CN112591951A

CN112591951A - Catalytic electrolysis purification system and purification method for municipal sewage

Info

Publication number: CN112591951A
Application number: CN202110004741.7A
Authority: CN
Inventors: 罗依依
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-01-04
Filing date: 2021-01-04
Publication date: 2021-04-02

Abstract

The invention discloses a municipal sewage catalytic electrolysis purification system and a purification method, comprising a primary treatment device, a physicochemical purification device, a catalytic electrolysis deep purification device, a reduction device and a sludge treatment device, wherein the primary treatment device comprises a coarse grid, a fine grid and a grit chamber; the physicochemical purification is one of air flotation or coagulating sedimentation decontamination devices, and comprises a pH adjusting tank, a coagulation aiding tank, an air flotation tank or a sedimentation tank; the catalytic electrolysis deep purification device comprises an electrolysis machine and a degassing pool, wherein a sewage inlet and a sewage outlet of the electrolysis machine are respectively connected with the intermediate water pool and the degassing pool; the pipeline mixer of the reduction device is connected with the water outlet pipe of the degassing pool, and the water outlet of the pipeline mixer is connected with the water distributor at the bottom of the reduction pool. The invention can efficiently remove SS, chroma, COD, BOD, ammonia nitrogen, total nitrogen, animal and vegetable oil, petroleum and total phosphorus in the municipal sewage, kill fecal coliform bacteria, improve the concentration of dissolved oxygen and convert the sewage into recyclable water resources.

Description

Catalytic electrolysis purification system and purification method for municipal sewage

Technical Field

The invention relates to a municipal sewage catalytic electrolysis purification system and a purification method, in particular to a municipal sewage catalytic electrolysis purification system integrating physical purification, catalytic electrolysis denitrification, deep purification and other devices and a purification method thereof, belonging to the field of environmental protection.

Background

Municipal sewage is a polluted water body produced in the living and production processes of people. The concentration of main pollutants in municipal sewage in China is characterized by high concentration in south, low and north, and the general physical and chemical indexes are that COD is less than or equal to 700mg/L (mostly 200-500 mg/L, wherein the COD in the southern area is less than or equal to 500mg/L), BOD is less than or equal to 350mg/L (mostly 100-300 mg/L, and BOD in the southern area is less than or equal to 300mg/L), SS is less than or equal to 400mg/L, ammonia nitrogen is less than or equal to 50mg/L, total nitrogen is less than or equal to 70mg/L, and total phosphorus is less than or equal to. At present, municipal sewage at home and abroad mainly adopts a biochemical method, and is divided into primary treatment, secondary treatment and advanced treatment: the main process of the first-stage treatment comprises sewage collection, coarse grid filtration and fine grid filtration to an aeration sand settling tank and a primary settling tank; the main process of the secondary treatment comprises the following steps: three major types of activated sludge treatment, biofilm process and Membrane Bioreactor (MBR) processes. Moreover, the activated sludge treatment process applied to the urban sewage plant mainly has three series: (1) oxidation ditch series; (2) A/A/O series; (3) sequencing Batch Reactor (SBR) series. The biofilm process applied to the urban sewage treatment plant mainly comprises a Biological Aerated Filter (BAF) process and a Moving Bed Biofilm (MBBR) process. Membrane Bioreactors (MBR) are a new type of wastewater treatment process developed at the end of the 20 th century. The advanced treatment process applied at home and abroad mainly comprises a chemical dephosphorization and denitrification process. Since 1912, the biochemical treatment process of the sewage of clark invention has been for more than 100 years, the sewage treatment process has hardly changed significantly, but the existing biochemical treatment process of the sewage has eight outstanding problems:

1. unstable low-temperature operation: in a sewage treatment plant constructed by adopting an activated sludge treatment process, a biofilm process and a Membrane Bioreactor (MBR) process, the activity of nitrifying bacteria is strongly inhibited and the nitrification effect is poor due to low temperature in winter or some severe cold areas and when the water temperature is lower than 15 ℃, most of ammonia nitrogen in effluent is greater than 10mg/L, and some of ammonia nitrogen in effluent is even greater than 20 mg/L. Because the nitrification effect is poor, the denitrification effect is not guaranteed, and the total nitrogen of effluent is mostly more than 20 mg/L. Therefore, in winter, the effluent of the northern sewage treatment plant can not meet the quasi IV-class water quality of the environmental quality standard for surface water (GB3838-2002), which is the first grade A standard of the pollutant discharge standard for urban sewage treatment plant (GB 18918-2002).

2. The occupied area is large: when the activated sludge treatment process, the biofilm process and the Membrane Bioreactor (MBR) process are adopted to build a sewage treatment plant to treat sewage, the sewage retention time is more than 17 hours, the land area of the sewage treatment plant with more structures and ten thousand tons is 10-15 mu, the land occupation is large, and a large amount of waste of land resources is caused.

3. The effluent quality is not high: when the sewage treatment plant is constructed by adopting an activated sludge treatment process, a biofilm process and a Membrane Bioreactor (MBR) process to treat the sewage, the effluent quality is mostly quasi IV (mainly the total nitrogen can only reach about 10 mg/L) of pollutant discharge standard (GB 18918-.

4. Capacity expansion is achieved: due to the rapid economic development of the last forty years, most of the existing sewage treatment plants are located in urban centers, and when most of sewage is planned and constructed, the social and economic development is not estimated sufficiently, and enough extension land is not reserved, so that when the current capacity expansion is needed, no construction land is available.

5. The main root cause of water eutrophication is as follows: the eutrophication of the water body is mainly caused by the fact that the nitrogen and phosphorus content in the water body accumulates day by day and continuously and seriously exceeds the standard, and one of the main reasons for the result is the sewage discharge of a municipal sewage treatment plant. At present, according to the discharge standard of pollutants for urban sewage treatment plants, most of ammonia nitrogen in effluent of a sewage treatment plant constructed by an activated sludge process is larger than 1mg/L, most of total nitrogen is larger than 10mg/L, most of total phosphorus is larger than 0.4mg/L, a large amount of nitrogen and phosphorus in the effluent are discharged into a water body, and the content of the nitrogen and phosphorus accumulates day by month and continuously, so that eutrophication of the water body is caused, and a large amount of algae is proliferated and water bloom is erupted repeatedly.

6. Difficulty of sludge dehydration and odor of taste: when the biochemical method is adopted for treatment, the sludge contains a large amount of microbial colonies, the microbial colonies contain a large amount of intercellular water, and the sewage can be dehydrated to the water content of below 60 percent by adopting high-pressure plate-and-frame filter pressing after high-temperature cooking or physicochemical conditioning. In addition, because the sewage contains a large amount of organic matters and anaerobic bacteria, in the process of collecting, dehydrating and transferring the sludge, the organic matters can release a large amount of stink difficult to smell under the action of the anaerobic bacteria, and the production environment of a sewage treatment plant and the living environment around the sewage treatment plant are influenced.

7. The odor disturbs people: when the biochemical method is adopted for treatment, a large amount of gas with odor is generated in the anaerobic process and the anoxic process, and in order to eradicate the odor which disturbs people, more capital needs to be invested, and an odor collecting and treating device is built.

8. The carbon source needs to be added: firstly, when the COD concentration of inlet water is low and the carbon-nitrogen ratio is inconsistent; and secondly, when denitrification total nitrogen removal is required, carbon sources are required to be added.

Therefore, the reduction of nitrogen and phosphorus emission of urban sewage treatment plants is the primary target of municipal sewage treatment at present and is also an important problem. Therefore, although the classical sewage treatment processes are applied for more than a hundred years, the quality of the effluent cannot meet the index requirements of social and economic development and the quality standard of surface water environment (GB3838-2002) so far, and therefore, a novel sewage treatment process which has the advantages of high effluent quality (meeting the requirement of water resource utilization), short sewage retention time, small land area, few structures, low operation cost and greatly shortened construction time is urgently needed.

Disclosure of Invention

In order to solve the technical problems, the invention aims to provide a municipal sewage catalytic electrolysis deep purification system and a municipal sewage catalytic electrolysis deep purification method, which have the advantages of short process flow, short sewage treatment retention time, low operation cost, strong adaptability to water quality, good continuous effect and high effluent water quality, aiming at the defects of large occupied area, poor effluent quality, large investment, long purification time, unstable operation of northern sewage treatment plants in winter and high nitrogen and phosphorus content in effluent and water eutrophication in the existing sewage treatment plant treatment process.

The invention relates to a municipal sewage catalytic electrolysis purification system and a purification method, wherein the purification system comprises a primary treatment device, a physicochemical purification device, a catalytic electrolysis deep purification device, a reduction device and a sludge treatment device, the primary treatment device, the physicochemical purification device and the catalytic electrolysis deep purification device are sequentially connected, and sludge of the primary treatment device and the physicochemical purification device can enter the sludge treatment device for sludge treatment, so that the municipal sewage deep purification is realized.

After the municipal sewage is treated by the catalytic electrolysis purification system and the purification method, the effects of removing main sewage in the steps of water purification are shown in the table 1.1:

TABLE 1.1 Water purification Effect of Each step in removing Main Sewage

Processing unit

CODcr

BOD₅

SS

Ammonia nitrogen

Total phosphorus

Total nitrogen

Petroleum products

The water inflow is less than or equal to

700

350

300

50

10

70

-

The first-stage treatment is less than or equal to

630(10％)

315(10％)

210(30％)

50(-)

10(-)

70(-)

-

Physicochemical purification is less than or equal to

72(89％)

63(80％)

10(95％)

47.5(5％)

0.2(98％)

56(20％)

0.5(90％)

Electrolytic purification is less than or equal to

25.2(65％)

3.2(95％)

9(10％)

0.5(99％)

0.2(10％)

3.0(96％)

0.3(40％)

Elimination of sodium hyporeduction

25.2(-)

3.2(-)

9(-)

0.5(-)

0.2(-)

3.0(-)

0.3(-)

Standard of earth surface VI

≤30

≤6

-

≤1.5

≤0.3

≤1.5

≤0.5

Description of the drawings: 1. physicochemical purification following COD and BOD₅The removal rate is increased due to the increase of the concentration, and the COD is higher than 500mg/L (chemical oxygen demand), BOD₅The removal rate of the municipal sewage higher than 250mg/L is up to more than 90 percent, and the COD is 200-500 mg/L, BOD₅COD and BOD of municipal sewage of 150-250 mg/L₅The removal rate is 75-90%, and the COD is lower than 200mg/L (chemical oxygen demand) and BOD₅COD and BOD of municipal sewage higher than 100mg/L₅The removal rate is 65-80%; the physicochemical purification has poor ammonia nitrogen removal effect, the total nitrogen removal rate is 5-30%, and the total phosphorus removal rate is as high as 95-98%; 2. the removal rate of ammonia nitrogen in municipal sewage by catalytic electrolysis is up to 97-99%, the removal rate of total nitrogen is up to 90-96%, and meanwhile, the treatment effect on chromaticity, COD and BOD5 is good.

The residence time of each step after the above purification treatment is shown in Table 1.2.

Table 1.2 residence time units for the procedure: min

First stage treatment	Physicochemical purification	Electrolytic deep purification	Reduction of	Total up to
					5～10	15～20	20～60	20～30	60～120

After the municipal sewage purification system adopting the physicochemical purification and the electrolytic deep purification is treated by the steps, 95 percent of COD in the water body can be removed, the COD of the effluent is less than or equal to 30mg/L, 95 to 99 percent of BOD is removed, the BOD of the effluent is less than or equal to 6mg/L, 90 to 95 percent of total phosphorus is removed, the total phosphorus of the effluent is less than or equal to 0.3mg/L, 98 to 99.99 percent of ammonia nitrogen is removed, the ammonia nitrogen of the effluent is less than or equal to 1.5mg/L, the total nitrogen is removed by more than or equal to 96 percent, the total nitrogen of the effluent is less than or equal to 3.0mg/L, 80 to 95 percent of chroma is removed, the dissolved oxygen is increased to more than 3mg/L, and other indexes meet the requirements of the environmental quality Standard for surface Water (GB 38. Is particularly suitable for the purification treatment of municipal sewage, and leads the water body to reach the IV-class water quality standard of the environmental quality standard of surface water (GB 3838-2002). The main indexes of inlet and outlet water of sewage after deep purification by catalytic electrolysis are shown in table 1.3.

TABLE 1.3 Main indices of inlet and outlet water for purifying sewage or water

The invention eliminates the defects of poor effluent quality, large investment, long purification period and large occupied area of the existing sewage treatment process of the sewage treatment plant, so that the effluent of the sewage treatment plant reaches the IV-class or even III water quality standard of the quality standard of surface water environment (GB3838-2002), becomes a water resource which can be recycled, and the purified water is discharged to a natural water system, so that the water quality of the water body is improved, the water ecological system is recovered, and the reconstruction and the healthy sustainable development of river and lake ecological systems are realized. Compared with the prior art, the invention has the following outstanding effects:

1. high water quality and changing sewage into recyclable water resource

After the municipal sewage is purified by adopting the catalytic electrolysis deep purification system and the method thereof, except that the total nitrogen is less than or equal to 3mg/L, other indexes all reach IV-class water quality and even III-class standard of surface water environmental quality standard (GB3838-2002), the content of dissolved oxygen is higher than 7mg/L, the sewage is converted into water resource which can be recycled, and the water resource is discharged into natural water, so that the dissolved oxygen of the water body can be effectively improved, the growth of algae is effectively inhibited, the water quality is comprehensively improved and promoted, and meanwhile, the system and the method can be used as industrial and agricultural production and commercial water.

2. Eliminate nitrogen and phosphorus pollution from source

At present, the discharge standard of sewage is that total nitrogen is less than or equal to 15mg/L and total phosphorus is less than or equal to 0.5mg/L, and a large amount of nitrogen and phosphorus enter a water body along with the discharge water of the sewage treatment plant, so that nitrogen and phosphorus in the water body are greatly enriched, therefore, the discharge water of the sewage treatment plant is one of main sources of nitrogen and phosphorus in water bodies of rivers and lakes, and the nitrogen and phosphorus in the water body accumulate day by day and month, so that the nitrogen and phosphorus are seriously out of standard, the eutrophication of the water bodies of the rivers and lakes is caused, and the blue algae in the main lakes in China are erupted year after year. In order to radically treat blue algae, China invests a great deal of financial resources, manpower and material resources, but the yield is not high. After the municipal sewage catalytic electrolysis deep purification system and the method thereof are adopted to purify the sewage, the total nitrogen of the water body is less than or equal to 3mg/L, and the total phosphorus is less than or equal to 0.1mg/L, which both reach the III or IV water quality standard of the environmental quality standard of surface water (GB3838-2002), and the nitrogen and phosphorus pollution of the water body can be thoroughly eradicated from the source.

3. Simple process flow and simple operation

The sewage treatment by the method only comprises two main processes of physicochemical purification and catalytic electrolysis, and the production process flow is simpler than the existing sewage treatment production process flow, the number of building structures is less, and the operation is simpler.

4. Four-fifths of land is saved

At present, when sewage treatment plants constructed by an activated sludge method are adopted at home and abroad to treat sewage, most of the sewage stays for 13-20 hours, some of the sewage stays even for more than 20 hours, the land occupation of each ten thousand tons of sewage treatment facilities is 0.6-1 hectare, and the land occupation is large. When the municipal sewage catalytic electrolysis purification system is used for treating the municipal sewage, the retention time of a water body is only 1.0-2.0 hours, the occupied area of the device is only one fifth of that of the traditional device, the occupied area is small, a large amount of land resources can be saved, and the system is particularly suitable for cities with shortage of land resources and is more suitable for the capacity expansion transformation and the upgrading transformation of the existing sewage treatment plant with shortage of land resources.

5. Investment saving

At present, the investment for construction of ten thousand tons of fixed assets of urban sewage treatment plants per day of mainstream urban sewage treatment processes at home and abroad is about 3500-5000 ten thousand yuan, while the investment for construction of ten thousand tons of fixed assets of urban sewage treatment plants per day of the urban sewage treatment processes adopting the deep water purification system is about 4000-4500 ten thousand yuan, so that the investment can be saved compared with the existing process.

6. Low running cost

The operation cost of the municipal sewage catalytic electrolysis deep purification system for deep purification treatment of sewage is lower than that of the existing urban sewage treatment plant, but the water quality is much higher, and the effluent is a recyclable water resource, so the operation cost is relatively lower.

7. Short construction period

The main equipment physicochemical purification device, the electrolysis device and the like of the municipal sewage catalytic electrolysis deep purification system are all sizing equipment, the main equipment is produced in factories, and when the equipment is used for building a sewage treatment plant, the sizing equipment is assembled in the sewage treatment plant without building a large number of structures, so that the construction period of the sewage treatment plant is shortened by more than half compared with the construction period of the traditional sewage treatment plant, and the construction period is short.

In addition, the sludge of the sewage treatment plant constructed by the invention does not contain a large amount of microbial colonies, and the dehydration is relatively easy. Meanwhile, as the anaerobic treatment process is not adopted, no odor is generated in the running process of the sewage treatment facility, and the investment of a deodorization device is avoided.

Drawings

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

FIG. 1 is a schematic connection diagram of the municipal sewage catalytic electrolysis deep purification device of the invention.

FIG. 2 is a schematic diagram of the connection of the primary treatment apparatus of the present invention.

FIG. 3 is a schematic diagram of a physical and chemical purification device of the present invention as a coagulating sedimentation device.

FIG. 4 is a schematic view of the physical-chemical purification apparatus of the present invention being an air-floating purification apparatus.

FIG. 5 is a schematic view of a catalytic electrolysis apparatus of the present invention.

FIG. 6 is a schematic view of the sludge dehydrating apparatus of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without any inventive step, are within the scope of the present invention.

Referring to fig. 1, a catalytic electrolytic purification system for municipal sewage, comprising: the device comprises a primary treatment device (100), a materialization purification device (200), a catalytic electrolysis deep purification device (300), a reduction device (400) and a sludge treatment device (500), and specifically comprises the following components:

first-level processing device (100)

Referring to fig. 2, the primary treatment device (100) comprises a coarse grating (110), a fine grating (120), a grit chamber (130) and a lift pump (140), wherein an input port of the coarse grating (110) is communicated with a sewage pipe network, an output port of the coarse grating (110) is communicated with an inlet of the fine grating (120), an output port of the fine grating (120) is communicated with a water inlet of the grit chamber (130), and a water outlet of the grit chamber (130) is communicated with the lift pump (140); wherein, this primary treatment device (100) is used for getting rid of big particulate matter such as leaf, branch, peel, discarded plastics, paper and muddy sand in the sewage.

Materialization purification device (200)

The materialized purification device (200) is one of air-float purification or coagulating sedimentation purification device, and the materialized purification device (200) is used for removing SS, chroma, water-insoluble COD and BOD in the sewage₅Petroleum based, anionic surfactant and total phosphorus.

Referring to fig. 4, the materialized purification device (200) is an air flotation purification device, and the air flotation purification of the materialized purification device (200) is one of dissolved air flotation or shallow layer air flotation; wherein the materialized purification device (200) comprises a pH adjusting tank (210), a coagulation tank (220), a coagulation aiding tank (230), an air floatation tank (240) and a middle water tank (250); the water inlet of the pH adjusting tank (210) is connected with the water outlet of a lifting pump (140) behind the grit chamber (130), the water outlet of the pH adjusting tank (210) is connected with the water inlet of the coagulation tank (220), the water outlet of the coagulation tank (220) is connected with the water inlet of the coagulation aiding tank (230), the water outlet of the coagulation aiding tank (230) is connected with the water inlet of the air flotation tank (240), a scum outlet (241) is further arranged at the upper part of the air flotation tank (240), a clear water outlet (242) is arranged at the lower part of the air flotation tank (240), the clear water outlet (242) is connected with the water inlet of the middle water tank (250), and the scum outlet (241) is connected with a sludge pump (244).

In another preferred embodiment, referring to fig. 3, the materialized purifying device (200) is a coagulating sedimentation device, and the coagulating sedimentation device is one of a high-efficiency sedimentation device, a magnetic coagulation device and a supermagnetic coagulating sedimentation device. The materialized purification device (200) comprises a pH adjusting tank (210), a coagulation tank (220), a coagulation aiding tank (230), a sedimentation tank (240') and a middle water tank (250); the water inlet of the pH adjusting tank (210) is connected with the water outlet of a lifting pump (140) behind the grit chamber (130), the water outlet of the pH adjusting tank (210) is connected with the water inlet of the coagulation tank (220), the water outlet of the coagulation tank (220) is connected with the water inlet of the coagulation aiding tank (230), the water outlet of the coagulation aiding tank (230) is connected with the water inlet of a sedimentation tank (240 '), the top of the sedimentation tank (240') is provided with a supernatant outlet (242 '), and the supernatant outlet (242') is connected with the water inlet of the intermediate water tank (250); the bottom of the sedimentation tank (240 ') is provided with a sludge outlet (241 '), and the sludge outlet (241 ') is connected with a sludge pump (244). Preferably, the coagulation tank (220) further comprises a coagulant dosing device and a coagulation mixer, wherein one of a PAC solution, a ferric sulfate solution or a ferric trichloride solution with the mass ratio of 1-20% is stored in the coagulant dosing device; the coagulant aid tank (230) further comprises a coagulant aid dosing device and a stirrer, wherein a PAM solution with the mass ratio of 1-2 per mill is stored in the coagulant aid dosing device.

Further, the materialized purification device (200) further comprises a sludge return pump (243) for returning part of sludge in the sedimentation tank (240 or 240') to the coagulation aiding tank (230), an input port of the sludge return pump (243) is communicated with the sludge port, and an output port of the sludge return pump (243) is communicated with the coagulation aiding tank (230).

Deep purification device of catalytic electrolysis (300)

Referring to fig. 5, the catalytic electrolysis deep purification device (300) comprises an electrolysis machine (310), a direct current power supply (320), a degassing tank (330), an electrolyte adding device (340) and an electrode cleaning device (350), wherein a water inlet of the electrolysis machine (310) is connected with a water outlet of the intermediate water tank (250), a water outlet of the electrolysis machine (310) is connected with a water inlet (331) of the degassing tank, a water outlet (333) of the degassing tank is connected with a water inlet pipe (410) of a reduction device, a water outlet (430) of the reduction device (400) is communicated with a water discharge pipe and a water inlet of the air flotation tank (240) is provided with a circulating water pump (340) for returning part of the effluent to the physicochemical purification device (200); the clean water after the electrolysis deep purification firstly enters a water distributor (332) at the bottom of the degassing tank (330) through a water inlet (331) and then enters a water distributor (420) at the bottom of the reduction device (400) through a water inlet pipe (410) arranged at the upper part of the degassing tank (330); the electrolyte adding device (340) is composed of an electrolyte solution storage tank (341), an electrolyte solution delivery pump (342) and an electrolyte solution flowmeter, and the electrolyte adding device (340) is arranged on a pipeline from the lift pump to the electrolysis machine (310) and is mixed with sewage by adopting a pipeline mixer; the electrode cleaning device (350) is composed of an acid cleaning solution storage tank (351) and an acid cleaning solution delivery pump (352), wherein the acid cleaning solution adopts 2% -3% hydrochloric acid solution or 4% -5% citric acid solution, when the electrode of the catalytic electrolysis deep purification device is polluted and scaled and the electrolysis efficiency is reduced, the catalytic electrolysis device stops working, the electrode cleaning device (350) is started to remove the scale deposited on the surface of the electrode, and the wastewater of the electrode cleaning device (350) enters the physicochemical purification device (200) for treatment; the bottoms of the degassing pool (330) and the reduction device (400) are also provided with a drain outlet (334), and the drain outlet (334) is connected with a water inlet pipe of the physicochemical purification device (200); the catalytic electrolysis deep purification device (300) is used for removing ammonia nitrogen, total nitrogen and residues left after the treatment of the materialized purification device (200)Color, water-soluble COD and BOD₅Petroleum based and anionic surfactants.

Further, the working voltage of the electrolysis machine (310) can be 5-300V, and the current density can be 10-150 mA/cm². The electrolysis machine (310) further comprises an electrolyte adding device, and the electrolyte adding device comprises an electrolyte storage tank and a metering dosing pump. More specifically, the electrolyte adding device is used for adding 3-12% of sodium hypochlorite solution or 2-6% of sodium chloride solution into the catalytic electrolysis deep purification device (300). Preferably, during the deep purification of the catalytic electrolysis, according to the concentration of ammonia nitrogen in the water body, an electrolyte adding device is adopted for adding 10-12% of sodium hypochlorite solution into the deep purification device of the catalytic electrolysis, the adding amount is three-ten-thousandth to one-thousandth (volume ratio), and more preferably, the electrolyte adding device is adopted for adding 10-12% of sodium hypochlorite solution into the deep purification device of the catalytic electrolysis, the adding amount is three-ten-thousandth to six-thousandth (volume ratio).

Furthermore, a water inlet (331) of a degassing tank (330) of the catalytic electrolysis deep purification device (300) is connected with a water distributor (332) at the bottom of the degassing tank (330), a water outlet at the upper part of the degassing tank (330) is connected with a water inlet pipe of the reduction device (400), and the top of the degassing tank (330) is also provided with a slag scraper and a scum collecting tank for removing and collecting bubbles and scum generated by a large amount of nitrogen and carbon dioxide released during the electrolysis deep purification; the slag scraper is a reciprocating type or a rotary type slag scraper.

Reduction device (400)

The reducing device (400) comprises a water inlet pipe (410), a pipeline mixer arranged on the water inlet pipe, a water distributor (420), a reducing agent solution storage tank and a reducing agent solution metering and conveying pump; the water inlet pipe (410) is connected with a water outlet (333) at the top of a degassing tank (330) of the catalytic electrolysis deep purification device (300), and the middle part of the water inlet pipe (410) is provided with a pipeline mixer; the reducing agent solution storage tank is communicated with the water inlet pipe (410) through a reducing agent solution metering and conveying pump and is arranged in front of the pipeline mixer; the reduction device (400) is used for removing the residual sodium hypochlorite treated by the catalytic electrolysis deep purification device (300) to recover and purify the water body.

Specifically, the reduction device (400) is sleeved in the degassing pool (330), a water inlet pipe (410) of the reduction device is connected with a water outlet of the degassing pool (330), the water inlet pipe (410) is connected with a water distributor (420) at the bottom of the reduction device (400) from top to bottom, and the water outlet of the reduction device (400) is connected with a water drainage pipe; the reducing device (400) is also provided with a reducing agent solution storage tank, a reducing agent solution metering and conveying pump and a stirrer; the bottom of the degassing tank (330) and the bottom of the reduction device (400) are provided with drain outlets (334), and the drain outlets (334) are connected with the water inlets of the air floatation or coagulation sedimentation device (200).

Sludge treatment equipment (500)

Referring to fig. 6, the sludge treatment device (500) comprises a sludge pump (244), a sludge concentration tank (510), a physicochemical adjusting tank (520), a dehydrator (530) and a sludge tank (540); the inlet of the sludge pump (244) is connected with the sludge outlet (241') of the materialized purification device; an outlet of the sludge pump (244) is connected with an inlet of the sludge concentration tank (510), a supernatant outlet (511) is arranged at the upper part of the sludge concentration tank (510), and a concentrated sludge outlet (512) is arranged at the bottom of the sludge concentration tank (510); the supernatant water outlet (511) is connected with the water inlet of the physicochemical purification device (200), the concentrated sludge outlet (512) is connected with the inlet of the physicochemical adjusting tank (520), the outlet of the physicochemical adjusting tank (520) is connected with the dehydrator (530), the water outlet (531) of the dehydrator (530) is connected with the water inlet of the physicochemical purification device (200), and the sludge outlet of the dehydrator (530) is connected with the sludge tank (540).

In a specific embodiment, the sludge concentration tank (510) is a gravity concentration tank, the outlets of the sludge port, the sludge outlet (241') or the scum outlet (241) are respectively communicated with the input port of the sludge pump (244), the output port of the sludge pump (244) is communicated with the inlet of the gravity concentration tank (510), the gravity concentration tank (520) comprises an upper clear liquid zone and a lower sludge concentration zone from top to bottom, the water outlet of the upper clear liquid zone is used for being communicated with the water inlet pipe of the air flotation or coagulation sedimentation device (200), the sludge outlet of the lower layer is communicated with the inlet of the dehydrator (530), and the inlets of the gravity concentration tank (510), the physicochemical conditioning tank (520) and the dehydrator (530) are sequentially communicated.

Specifically, the catalytic electrolysis purification system for municipal sewage can adopt one of an underground type, a semi-underground type or an above-ground type.

A municipal sewage catalytic electrolysis deep purification method adopts the municipal sewage catalytic electrolysis deep purification system, and comprises the following steps:

step (1): first stage treatment

Municipal sewage sequentially passes through the coarse grating (110) and the fine grating (120) to be filtered to remove large-particle solids, then is output and flows into the grit chamber (130) to remove silt.

Step (2): physicochemical purification

Inputting the effluent water obtained in the step (1) into a pH adjusting tank (210), and adding 3-10 g/m³Continuously stirring the sodium hydroxide or sodium carbonate solution at the stirring speed of 80-200 r/min for 5-10 min, and adjusting the pH of the sewage to 9-9.5; the pH value is adjusted to 9-9.5, the mixture is sent into a coagulation tank (220), and 6-20 g/m is added through a coagulation dosing device³Continuously stirring the coagulant solution at the stirring speed of 100-200 r/min for 3-6 min; the effluent after the coagulant is added is input into a coagulation aiding tank (230), PAM is added through a coagulation aiding and medicine adding device, and the relation between the weight of the added PAM and the volume of the sewage is 0.1-1 g/m³Stirring and reacting for 3-10 min at a stirring speed of 20-80 r/min; the effluent of the coagulation-aiding tank (230) is input into an air flotation tank or a sedimentation tank (240 or 240 ') for solid-liquid separation, clear liquid is concentrated at the bottom of the air flotation tank (240) or the upper layer of the sedimentation tank (240'), scum or solid substances are collected at the upper part of the air flotation tank (240) or the bottom of the sedimentation tank (240 '), a solid-liquid separation middle area is formed in the middle of the air flotation tank or the sedimentation tank (240 or 240'), whether the sediment amount formed in the coagulation-aiding tank (230) is sufficient or not is judged, if not, a sludge reflux pump (243) is started, part of sludge flows back into the coagulation-aiding tank (230) from the air flotation tank or the sedimentation tank, flocculent sediment generation is promoted, and clear sewage obtained through physicochemical purification is input into an intermediate water tank (250). The main water quality of the effluent of the municipal sewage after physicochemical purification treatment is that the pH is 6-9, the chroma is less than 10, the COD (chemical oxygen demand) is less than or equal to 80mg/L, the total phosphorus (counted by P) is less than or equal to 0.3mg/L, and the anion surface activity isThe dosage is less than or equal to 0.5mg/L, and the dosage is less than or equal to 0.5mg/L for petroleum.

And (3): catalytic electrolysis deep purification

Conveying the purified clean water in the step (2) to an electrolytic machine (310) of a catalytic electrolysis deep purification device (300) through a lifting pump, and carrying out electrolysis deep purification on the clean water, wherein the sewage stays in the electrolytic machine (310) for 30-210 s; when sewage enters an electrolysis machine, adding 10-12% of sodium hypochlorite according to the proportion of 0.3-1 per mill (volume ratio), uniformly mixing by a pipeline mixer, and conveying the mixture into the electrolysis machine (310) for electrolysis and purification; hypochlorous acid generated by the electrolysis machine (310) reacts with ammonia nitrogen in the sewage to be converted into nitrogen, the generated nascent hydrogen reacts with nitrate radical and nitrite radical to generate nitrogen and water, and the generated nascent oxygen reacts with COD and BOD in the sewage₅Reacting to generate carbon dioxide and water; the working voltage of the electrolysis machine (310) is 5-300V, and the current density is 10-150 mA/cm²(ii) a Delivering the effluent obtained by electrolysis to a degassing tank (330), wherein the retention time is 10-60 min, and sodium hypochlorite generated by an electrolysis machine (310) reacts with COD in the water body to further remove COD and BOD in the water₅(ii) a Meanwhile, the oxygen of the new ecology generated by the electrolysis machine (310) reacts with the organic matters to remove COD and BOD in the sewage; a large amount of gases such as nitrogen, carbon dioxide and the like generated by electrolytic purification are released in a degassing pool (330) to generate a large amount of bubbles, and scum is collected in a scum collecting tank by a scum scraper; the clean water after the electrolytic denitrification and the deep purification is injected into a reduction device (400); the catalytic electrolysis deep purification device (300) is used for removing ammonia nitrogen, total nitrogen and residual chroma, water-soluble COD and BOD after treatment by the physicochemical purification device (200)₅Petroleum, anionic surfactant, the main indexes of effluent water are as follows: the pH value is 6-9, the chroma is less than 4, and the COD (chemical oxygen demand) is less than or equal to 30mg/L, BOD₅(five-day biochemical oxygen demand) is less than or equal to 6mg/L, NH3-N (ammonia nitrogen) is less than or equal to 1.5mg/L, total nitrogen is less than or equal to 3.0mg/L, total phosphorus (counted by P) is less than or equal to 0.3mg/L, anionic surfactant is less than or equal to 0.3mg/L, petroleum is less than or equal to 0.5mg/L, fecal coliform group is less than or equal to 10 (per L), dissolved oxygen is more than or equal to 3mg/L, and other indexes meet the requirements of surface water environmental quality standard (GB3838-2002) Table 1.

And (4): reduction of

And (3) quantitatively adding a 5-20% sodium sulfite solution into the reduction device (400), and eliminating excessive sodium hypochlorite in the clear water to recover the water body to form regenerated water meeting the requirements of life, production and application.

And (5): sludge dewatering

Respectively conveying the sludge generated after the primary treatment and the physicochemical purification in the step (1) and the step (2) and the scum subjected to catalytic electrolysis deep purification into a sludge concentration tank (510), and performing gravity concentration to form supernatant at the upper part and sludge at the bottom; conveying the supernatant in the supernatant layer to a water inlet pipe of an air floatation or coagulating sedimentation device (200), and conveying bottom sludge into a physicochemical adjusting tank (520); adding a physical and chemical conditioner into the physical and chemical regulating tank (520), conveying the physical and chemical conditioner into a dehydrator (530), processing the physical and chemical conditioner into organic mud blocks, and collecting the organic mud blocks, wherein the physical and chemical conditioner comprises lime, ferric trichloride and polyaluminium chloride.

In the coagulation, coagulation aiding and precipitation processes in the step (2), phosphate radicals and hydrogen phosphate radicals in the sewage react with trivalent aluminum ions or trivalent iron ions to generate iron phosphate precipitates, so that total phosphorus in the sewage is removed;

3Al³⁺+2PO₄ ^3-＝Al₃(PO₄)₂↓

in addition, as a large amount of generated floc precipitates have huge specific surface area and are charged, organic matters in the sewage can be adsorbed, and the chromaticity and COD in the sewage can be removed simultaneously; after physicochemical purification treatment, 80-95% of SS in the water body is removed, the SS in the water body is less than or equal to 50mg/L, 90-95% of total phosphorus in the water body is removed, the total phosphorus in the water body is less than or equal to 0.2mg/L, and 85-95% of COD in the water body is removed together, so that the COD in the sewage is less than or equal to 80 mg/L.

In step 3), the specific steps of the catalytic electrolysis deep purification can be as follows:

catalytic electrolysis: conveying the sewage subjected to physicochemical purification to an electrolysis machine (310) through an intermediate water tank (250) and a lifting pump for electrolysis for 30-210 s; during electrolysis, 10-12% of sodium hypochlorite solution or 2-6% of sodium chloride solution is added through an electrolyte adding system.

During the catalytic electrolysis deep purification, in the electrolysis equipment, the sodium hypochlorite generated by electrolysis reacts with ammonia nitrogen to generate nitrogen and sodium chloride, and the sodium chloride is electrolyzed to generate sodium hypochlorite.

NaOCl+H₂O→HOCl+NaOH

NH₃+HOCl→NH₂Cl+H₂O (monochloramine)

NH₂Cl+HOCl→NHCl₂+H₂O (dichloramine)

2NHCl₂+NaOCl→N₂↑+3NaCl+H₂O (denitrogenation main reaction one)

The main reaction formula is as follows:

2NH₃+3NaOCl→N₂↑+3NaCl+3H₂O

the generated sodium chloride is electrolyzed to generate sodium hypochlorite for repeated use, and the sodium hypochlorite plays a role as a catalyst.

Principle of deammoniation (side reaction)

At the same time, the radical O.produced by electrolysis reacts with ammonia to produce nitrate radical.

2NH₄ ⁺+5O₂→2NO₃ ^-+4H₂O

In addition, hydrogen generated by electrolysis reacts with nitrate and nitrite in the water body under the action of the catalyst to generate nitrogen, so that nitrate nitrogen in the water body is removed.

NO₃ ^-+H₂—→NO₂ ^-+H₂O

2NO₂ ^-+2H₂—→N₂↑+2H₂O (total nitrogen removal reaction)

Clear water after catalytic electrolysis deep purification flows into the water distributor at the bottom of the reduction tank through the top of the oxidation tank, the clear water flows from bottom to top, and the content of sodium hypochlorite in the produced excessive sodium hypochlorite reduced by 5-20% of sodium sulfite is less than or equal to 0.1 mg/L.

Specific examples are given below.

Example 1

The municipal sewage treatment plant constructed by the production process comprises primary treatment, physicochemical purification, catalytic electrolysis deep purification, sodium sulfite solution reduction and sludge dehydration, wherein: the primary treatment adopts a process of a coarse grating, a fine grating and an aeration desilting tank; the physicochemical purification adopts a coagulating sedimentation (high density sedimentation) process.

TABLE 1 Water quality index of influent water from certain Sewage treatment plant

Serial number	Item	Inflow (mg/L)	Water outlet (mg/L)	Removal Rate (%)
					1	COD	500	30	94.00
2	BOD	230	6	97.39
					3	SS	200	10	95.00
4	Total nitrogen (in N)	50	3	94.00
					5	Ammonia nitrogen (in N)	35	1.5	95.71
6	Total phosphorus (in terms of P)	8	0.3	96.25
					7	Chroma (dilution multiple)	80	5	93.75
8	pH	6～9	6～9	-

The urban domestic sewage enters a catalytic electrolysis purification system of the sewage treatment plant, and the catalytic electrolysis purification system comprises a primary treatment device (100), a physicochemical purification device (200), a catalytic electrolysis deep purification device (300), a reduction device (400) and a sludge treatment device (500).

The materialized purification device (200) is a coagulating sedimentation device.

The sewage enters a primary treatment device (100), a coagulating sedimentation device (200), a catalytic electrolysis deep purification device (300) and a reduction device (400) in sequence.

Adding 20% sodium hydroxide solution into sewage to adjust the pH to 9, adding 10% polyaluminium chloride (PAC) solution coagulant with the addition amount of 12mg/L (calculated by PAC), carrying out coagulation reaction at the rotating speed of 100 revolutions per minute, adding 1mg/L coagulant aid PAM, reacting at the rotating speed of 20 revolutions per minute, and separating in a sedimentation tank, wherein the water quality of the coagulating sedimentation effluent is shown in Table 2.

TABLE 2 Water quality index after high-efficiency precipitation treatment of a certain sewage treatment plant at a certain day

As can be seen from Table 2, the physicochemical purification device (200) (coagulating sedimentation) has good removal effects on SS, COD, BOD, total phosphorus, animal and plant oil, petroleum and chromaticity, but has poor removal effects on ammonia nitrogen and total nitrogen. The sewage after coagulating sedimentation enters a catalytic electrolysis deep purification device (300) for treatment, the treated water body enters a reduction device (400) for eliminating sodium hypochlorite, so that the water quality is reduced, and the effluent indexes are shown in table 3. The working voltage of the electrolytic machine (310) for catalytic electrolysis is 36.5V, and the current density is 11mA/cm². When the electrolysis machine works, a sodium hypochlorite solution with the concentration of 12 percent is added according to four ten-thousandth of the volume ratio and is uniformly mixed into the sewage through a pipeline mixer.

TABLE 3 Water quality index of a certain sewage after coagulating sedimentation and electrolytic denitrification

Serial number	Item	Coagulation water (mg/L)	Purified water (mg/L)	Removal Rate (%)
					1	COD	72.05	21.35	70.37
2	BOD	66.51	Not detected out	-
					3	SS	15	6	60.00
4	Animal and vegetable oil	0.5	0.4	20
					5	Petroleum products	0.3	0.2	33.33
6	Total nitrogen (in N)	45.31	2.63	94.20
					7	Ammonia nitrogen (in N)	40.09	0.72	97.21
8	Total phosphorus (in terms of P)	0.26	0.21	19.23
					9	Dissolved oxygen	2.5	8.91	-
10	Chroma (dilution multiple)	20	2	-
					11	pH	6～9	6～9	-

The water quality of the sewage treatment plant operating continuously for 7 days is shown in table 4.

Table 4 water quality index recording table unit for a certain sewage treatment plant operating for one continuous week: (mg/L)

As can be seen from Table 3, the effluent indexes of the municipal sewage after the catalytic electrolysis deep purification are less than 3mg/L, except that the total nitrogen, the effluent indexes completely meet the water quality standards of class VI in the quality standards of surface water environments (GB 3838-2002). As can be seen from Table 4, the effluent water obtained by the municipal wastewater treatment process provided by the invention all meets the Water quality Standard of the surface Water Environment (GB3838-2002) class VI (excluding total Nitrogen), and the operation is stable, even though the fluctuation of the quality of the influent water is large.

Example 2

The municipal sewage treatment plant of 20000 tons/day constructed by the production process mainly comprises primary treatment, physicochemical purification, catalytic electrolysis deep purification, sodium sulfite solution reduction and sludge treatment. Wherein: the primary treatment adopts a process of a coarse grating, a fine grating and a rotational flow desilting tank; the physicochemical purification adopts a super-magnetic precipitation separation process; the sludge dewatering adopts a centrifugal dewatering process. The sewage treatment plant is characterized by smaller treatment scale, lower COD (chemical oxygen demand) of inlet water, higher ammonia nitrogen and total nitrogen and unbalanced nutrition, if the traditional AAO sewage treatment process is adopted, a carbon source must be continuously added during operation, the operation cost is high, the total nitrogen of outlet water is higher, the technical requirement that the total nitrogen of the outlet water is less than or equal to 3mg/L cannot be met, and in addition, the urban center is treated by the project, and the land use is very short.

TABLE 5 Water in and out index of certain sewage plant

Serial number	Item	Inflow (mg/L)	Water outlet (mg/L)	Removal Rate (%)
					1	COD	300	30	90.00
2	BOD	130	6	95.38
					3	SS	100	10	90.00
4	Total nitrogen (in N)	50	3	94.00
					5	Ammonia nitrogen (in N)	35	1.5	95.71
6	Total phosphorus (in terms of P)	3	0.3	90.00
					7	Chroma (dilution multiple)	100	5	95.00
8	pH	7～9	7～9	-
					9	Dissolved oxygen	-	6.5	-

The system comprises a catalytic electrolysis deep purification system for municipal sewage, a water body purification system and a sludge treatment device, wherein the water body purification system comprises a primary treatment device (100), a physicochemical purification device (200), a catalytic electrolysis deep purification device (300), a sodium sulfite reduction device (400) and a sludge treatment device (500); the primary treatment device (100) is a coarse grating, a fine grating and a rotational flow desilting tank; the materialized purification device (200) is a super-magnetic precipitation separation device.

The water body sequentially enters a primary treatment device (100), a physicochemical purification device (200), a catalytic electrolysis deep purification device (300) and a sodium sulfite reduction device (400).

Adding 10% sodium hydroxide solution into sewage to adjust the pH value to 9, adding 20% PAC solution into the sewage in the physicochemical purification device (200), performing coagulation reaction at the rotation speed of 100 revolutions, adding 1mg/L of coagulant aid PAM, reacting at the rotation speed of 20 revolutions, and separating in a sedimentation tank, wherein the water quality of the coagulation sedimentation water is shown in Table 6.

TABLE 6 Water quality index of certain sewage after ultra-magnetic treatment

The water body after the ultra-magnetic precipitation treatment enters a catalytic electrolysis deep purification device (300) for treatment, the treated water body enters a reduction device (400) for reduction, sodium hypochlorite in the water body is eliminated,the effluent index is shown in Table 7. The working voltage of the electrolysis machine (310) is 5V, and the current density is 150mA/cm². When the electrolysis machine works, 12 percent of sodium hypochlorite solution is added into the sewage according to six ten-thousandth of volume ratio and is uniformly mixed through a pipeline mixer.

TABLE 7 Water quality index of municipal sewage after being subjected to ultramagnetic and catalytic electrolysis deep purification

Serial number	Item	Supermagnetic water outlet (mg/L)	Electrolyzed outlet water (mg/L)	Removal Rate (%)
					1	COD	80.00	30.00	62.50
2	BOD	65.00	6	90.77
					3	SS	10	10	0.00
4	Animal and vegetable oil	0.3	0.3	0.00
					5	Petroleum products	0.2	0.2	0.00
6	Total nitrogen (in N)	45.01	3.00	93.33
					7	Ammonia nitrogen (in N)	34.29	1.00	97.08
8	Total phosphorus (in terms of P)	0.30	0.20	33.33
					9	Dissolved oxygen	2.5	6.50	-
10	Chroma (dilution multiple)	30	5	83.33
					11	pH	7～9	7～9	-

The water quality of the sewage treatment plant which was continuously operated for one week is shown in Table 8.

Table 8 water quality index units for one week of continuous operation of a municipal sewage plant: mg/L

As can be seen from Table 7, the effluent indexes of the municipal sewage treated by the catalytic electrolysis advanced purification system (primary treatment, supermagnetic purification, catalytic electrolysis advanced purification and sodium sulfite reduction) completely meet the water quality standards of class VI in the Water environmental quality Standard (GB3838-2002) except total nitrogen. As can be seen from Table 8, the catalytic electrolysis deep purification system using the municipal sewage operates stably, and the quality of the effluent water completely meets the Water quality Standard of class VI of environmental quality Standard for surface Water (GB3838-2002) except for the total nitrogen.

Example 3

The municipal sewage treatment plant constructed by the production process comprises primary treatment, physicochemical purification, catalytic electrolysis deep purification, sodium sulfite solution reduction and sludge dehydration, wherein: the primary treatment adopts a process of a coarse grating, a fine grating and an aeration desilting tank; the materialization and purification adopts a magnetic coagulation process.

TABLE 9 Water quality index of municipal sewage plant in North China

Serial number	Item	Inflow (mg/L)	Water outlet (mg/L)	Removal Rate (%)
					1	COD	750	30	96.00
2	BOD	350	6	98.28
					3	SS	200	10	95.00
4	Total nitrogen (in N)	70	3	95.71
					5	Ammonia nitrogen (in N)	55	1.5	97.27
6	Total phosphorus (in terms of P)	8	0.3	96.25
					7	Chroma (dilution multiple)	80	5	93.75
8	pH	6～9	6～9	-

Sewage gets into municipal administration sewage's catalytic electrolysis deep purification system, purification system include primary treatment device (100), materialization purifier (200), catalytic electrolysis deep purification device (300), sodium sulfite reduction unit (400) and sludge treatment device (500).

The sewage enters a primary treatment device (100), a physicochemical purification device (200), a catalytic electrolysis deep purification device (300) and a sodium sulfite reduction device (400) in sequence.

Adding 15% of sodium hydroxide solution into the magnetic coagulation device to adjust the pH value of the sewage to 9, adding 15% of ferric sulfate coagulant with the addition amount of 30mg/L, carrying out coagulation reaction at the rotation speed of 100 revolutions, adding 1mg/L of coagulant aid PAM, reacting at the rotation speed of 30 revolutions, and then separating in a sedimentation tank, wherein the water quality of the magnetic coagulation effluent is shown in the table 10.

TABLE 10 Water quality index after magnetic coagulation treatment in actual operation of certain sewage plant

As can be seen from Table 10, the magnetic coagulation showed high COD and BOD₅(COD is higher than 500mg/L, BOD is higher than 250mg/L) municipal sewage has fine removal effect, and it gets into catalytic electrolysis deep purification device (300) purification treatment to the sewage after magnetic coagulation handles, and the water gets into sodium sulfite reduction pond (400) and takes off sodium hypochlorite reaction after handling, and the index of going out water is as table 11. The working voltage of the electrolysis machine (310) is 39V, and the current density is 10mA/cm². When the electrolysis machine works, a sodium hypochlorite solution with the concentration of 12 percent is added into the electrolysis machine according to one thousandth of the volume ratio and is uniformly mixed into sewage through a pipeline mixer.

TABLE 11 Water quality index of municipal sewage after catalytic electrolysis purification

Serial number	Basic control items	Magnetic coagulation water (mg/L)	Electrolyzed outlet water (mg/L)	Removal Rate (%)
					1	COD	73.5	21.3	71.0
2	BOD	61.3	1.1	60.2
					3	SS	9	8	11.1
4	Animal and vegetable oil	0.3	0.2	33.3
					5	Petroleum products	0.2	0.2	0
6	Total nitrogen (in N)	65.5	2.8	95.7
					7	Ammonia nitrogen (in N)	54.1	1.1	98.0
8	Total phosphorus (in terms of P)	0.23	0.19	17.4
					9	Dissolved oxygen	1.3	7.8	-
10	Chroma (dilution multiple)	5	2	60.0
					11	pH	7	7	-

The water quality of the wastewater treatment plant operating continuously for one week is shown in Table 12.

TABLE 12 operation record chart of catalytic electrolysis deep purification process for municipal sewage in certain factory

As can be seen from Table 11, the effluent indexes of the municipal sewage after being treated by the catalytic electrolysis advanced purification system (primary treatment, magnetic coagulation purification, catalytic electrolysis advanced purification and sodium sulfite reduction) completely meet the water quality standards of class VI in the Water environmental quality Standard (GB3838-2002) except for the total nitrogen. As can be seen from Table 12, the catalytic electrolysis deep purification system using the municipal sewage operates stably, and the water quality of the outlet water completely meets the Water quality Standard of class VI of environmental quality Standard for surface Water (GB3838-2002) except for the total nitrogen.

Example 4

The production process of the invention is adopted for construction of a certain municipal sewage plant, and comprises primary treatment, physicochemical purification, catalytic electrolysis deep purification, sodium sulfite solution reduction and sludge dehydration, wherein: the primary treatment (100) comprises: a coarse grating, a fine grating and an aeration desilting tank; the materialization purification device (200) adopts a shallow air flotation device.

Municipal sewage enters a primary treatment device (100) for treatment and then enters a shallow air flotation device (200), 1% of sodium hydroxide solution is firstly added into the shallow air flotation device (200) to adjust the pH value of the sewage to 9, 1% of ferric trichloride coagulant is added, the addition amount is 30mg/L, after coagulation reaction is carried out under the condition of 100 revolutions, coagulant aid PAM is added according to 1mg/L, reaction is carried out under the condition of 30 revolutions, then the sewage enters an air flotation tank for air flotation separation, effluent is subjected to deep purification through an electrolysis machine (310), effluent treated by the electrolysis machine enters a degassing tank (330) for degassing, effluent of the degassing tank (330) flows through a sodium hypochlorite reduction tank (400) to eliminate residual sodium hypochlorite, and water is recovered to obtain deep purified water. The water inlet and outlet indexes of the process are shown in the table 13.

TABLE 13 Water quality index of Water from municipal wastewater treatment plant

Serial number	Item	Inflow (mg/L)	Water outlet (mg/L)	Removal Rate (%)
					1	COD	300	30	90.00
2	BOD	150	6	96.00
					3	SS	200	10	95.00
4	Total nitrogen (in N)	50	3	94.00
					5	Ammonia nitrogen (in N)	35	1.5	95.71
6	Total phosphorus (in terms of P)	5	0.3	94.00
					7	Chroma (dilution multiple)	100	5	95.00
8	pH	6～9	6～9

The municipal sewage being fed into the sewageAfter being treated by a primary treatment device of the catalytic electrolysis deep purification system, the wastewater enters a shallow air flotation device (200) for purification to remove SS, COD and BOD₅And the water quality of the effluent is shown in table 14 after pollutants such as total phosphorus, animal and plant oil, petroleum and the like.

TABLE 14 Water quality index of municipal wastewater after passing through shallow air flotation device

As can be seen from Table 14, when the municipal wastewater concentration is low, the removal rate of pollutants such as COD by the physicochemical purification device is reduced. The shallow air flotation device (200) has good removal effect on SS, COD, BOD, total phosphorus, animal and plant oil, petroleum and chromaticity, but has poor removal effect on ammonia nitrogen and total nitrogen. The effluent purified by the shallow air flotation device (200) is subjected to deep purification by an electrolysis machine (310), the effluent purified by the electrolysis machine (310) enters a degassing tank (330) for degassing to remove nitrogen, carbon dioxide and foams generated by degassing, the effluent of the degassing tank (330) flows through a sodium hypochlorite reduction device (400) to remove residual sodium hypochlorite, so that the sewage is subjected to deep purification, and the effluent quality is as shown in Table 15.

TABLE 15 Water quality index of shallow air-floated effluent from certain sewage plant after deep electrolytic purification

The effect of the whole process of catalytic electrolysis deep purification of municipal sewage on the removal of main pollutants of sewage is shown in Table 16.

TABLE 16 removal effect of catalytic electrolysis for deep purification of municipal wastewater

Serial number	Item	Inflow (mg/L)	Electrolyzed outlet water (mg/L)	Removal Rate (%)
					1	COD	232.80	24.30	89.56
2	BOD	113.56	0.76	99.33
					3	SS	180	8	95.55
4	Animal and vegetable oil	1.2	0.2	83.33
					5	Petroleum products	0.7	0.2	71.43
6	Total nitrogen (in N)	47.70	2.93	93.86
					7	Ammonia nitrogen (in N)	42.52	0.18	99.58
8	Total phosphorus (in terms of P)	3.5	0.15	95.71
					9	Dissolved oxygen	2.6	7.93	-
10	Chroma (dilution multiple)	100	2	98.00
					11	pH	7	7.5	-

The water quality of the sewage treatment plant which was continuously operated for one week is shown in Table 17.

TABLE 17 operation record chart of catalytic electrolysis deep purification process for municipal sewage in certain factory

As can be seen from Table 16, the effluent indexes of the municipal sewage after being treated by the catalytic electrolysis deep purification system (primary treatment, shallow air flotation purification, catalytic electrolysis deep purification and sodium sulfite reduction) completely meet the water quality standards of class VI of the Water environmental quality Standard (GB3838-2002) except for the total nitrogen. As can be seen from Table 17, the catalytic electrolysis deep purification system using the municipal sewage operates stably, and the quality of the outlet water completely meets the Water quality Standard of class VI of the environmental quality Standard of surface Water (GB3838-2002) except for the total nitrogen, and meets the design requirements. However, when the COD concentration of the sewage is 150-300 mg/L, the removal rate of the sewage to COD is correspondingly reduced, and is between 85-97%, and the average is 90%.

Example 5

The production process of the invention is adopted for construction of a certain municipal sewage plant, and comprises primary treatment, physicochemical purification, catalytic electrolysis deep purification, sodium sulfite solution reduction and sludge dehydration, wherein: the primary treatment (100) comprises: a coarse grating, a fine grating and an aeration desilting tank; the materialization purification device (200) adopts a dissolved air flotation device.

Municipal sewage enters a primary treatment device (100) for treatment and then enters a dissolved air flotation device (200) for purification, effluent is subjected to deep purification through an electrolysis machine (310), effluent treated by the electrolysis machine enters a degassing tank (330) for degassing, and effluent of the degassing tank (330) flows through a sodium hypochlorite reduction device (400) to remove residual sodium hypochlorite, so that water is recovered to obtain deep purified water. The water inlet and outlet indexes of the process are shown in the table 18.

TABLE 18 Water quality index of Water from municipal Sewage treatment plant

Serial number	Item	Inflow (mg/L)	Water outlet (mg/L)	Removal Rate (%)
					1	COD	300	30	90.00
2	BOD	150	6	96.00
					3	SS	200	10	95.00
4	Total nitrogen (in N)	50	3	94.00
					5	Ammonia nitrogen (in N)	35	1.5	95.71
6	Total phosphorus (in terms of P)	5	0.3	94.00
					7	Chroma (dilution multiple)	80	5	93.75
8	pH	6～9	6～9	-

The municipal sewage enters a primary treatment device of a catalytic electrolysis deep purification system of the sewage for treatment, then enters a dissolved air flotation device (200) for purification, 1 percent of sodium hydroxide solution is added into the dissolved air flotation device (200) to adjust the pH value of the sewage to 9, then 5 percent of PAC solution is added, and the adding amount is 12g/m³Air floating to remove SS, COD and BOD₅And the water quality of the effluent is as shown in table 19 after pollutants such as total phosphorus, animal and plant oil, petroleum and the like.

TABLE 19 Water quality index of effluent after dissolved air flotation purification in certain sewage plant

Serial number	Item	Sewage plant influent (mg/L)	Air-float water outlet (mg/L)	Removal Rate (%)
					1	COD	217.80	44.40	79.61
2	BOD	100.59	39.00	61.23
					3	SS	165	8	95.15
4	Animal and vegetable oil	-	0.2	-
					5	Petroleum products	-	0.3	-
6	Total nitrogen (in N)	46.48	39.62	14.76
					7	Ammonia nitrogen (in N)	41.31	42.63	-3.2
8	Total phosphorus (in terms of P)	3.9	0.18	95.38
					9	Dissolved oxygen	2.2	4.2	-
10	Chroma (dilution multiple)	90	5	94.44
					11	pH	7	7.5	-

The effluent purified by the dissolved air flotation device (200) is subjected to deep purification by a catalytic electrolysis machine (310), the effluent purified by the electrolysis machine (310) enters a degassing tank (330) for degassing to remove nitrogen, carbon dioxide and foams generated by degassing, the effluent of the degassing tank (330) flows through a sodium hypochlorite reduction device (400) to remove residual sodium hypochlorite, so that the sewage is subjected to deep purification, and the effluent quality is as shown in table 20.

TABLE 20 Water quality index of dissolved air flotation effluent from certain sewage plant after deep purification by electrolysis

Serial number	Item	Air-float water outlet (mg/L)	Electrolyzed outlet water (mg/L)	Removal Rate (%)
					1	COD	44.40	17.70	26.70
2	BOD	39.00	Not detected out	100
					3	SS	8	7	12.50
4	Animal and vegetable oil	0.2	0.2	0
					5	Petroleum products	0.3	0.2	33.33
6	Total nitrogen (in N)	39.62	2.46	93.79
					7	Ammonia nitrogen (in N)	42.63	1.28	97.00
8	Total phosphorus (in terms of P)	0.18	0.15	16.67
					9	Dissolved oxygen	4.2	8.5	-
10	Chroma (dilution multiple)	5	2	90.0
					11	pH	7.5	7.5	-

The effect of the whole process of catalytic electrolysis deep purification of municipal sewage on the removal of main pollutants of sewage is shown in table 21.

TABLE 21 Effect of catalytic electrolytic deep purification on removal of major pollutants of municipal wastewater

As can be seen from Table 21, the effluent indexes of the municipal sewage after being treated by the catalytic electrolysis deep purification system (primary treatment, dissolved air flotation purification, catalytic electrolysis deep purification and sodium sulfite reduction) completely meet the water quality standards of class VI in the Water environmental quality Standard (GB3838-2002) except for the total nitrogen.

While the foregoing description shows and describes the preferred embodiments of the present invention, it is to be understood that the invention is not limited to the forms disclosed herein, but is not to be construed as excluding other embodiments and is capable of use in various other combinations, modifications, and environments and is capable of changes within the scope of the inventive concept as described herein, commensurate with the above teachings, or the skill or knowledge of the relevant art. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A catalytic electrolysis purification system for municipal sewage is characterized by comprising a primary treatment device, a physicochemical purification device, a catalytic electrolysis deep purification device, a reduction device and a sludge treatment device, wherein,

the primary treatment device comprises a coarse grating, a fine grating, a grit chamber and a lift pump which are connected in sequence, wherein an input port of the coarse grating is communicated with a sewage pipe network, and a water outlet of the lift pump is communicated with the physicochemical purification device;

the materialized purification device is one of an air flotation purification device or a coagulating sedimentation purification device, the air flotation purification device comprises a pH adjusting tank, a coagulating tank, a coagulation assisting tank, an air flotation tank and a middle water tank which are sequentially connected, a water inlet of the pH adjusting tank is connected with a water outlet of the lift pump, a scum outlet is further formed in the upper part of the air flotation tank, a clear water outlet is formed in the lower part of the air flotation tank, the clear water outlet is connected with a water inlet of the middle water tank, and the scum outlet is connected with a sludge pump; or the coagulating sedimentation purification device comprises a pH adjusting tank, a coagulating basin, a coagulation assisting tank, a sedimentation basin and an intermediate water tank which are connected in sequence, wherein a supernatant outlet is arranged at the top of the sedimentation basin and is connected with a water inlet of the intermediate water tank, a sludge outlet is arranged at the bottom of the sedimentation basin and is connected with a sludge pump;

the catalytic electrolysis deep purification device comprises an electrolysis machine, a degassing tank, an electrolyte feeding device and an electrode cleaning device, wherein a water inlet of the electrolysis machine is connected with a water outlet of the middle water tank, a water outlet of the degassing tank is connected with a water inlet pipe of a reduction device, a water outlet of the reduction device is communicated with a water discharge pipe and is also provided with a circulating water pump between the water inlet of the flotation tank or the sedimentation tank, the electrolyte feeding device is arranged on a pipeline between the lifting pump and the electrolysis machine and is mixed with sewage by adopting a pipeline mixer, the electrode cleaning device is composed of an acid pickling solution storage tank and an acid pickling solution delivery pump, and the acid pickling solution adopts 2-3% hydrochloric acid solution or 4-5% citric acid solution;

the reducing device comprises a water inlet pipe, a pipeline mixer, a water distributor, a reducing agent solution storage tank and a reducing agent solution metering and conveying pump, wherein the pipeline mixer, the water distributor, the reducing agent solution storage tank and the reducing agent solution metering and conveying pump are installed on the water inlet pipe;

the sludge treatment device comprises a sludge pump, a sludge concentration tank, a physicochemical adjusting tank, a dehydrator and a sludge tank, wherein the inlet of the sludge pump is connected with the sludge outlet of the physicochemical purification device; the outlet of the sludge pump is connected with the inlet of the sludge concentration tank, the upper part of the sludge concentration tank is provided with a supernatant outlet, and the bottom of the sludge concentration tank is provided with a concentrated sludge outlet; the supernatant outlet is connected with the water inlet of the physicochemical purification device, the concentrated sludge outlet is connected with the inlet of the physicochemical adjusting tank, the outlet of the physicochemical adjusting tank is connected with the dehydrator, the water outlet of the dehydrator is connected with the water inlet of the physicochemical purification device, and the sludge outlet of the dehydrator is connected with the sludge tank.

2. The catalytic electrolytic purification system for municipal sewage according to claim 1, wherein the air flotation purification apparatus is one of a dissolved air flotation apparatus or a shallow air flotation apparatus.

3. The system of any one of claims 1 or 2, wherein the coagulation sedimentation purification device is one of a high efficiency sedimentation device, a magnetic coagulation device and a supermagnetic coagulation sedimentation device.

4. The system of claim 1, wherein the degassing tank has a water inlet connected to a water distributor at the bottom of the degassing tank, and a water outlet at the upper part of the degassing tank is connected to a water inlet pipe of the reduction unit, and the top of the degassing tank is further provided with a scum scraper and a scum collection tank.

5. The catalytic electrolysis purification system for municipal sewage according to claim 1, wherein the coagulation tank comprises a coagulant dosing device and a coagulation mixer, wherein one of a PAC solution, a ferric sulfate solution or a ferric trichloride solution is placed in the coagulant dosing device at a mass ratio of 1-20%; the coagulant aid tank comprises a tank body, a coagulant aid feeding device and a stirrer, wherein a PAM solution with the mass ratio of 1-2 per mill is stored in the coagulant aid feeding device.

6. The system of claim 1, wherein the device further comprises a sludge reflux pump, an input port of the sludge reflux pump is communicated with the sludge port, and an output port of the sludge reflux pump is communicated with the coagulation aiding tank.

7. The system of claim 1, wherein the sludge concentration tank is a gravity concentration tank, and the outlet of the sludge pump is communicated with the inlet of the gravity concentration tank; including the clear liquid district on upper strata and the sludge concentration district of lower floor from top to bottom in the gravity concentration pond, the delivery port in the clear liquid district on upper strata is used for the intercommunication materialization purifier, the sludge concentration district of lower floor with the import intercommunication of hydroextractor.

8. The system of claim 1, wherein the degassing tank and the reduction device are provided with a drain outlet at the bottom, and the drain outlet is connected with the water inlet of the physicochemical purification device.

9. A catalytic electrolysis purification method of municipal sewage is characterized by comprising the following steps:

(1) primary treatment: filtering the municipal sewage through a coarse grating and a fine grating in sequence to remove large-particle solid matters, outputting the municipal sewage and flowing into a grit chamber to remove silt;

(2) physicochemical purification: inputting the effluent water obtained in the step (1) into a pH adjusting tank, and adding 3-10 g/m³Continuously stirring sodium hydroxide or sodium carbonate solution at the stirring speed of 80-200 r/min for 5-10 min, adjusting the pH of the sewage to 9-9.5, then sending the adjusted sewage into a coagulation tank, and adding 6-20 g/m of the sewage into the coagulation tank through a coagulation medicine adding device³Continuously stirring the coagulant solution at the stirring speed of 100-200 r/min for 3-6 min; the effluent after the coagulant is added is input into a coagulation-aiding tank, PAM is added through a coagulation-aiding dosing device, and the relation between the weight of the added PAM and the volume of the sewage is 0.1-1 g/m³Stirring and reacting for 3-10 min at a stirring speed of 20-80 r/min; the effluent of the coagulation aiding tank is input into an air floatation tank or a sedimentation tank for solid-liquid separation, sewage clear liquid obtained by physicochemical purification is input into an intermediate water tank, whether the precipitation amount formed in the coagulation aiding tank in the step is sufficient or not is judged, if not, a sludge reflux pump is started, and part of sludge flows back into the coagulation aiding tank from the air floatation tank or the sedimentation tank to promote generation of flocculent precipitate;

(3) deep purification by catalytic electrolysis: conveying the clean water which is subjected to physicochemical purification in the step (2) and is input into an intermediate water tank to an electrolysis machine through a lifting pump for deep electrolysis purification, allowing the sewage to stay in the electrolysis machine for 30-210s, adding 10-12% of sodium hypochlorite according to the volume ratio of 0.3-1 per mill when the sewage enters the electrolysis machine, uniformly mixing the sodium hypochlorite and the sewage through a pipeline mixer, and conveying the mixture to the electrolysis machine for deep electrolysis purification, wherein the working voltage of the electrolysis machine is 5-300V, and the current density is 10-150 mA/cm²(ii) a Conveying the effluent obtained by electrolysis to a degassing tank, keeping the effluent for 10-60 min, and then injecting the effluent in the degassing tank into a reduction device;

(4) reduction: quantitatively adding a 5-20% sodium sulfite solution into the reduction device to recover the water body;

(5) sludge dewatering: conveying sludge or scum generated after primary treatment and physicochemical purification in the step (1) and the step (2) into a sludge concentration tank for gravity concentration to form an upper clear liquid area and a lower sludge concentration area from top to bottom; conveying the liquid in the upper clear liquid area to a physical and chemical purification device, and conveying the sludge in the lower sludge concentration area to a physical and chemical regulation pool; and adding a physical and chemical conditioner into the physical and chemical conditioning tank, and conveying the physical and chemical conditioner into a dewatering machine for dewatering, wherein the physical and chemical conditioner comprises lime, ferric trichloride and polyaluminium chloride.

10. The catalytic electrolysis purification method for municipal sewage according to claim 1, wherein the effluent indexes after the treatment in steps (1) to (4) are as follows: COD of the effluent is less than or equal to 30mg/L, BOD of the effluent is less than or equal to 6mg/L, total phosphorus of the effluent is less than or equal to 0.3mg/L, ammonia nitrogen of the effluent is less than or equal to 1.5mg/L, total nitrogen of the effluent is less than or equal to 3.0mg/L, chromaticity is removed by 80-95%, and dissolved oxygen is increased to be more than 3 mg/L.