60 classic questions and answers of water treatment technology

Installation and commissioning of Shenzhen Hongjie water production pure water equipment ultra pure water equipment reverse osmosis system project

1. Q: how to dispose the methane produced by anaerobic digestion? How to use?

A: there are many ways available, such as fuel and power generation, but if used, the safety requirements are very high and the investment cost is also high. Therefore, it is generally discharged after combustion at home and abroad. For example, the methane produced by anaerobic treatment devices such as AF and IC is automatically ignited and burned by torch. It can also be used for biogas blower, which is a good way to use. This kind of blower can be powered by electricity and biogas respectively.

2. Q: submerged biofilm is used in this process. Considering that the additional carbon source needs to increase the amount of labor and is not economical, reduce the dissolved oxygen, and the removal effect of ammonia nitrogen is also good. The nitrate in the effluent is 11mg / L, but the nitrite is very high. Ask: can the denitrification effect be improved under the condition of low C / N?

A: short cut denitrification can be adopted, because short cut denitrification directly denitrifies nitrite nitrogen into nitrogen, which can greatly save energy consumption. Just because nitrite nitrogen is unstable and difficult to accumulate, since the effluent nitrite nitrogen is so high, why not try it? If it can be achieved, it is also cost-effective to add carbon sources.

3. Q: Pig wastewater, influent: cod1500, ammonia nitrogen 500, tp60, alkalinity 3000, nitrate nitrogen and nitrite nitrogen can not be detected by the instrument, and the positive value is very low. Effluent: ammonia nitrogen 120, cod700, but nitrate nitrogen up to 1200, nitrite nitrogen 250. SRT: 1 day. Is this normal? Where does such high nitrate come from? How to explain?

A: if the data is measured correctly, there is only one explanation, that is, when the total nitrogen is much higher than ammonia nitrogen, the nitrogen-containing organic matter is continuously ammoniated and ammonia nitrogen is continuously nitrated. At this time, the treatment system is under aerobic conditions, and nitrate nitrogen cannot be denitrified and accumulated in large quantities. In this case, if the treatment time increases, the effluent ammonia nitrogen can decrease and the effluent nitrate nitrogen will increase.

4. Q: I debug a food wastewater. Before UASB generates granular sludge, the raw water cod2000-3000 and the effluent has been about 750. This period is about 50 days. During this time, run a small amount of floc mud. After that, the wastewater concentration reached 4000-5000, reducing the treated water volume and keeping the effluent less than 1000. Then start to increase the processing capacity. The mud running is more serious, the mud production is large, and the three-phase separator is not good. When reaching half of the designed treatment capacity, the company asked me to quickly increase the water volume because of the large aerobic capacity. In the process of accelerating water volume, the gas production is continuously reduced, and the effluent is 1100-1500. Close to the design flow after 15 days, but the cooperation with Party A is not good and the sampling acceptance is failed. After that, the output of party a decreased, but the water quality concentration changed greatly by 3000-5500. After reducing the flow, the gas production began to increase slightly, but the granular sludge flowed out with a large amount of water, mainly non bubbles. Even if there was no water inflow, a large amount of sludge would float up and never sink. This phenomenon has existed for more than ten days. What's going on?

A: it may be that the load is too large, which prolongs the acidic fermentation process and causes the incomplete alkaline fermentation process. For the treatment unit with unstable influent load, it is best to pre acidify the sewage and then enter the UASB unit, so as to improve the pH and better ensure the treatment effect.

5. Q: I'm doing UASB anaerobic biochemical treatment experiment of molasses alcohol waste liquid. At present, the influent concentration is 30000 ~ 50000mg / L, the removal rate is 55 ~ 60%, and the load is 20kg. Many difficulties are encountered, mainly due to the influence of sulfate, serious loss of inoculated sludge (non granular sludge) and poor biodegradability. I think the main reason is that the acidification stage is not good. I wonder if it is so?

A: two suggestions for reference: (1) acidification time should not be long to avoid low pH affecting subsequent biochemical treatment; (2) When cultivating granular sludge, an appropriate amount of activated carbon or PAM can be added to the inoculated sludge, which is conducive to the formation of granular sludge. Because I don't know the specific situation, it's for reference only

6. Q: what should be paid attention to in the operation and management of simultaneous phosphorus and nitrogen removal process by denitrifying phosphorus accumulating bacteria (DPB)?

A: there are many requirements for operation management. For example, the anaerobic tank cannot have oxygen, but how to control it? Insufficient oxygen in the aerobic area will affect nitrification and phosphorus accumulation. Too high oxygen will produce a micro oxygen environment in the anaerobic area and affect phosphorus release. Sometimes the dissolved oxygen in the aerobic area is not high, and there may be micro oxygen in the anaerobic area. This is not only related to the dissolved oxygen in the aerobic area, but also related to the residence time of the sewage sedimentation tank, the degree of hypoxia and other factors. In addition, the sludge should be discharged in time according to the process requirements. The final way of phosphorus removal is through the discharge of surplus sludge. If it is not discharged in time, the cycle of phosphorus accumulation and phosphorus release will be carried out in the system again and again.

7. Q: an enterprise here is going to reuse the treated sewage. The treatment process is: regulating tank - anaerobic tank - aerobic tank - primary sedimentation tank - air flotation tank - sewage outlet. Ferrous sulfate and lime are added to the primary sedimentation tank and aluminum chloride and polyacrylamide are added to the air flotation tank. The iron ion in the outlet water quality is very high. I don't know if there is any good way to reduce its content, Of course, the cost should not be too high?

A: don't use air flotation. Add lime to the water after aerobic treatment, adjust it to about pH 8, add PAM, and control the flocculation conditions such as stirring. This can improve the removal rate of iron ions. You can try it.

8. Q: in the relationship between BOD and COD, is cod greater than BOD, and cod-bod is about equal to non biochemical organic matter

A: This is not accurate, because cod = cod (b) + cod (NB). The former is the biochemical part and the latter is the non biochemical part. It takes about 20 days for microorganisms to complete the carbonization process at 20 degrees (that is, bod20 is close to CoDB).

9. Q: a county with a population of about 200000 has a pre built urban sewage treatment plant with a scale of 20000 tons / day. Due to the limited government funds, the construction cost wants to be controlled at about 15 million. Which process is more appropriate?

A: it is suggested to use nano diatom refined soil method for treatment. This method is especially suitable for urban sewage treatment. The generated sludge can be used as thermal insulation materials, with less investment and operation cost only half of that of the traditional method. The difference between Nano diatomite and general diatomite is that it has a strong electric neutralization effect through special treatment, and the specific surface area is also greatly improved.

10. Question: this sewage treatment plant is used to treat pulp and paper wastewater. The complete mixing method is used. Recently, the SV of sludge has decreased to 5-6. There are only bell worms and rotifers in the sludge, and the treatment effect is general. Recently, f / M is 0 About 3, the temperature is high, and the temperature of the aeration tank is 37-39 degrees. Is it sludge poisoning? Or something else?

A: F / M is not too low. Biologically, it doesn't look like poisoning, because bell worms are very sensitive to toxic substances. It may be due to the high water temperature. Generally speaking, when the water temperature exceeds 38 ℃, it will have some impact on the activities of aerobic microorganisms.

11. Q: I am now debugging SBR to treat slaughterhouse wastewater. After sedimentation in recent days, there are always fine mud particles suspended in the supernatant, which can not be precipitated, resulting in the effluent COD and SS can not meet the standard, and the water temperature is about 35-37 degrees. Is it caused by too high temperature? What should I do?

A: the sludge has signs of aging. Such temperature has some impact on microbial activities, but it is not the main reason. The main reason is that the aeration time is too long. To reduce the aeration time (such as intermittent aeration), it is also necessary to discharge sludge. Reducing the aeration time is to reduce the time of the reaction stage. Since the time of an operation cycle is fixed, the time of the idle stage can be increased accordingly. If unlimited aeration is adopted in the inlet stage, it will be changed to limited aeration.

12. Q: for wastewater containing acrylonitrile, add PAC and PAM, and then through biochemistry, the ammonia nitrogen content is up to 217mg / L. The analysis may be that acrylonitrile is transformed into acrylic acid and then into ammonia nitrogen, and amide may also increase ammonia nitrogen. There is no basis for theoretical and experimental data. Can it be explained?

A: This is normal because of ammoniation. This kind of wastewater needs a long treatment time. The high ammonia nitrogen in the effluent indicates that the ammoniation process of acrylonitrile has not been completed. In order to make the ammonia nitrogen meet the standard, it is necessary to increase the biochemical reaction time.

13. Q: how does the sludge return from three oxidation ditches and two secondary sedimentation tanks? Two secondary sedimentation tanks are equipped with a sludge pump room. How can the returned sludge be evenly divided into three oxidation ditches?

Answer: a sludge collecting tank is set in front of the sludge pump. After being lifted by the pump, the returned sludge is transported to the oxidation ditch through a return sludge main pipe, and then divided into three branch pipes to enter each oxidation ditch.

14. Question: the existing high concentration wastewater (BOD value is about 6000). Is it appropriate to take a very large value (such as 20000) for MLSS value to meet the requirements of sludge load when using activated sludge method (SBR method)? What problems will arise? What better way to avoid problems?

A: such a high concentration should not be treated directly by aerobic method. Anaerobic treatment should be used before aerobic treatment. Whether SBR process or other activated sludge process, MLSS should be controlled according to f / m value and limited by factors such as sedimentation time and oxygen supply capacity.

15. Q: I'm working on the wastewater treatment scheme for aquatic products processing, using UASB. The water quality is as follows: q = 200t / D, COD = 3000, BOD = 1000, SS = 300, total nitrogen = 200, ammonia nitrogen = 20. Sewage discharge standard: effluent requirements: cod < 300, BOD < 150, SS < 200, total nitrogen < 40, ammonia nitrogen < 25.

Consult the following water quality conditions: (1) do not reduce BOD after BOD < 150 to save project investment. Can total nitrogen be removed? (2) Is the end point of reaction to nitrogen in UASB NH4 + and NH3?

A: the conversion of nitrogen by UASB is mainly the ammoniation of organic nitrogen, so ammoniation, nitrification and denitrification should continue after UASB. It is suggested to adopt A2 / 0 contact oxidation method after UASB.

16. Q: Pig wastewater COD: 10000, ammonia nitrogen 400, cod: 150 after Anaerobic + SBR, ammonia nitrogen 150300 m3 / day, 15 mu of stabilization pond, which can store water 1-1.5 meters deep. How to design the stabilization pond, what plants will be planted in early June, and whether the effluent can reach grade I?

A: two-stage stabilization pond, the first stage aeration pond and the second stage static pond can be used. A small number of floating aerators can be installed in the aeration pond (the same as that in the fish pond). Generally, aeration is not often. Aquatic plants such as water hyacinth can be bred in the static pond.

17. Q: I am now experimenting with the treatment of chemical wastewater. The main difficulties are: poor biodegradability; Discoloration (more serious than the discoloration of dye wastewater); And the wastewater is highly corrosive, and its pH value is about 2; Cod after biochemistry is high and low, and the main pollutants are substances with benzene ring. What kind of process should be used?

Answer: biochemical treatment is required after pretreatment. Electrolysis, fast ion removal or acidification can be used for pretreatment.

18. Q: the plant is a large-scale urban sewage treatment plant with a daily treatment capacity of 300000 tons. The improved oxidation ditch process is adopted. Recently, the secondary sedimentation tank is particularly easy to run mud, and the oxidation ditch MLSS has been stable at 4000-5000mg / L. why is this?

A: it may be caused by partial sludge flocculation due to sludge oxidation. In this case, the sludge discharge volume should be increased and the aeration volume should be reduced.

19. Q: there is a sewage treatment plant, which adopts ordinary aeration tank and perforated pipe aeration. The sewage volume has exceeded the design water volume, so the treatment capacity needs to be improved. What measures can be taken to improve the treatment capacity of the aeration tank without changing the volume of the aeration tank?

A: the following measures are for reference: (1) fiber filler is set in the tank and biological contact oxidation method is adopted; (2) When the perforated pipe is changed to microporous aeration hose, the utilization rate of oxygen can be increased several times. In this way, the volume load of aeration tank can be more than doubled.

20. Q: there is less and less sludge in the aeration tank. The influent cod is about 100 ~ 200mg / 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 method can be adopted to discharge some sludge in an appropriate amount, although the amount of sludge is small, and it will be less if it is not discharged.

21. Question: the BOD of the influent should not be too high for the treatment of wastewater by contact oxidation method. Can contact oxidation after hydrolysis and acidification ensure the BOD requirements of the influent of the contact oxidation tank? If not, what should I do?

A: the removal of COD by hydrolysis acidification is very limited, mainly to improve the biodegradability of wastewater. For example, if the inlet BOD of contact oxidation tank is too high, anaerobic process or other methods can be used for pretreatment.

22. Q: how to determine the amount of microorganisms in the contact oxidation aeration tank? The traditional activated sludge process can be expressed by sludge concentration (MLSS) and sludge sedimentation ratio (SV30). How to intuitively express the amount of microorganisms in the contact oxidation aeration tank? Some people say that observing the thickness of biofilm, what is the standard of thickness?

A: it is impossible and unnecessary to measure the amount of biofilm in contact with the oxidation tank. If the film on the filler is too thick, the specific surface area is small, the amount of active biofilm per unit volume is small, and it is not good to have too little film. In the actual operation, controlling the thickness of organisms is one of the keys in operation management. If the membrane is too thick, it is necessary to increase the air volume or scouring. Since the biofilms are installed under the water surface in the pool, it is best to observe the fillers installed on the side of the pool. The thickness of the biofilm is the best to just cover the fillers.

23. Q: in some a / O processes, Section A is anaerobic. Why do you need air pipe aeration?

Answer: air pipe aeration can be used for anaerobic operation, anoxic or aerobic operation. At the same time, aeration pipe can be used to assist mixing when the mixing effect is not good to prevent sludge sedimentation. Although section A should be anoxic, there is no problem with appropriate aeration (do < 0.5mg / L).

24. Q: in the process of Anaerobic + aerobic treatment, if there is still a large amount of sulfur after anaerobic treatment, how can it be removed?

A: if there is a large amount of hydrogen sulfide after anaerobic, it means that the anaerobic reaction is incomplete, and the reaction conditions should be controlled.

25. Q: the secondary sedimentation tank we designed is the sedimentation tank behind the orbel oxidation ditch. The concentration of returned sludge in the oxidation ditch is required to be 8g / L. it is afraid that the concentration of returned sludge in the middle inlet and out of the week can not be reached. Therefore, experts suggest that the weekly inlet and out of the week can be used. The manufacturer introduces the single pipe sludge suction machine for this process, and the concentration of returned sludge can reach 8-12 g / L, right?

A: it should be used with caution. Devices with poor sludge sedimentation performance should not be used in and out of the sedimentation tank, and single pipe mud suction machine is not suitable.

26. Q: for the 100 ton pilot project I have done, the ammonia nitrogen removal effect is not good recently. According to the current observation, the oxygen supply should be OK, the alkalinity is sufficient, the biological activity is OK and there is no obvious toxicity, and the sewage is still not exposed. Can we think that the load is not a problem? Is the ammoniation and nitrification of organic nitrogen carried out at the same time, in which ammoniation is slightly ahead of nitrification? Are there any other factors affecting nitrification?

A: the ammoniation process of nitrogen-containing organic matter precedes the nitrification process, which is slower than the carbonization process of organic matter, but faster than the nitrification process of ammonia nitrogen. Nitrification can only occur at low organic loading. Although it cannot be said that the nitrification process can be started after the completion of the ammoniation process, it can be considered that the ammoniation process will occur in the early stage of the nitrification process, and the two processes will coexist in a certain period of time. The ammonia nitrogen in the influent of some units is very low and the total nitrogen is very high. After biochemical treatment, the ammonia nitrogen in the effluent is higher than that in the influent, which indicates that the unit not only does not have enough nitrification reaction time, but also does not necessarily complete the ammoniation process. From what you said, the load should be no problem. We should also confirm whether the nutrition ratio is satisfied, such as whether there is lack of phosphorus, etc.

27. Q: we are doing a fruit juice wastewater treatment, using UASB + contact oxidation process. Cod is around 8000 and BOD is around 4000. The pH fluctuates greatly. It is around 9-13. Sometimes there is a pH of about 5. The incoming water volume is 1200. The water volume is unstable. What should be paid attention to in commissioning?

A: the water quality and quantity regulation of this kind of water is very important. The capacity of the regulating tank should be large enough to make the treatment device operate stably.

28. Q: the amount of alkali washing waste alkali liquor from refinery (liquefied gas, straight run diesel, catalytic cracking gasoline) is about 4kl / HR, and the COD is about 40000. What method is used for pretreatment?

It is suggested to set up a storage tank to neutralize the alkali containing waste oil and then decant the alkali containing waste oil. Generally, the waste alkali liquor also contains high concentration sulfide, which can be treated by air or other oxidation methods (before the neutralization process).

29. Ask several questions: how to operate the waste alkali liquor regulating tank with oil decanting function? Separated by gravity? What if emulsification is serious? Recently, due to the blockage of the tower pipe of the sewage cooling tower, the water temperature can be as high as 44.7 after opening the bypass. Although it can speed up the reaction rate, it is also close to the top limit of medium temperature microorganisms. (t h is set at 45C) it has to cut out the tributary with the highest temperature in the inlet pipe from the system; Is there any limitation on methanol content in influent by activated sludge process? Because the methanol storage tank has problems and needs to be cleaned up, it is also worried about the impact on the biochemical treatment site. After checking some data, some say it has high biochemical property, while others say it will be toxic if it is too high, don't you know?

Answer: the answers to the three questions are as follows: (1) strictly speaking, if there is oil in the waste alkali liquor, it should be washed with gasoline first, and the alkali liquor storage tank should also have the function of oil decanting. The simple way is to set oil drain pipes at different heights between the upper and middle of the tank, and install valves, so that the oil can be decanted at different liquid levels. (2) Such temperature will seriously affect the effect of biochemical treatment (unless it is anaerobic method), and cooling measures shall be taken. (3) Although methanol has good biodegradability, it cannot be used if the concentration is too high, unless it is anaerobic.

30. Q: our factory adopts improved SBR. The so-called improvement is to realize continuous water inflow, but the reaction tank is divided into two steps with a retaining wall. A so-called pre reaction area is connected with the main reaction tank. There is a 2 square meter cavity at the lower part of the retaining wall, and there is no sludge reflux. The pre reaction area is exactly the same as the main reaction tank. The pre reaction area is 3.5 meters long, the main reaction tank is 36 meters long and the tank depth is 4.7 meters, The tank is 12.5m wide and 1.3m high. The influent is mainly domestic sewage cod 400 BOD 180 total nitrogen 80 total phosphorus 8. The influent is 10000 cubic meters per day. Now the two reaction tanks are in operation! What is the appropriate sludge concentration? The aeration hose is used for aeration. It may be that the aeration pipe is not very good. The reaction tank is only aerated at both ends, and there is no aeration in the middle! After half a year of operation, the effluent is not up to standard. The total COD is about 80 and the sludge concentration is about 6000. Four hours a cycle, two hours of aeration, one hour of static sedimentation and one hour of decanting! Please give advice! Dissolved oxygen during aeration is 2!

A: according to what you said, it should be ICEAS process. It is suggested that you check whether the air bag is installed in the air transmission pipe in front of the aeration hose and whether the exhaust pipe (also known as blowdown pipe) is set in the air transmission pipe system, because these are related to the situation that there is air at both ends of the aeration pipe and no air in the middle. As for the high MLSS, this is only one reason, as well as factors such as aeration time.

Q: I am commissioning a slaughterhouse wastewater. The process is: septic tank (HRT > 2D) - regulating tank - hydrolysis tank (HRT = 5) - contact oxidation tank (HRT = 6) - secondary sedimentation tank. Since the COD of the effluent from the front 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 submersible aerator is limited, and the do is generally below 0.5, The original aeration tank DO is normal. The SV of the two tank can reach 20-30. Now the water intake is 70% of the designed water volume, the water quality 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?

Answer: COD700 is very normal. The foam is not related to ammonia nitrogen. To determine whether it is biological foam or chemical foam? If chemical foam is maintained at such a sludge concentration, it will gradually decrease. It is not possible to use water spray to remove bubbles. I feel that your sludge activity is very poor. The reason may be that the nutrition is better than not controlled, such as nitrogen and phosphorus.

32. Q: one of our projects has been running for one year. Recently, due to the deterioration of influent water quality, the content of s in the biochemical unit has reached about 100. Now the influent s is about 10. It has been five days since the recovery. The influent cod is about 600 and the effluent is about 300. Under the 10x16 microscope, we can see some dendrimers and some tiny (needle tip size) things. I don't know what it is, and the sludge concentration is almost zero, How to adjust now? Should the sludge be oxidized and the gas volume be reduced?

A: it means that the sludge has been seriously damaged and disintegrated, so it should be re cultured.

33. Q: the sewage treatment system has just been built and is ready to start operation. The process: regulating tank - hydrolysis tank - anaerobic tank - aerobic tank - sedimentation tank - sludge treatment system will start trial operation soon. It is planned to use inoculation and domestication. What are the specific precautions in driving and Domestication?

A: static culture should be adopted at the initial stage of culture. After the initial formation of sludge, attention should be paid to prevent excessive self oxidation of sludge. This kind of situation has occurred in many plants. The sludge does not increase or even decrease for a long time. The reason is that the nutrition and aeration time are not well controlled, and the sludge is growing while constantly oxidizing itself. In the later stage of activated sludge culture, although the sludge concentration is low, some sludge should be properly discharged, which will be conducive to the further growth and reproduction of microorganisms.

34. Q: the anaerobic treatment unit of our unit will start commissioning. Please talk about the anaerobic sludge culture method and precautions in the commissioning process.

A: there are many ways to cultivate anaerobic sludge. It is recommended to adopt the step-by-step culture method. The general process is as follows: the excess sludge (anaerobic) from the aerobic system through the concentration tank is put into the anaerobic reaction tank, and the dosage is about 20 ~ 30% of the reactor capacity. Then it is heated (if heating is required), and the temperature is gradually raised to 1 ℃ per hour, Maintain the temperature when the temperature rises to the temperature required for digestion (according to the design temperature). The amount of nutrients should be gradually increased with the increase of microbial biomass, and should not be too hasty. When the organic matter is hydrolyzed and liquefied (one or two months), the sludge is mature and generates biogas, analyze the biogas composition, carry out ignition test when normal, and then use the biogas and put it into daily operation. The initial control organic load is low. When the removal rate of CODCr reaches 80%, the organic load can be gradually increased. The acetic acid concentration after startup shall be controlled below 1000mg / L. The above is only a general requirement. It's best to invite experienced people to guide.

35. Q: our plant is an oil refinery, and the current sewage treatment process is as follows: after the high concentration sewage is treated in the biological aerated filter, part of it is sent to the contact oxidation tank of the low concentration sewage treatment system, and part of it is used as the dilution water of SBR (alkali residue after wet oxidation). After SBR treatment, it is sent to the contact oxidation tank of the low concentration sewage treatment system, The low concentration sewage treatment system includes oil separation, air flotation, contact oxidation tank, secondary sedimentation tank, sand filter and reuse. There is a problem that the ammonia nitrogen before the high concentration sewage enters the biological aerated filter is always higher than the water out of the biological aerated filter. What is the reason?

A: it's normal because part of ammonia nitrogen is removed in the biofilter. It is not removed by alienation, but by assimilation, that is, by bacterial synthesis.

36. Q: I'd like to inquire about the removal rate. If the BOD / COD of the sewage treatment plant dominated by domestic sewage is 0.4 ~ 0.5, can the BOD / COD of the effluent reach 0.8 ~ 0.9, that is, the COD of the effluent is 40 ~ 50, but the BOD can't meet the standard. Why does this happen and how to adjust the process (the treatment process is SBR or oxidation ditch)?

A: This is abnormal. It is necessary to confirm whether there is a problem in the determination of BOD5, such as whether a blank control is made during the determination; When sampling, the fine flocs in the effluent cannot be taken in.

37. Q: our sewage pool is 9 meters deep, 50 meters long and 15 meters wide. Now there is a lot of sludge at the bottom of the pool. How to remove it? The pool has water all year round

A: what kind of technology should we make clear? What pool is it? It is estimated that it is the regulating tank. The regulating tank should be equipped with mixing equipment to homogenize the sewage. If not, it should be vented and cleaned.

Q: if the secondary effluent of urban sewage is only used directly through filtration, what should be the filtration method and how to filter out some impurities such as particles, hair and algae? May I ask you

A: it depends on the requirements of reuse water. For example, as a general miscellaneous water, it must go through at least three processes: coagulation, filtration and sterilization. There are many filtration methods. The more economical and effective one is to filter with quartz sand. As for substances such as hair in the water, they should be removed in the front sewage treatment device.

39. Q: the anaerobic process I use is UASB without heating device. There is no sludge return system in the whole process. The wastewater overflows to the aerobic tank through UASB, and the aerobic tank adopts biofilm method. Now we need to carry out sludge culture. What should we pay attention to in the process of culture?

Answer: UASB sludge can be cultivated by transplanting anaerobic sludge concentrated by other sewage plants. The amount of sludge added is about 1 / 3 of the height of anaerobic reaction device, and the sludge layer is at least 1m. If there is no anaerobic sludge, it can also be transplanted and cultured with aerobic sludge after being placed for a period of time, because it is not necessary to pursue strict anaerobic in the initial stage of culture, even if the oxygen in the transplanted sludge will be consumed quickly and anaerobic conditions will be formed, but the culture time will be longer. In the process of culture, the pH must be measured frequently, controlled at about 7, and the nutrition must be well controlled. For specific training requirements, please refer to relevant materials.

40. Q: we treat semiconductor wastewater (containing fluoride, ammonia nitrogen and phosphate). Due to the poor consideration of the original design, now there is only one aerobic tank instead of anaerobic tank. The influent ammonia nitrogen of the aerobic tank is about 30mg / L (the average flow is 30t / h). Add sodium carbonate to adjust the pH value and alkalinity. The pH value is generally about 7.5 and aerate for 24 hours; A 5t / h sludge pump is placed at the bottom of the subsequent sedimentation tank, which also returns for 24 hours. Due to poor control, sometimes sludge and sometimes sewage return, and the ammonia nitrogen in the effluent is almost 0. It has been running stably for 2 months. Can it run stably like this?

A: it is unreasonable in two aspects: first, there is no phosphorus removal function, and anaerobic should not be cancelled; Second, the amount of returned sludge should be relatively stable, and it is impossible to discharge it by pump at the bottom of the tank. From the reaction time of the aerobic tank and the concentration of ammonia nitrogen in the influent, the removal of ammonia nitrogen should be no problem.

41. Q: our company adopts the pre Aubel oxidation ditch process, which has problems in operation recently. Design water inflow of 50000 tons / day, cod350, bod150, ss220, actual water inflow of 5000m3 / D per day, cod300, bod120, ss180; The operation mode is that four thrusters in the inner and outer ditches are fully opened, and the dissolved oxygen in the inner and outer ditches is controlled at 3mg / L (the dissolved oxygen detected in the laboratory is different from the data of the online instrument recently, and the instrument is 3mg / L higher than the test data, and the test starts after two months of operation.) Intermittent aeration, aeration for 5 hours, static sedimentation for 1 hour (all thrusters are closed), water inflow for 1.5 hours, water inflow for one minute, start the thruster and start aeration. The sludge concentration in the oxidation ditch is about 100, a reflux pump returns the sludge for a long time, the flow is 700m3 / h, the reflux sludge concentration is about 100, and the sludge concentration in the oxidation ditch remains unchanged at about 200, The effluent cod140 is preferably about 100, bod50, SS50, and the effluent of secondary sedimentation tank is turbid. (1) The sludge in the secondary sedimentation tank does not settle, and the whole tank surface is very turbid. (2) the sludge in the oxidation ditch has no flocs, but all are very fine particles. (3) Microscopic examination found only one microorganism, which looked like bean seeds, with bubbles in the middle and more on the head. (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 analyze the reasons for this situation.

A: it means that the sludge has been seriously aged and disintegrated, which is caused by too low sludge load and too long aeration time. During the cultivation process, the sludge is growing and oxidizing itself. Of course, the sludge concentration will not increase. The sludge needs to be re cultivated, but the problem is how to maintain the cultivated sludge if the inflow and sewage concentration do not increase? Your current operation mode is not good. High dissolved oxygen is not the main reason. The key is the control of aeration time. If intermittent aeration is adopted, the underwater propeller does not need to stop, and the inner ditch does not need aeration, it can be used as the aisle of the mixed liquid to the sedimentation tank, but the propeller cannot stop.

42. Q: for the secondary sedimentation tank with surrounding water inlet and surrounding water outlet, has it overcome the shortcomings of the secondary sedimentation tank with central water inlet and surrounding water outlet? Moreover, I found that the auxiliary flow secondary sedimentation tank here will have the phenomenon that the liquid level will turn over very small sludge flocs. What is the reason?

A: I think that the surrounding influent sedimentation tank only reduces the impact of influent water energy on sedimentation and the problem of short flow of central mixed liquid, and does not comprehensively change the problems existing in the amplitude flow sedimentation tank. Theoretically speaking, the peripheral sedimentation efficiency should be very high, and the requirements for inlet water distribution are very high.

43. Q: it is often seen in some forums that "if the aeration is too large, do is too high, bacteria oxidize themselves, the load is too low, and microorganisms oxidize themselves, resulting in flocculation". In ASM1 #, asm2 #, ASM3 # models and McCarty, the leader of wastewater biological treatment, the attenuation coefficient of microorganisms is taken as a constant, expressed by B, that is, the attenuation (self oxidation) occurs at any time according to a certain proportion B. The growth coefficient of microorganism is closely related to the substrate concentration, which is a variable. When the organic load is low and the oxygen supply is sufficient, the microorganism will quickly consume the BOD in the water, stop the growth and only decay, resulting in a net increase of 0 or even negative, so that the biomass will not increase but decrease. Therefore, it is said that self oxidation occurs at any time, rather than under low load and high do. Is it appropriate to say so?

Answer: Yes in theory, but the understanding of sludge aging in actual operation is not limited to this. Although sludge aging is mainly caused by the lack of nutrition of microorganisms for a long time, that is, the imbalance between nutrition and microbial biomass, and microorganisms can not grow normally, the actual operation of the treatment unit is more complex, and the activity of sludge is also related to the operation control conditions Nutrition ratio and other factors. In some units, the following situations will occur: when the influent concentration is normal and the carbon nitrogen ratio or carbon phosphorus ratio is low, the activity of sludge will also be very poor, limiting the degradation of organic matter by microorganisms and reducing the energy generated; When the influent concentration and nutrient ratio are normal, but the excess sludge is not discharged as required, and the aeration time is too long, it will also make the sludge loose and poor activity. This kind of sludge is also known as aging.

Question 44: there is a 25000t domestic sewage treatment plant, which adopts Orbal oxidation ditch process. The designed influent cod is 370mg / L, the actual influent cod is about 150mg / L, TP is about 2mg / L, ammonia nitrogen is about 20mg / L, total nitrogen is about 6mg / L higher than ammonia nitrogen, MLSS is between 2000 ~ 2500mg / L, SV is less than 15%, SVI is about 50ml / g, MLVSS / MLSS = 0.5. The effluent COD is less than 40mg / L, TP has little removal effect, ammonia nitrogen is about 8mg / L, and the total nitrogen removal rate is less than 50%. At present, the problem is that there is mud running on the outlet weir of the secondary sedimentation tank. It has never been interrupted since it began to operate in July last year. In addition, there are four rotary brush aerators in each of the three ditches. Now, due to the low load, one, two and two aerators are opened in the outer, middle and inner circles respectively. The dissolved oxygen in the inner ring is about 2.0mg/l, and the minimum OBP of the outer ring online monitoring is - 400. Excuse me: what is the reason for the second sedimentation and mud running? Is it appropriate to control the aeration mode in this way?

A: the sludge has aged to a certain extent, and the activity is very poor. The effluent brings out the aged deflocculation sludge. The main reason is that the sludge load is too low. Countermeasures: (1) reduce the aeration time, stop the outer ditch and directly feed the sewage into the middle ditch; (2) The outer ditch can also not be shut down to increase the sludge discharge and greatly reduce MLSS. These two measures are to increase the sludge load. The former is to increase the sludge load by reducing the reaction time, and the latter is to increase the load by reducing the sludge concentration. Of course, in order to maintain the three-phase balance of water, gas and sludge, the aeration volume should not be too large.

45. Q: Zhou Jinzhou has strict requirements for water distribution. In fact, there is a baffle at the inlet and outlet of the week, which goes deep into the bottom of the secondary sedimentation tank, but I can't find any information about how deep it is. It is said that the technology is imported directly from abroad, and its calculation is not available. Do you have any opinion on this problem?

A: you're right. There are baffle plates at the surrounding water inlets. It is estimated that there are many inlet holes under the inlet tank, which flow downward after the water energy dissipates, and then diffuse from the bottom of the inlet baffle to the pool. I can't tell the specific location. It should be about 2 meters above the water surface. I think the key technology should be uniform water distribution and water energy dissipation.

46. Q: how to distinguish sludge poisoning from sludge aging?

A: Generally speaking, serious aging of sludge will have a development process, and sludge poisoning will soon cause cell disintegration. The effluent ess will increase significantly during sludge aging and poisoning, which can be distinguished by experienced people. When the sludge is aged, the suspended solid particles in the effluent are relatively larger, mostly in fragment shape. When sludge is poisoned, the suspended solid particles in the effluent are relatively small.

Sludge poisoning and sludge aging can also be distinguished from the change of do value. The process of sludge poisoning is fast, which will increase do in a short time. However, sludge aging has a gradual process, and the rising process of do is also gradual.

47. Q: the moisture content of the sludge cake after dehydration increases obviously without any change in the amount of sludge fed into the sludge dehydrator. What is the reason?

A: except for the operation of the dehydrator itself, there may be a problem in the sludge dosing and conditioning process, or it may be caused by the failure shutdown of the mixer in the previous sludge homogenization tank or the failure shutdown of the sludge scraper in the sludge thickening tank.

48. Q: Recently, the filter cloth of our sludge dehydrator (belt filter press) often deviates. What is the reason?

Answer: confirm whether the roller surface is bonded or worn, whether the parallelism of the roller shaft is good, etc. if the filter belt is damaged, replace it in time.

49. Q: there is a lot of oil in wastewater recently, especially in the place of gecui well, there is black scaling oil. How do you usually deal with it?

Answer: first use manual cleaning and fishing, and then use oil absorbent felt or oil absorbent medium to absorb oil.

50. Q: contact oxidation has many advantages in treating low concentration domestic sewage (small community), but it is difficult for N and P to meet the discharge standard (Level II). How to improve the process to remove N and P?

A: I don't think it's the poor effect of nitrogen and phosphorus removal by contact oxidation method, but may be caused by problems in the control link. For example, the do control of aerobic tank must be higher than that of activated sludge method, the anoxic area should have full mixing function, alkalinity control and other factors.

51. Q: now the thickener is full of floating mud, (the color is gray). We have extended the mud age and reduced the mud inlet into the thickener. But why is there such a phenomenon?

A: such measures are not targeted. The sludge output of the thickener should be increased to reduce the residence time of sludge in the thickener to prevent anaerobic fermentation.

52. Q: can UNITANK process be used in large-scale sewage plants? Engineers who have used this new process say that it should not be used in large-scale sewage plants because automatic control is very complex and phosphorus removal effect is poor. Is that right? Guangdong Liede Sewage treatment plant is 220000 tons / day, and Shanghai Shidongkou sewage treatment plant is 400000 tons / day (recently). It is said that the overall operation is good, and Shidongkou sewage treatment plant will compete for Zhan Tianyou award. How is this process used in large sewage treatment plants? Please answer.

A: I think UNITANK process is also suitable for large-scale sewage plants, but it is not suitable for sewage with high phosphorus removal requirements.

53. Q: our aerobic tank is a biological contact oxidation tank, which aims to reduce ammonia nitrogen from 30 to less than 10. In fact, it is almost blank after adding color developer. Add sodium carbonate to adjust the alkalinity and return sludge from the rear sedimentation tank. Because the return is not easy to control, it is sometimes mud and sometimes water. It was previously found that when there is no sludge reflux, the pH value of the whole aerobic tank decreases sharply with the direction of water flow, but not when there is sludge reflux, which can ensure that the pH value of effluent is between 6.5-7. 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 indicators of influent water and sodium carbonate have not changed, and the ammonia nitrogen concentration is still not measured). Even if the sludge reflux state is improved compared with the past, what is the reason? In addition, the sedimentation tank behind our aerobic tank is a vertical flow sedimentation tank (148m3, water volume 30m3 / h), and there are four small sludge buckets below. Under the existing conditions, what measures should be taken to improve the return sludge state of the aerobic tank?

A: the sludge (fallen biofilm) in the contact oxidation sedimentation tank generally does not return, so it is necessary to first confirm whether the biofilm on the filler is normal? If the biological is too thick, it is to increase the gas scouring, otherwise it will seriously affect the treatment effect.

The decline of pH is abnormal, which cannot be explained theoretically, because the influent ammonia nitrogen is not high, and the hydrogen ion produced in the nitrification process will not fall by more than one pH unit. The only possibility is that there is too much sludge in the sedimentation tank. Under the condition of hypoxia, the acidification bacteria in the sludge multiply in large numbers, and acidification occurs after returning to the aerobic tank. Of course, it is only speculation. Therefore, it is suggested to confirm the growth of biofilm on the filler, and the precipitated sludge shall not be refluxed temporarily, and it shall be observed for a period of time.

54. Q: (the question after the reply of the previous post) our system did not return flow before. Of course, ammonia nitrogen did not need to be considered at all in the design. This aerobic tank had not been taken seriously before. During monitoring, it was found that the pH value of the whole aerobic tank decreased (according to the flow direction of 6.3-5.5-5.3-5.1); At the same time, due to the increase of ammonia nitrogen influent concentration, there are two suggestions: one is to improve the alkalinity, and the other 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 still decreased greatly and it was difficult to control. Later, sludge reflux was carried out and found to have a good effect on the stability of pH value. Now it has been reflux. I feel very uneasy about the aerobic tank system. Firstly, through the aerobic process, nitrogen is only transformed from ammonia nitrogen to nitrate nitrogen, which is not removed from the water and the harm to the environment is not reduced; Second, I often doubt the stability and persistence of this system. Please help analyze and propose solutions.

A: it's not necessarily accurate to talk on paper. It can only be used for reference. If the pH of the biochemical tank is stable after reflux, there is only one explanation, that is, the sludge is denitrified in the sedimentation tank, and the reflux liquid contains Oh -, which can neutralize part of H + after entering the aerobic tank. Of course, it's just speculation, but anyway, it shows that the effect of ammonia nitrogen removal by the system is good. If denitrification is required, I don't know whether the reaction time is enough. Try to set an anoxic area in the middle of the aerobic tank (residence time is about half an hour to one hour, a small amount of aeration, do below 0.5), so as to remove part of nitrate nitrogen and stabilize pH. Also note: the do in the second half of the aerobic tank is higher, at least above 3mg / L.

Supplementary note: in the analysis of my previous post, the reason why the pH of the aerobic tank decreases may be that there is too much sludge in the sedimentation tank. Under anaerobic conditions, acidification bacteria in the sludge multiply in large numbers and acidify occurs after returning to the aerobic tank; In the latter post, it is said that the sludge is denitrified in the sedimentation tank, and the return liquid contains Oh -. After entering the aerobic tank, it can neutralize part of H +, and stabilize the pH of the aerobic tank. These two stickers seem contradictory, but this is an analysis of two possibilities. The former is if the sludge has been anaerobic fermentation into acidification, and the latter may be anoxic and denitrification. Now it seems that the latter is more likely.

55. Ask: how much range of dissolved oxygen should be controlled in the hydrolysis acidification tank? Do you need to install aeration and mixing devices?

Answer: whether the hydrolysis acidification tank adopts the mud method or the membrane method. If it is the mud method, it can be equipped with an agitator. If it is the contact oxidation method, in addition to installing the agitator, it is better to set up aeration devices such as perforated pipes or aeration hoses, which mainly plays an auxiliary role in mixing. There is no need to worry that aeration will affect the acidification effect, because the load of acidification tank is high, and the impact of charging some oxygen on it is insignificant.

56. Q: our plant is located in Beijing, with a scale of 30000 tons. It adopts hydrolysis + biological contact oxidation treatment process. After two years of operation, if two pumps are opened, there is always floating mud in the secondary sedimentation tank (with a load of about 0.9), and sometimes needle like flocs. Affect effluent SS. But the effect is very good when you turn on one too pump. Please diagnose it!

A: the main reason is that the surface load of the secondary sedimentation tank is too small, because the sedimentation performance of the biofilm is worse than that of the activated sludge method, and its surface load should be at least twice that of the activated sludge sedimentation tank in the design.

57. Q: we treat papermaking wastewater and chemical mixed wastewater, using Carrousel 2000 oxidation ditch. In the past year, the influent ammonia nitrogen has been increasing, about 250, and the removal rate of ammonia nitrogen is about 30% - 40%. What effect does the increase of ammonia nitrogen have on the operation of the system? What should be done? If the influent ammonia nitrogen is controlled at 80, how can it be treated to meet the standard?

Answer: to confirm whether the nitrification conditions such as sludge load and alkalinity are met? If these basic conditions are met, the oxygen charge in the aerobic zone can be increased and the internal reflux gate can be opened larger, so as to increase the do in front of the anoxic zone and make some anoxic zones have certain nitrification function.

58. Q: how to determine the residence time of hydrolysis acidification? What standard is used to determine the degree and effect of hydrolysis and acidification of sewage?

A: the acidification time should be determined through the operation test. Generally speaking, the pH of the effluent from the acidification tank decreases and the BOD / COD ratio increases, indicating that the acidification is effective.

59. Q: our plant adopts CASS process, and the influent concentration has increased from an average of 250PPM cod last year to about 350ppm now. At the same time, the influent suspended solids are much more than last year. The treatment cycle is 4 hours, intermittent aeration. The method of aeration while entering the water for 2 hours is adopted. When the influent concentration is not so high, the treatment method of influent for 1 hour and aeration for 1 hour is basically adopted. At the end of the aeration stage, the do basically remains above 2ppm, but the color of activated sludge is still black. There is no big change in the amount of water entering each batch. The previous method has been adopted for more than half a month. After treatment, the effluent is still maintained at about 150ppm, the suspended solids are at 50 ~ 60ppm, the sludge is black, the flocculation of activated sludge is poor, the structure is loose, and it is difficult to see primary microorganisms. The MLSS is 1700ppm and the influent BOD is about 120.

A: my preliminary judgment is that the aeration time is not enough. The reason is that after the influent concentration increases, you adopt the unrestricted aeration method. On the surface, it increases the aeration time by one hour. In fact, it is not, because most of the time in the influent period, due to the low water level, the utilization rate of oxygen is very low, and more importantly, due to the increased load, At the end of the aeration stage of the previous cycle, the biochemical process has not been completed, which exacerbated the sludge anaerobic in the static sedimentation stage. Although the aeration is in the water inlet stage of the next cycle, the aeration during this period is actually only the recovery or partial recovery of sludge activity, and the actual biochemical reaction time does not increase much.

The basic idea of process adjustment is correct. It is suggested that: (1) the sludge of each tank is stuffy aerated in turn until the mud color turns brown initially, and then the water is aerated; Also confirm whether there is enough nitrogen or phosphorus? Because the nutrient ratio may be out of balance after the influent COD concentration increases. I just speculate from the surface for reference only.

60. Q: pharmaceutical wastewater, sulfate 3000-4000, cl-3000-4000, cod3000-4000, wants to hang filler in the hydrolysis acidification tank, but it is very difficult to hang membrane in the pilot test; I don't know whether it is the improper selection of filler or the High Cl -? Environmental protection companies say that if Cl - exceeds 3000, the filler cannot hang the film.

A: such Cl concentration will affect the biofilm culture speed, but if the biofilm can still be hung, it is best to introduce activated sludge or anaerobic sludge, which can increase the membrane hanging speed. From the perspective of fillers, soft fillers are the most likely to hang film, followed by elastic fillers, and semi soft fillers are poor, but elastic fillers are easy to agglomerate, so they should be used with caution.