What are the latest treatment processes for industrial wastewater?

AB Method Process Wastewater Treatment The AB method process was first developed by Prof. BOHUKE of Germany. The process divides the aeration tank into two sections of high and low loads, each with its own independent sedimentation and sludge return system. The high load section (section A) has a residence time of about 20-40 minutes, with biological flocculation and adsorption as the main action, and incomplete oxidation reaction occurs at the same time, the biological community is mainly short-generation bacteria, and the removal of BOD reaches more than 50%. B section is similar to conventional activated sludge method, with lower load and longer mud age.　The AB method has high efficiency and strong buffer capacity in section A. Section B plays the role of water gatekeeper and has better treatment stability. For high concentration of wastewater treatment, the AB method has good applicability and high energy efficiency. Especially in the sludge digestion and biogas utilization process, the advantage is most obvious.　The main treatment structures in the B-method are A section aeration tank, intermediate sedimentation tank, B section aeration tank and secondary sedimentation, etc. Usually, there is no primary sedimentation tank, and A section is the primary treatment system. A section and B section have their own unique sludge reflux system, and therefore have their own unique microbial population, which is conducive to the stabilization of the system's function.　However, the sludge yield of the AB method is relatively high, and the organic content of the sludge in section A is extremely high, so subsequent stabilization of the sludge is necessary, which will increase the investment and cost. In addition, since the A section removes more BOD, it may cause insufficient charcoal source to realize the nitrogen removal process. For occasions with low sewage concentration, it is more difficult to run the B section, and it is also difficult to play an advantage.　At present, there are only A section of the practice, the effect is better than the primary treatment, as a transitional process, in the performance-price ratio has a better advantage. Generally applicable to the discharge of the river, the discharge of the sea occasions.　At present, AB method has been widely used in Europe, by 1987, there have been 22 AB method of sewage treatment plant production, 21 in the construction and planning. In recent years, the domestic units have also carried out research on the AB method, and achieved some results, practice has proved that the process is a modern sewage treatment technology in a new development.AB process by the A-class aeration tank, intermediate sedimentation tank, B-class aeration tank and the final sedimentation tank composed of the main features of the AB process are: 1. A-class sludge load is very high, B-class sludge load is low. 2.　2. The microbial groups of class A and class B are obviously different in characteristics, and are strictly separated by two sets of return flow systems which are not related to each other.　3. There is no primary settling tank, making the A-stage an open biodynamic system.　4. Class A can be operated aerobically or anoxically according to the different components of sewage.　　Typical design parameters of AB process Table 1 Level F/M kgBOD5/kgMLSS-d Hydraulic retention time h MLSS g/L Mud age DO Level A 2～6 0.5 2.0 4～10h 0.2～0.7 Level B 0.10～0.30 2～4 3.5 15～20d 0.7～1.5 2. Operation mechanism of AB process 1. Removal of BOD, COD and SS The AB process is actually a treatment system consisting of an urban drainage network and a sewage treatment plant. Urban dwellers continuously excrete bacteria, about 5-10% of which can survive and proliferate under aerobic/parthenogenetic anaerobic conditions. Biological processes such as bacterial proliferation, adaptation and selection occur in the drainage network, resulting in the emergence of microbial communities in the raw sewage that are vigorous and adaptable to the raw sewage environment. Therefore, municipal wastewater is essentially a **** depository of pollutants and microbial communities. The biodynamic potential present in raw sewage is fully utilized in Class A of the AB process. The phenomena observed in the Tai'an City wastewater treatment test show that the removal of BOD and COD by the A-stage is not dominated by the rapid proliferation and degradation of bacteria, but by the flocculation and adsorption of bacteria. The static test showed that there are a large number of microorganisms in the raw sewage that have been adapted to the raw sewage, and these microorganisms have spontaneous flocculation. When they enter the A-level aeration tank, they flocculate together quickly under the induction and promotion of the original bacterial colloid in the A-level, the structure of the flocculent is similar to that of the bacterial colloid, and the flocculent combines with the original bacterial colloid at the same time of flocculation and becomes an integral part of the sludge in the A-level, with strong adsorption capacity and excellent settling performance. The amount of microorganisms being flocculated was related to the concentration of class A sludge, and the flocculation effect was poor when the sludge concentration was lower than 1 g/L. At the same time as flocculation and adsorption occurred, the microorganisms appeared to have a limited degree of proliferation, which may be related to the production of pro-flocculation effects (or substances) of class A sludge. According to the test of Tai'an City wastewater treatment, the microbial amount expressed in the form of SS in the influent water is 150mg/L, and the microbial amount in the effluent water of class A is 70mg/L. Then the sludge concentration Xi formed by the influent microorganisms in the class A can be calculated according to the following formula: Xi=Q△SQ c /V where:Q - influent water flow; Q c --Q c - the age of sludge in level A; △S - the amount of microorganisms retained in level A; V - the volume of aeration tank in level A.　Substitute the data into the above equation: Xi=4L/h×80mg/L×10h/2L =1600mg/L. The actual sludge concentration of class A is 2000mg/L, that is to say, the influent microorganisms in the sludge of class A account for about 80%, and only about 20% of it is produced by proliferation. Therefore, flocculation removal in Class A accounts for about 65% of the BOD removal in Class A, and removal due to adsorption and proliferation accounts for about 35%. The BOD removed by proliferation is basically dissolved BOD. 2. Removal of difficult to degrade substances in class A When the influent water is a mixture of municipal sewage and industrial wastewater or just industrial wastewater, the wastewater often contains many difficult to degrade substances, such as polycyclic aromatic compounds, halogenated hydrocarbons. If completely aerobic treatment, not only consume a lot of oxygen, and BOD removal often does not meet the required indicators. When the feed water is high in non-degradable substances, the A-class implementation of anoxic operation, in this case, a part of the microorganisms in the A-class through anaerobic digestion and incomplete oxidation and other ways to the BOD 5 undetectable, COD can be detected by the non-degradable organic matter into a BOD 5 easily detected easily degradable organic matter, this transformation is often difficult to achieve under aerobic conditions.　3.A level of shock load resistance A level of the microbial community of organic pollutants and toxic shock load has a significant buffer capacity, shock load stops after the A level can quickly return to normal, so the existence of the A level of changes in the quality of incoming water, pollutants and toxic shock load does not affect the subsequent process of stabilizing the operation.　In addition to adsorption, the shock load resistance of class A is also closely related to the following two biological processes.　(1) Microbial mutation Any bacterial population in activated sludge can respond to environmental changes in a variety of ways. At the beginning of the formation of a new environment, bacteria that are not adapted to the new environment die and subsequently disappear from the system. At the same time, the new environment provides favorable conditions for the dominant proliferation of other bacteria. An important source of adapted bacteria is mutations, which can be caused by mutagenic substances, i.e. changes in genetic material. Only one in a thousand of these mutations are positive mutations that can survive, the rest are lethal mutations. Considering the high bacterial population in the activated sludge within Class A, 7.5 x 10 5 positive mutations per population equivalent per day are possible. In addition to X-rays and Y-rays, chemicals such as nitrites are also mutagenic. Mutations can also be induced by the long-term effects of acids, alkalis and toxic substances prevalent in sewage. Mutations provide a biogenetic basis for activated sludge to adapt to new environments and degrade difficult-to-degrade substances. In contrast, the resistance of class A sludge to toxic substances stems from: (2) Plasmid transfer In medical treatment, plasmid transfer often results in the rapid spread of resistance genes, which causes medical difficulties, and the class A environment in the AB process is particularly conducive to plasmid transfer. Plasmids are circular DNA molecules that are not governed by chromosomes and can invade the bacterium and proliferate by self-replication using the bacterium's replication system. Plasmids generally carry resistance genes, and some plasmids also carry special genes that are not available in general bacteria, such as genes for degrading PCB. Numerous plasmids constitute the bacterial resistance gene pool and the gene pool for degradation of special organic substances. In selective process environments (e.g., shock loading), the plasmids' genes for resistance to toxicity and genes for degradation of specialized substances confer a clear advantage to the bacteria. In normal cell division, plasmids can pass on to daughter cells. Plasmids are also capable of transferring plasmid-carrying bacteria into plasmid-free bacteria by splicing, a process that is not limited by bacterial species or plasmid source, and is favored by the presence of high-density suspension of bacteria in Class A. The splicing process of enteric bacteria, which are dominant in Class A, takes 1.5-2.0 h. Assuming an age of 8 h for Class A sludge, at least four splices can occur in Class A microorganisms, during which approximately 10% of the bacteria are invaded by the plasmid. The propagation of plasmids in activated sludge increases the resistance of activated sludge to environmental changes, especially chemical changes. For sewage treatment plants (especially industrial wastewater treatment plants), the treatment effect and process stability is closely related to the presence or absence of plasmids.　4.AB Process and Nitrogen and Phosphorus Removal Due to the growing problem of eutrophication of water bodies and water scarcity; many wastewater must be treated with phosphorus and nitrogen removal, and then discharged into the water body or reuse. If other processes are used to replace the B level of the AB process, the AB process can be made to have a deep treatment effect.　(1) AB process with nitrogen removal In this type of process, B-level by aerobic process into a pre-denitrification process (such as anoxic/aerobic process).　A level of nitrogen and organic removal than conventional mechanical treatment of many times higher, significantly improving the nitrification conditions of the B level, so that the proportion of nitrifying bacteria in the B level sludge is significantly increased, the nitrification rate and then substantially increase the volume of the aeration zone can be correspondingly reduced. For denitrification, the removal rate of class A can be adjusted by changing the sludge load and operation mode of class A, so that the BOD 5 /TN ratio (3 or so) required for denitrification can be optimally adjusted. The test results showed that the proportion of denitrifying bacteria in the B-stage sludge was higher than that in the sludge of the conventional biological denitrification system, and the denitrification rate was two to three times higher, e.g., the denitrification rate of the B-stage sludge from the ARAKREFELD wastewater treatment plant without an additional carbon source was 6.3mgNO 3 -N/gMLSS-h. Due to the high rate of nitrification and denitrification of AB with nitrogen removal, the total process volume was about 20% less than that of the conventional biological denitrification process. The total volume of the process is about 20% less than that of the conventional biological nitrogen removal process.　(2) AB process with the function of phosphorus removal Due to the high phosphorus content of sludge and large sludge discharge, A level can remove 20-50% of the total phosphorus in the influent water. If the B level is replaced with anaerobic / aerobic (A/O) phosphorus removal process, the phosphorus concentration of the process final precipitation effluent will be very low (0.5mg / L or less). It is also possible to add a chemical method of phosphorus removal in the B level. The investment cost of the former is about 10% lower than the ordinary activated sludge method, and the latter is 5-20% higher. The operation cost of the former is about 10~20% lower than that of ordinary activated sludge method, while the latter is more than 10% higher.　(3) The combination of AB process and biological phosphorus removal and denitrogenation process Tai'an City Wastewater Treatment Plant will use this type of process, the process consists of A level plus biological phosphorus removal and denitrogenation process (such as A / A / C improved process). For the original sewage water quality fluctuations, BOD 5 and BOD 5 / TN ratio of high sewage, this type of process can not only ensure that the treatment effect meets the requirements, and process stability, energy saving effect is obvious.　　Design Points The necessary condition for normal operation of Class A is that there must be enough microorganisms in the raw sewage that have been adapted to the sewage. In municipal wastewater, these microorganisms basically come from human excreta. Since the removal efficiency of Class A is directly related to the amount of microorganisms in the influent water, it is not advisable to set up a primary sedimentation tank before Class A. In industrial wastewater and some municipal wastewater, the concentration of microorganisms that have been adapted to the sewage environment is very low or the microorganisms flocculate poorly, and the efficiency of class A decreases significantly. For this type of wastewater, the AB process is not suitable.　　In order to make full use of flocculation and adsorption effect, to ensure the efficient operation of class A, class A retention time is best controlled at 25 ~ 30 minutes, retention time increases rather unfavorable. the best sludge load of class A is 3-4kgBOD5/kgNLSS-d. The sludge concentration is too low or too high for the operation of the class A is not good, control at 2-2.5g/L better. The control of sludge age depends on the characteristics of sewage and the sludge concentration of class A. In class A, the sludge concentration is basically proportional to the sludge age, and the best control of the sludge age should be obtained through experiments or production practice.　　Class A sludge settling performance is excellent, SVI value is lower than 50, so the hydraulic retention time of the intermediate sedimentation tank can be controlled within 1.5h, and the sludge reflux ratio can be controlled within 70%.The design of class B is the same as the conventional method, and it must be noted that, when designing the class B, the influent quality should be adopted as the effluent quality of the class A. When designing the high-level AB process, the BOD5/TN ratio of the influent in class B should be guaranteed to be ≥ 3. The BOD5/TN ratio of class B is 3.3, the BOD5/TN ratio of class B is 3.3. BOD5/TN in about 3 sewage, set A level for biological phosphorus removal and nitrogen removal is unfavorable, and should not be used in advanced AB process (physical or chemical method of phosphorus removal and nitrogen removal exceptions).　　In China, sludge disposal is a headache. Due to the large amount of sludge produced by AB process, a reasonable solution to the problem of sludge disposal will help the popularization and application of AB process. In other words, the sludge problem is the main obstacle to the popularization of the AB process.　　Advantages Excellent pollutant removal effect, strong shock load resistance, good nitrogen and phosphorus removal effect and low investment and operation cost, etc.　　1: High removal efficiency of organic substrate.　　2: System operation is stable. Mainly in: small fluctuation of effluent water quality, strong shock load resistance, good sludge settling performance.　　3: Good effect of nitrogen and phosphorus removal.　　4: Energy saving. Low operating costs, low power consumption, can recover biogas energy. Tests have proved that the AB process saves 20%~25% of the running cost compared with the traditional one-section process.　　Disadvantages Disadvantages I: If the A section is not well controlled in operation, it is easy to produce odor, affecting the environmental health of the neighborhood, which is mainly due to the fact that the A section works under ultra-high organic load, so that the A section of the aeration tank operates under anaerobic conditions, resulting in the production of hydrogen sulfide, fecal matter, and other malodorous gases.　　Disadvantage 2: When the requirements for phosphorus removal and denitrogenation are very high, the A section should not be the original AB method to go to the distribution ratio of organic matter to remove BOD55% to 60%, because of this the B section of the aeration tank of the influent carbonaceous organic content of carbon, nitrogen, low ratio, can not be effective in denitrogenation.　　Disadvantage 3: High sludge yield, the sludge produced in section A is large, accounting for about 80% of the sludge production of the entire treatment system, and the high organic content in the residual sludge, which puts more pressure on the final stabilization and disposal of sludge.　　History The research and application of AB process in China has gone through the following three stages: Stage I: From the late 1970s to the early 1980s, many Chinese experts and scholars conducted in-depth, comprehensive and systematic research on the characteristics, operation mechanism, treatment process and stability of the AB process and played an active role in the application and popularization of the AB process in China. This has played a positive role in the application and popularization of "AB method" in China.　　The second stage: from the late 1970s to the 1980s, many universities and colleges in China have set up special research courses, especially the design and research departments have also carried out large-scale experimental research on the treatment of municipal wastewater and industrial wastewater by the AB method, which has gained a large amount of data and practical experience for the engineering design and application of the AB method, and played a very crucial role in its engineering application in China.　　The third stage: since the 1980s, China gradually began to "AB method" applied to municipal wastewater treatment and industrial wastewater treatment projects, has built a considerable number of AB process of municipal wastewater treatment plants, the results are remarkable, and achieved very considerable social and environmental benefits.　　Compared with the traditional activated sludge method, AB method has obvious advantages in terms of treatment efficiency, operation stability, project investment and operation cost. In general, AB process is suitable for high concentration of sewage, with sludge digestion and other subsequent treatment facilities of large and medium-sized municipal wastewater treatment plants, with obvious energy-saving effect