the long-term lack of nutrition of microorganisms, that is, the imbalance between nutrition and microbial biomass, and the normal growth of microorganisms, the actual operation of the treatment unit is more complex, and the activity of sludge is also related to operation control conditions, nutrition ratio and other factors. 。 Some devices will have the following conditions: when the influent concentration is normal, and the carbon-nitrogen ratio or carbon-phosphorus ratio is low, the sludge activity will be very poor, which limits the degradation of organic matter by microorganisms and reduces the energy generated; when the influent concentration and nutrient ratio are normal, but because the excess sludge is not discharged as required, and the aeration time is too long, the sludge will be loose and inactive. Such sludge is also known as ageing.

8. Q: This unit adopts the front-end Obel oxidation ditch process, which has some problems in operation recently. Design water intake 50,000 tons per day, COD350, BOD150, ss220, actual water intake 5000m3/d per day, COD300, BOD120, SS180; Operation mode is that four thrusters are fully opened inside and outside ditches, dissolved oxygen in inside and outside ditches is controlled at 3mg/L (recent laboratory test of dissolved oxygen is different from on-line instrument data, instrument is 3 mg/L higher than the test data, and only two months of operation begins. ) Intermittent aeration, 5 hours of aeration, 1 hour of static settling (all propellers closed), 1.5 hours of water intake, 1 minute of water intake to start the propeller, start aeration, from the sludge concentration in the oxidation ditch around 100, a reflux pump long-term reflux sludge, flow rate 700 m3/h, reflux sludge concentration around 100, sludge concentration in the oxidation ditch has remained unchanged around 200, COD140 effluent is best at 100. About, BOD50, SS50, the effluent of secondary clarifier is turbid. (1) The sludge of the secondary clarifier does not settle, the whole surface of the tank is very turbid, (2) the sludge of the oxidation ditch has no flocculant, all of which are very fine particles. (3) Microscopic examination revealed only one microorganism, which looked like bean seeds, with bubbles in the middle and more heads. (4) there is always a white viscous foam in the oxidation ditch. (5) all of our disposal is domestic sewage. After running for 3 months, the sludge concentration does not come up, and the effluent is not good. Please help us to analyze the reasons for this situation.

A: It shows that sludge has been severely aged and disintegrated, which is caused by too low sludge load and too long aeration time. During the cultivation process, sludge is growing while oxidizing itself, and sludge concentration will certainly not increase. Sludge should be re-cultured, but the problem is how to maintain the well-cultured sludge if the water inflow and sewage concentration are not increased. Your current operation mode is not feasible. High dissolved oxygen is not the main reason, but the key is the control of aeration time. The underwater propeller with intermittent aeration does not need to be stopped, and the inner ditch does not need to be aerated. It can be used as the passage for mixed liquid to flow to the sedimentation tank, but the propeller can not be stopped.

9. Q: The anaerobic process is UASB, there is no heating device, there is no sludge reflux system in the whole process, wastewater is overflowed to the aerobic tank through UASB, and the aerobic tank uses biofilm method. Now, sludge cultivation is needed. What should be paid attention to in the process of cultivation?

A: UASB sludge culture can be transplanted and cultured by anaerobic sludge after concentration in other sewage plants. The amount of sludge added is more than 1/3 of the height of anaerobic reactor, and the sludge layer is at least 1 m. If there is no anaerobic sludge, the aerobic sludge after a period of time can be used to transplant and cultivate, because there is no need to pursue strict anaerobic in the initial stage of cultivation, even if the aerobic in the transplanted sludge will be quickly depleted, and the anaerobic conditions will be formed, but the cultivation time will be longer. In the process of cultivation, pH must be measured frequently, controlled at about 7, and nutrition must be well controlled. Specific training requirements can refer to relevant materials.

10. Q: For the secondary clarifier with peripheral inflow and effluent, has it overcome the shortcomings of the secondary clarifier with central inflow and peripheral effluent? Moreover, I find that the secondary clarifier with auxiliary flow here will have the phenomenon of sludge flocs with very small liquid surface turning over. What is the reason?

A: I think the peripheral influent sedimentation tank only reduces the influence of influent water energy on sedimentation and the problem of short flow of central mixed liquid, but does not completely change the problem of amplitude flow sedimentation tank. In theory, the efficiency of peripheral precipitation should be very high, and the requirement of water distribution is very high.

11. Q: There is a 25 000 T domestic sewage treatment plant, which adopts Orbal oxidation ditch process to design influent COD: 370 mg/L. The actual influent COD is about 150 mg/L, TP is about 2 mg/L, ammonia nitrogen is about 20 mg/L, total nitrogen is about 6 mg/L higher than ammonia nitrogen. MLSS is between 2000 and 2500 mg/L, SV is less than 15%, SVI is about 50 ml/g, MLVSS/MLSS = 0.5. The COD of effluent is less than 40 mg/L, TP has little removal effect, ammonia nitrogen is about 8 mg/L, total nitrogen removal rate is less than 50%. Now the problem is that the outlet weir of the secondary sedimentation pond has run mud, which has never been interrupted since last July. In addition, there are four rotary brush aerators in each of the three ditches. Now, due to the low load, there are 1, 2 and 2 aerators in the outer, middle and inner circles respectively. The dissolved oxygen in the inner circle is about 2.0 mg/L, and the OBP in the outer circle can be monitored online as low as - 400. Excuse me: What is the reason for secondary sinking and mud running? Is it proper to control aeration?

A: Sludge has undergone a certain degree of aging, the activity has been very poor, the effluent brings out the aged flocculation sludge. The main reason is that the sludge load is too low. The countermeasures include: (1) reducing aeration time, shutting down the outer ditch and sewage directly entering the middle ditch; (2) also shutting down the outer ditch, increasing the amount of sludge discharged and greatly reducing MLSS. These two measures are to increase the sludge load. The first one is to increase the sludge load by reducing reaction time, the second one is to increase the load by reducing sludge concentration. Of course, in order to maintain the three-phase balance of water, air and sludge, the aeration can not be too large.

12. Q: Our aerobic tank is a biological contact oxidation tank. Its purpose is to reduce ammonia nitrogen from 30 to less than 10. Actually, it is almost the same as the blank after adding color reagent. Sodium carbonate is added to adjust the alkalinity, and sludge is returned from the back sedimentation tank. Sometimes it is mud and sometimes it is water, because the reflux is not well controlled. Previously, it was found that the pH value of the whole aerobic tank decreased sharply with the direction of flow without sludge reflux, but it did not when sludge reflux, which ensured that the pH value of the effluent was between 6.5 and 7. However, in recent days, it has been found that the pH value of the whole aerobic tank is low, the front end is only 6.9, and the effluent is about 5.8 (all the indexes of influent and the amount of sodium carbonate remain unchanged, and the concentration of ammonia nitrogen can not be measured). Even if the sludge reflux condition is improved relatively before, what is the cause? In addition, the sedimentation tank behind our aerobic tank is a vertical flow sedimentation tank (148 m3, water volume 30 m3/h). There are four small mud buckets below. What measures should be taken to improve the sludge reflux status of aerobic tank under the existing conditions?

A: Sludge from contact oxidation sedimentation tank (fallen biofilm) is generally not reflux, so it is necessary to confirm whether the biofilm on the filler is normal or not. If the biofilm is too thick, it will increase air scour, otherwise it will seriously affect the treatment effect. The decrease of pH is somewhat abnormal, which can not be explained in theory, because the influent ammonia nitrogen is not too high, and the hydrogen ion produced during nitrification process will not decrease by more than one pH unit. The only possibility is that the sediment tank accumulates too much mud. Acidifying bacteria multiply in sludge under anoxic conditions, and acidification occurs after reflux to the aerobic tank. Of course, it is only speculation. Therefore, it is suggested to confirm the growth of biofilm on the filler, and not reflux the sediment sludge for a while.

13. Q: Our system was not reflux before, of course, because ammonia nitrogen didn't need to be considered at all in the design. We didn't take this aerobic tank seriously before. When monitoring, we found that the pH value of the whole aerobic tank declined (according to the direction of flow 6.3-5.5-5.3-5.1). At the same time, because the concentration of ammonia nitrogen can't be increased, there are two suggestions for people to see. The first is to improve alkalinity, and the second is sludge reflux. At that time, only the first suggestion was adopted. After adding sodium carbonate, ammonia nitrogen was effectively removed, but the pH value was still reduced by a large margin and was not well controlled. Later, sludge reflux was carried out, and it was found that it had a better effect on the stability of pH value, and now it has been reflux. I am not confident about the aerobic tank system. First, through the aerobic process, nitrogen is only converted from ammonia nitrogen to nitrate nitrogen, which is not removed from water, and the harm to the environment is not reduced. Second, I often doubt the stability and persistence of the system. Please help to analyze and propose solutions.

A: Talking about soldiers on paper is not necessarily accurate, but for reference only. If the pH of biochemical pond is stable after reflux, there is only one explanation, that is, sludge denitrification occurs in sedimentation pond, the reflux liquid contains OH-, and can neutralize part of H+ after entering aerobic pond. Of course, it is only speculation, but in any case, the effect of ammonia nitrogen removal by the system is good. If denitrification is needed, if the reaction time is not enough, try to set up an anoxic zone in the middle of the aerobic tank (residence time is about half an hour to one hour, a little aeration, DO below 0.5), which can remove part of nitrate and stabilize the pH. Also note: DO in the second half of the aerobic tank is higher, at least over 3mg/L. Supplementary Notes: In my previous post analysis, it was suggested that the decrease of pH in aerobic tank might be due to excessive sludge accumulation in sedimentation tank. Acidifying bacteria multiplied in sludge under anaerobic conditions and acidified after reflux to aerobic tank. In the latter post, it was also said that sludge denitrified in sedimentation tank, and the reflux liquid contained OH-, which could neutralize part of H+, and stabilize the pH of aerobic tank. These two stickers seem contradictory, but this is an analysis of two possibilities, the former is that if sludge has been anaerobically fermented into acidification reaction, the latter is likely to occur denitrification due to anoxia. Now it seems that the latter is more likely.

14. Q: Our aerobic tank is a biological contact oxidation tank. The ammonia nitrogen in the effluent has been reduced from 30 mg/L to less than 10 mg/L in design. At present, there is almost no ammonia nitrogen in the effluent. Sodium carbonate is added to adjust alkalinity during operation, and sludge is returned from the back sedimentation tank. Because the backflow is not well controlled, the sludge is sometimes sludge and sometimes water. Previously, it was found that the pH value of the whole aerobic tank decreased sharply with the direction of flow without sludge reflux, but it did not when sludge reflux, which ensured that the pH value of the effluent was between 6.5 and 7. However, in recent days, it has been found that the pH value of the whole aerobic pond is low, the front end is only 6.9, and the effluent is about 5.8 (all the indexes of influent and the amount of sodium carbonate remain unchanged, and the concentration of ammonia nitrogen can not be measured), even if the sludge reflux status is improved relatively before. What is the reason? We use vertical flow sedimentation tank. There are four small mud buckets below. What measures should be taken to improve the sludge reflux status of aerobic tank under the existing conditions?

A: Sludge from contact oxidation sedimentation tank (fallen biofilm) is generally not reflux, so it is necessary to confirm whether the biofilm on the filler is normal? If the biofilm is too thick, it is necessary to increase air scour, otherwise it will seriously affect the treatment effect. The decrease of PH is somewhat abnormal, which can not be explained in theory, because the influent ammonia nitrogen is not high, and the hydrogen ion produced during nitrification is not likely to decrease by more than one pH unit. The only possibility is that the sediment tank accumulates too much mud. Acidifying bacteria multiply in sludge under anoxic conditions, and local acidification occurs after reflux to the aerobic tank (DO in front of the aerobic tank is usually very low), of course. It's just speculation. Therefore, it is suggested to confirm the growth of biofilm on the filler, and not reflux the sediment sludge for a while.

15. Q: There is a synthetic chemical wastewater, which is being debugged by SBR process. Because of a toxic impact, it can only stop feeding water for five days. The COD of wastewater decreases slowly (from 1600 mg/L to 900 mg/L), but the sludge concentration rises from 1300 to 6500 mg/L, SV is only 14%. What is the cause?

A: The decrease of SV can be explained by the fact that the sludge is mineralized to a certain extent due to excessive aeration. In this case, although the sludge is poisoned, it is not completely inactive. It is impossible to explain the rising of sludge concentration without decreasing, but it is necessary to confirm whether the sampling time of each sludge concentration measurement is basically the same, because unlike traditional activated sludge aeration tank, the sludge concentration in the aeration stage of SBR tank changes with time, so the sampling time needs to be fixed, otherwise there is no comparability.

16. Q: Now the concentration tank is full of floating mud (the color is grey). We have prolonged the mud age and reduced the mud inflow into the concentration tank. Why is there such a phenomenon?

A: Such measures are not targeted. We should increase the amount of sludge discharged from the concentrator to reduce the residence time of sludge in the concentrator in order to prevent anaerobic fermentation.

17. Q: We use a peripheral drive scraper and suction machine. There are 10 suction points. The sedimentation tank DN = 30m, and the 30 minute sludge sedimentation ratio of the aeration tank is 5-9%. We can only determine NH3-N, CODcr and total copper. There are no equipment and conditions for the others. In the first two days, the temperature decreased, and the bulk sludge floating on the sedimentation tank was much less, the temperature increased slightly, and the sludge mass appeared again. When the temperature is low, the sludge is very small, but in some places there is a large sludge gushing out, and in some places the effluent is relatively clear and irregular. I don't know if the effluent chroma has anything to do with drifting mud. Now the effluent chroma has remained around 8.

A: From two aspects: on the one hand, the reason may be that the sludge has signs of aging, mainly because of the low load and long reaction time, and the aeration time should be controlled well; on the other hand, the phenomenon of large sludge floating in the sedimentation tank may be the problem of the sedimentation tank itself. The so-called suction machine is actually the suction machine, and there is a dead angle at the bottom of the suction pipe. I estimate that the bottom of the suction pipe is one. A flat and long suction nozzle? The factory may think that this flat and long suction nozzle has both the function of containing and sucking mud. In fact, otherwise, the suction effect of such a scraper and suction machine is very poor. It is also necessary to confirm whether the flat and long suction opening at the bottom of the suction pipe at the outermost part of the suction tank is close to the wall of the suction tank. If not, it indicates that there is a problem in the design of the suction machine, which will cause the suction of mud in some areas at the bottom of the suction tank. In addition, attention should also be paid to adjusting the sludge output of each suction pipe in the management of the sedimentation tank. The sludge output of the suction pipe near the side of the tank should be increased, and the sludge output of the central suction pipe should be small. It should be good to keep the chroma of effluent around 8. The national discharge standard is less than 50.

18.Q: The SV30 of the aeration tank in our unit is 7%, MLSS 2800 mg/L. It has been measured for several consecutive days. I also know that the sludge is over mineralized and contains too much inorganic substances. But some experts say that it is impossible. They say that the determination of SV or MLSS must be wrong. I don't know whether such a low sludge index is possible.

A: Sludge index is only 25, which is somewhat abnormal, but it can not be said that it is impossible. MLSS gravimetric method will not make a great error. Severe mineralization also occurs. Some devices are impacted by high concentration of saline wastewater, and the accumulation of salts in sludge will make the sludge index drop dramatically. However, no matter what the reason, such sludge should be bioremediated or re-cultured.

19.Q: For the treatment of wastewater containing high ammonia nitrogen, the results of commissioning show that the COD and ammonia nitrogen in the effluent are on the high side. Some people suggest extending SRT, will it be effective? Now SRT is 20 days, using SBR process, I think that although prolonging SRT can improve the proportion of nitrifying bacteria in organisms, prolonging SRT can also reduce the activity of bacteria as a whole and COD removal efficiency. I wonder if my idea is right?

A: It is correct to extend SRT when both COD and ammonia nitrogen are on the high side. Generally, it will not affect the removal efficiency of COD. Because the carbonization rate is faster than the nitrification rate of ammonia nitrogen, nitrification process occurs at the later stage of carbonization process, when sludge load is low, so SRT should be prolonged. Unconstrained aeration or increasing sludge concentration can also be used to reduce sludge load. The purpose is the same, of course, DO should also be confirmed. The alkalinity and other factors are satisfied.

20.Q: We are a domestic sewage treatment plant. The influent COD 280 mg/L, BOD 70 mg/L, effluent 129 mg/L and BOD 50.6 mg/L. The MLSS of aeration tank is 1980 mg/L, and the sedimentation ratio is 70%~80%. The problem now arises: all the precipitation in the measuring cylinder is yellow and turbid, and the liquid on it is very clear. Observing the surface water of the secondary sedimentation tank, the senses are also very good. In addition, the soil salinity in our region is two higher. Please analyse it, how to deal with it?

A: Although it is domestic sewage, the B/C ratio is too low and the biodegradability of sewage is very poor. In this case, the COD of effluent is high and the BOD5 is low. That is to say, it is difficult for this kind of sewage to reach the standard by biochemical treatment only. The high salt content of sewage also inhibits the biochemical reaction. From the data, sludge sedimentation performance is not good, some abnormal, the main reason is poor biodegradability, chemical coagulation process should be added after the sedimentation tank to further remove COD.

21.Q: In some sewage treatment plants, the concentration of activated sludge is controlled at about 1500mg/L during the domestication stage after sludge cultivation. My idea is that if domesticated bacteria are suitable for these industrial wastewater, we should try to maintain a high sludge concentration in the early stage, and then adjust the sludge concentration to a more suitable level according to the actual situation after the sludge adapts to the water quality.

A: Sludge concentration should not be high in the process of sludge acclimation, because the inflow of sludge acclimation process is increasing gradually. Excessive sludge concentration will cause nutritional deficiency. In addition, due to the poor ability of microorganisms to degrade toxic substances in the process of acclimation, a large number of toxic substances will accumulate in sludge.

22.Q: There is a thick layer of sludge on the sedimentation tank. The effluent contains a large amount of sludge. After stirring slightly, the sludge can sink and the effluent becomes clearer. The dosage tube is sampled in the aerobic tank. After the sludge settles for one hour, it begins to float, stirs gently and sinks again. How to deal with this situation?

A: There are two possibilities: (1) denitrification in the sludge layer of the sedimentation tank results in the removal of some sludge from the water surface and accumulation of nitrogen in the denitrification process; (2) the aeration is large, and the bubbles in the sludge can not be fully released before entering the sedimentation tank. If the former is the case, nitric acid nitrogen should be removed in the anoxic zone of the biochemical tank, or aeration should be increased to increase the amount of reflux sludge, so as to reduce the residence time of sludge in the sedimentation tank and prevent the sludge from being anoxic in the sedimentation tank. In the latter case, the pool surface of the biochemical tank, the settling tank, the water well and the slag and foam on the surface of the central draft tube should be removed for the release of bubbles in the mixture.

23.Q: when the CASS system is subjected to a certain load impact (water COD rises), the outlet water quality deteriorates, and the sludge settling quickly. After settling, the upper part of the water is cloudy, and the small floc is not sinking. When the aeration is increasing, the foam is more and more, the foam is sticky, not easy to break, and the load is not effective. The sludge concentration is maintained at about 2500. What is the reason? Is the sludge not suitable for the new water quality and ageing?

A: If it is caused by the impact of organic load, the measures you take are inappropriate and violate the basic control principle of three-phase equilibrium of activated sludge process. Because the concentration of influent increases, in order to maintain the stability of sludge load, it is necessary to increase the concentration of sludge and increase oxygen supply, while you are reducing the concentration of sludge. In this case, there is no problem of sludge aging. I guess it is caused by excessive sludge load and incomplete biochemical reactions. It is also necessary to confirm whether dissolved oxygen is satisfied.

24. Q: There is a large amount of sludge suspended in the middle of the secondary clarifier. Is the sludge activity too poor, sludge renewal too slow and sludge age too long? How to improve it?

A: there are a lot of sludge in the two sink pond in the middle of the pool. If it is normal in the central diversion well or outside, it is normal if it is in the circle. As long as it often clears up, if there is such a situation outside the central circle, there are many reasons. Besides the aging of the sludge, there are other factors. Some of them are very important for running fault diagnosis. It's difficult for me to diagnose them just by saying so.

25. Q: Our factory adopts Obel oxidation ditch with a designed treatment capacity of 25,000 m3/d. The system's influent and reflux sludge are first entered into a square anaerobic tank and then into the outer ditch, the middle ditch, the inner ditch and the effluent. Now we need to formulate the sludge operation plan. Is the inoculated sludge put into the oxidation ditch for cultivation or into each pond for cultivation at the same time? What should we do specifically?

A: Series enlargement culture method can be used, first in the inner ditch culture, sludge formation and increase, then gradually introduced into the middle and outer ditches. It can also be cultured in three ditches at the same time (depending on the amount of water inflow, the concentration of water inflow and the convenience of transportation of inoculated sludge, etc.). Anaerobic sludge need not be specially cultured. After the oxidation ditch is in normal operation, the excess sludge discharged will be gradually introduced and allowed to be naturally anaerobic.