CN105693019B

CN105693019B - Method and system for treating wastewater containing nitrobenzene, aniline and cyclohexylamine

Info

Publication number: CN105693019B
Application number: CN201610092569.4A
Authority: CN
Inventors: 王林成; 赵坤; 冯殿兴; 张兆栋; 高永华
Original assignee: Shandong Huahong Chemical Co Ltd
Current assignee: SENNICS Co.,Ltd.
Priority date: 2016-02-19
Filing date: 2016-02-19
Publication date: 2020-02-04
Anticipated expiration: 2036-02-19
Also published as: CN105693019A

Abstract

The invention discloses a method and a device for treating wastewater containing nitrobenzene, aniline and cyclohexylamine. The invention breaks the multi-chain benzene ring material in the waste water into single-chain material in the catalytic oxidation tank, then passes through the neutralization tank, adds flocculating agent after adjusting the PH value, the flocculated waste water is separated from water in the sedimentation tank, the complex organic matter in the anaerobic system is decomposed into simple soluble organic matter under the action of the exoenzyme generated by the zymogenic bacteria, the hydrolysis of the hydrolysis acidification tank can improve the B/C ratio, improve the biodegradability of the waste water, the residual pollutant in the waste water is thoroughly degraded after the treatment of the SBR tank, the decoloration treatment is carried out through the active carbon adsorption tank, and the treated waste water reaches the discharge standard.

Description

Method and system for treating wastewater containing nitrobenzene, aniline and cyclohexylamine

Technical Field

The invention relates to the technical field of industrial wastewater treatment, in particular to a wastewater treatment method and system containing nitrobenzene, aniline and cyclohexylamine.

Background

The main components in the organic wastewater of nitrobenzene, aniline and cyclohexylamine (containing o-toluidine, m-dinitrobenzene and the like) are nitrobenzene, aniline, phenols, inorganic salts, organic salts, amines, heterocyclic compounds and the like, and the wastewater has the height of four, namely: high pollutant concentration, high salt content, high chroma and high toxicity, and has the features of low B/C content and poor biodegradability. The nitrobenzene wastewater is brownish red, and the aniline wastewater is black and has pungent smell and a certain amount of suspended matters, so that an effective pretreatment means is selected, the load of organic pollutants difficult to degrade in the wastewater is greatly reduced, the biodegradability of the wastewater is improved, and the method is a key for solving the problem of treatment of the wastewater.

Disclosure of Invention

The invention mainly solves the technical problem of difficult degradation of wastewater in the prior art, and the first purpose of the invention is to provide a wastewater treatment method containing nitrobenzene, aniline and cyclohexylamine.

The second object of the present invention is to provide a system for carrying out the above-mentioned method for producing nitrobenzene.

On one hand, the technical scheme adopted by the invention for realizing the first purpose is as follows:

a method for treating wastewater containing nitrobenzene, aniline and cyclohexylamine comprises the following steps,

s1, introducing wastewater containing nitrobenzene, aniline and cyclohexylamine into a water collecting tank, aerating and mixing, introducing into an acid adjusting tank, adjusting the pH value to 2-4, introducing into a catalytic oxidation tank, reacting under the action of a catalytic oxidation reagent,

s2, introducing the wastewater subjected to catalytic oxidation in the catalytic oxidation tank into a PH neutralization tank, adding an alkali liquor to adjust the PH value to 7-8, adding a flocculating agent reagent solution to perform flocculation treatment on the wastewater, introducing the wastewater subjected to flocculation treatment into a sedimentation tank to perform mud-water separation,

s3, introducing the wastewater on the upper layer of the sedimentation tank into a combined anaerobic system of a hydrolysis acidification tank and a UASB tank, wherein the hydrolysis acidification tank is used for improving the B/C ratio of the wastewater, the UASB tank is used for performing up-flow anaerobic treatment on the wastewater,

s4, sequentially introducing the wastewater treated in the combined anaerobic system into a contact oxidation tank and an SBR tank,

and S5, adsorbing the wastewater treated in the step S4 by using activated carbon.

Further, the catalytic oxidation reagent is a Fenton reagent, and comprises hydrogen peroxide and ferrous sulfate, and the proportion of the wastewater, the hydrogen peroxide and the ferrous sulfate in the catalytic oxidation tank is 1000: 9: 6.

further, the flocculant reagent liquid comprises an organic polymer polyacrylamide flocculant and iron salt.

Further, after the sludge and the water in the sedimentation tank are separated in the step S2, the sludge accumulated at the bottom of the sedimentation tank enters a pressure filtration system for pressure filtration and drying.

Further, the combined anaerobic system in the step S3 includes a hydrolysis acidification tank, a primary anaerobic tank, a secondary anaerobic tank, and a UASB tank, which are connected in sequence.

Further, the wastewater treated in the combined anaerobic system in the step S4 passes through the contact oxidation tank, then passes through the primary aerobic tank and the secondary aerobic tank in sequence, then passes through the SBR tank, and the contact oxidation tank, the primary aerobic tank, the secondary aerobic tank and the SBR tank are aerated by the blower.

Further, the contact oxidation tank, the primary aerobic tank, the secondary aerobic tank and the SBR tank are used for decomposing organic pollutants in the wastewater through aerobic microbial communities, wherein the aerobic microbial communities comprise pseudomonas, phenol-degrading polar bacillus, chlorella, coccoid sessile ciliates, creeping ciliates such as J ciliates, metazoan rotifers and rotifers, which phagocytose scattered sludge.

On the other hand, one technical solution adopted by the present invention to achieve the second object is:

the utility model provides a wastewater treatment system who contains nitrobenzene, aniline, cyclic ethylamine, is including the catch basin, transfer sour pond, catalytic oxidation pond, PH neutralization pond, sedimentation tank, hydrolysis-acidification pond, one-level anaerobism pond, second grade anaerobism pond, UASB pond, contact oxidation pond, one-level good oxygen pond, second grade good oxygen pond, SBR pond, buffer pool that connect gradually, the sedimentation tank still is connected with a filter pressing system.

Further, the wastewater outlet of the UASB pool is communicated with the second-stage anaerobic pool, and the wastewater outlet of the second-stage aerobic pool is communicated with the contact oxidation pool.

Compared with the prior art, the invention has the advantages that: the wastewater is treated in a catalytic oxidation tank in a sequential batch manner by an aerobic biomembrane method and an activated sludge process according to the operation cycle of SBR, the biochemical property of the wastewater is greatly improved, the wastewater passes through a neutralization tank, a flocculating agent is added after the pH value is adjusted, the flocculated wastewater enters a sedimentation tank for mud-water separation, the wastewater after mud-water separation is introduced into a combined anaerobic system of a hydrolytic acidification tank and a UASB tank, complex organic matters of the wastewater are decomposed into simple soluble organic matters under the action of extracellular enzymes generated by zymogenic bacteria and enter cells to be decomposed into fatty acids such as acetic acid, propionic acid, butyric acid, lactic acid and the like and alcohols such as ethanol by intracellular enzymes, hydrogen and carbon dioxide are generated simultaneously, the hydrolysis effect of the hydrolytic acidification tank can improve the B/C ratio and improve the biochemical property of the wastewater, then the wastewater enters a contact oxidation tank and the SBR tank, and (4) thoroughly degrading residual pollutants in the treated wastewater, and decoloring the wastewater by using an activated carbon adsorption tank, wherein the treated wastewater reaches the standard and is discharged.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a flow chart of the method for treating wastewater containing nitrobenzene, aniline and cyclohexylamine according to the invention

FIG. 2 is a schematic diagram showing the structure of a wastewater treatment system containing nitrobenzene, aniline and cyclohexylamine according to the present invention.

Description of reference numerals: 1. the system comprises a water collecting tank, 2, an acid adjusting tank, 3, a catalytic oxidation tank, 4, a PH neutralizing tank, 5, a sedimentation tank, 6, a hydrolysis acidification tank, 7, a primary anaerobic tank, 8, a secondary anaerobic tank, 9, a UASB tank, 10, a contact oxidation tank, 11, a primary aerobic tank, 12, a secondary aerobic tank, 13, an SBR tank, 14, a buffer tank, 15 and a filter pressing system.

Detailed Description

The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, and the scope of the present invention will be more clearly and clearly defined.

Referring to fig. 1 and 2, the method for treating wastewater containing nitrobenzene, aniline and cyclohexylamine according to the present invention comprises the following steps,

s1, introducing wastewater containing nitrobenzene, aniline and cyclohexylamine into a water collecting tank 1, aerating and mixing, introducing into an acid adjusting tank 2, adjusting the pH value to 2-4, introducing into a catalytic oxidation tank 3, reacting under the action of a catalytic oxidation reagent,

s2, introducing the wastewater after catalytic oxidation in the catalytic oxidation tank 3 into a PH neutralization tank 4, adding an alkaline solution to adjust the PH value to 7-8, adding a flocculating agent reagent solution to carry out flocculation treatment on the wastewater, introducing the wastewater after flocculation treatment into a sedimentation tank 5 to carry out mud-water separation,

s3, introducing the wastewater on the upper layer of the sedimentation tank 5 into a combined anaerobic system of a hydrolysis acidification tank 6 and a UASB tank 9, wherein the hydrolysis acidification tank 6 is used for improving the B/C ratio of the wastewater, the UASB tank 9 is used for performing up-flow anaerobic treatment on the wastewater,

s4, sequentially introducing the wastewater treated in the combined anaerobic system into a contact oxidation tank 10 and an SBR tank 13,

In the embodiment, wastewater containing nitrobenzene, aniline and cyclohexylamine is pumped into a water collecting tank 1, is fully aerated and uniformly mixed by an air blower, is conveyed to an acid adjusting tank 2 by a self-priming pump, is added with sulfuric acid to adjust the pH value to 2-4, then automatically overflows to a catalytic oxidation tank 3, and reacts under the action of a catalytic oxidant. The catalytic oxidant is a Fenton reagent generally, and comprises ferrous sulfate and hydrogen peroxide, when the proportion of the wastewater, the hydrogen peroxide and the ferrous sulfate in the catalytic oxidation tank 3 is 1000: 9: the best treatment effect is obtained when the treatment time is 6 hours. The multi-chain benzene ring substances in the wastewater after catalytic oxidation are broken into single-chain substances, the biodegradability of the wastewater is greatly improved, the wastewater automatically overflows to a PH neutralization tank 4 after the reaction is finished, an alkaline solution is added to adjust the PH value to 7-8, a PAM flocculant reagent solution is added to flocculate the wastewater, the flocculated wastewater enters a sedimentation tank 5 to be subjected to mud-water separation, and bottom sludge is accumulated and then enters a filter pressing system 15 to be subjected to filter pressing and drying.

The upper wastewater in the sedimentation tank 5 enters a combined anaerobic system of a hydrolysis acidification tank 6 and a UASB tank 9, the combined anaerobic system comprises the hydrolysis acidification tank 6, a primary anaerobic tank 7, a secondary anaerobic tank 8 and the UASB tank 9 which are sequentially connected, complex organic matters of the complex organic matters are decomposed into simple soluble organic matters under the action of extracellular enzymes generated by zymogenic bacteria, and enter cells to be decomposed into fatty acids such as acetic acid, propionic acid, butyric acid and lactic acid and alcohols such as ethanol by intracellular enzymes, and hydrogen and carbon dioxide are simultaneously generated. The hydrolysis of the hydrolysis acidification tank can improve the B/C ratio and improve the biodegradability of the wastewater. The effluent of the hydrolysis acidification tank 6 is pumped into the UASB tank 9 by a lift pump to continue the treatment of an upflow anaerobic sludge blanket, the wastewater pipe treated by the UASB tank can be connected back to the secondary anaerobic tank 8 by a branch, and the primary anaerobic tank 7, the secondary anaerobic tank 8, the hydrolysis acidification tank 6 and the UASB tank 9 implement anaerobic system circulation, so that the organic matters in the wastewater are decomposed more thoroughly.

The wastewater on the upper part of the UASB pool 9 overflows into a contact oxidation pool 10 and an SBR pool 13 in sequence, under the action of high-performance biomembrane and activated sludge, sequencing batch processing of an aerobic biomembrane method and an activated sludge method is carried out according to the operation period of the SBR in a jet aeration mode, the residual pollutants in the processed wastewater are thoroughly degraded, a primary aerobic pool 11 and a secondary aerobic pool 12 can be arranged between the contact oxidation pool 10 and the SBR pool 13, a wastewater outlet pipe in the secondary aerobic pool 12 can be connected back to the contact oxidation pool 10 by a branch, so that the residual pollutants in the wastewater are thoroughly decomposed, the contact oxidation pool 10, the primary aerobic pool 11, the secondary aerobic pool 12 and the SBR pool 13 all decompose the organic pollutants in the wastewater through aerobic microbiota, and the aerobic microbiota comprise pseudomonad, pseudomonas, chlorella and coccoid ciliates, The salt-tolerant effect of the stolon ciliates such as J ciliates, metazoan rotifers and immobilized rotifers which phagocytose scattered sludge is more obvious to high-concentration organic matters which are difficult to degrade in waste water, such as phenols, nitrobenzenes, aromatic hydrocarbons and the like, by adopting mixed strains which are well domesticated and screened, the waste water treated by the SBR tank 13 is decolorized by an activated carbon adsorption tank, and the treated waste water is discharged after reaching the standard.

The invention also provides a system for realizing the wastewater treatment method for producing nitrobenzene, aniline and ethylamine, which comprises a water collecting tank 1, an acid regulating tank 2, a catalytic oxidation tank 3, a PH neutralization tank 4, a sedimentation tank 5, a hydrolysis acidification tank 6, a primary anaerobic tank 7, a secondary anaerobic tank 8, a UASB tank 9, a contact oxidation tank 10, a primary aerobic tank 11, a secondary aerobic tank 12, an SBR tank 13 and a buffer tank 14 which are connected in sequence, wherein the sedimentation tank 5 is also connected with a filter pressing system 15. The wastewater containing nitrobenzene, aniline and cyclic ethylamine is conveyed to each pool in sequence through overflow or a self-sucking pump for reaction, the wastewater treatment effect is good, the automation degree is high, and the method is suitable for industrial wastewater treatment in batches in factories.

Preferably, in the wastewater treatment system for producing nitrobenzene, aniline and cyclohexylamine, the wastewater outlet of the UASB tank 9 is also communicated with the secondary anaerobic tank 8, the wastewater outlet of the secondary aerobic tank 12 is also communicated with the contact oxidation tank 10, part of the wastewater in the UASB tank 9 is recycled to the secondary anaerobic tank 8, the decomposition of organic matters in the wastewater is more thorough, and part of the wastewater in the secondary aerobic tank 12 is recycled to the contact oxidation tank 10, and the residual pollutants in the wastewater are basically and completely degraded.

The advantage of the present invention is that,

1. the Fenton reagent is used as a catalytic oxidation reagent, the Fenton reaction sedimentation tank is utilized to achieve good treatment effect, the Fenton oxidation technology is used for treating organic pollutants, namely-OH and the organic pollutants are reacted, the essence of the free radical oxidative degradation organic matters is that-OH propagates free radical chain reaction through electron transfer and other ways, part of-OH attacks organic matters RH and abstracts hydrogen to generate free radicals R-, and R-is further degraded into small molecular organic matters or mineralized into CO₂And HO2, wherein part of inorganic matters reacts with organic matters to cause C-C bonds or C-H bonds to be cracked and finally degraded into harmless matters. In addition, the nascent state Fe (OH)3 generated by the reaction has good adsorption and condensation functions, and can further reduce the concentration of residual pollutants in the wastewater and improve the quality of the effluent.

2. The process adopts high-efficiency primary and secondary anaerobic tanks (7 and 8) and a UASB (upflow anaerobic sludge blanket) type treatment process, the process can rapidly dilute and reduce the biotoxicity of the wastewater, and simultaneously, the organic pollutants containing benzene rings are destroyed by the facultative and anaerobic microorganism deep hydrolysis functions, so as to be beneficial to the implementation of aerobic biochemical reaction. Utilize multinomial efflux blender with the waste water of very low energy consumption with the waste water in the cell body intensive mixing fast, can keep the continuous even stirring of whole cell body simultaneously, make full use of cell body space. Has the advantages of low energy consumption and high organic load, andand the volume load of COD is generally 5-10KgCOD/m²And d, the COD substances can be greatly removed by strictly controlling the pH value and the temperature, the load of subsequent aerobic treatment is reduced, and the management and the maintenance are simple.

3. Adopts an aerobic activated sludge process: contact oxidation and SBR processes. The process generally adopts a contact oxidation method in China, and the adopted filler generally has low efficiency of adsorbing activated sludge, so that the sludge is easy to fall off, the effluent quality is turbid, and the settling efficiency of the sludge is poor. According to similar experience, the treatment effect of the single biochemical process on the nitrobenzene wastewater is not enough to reach the discharge standard, so that the series connection of the biochemical treatment process and the activated sludge process is required to be a complementary biological membrane biochemical treatment process. The contact oxidation tank 10 of the invention is followed by primary and secondary aerobic tanks (7, 8), and in order to be capable of continuous operation, high-efficiency adsorptive filler is adopted, which is beneficial to the attachment and growth of a large amount of activated sludge. The SBR tank is operated in a sequencing batch mode, a large amount of activated sludge in the tank is adsorbed and degraded by utilizing aeration, when the aeration is stopped, the activated sludge is deposited in a large amount, supernatant is guided out of the system by the water skimmer, and sludge at the lower layer is reserved.

The contact oxidation tank 10, the first-stage aerobic tank 11, the second-stage aerobic tank 12 and the SBR tank 13 are aerated by an air blower to ensure that the oxygen content in the water reaches about 2-4ppm, the waste water (COD is about 100ppm, the temperature is 32-34 ℃, the PH value is 7-8, the chroma is more than 20 times) received from an anaerobic system is treated, the COD is reduced to about 30ppm, the chroma is less than 20 times, and nitrobenzene and aniline substances are all less than 0.1ppm and far better than the related national standard.

The contact oxidation tank 10, the aerobic tank and the SBR tank 12 mainly have the function of converting organic pollutants in the wastewater into carbon dioxide and water by utilizing the life activities of aerobic microbial communities so as to achieve the aim of purifying the water. Similar engineering experience proves that the biggest difficulty of biochemical treatment of nitrobenzene wastewater is the maintenance of activated sludge and the overcoming of biotoxicity, and the wastewater treatment device effectively solves the problems by adding a small amount of broad-spectrum activated sludge and organic nutrient at regular intervals. Meanwhile, the invention can adopt a high-efficiency jet aerator, and can effectively improve the sedimentation performance of the activated sludge while obviously reducing the energy consumption (without using an air blower).

4. Unique mixed biochemical strains are used. Because nitrobenzene and aniline belong to organic aromatic hydrocarbon substances which are difficult to degrade, and the wastewater also contains phenols and thiophene substances which are difficult to degrade, the treatment difficulty is very high, organic pollutants in the wastewater are decomposed in the contact oxidation tank 10, the primary aerobic tank 11, the secondary aerobic tank 12 and the SBR tank 13 through aerobic microbial communities, wherein the aerobic microbial communities comprise pseudomonas, polar vibrio, chlorella, coccoid sessile ciliates, stolon ciliates such as J ciliate, metazoan rotifers and rotifers which phagocytize scattered sludge, and mixed strains which are well domesticated and screened are adopted. The strain has unique adaptability to industrial wastewater generated in the production processes of various dye intermediates such as nitrochlorobenzene, aniline, nitrobenzene, phenol, p- (o) aminoanisole, cyclohexanone and the like. The microorganism domesticated and cultured by the process has good tolerance to the substances, strong activity, high degradation rate and very stable effluent quality. The treatment rate is high, the removal rate reaches more than 99%, various effluent indexes can reach the GB8978-1996 first-class discharge standard, the effluent chromaticity is lower than 20 times, the operation is stable, and the treatment effect is good.

5. Adopts a high-efficiency sludge flocculation precipitation mixed reagent. When the wastewater is treated, a large amount of sludge in the wastewater needs to be settled firstly, so that the sludge and clear water are effectively separated, an efficient sludge flocculation precipitation reagent is adopted, the sludge flocculation precipitation reagent comprises an organic polymer polyacrylamide flocculant and an iron salt, and the sludge flocculation precipitation reagent is added under the condition of well controlling the pH value of the wastewater, so that the settling speed and the settling effect of the sludge are greatly accelerated, the sludge content in the wastewater entering a biochemical system is reduced to be below 5000ppm, and a foundation is laid for the operation of a subsequent wastewater treatment system.

Through the combination of the methods, the wastewater treatment effect is good, and various effluent indexes can reach the GB8978-1996 primary discharge standard.

The above description is only an embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that are not thought of through the inventive work should be included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope defined by the claims.

Claims

1. A method for treating wastewater containing nitrobenzene, aniline and cyclohexylamine is characterized in that: comprises the following steps of (a) carrying out,

s1, introducing wastewater containing nitrobenzene, aniline and cyclohexylamine into a water collecting tank (1), aerating and mixing, introducing into an acid adjusting tank (2), adjusting the pH value to 2-4, introducing into a catalytic oxidation tank (3), reacting under the action of a catalytic oxidation reagent,

s2, introducing the wastewater after catalytic oxidation in the catalytic oxidation tank (3) into a pH neutralization tank (4), adding an alkali liquor to adjust the pH value to 7-8, adding a flocculating agent reagent solution to perform flocculation treatment on the wastewater, and introducing the wastewater after flocculation treatment into a sedimentation tank (5) to perform mud-water separation, wherein the flocculating agent reagent solution comprises an organic polymer polyacrylamide flocculating agent and an iron salt;

s3, introducing the wastewater on the upper layer of the sedimentation tank (5) into a combined anaerobic system of a hydrolysis acidification tank (6) and a UASB tank (9), wherein the hydrolysis acidification tank (6) is used for improving the B/C ratio of the wastewater, the UASB tank (9) is used for performing up-flow anaerobic treatment on the wastewater,

s4, sequentially introducing the wastewater treated in the combined anaerobic system into a contact oxidation tank (10) and an SBR tank (13),

s5, adsorbing the wastewater treated in the step S4 by using activated carbon;

wherein the combined anaerobic system in the step S3 comprises a hydrolysis acidification tank (6), a primary anaerobic tank (7), a secondary anaerobic tank (8) and a UASB tank (9) which are connected in sequence;

wherein the wastewater treated in the combined anaerobic system in the step S4 passes through the contact oxidation tank (10), sequentially passes through the primary aerobic tank (11) and the secondary aerobic tank (12), then passes through the SBR tank (13), and is subjected to oxygenation and aeration through the contact oxidation tank (10), the primary aerobic tank (11), the secondary aerobic tank (12) and the SBR tank (13) by blowers; the contact oxidation tank (10), the primary aerobic tank (11), the secondary aerobic tank (12) and the SBR tank (13) decompose organic pollutants in the wastewater through aerobic microbial communities, wherein the aerobic microbial communities comprise pseudomonas, polar bacillus phenollyticus, pediococcus, coccid sessile ciliate, stolon ciliate, metazoan rotifers and rotifers which phagocytose scattered sludge;

the catalytic oxidation reagent is a Fenton reagent and comprises hydrogen peroxide and ferrous sulfate, and the proportion of the wastewater, the hydrogen peroxide and the ferrous sulfate in the catalytic oxidation tank (3) is 1000: 9: 6.

2. the method for treating wastewater containing nitrobenzene, aniline and cyclohexylamine according to claim 1, wherein: and (5) performing sludge-water separation on the wastewater in the sedimentation tank (5) in the step S2, and feeding sludge accumulated at the bottom of the sedimentation tank (5) into a filter pressing system for filter pressing and drying.

3. The method for treating wastewater containing nitrobenzene, aniline and cyclohexylamine according to claim 1, wherein: the creeping ciliates are J ciliates.

4. A system for realizing the wastewater treatment method containing nitrobenzene, aniline and cyclohexylamine according to any one of claims 1 to 3, characterized in that: including catch basin (1), accent sour pond (2), catalytic oxidation pond (3), pH neutralization pond (4), sedimentation tank (5), hydrolysis-acidification pond (6), one-level anaerobism pond (7), second grade anaerobism pond (8), UASB pond (9), contact oxidation pond (10), one-level good oxygen pond (11), second grade good oxygen pond (12), SBR pond (13), buffer pool (14) that connect gradually, sedimentation tank (5) still are connected with a filter-pressing system (15).

5. The system of claim 4, wherein: the wastewater outlet of the UASB pool (9) is communicated with the secondary anaerobic pool (8), and the wastewater outlet of the secondary aerobic pool (12) is communicated with the contact oxidation pool (10).