CN113968658A

CN113968658A - Biochemical effluent purification device for landfill leachate and deep purification method thereof

Info

Publication number: CN113968658A
Application number: CN202111109746.2A
Authority: CN
Inventors: 张世文
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-09-18
Filing date: 2021-09-18
Publication date: 2022-01-25

Abstract

The invention discloses a biochemical effluent purification device of landfill leachate and a deep purification method thereof, the device comprises a biochemical effluent device, a hardness removal device, a catalytic electrolysis denitrification device, a filter biochemical treatment device and a coagulating sedimentation device, the biochemical effluent treated by the landfill leachate sequentially passes through the purification device to be subjected to hardness removal, catalytic electrolysis denitrification, filter biochemical treatment and coagulating sedimentation, and the effluent reaches the standard of pollutant control standard of domestic garbage landfill (GB16889-2008), has no concentrated solution, and is particularly suitable for the reconstruction of the existing landfill leachate treatment plant.

Description

Biochemical effluent purification device for landfill leachate and deep purification method thereof

Technical Field

The invention relates to a purification system and a purification method for garbage percolation treatment, in particular to a purification system and a purification method for biochemical effluent of garbage percolation treatment, which are characterized in that the effluent after advanced treatment reaches all indexes in table 2 of domestic garbage landfill pollution control Standard (GB16889-2008), does not contain concentrated solution, and belong to the field of environmental protection.

Background

The landfill leachate is liquid seeped out by the actions of microbial fermentation, rainfall leaching and the like in a landfill site due to stacking and landfill, is high-ammonia nitrogen and high-COD organic wastewater, and mainly comes from the following three aspects: 1. water released by the fermentation and decomposition of microorganisms after the landfill; 2. the water contained in the garbage is separated out; 3. natural rainfall and runoff and groundwater infiltration in landfills. Typical values of the pollutant content of municipal landfill leachate are shown in table 1.

TABLE 1 general landfill leachate principal Components (except for pH and sensory index, in mg/L)

As can be seen from table 1, the quality of landfill leachate has the following basic characteristics: firstly, the concentration of pollutants such as ammonia nitrogen, total ammonia, COD, BOD and the like is high, and the concentration of the pollutants is more than dozens to hundreds of times of the national discharge standard of industrial pollutants. Secondly, the carbon nitrogen (C/N) ratio is seriously disordered, particularly the ammonia nitrogen concentration of most leachate is high, the nutrition ratio of the leachate is far away from the nutrition ratio required by the growth of microorganisms during the biological treatment, the high ammonia nitrogen inhibits the growth of the microorganisms, and certain difficulty is brought to the biological treatment. In addition, the pollution-free environment-friendly paint contains organic pollution components, inorganic pollution components and trace heavy metal pollution components, and has obvious comprehensive pollution characteristics.

The ammonia nitrogen content and the COD concentration of the landfill leachate are high, so that the ground water body is anoxic and the water quality is deteriorated; the nutrient substances such as nitrogen and phosphorus are the causes of water eutrophication, and can also seriously affect the drinking water source; generally, the COD, BOD, BOD/COD decreases with "age" of the landfill and the alkalinity content increases. In addition, with the increase of the stacking age, the fresh garbage is gradually changed into the stale garbage, the content of organic matters in the percolate is reduced to some extent, but the content of ammonia nitrogen is increased, and the biodegradability is reduced, so the treatment difficulty is very high.

The key point for treating the landfill leachate is treatment of COD, BOD and ammonia nitrogen, in particular treatment of ammonia nitrogen. The existing mainstream technology comprises the steps of pretreatment, flocculation precipitation, biochemical treatment, chemical strong oxidation, MBR, ultrafiltration, nanofiltration, reverse osmosis and the like, and combines the means of physical treatment, chemical treatment and biological treatment. Similarly, the landfill leachate disclosed in CN1478737 is a combined treatment of physical and chemical treatment and biological treatment, in which the leachate after electrolytic oxidation treatment is subjected to reverse osmosis treatment by using ceramic membrane. The technology achieves certain effect on treating the landfill leachate, but has the following outstanding problems:

1. in China, except for warm climate in southern regions, low temperature exists in winter in most regions, when the water temperature is lower than 15 ℃, the activity of nitrifying bacteria in a landfill leachate treatment facility is greatly reduced, and the nitrification effect is poor, so that the ammonia nitrogen concentration of biochemical effluent reaches 500-1000 mg/L, some of the biochemical effluent is even higher, and the ammonia nitrogen cannot be eliminated by subsequent membrane treatment, so that the ammonia nitrogen of the effluent seriously exceeds the standard;

2. the existing garbage leachate treatment technology combining biochemistry and membrane filtration technology has membrane treatment comprising MBR, ultrafiltration, nanofiltration and reverse osmosis, long treatment process, more investment, more operation posts and high operation cost, and particularly about 40 percent of concentrated solution can only be re-filled into a landfill site except evaporation crystallization treatment, so that ammonia nitrogen, total phosphorus, salt and the like are continuously accumulated, and the ammonia nitrogen content and the salt content of leachate are higher and higher. If evaporation treatment is adopted, the operating cost of concentrated solution treatment is as high as 150-200 yuan/ton, and the concentrated solution is spread to reach more than 50 yuan/ton per ton of landfill leachate.

3. After the leachate of most landfill sites is treated, the subsequent membrane process treatment is disturbed by the high ammonia nitrogen in MBR effluent.

4. Most garbage leachate treatment plants do not build concentrated solution treatment facilities, and concentrated solution can only be recharged to a landfill site, so that pollutants are accumulated continuously, and the ammonia nitrogen content and the salt content of leachate are higher and higher. But also causes the repeated treatment of leachate, and brings great economic burden to local governments.

5. The concentrated solution is returned to the regulating tank after being refilled to the landfill, so that a large amount of leachate is stored in the regulating tank, and most of the landfill sites need to be subjected to emergency treatment at regular intervals, so that the cost is high, and potential safety hazards exist.

Therefore, a new purification device and technology for biochemical effluent of garbage leachate are urgently needed to solve the problems of unqualified drainage quality and concentrated solution recharging.

Disclosure of Invention

The invention aims to overcome the defects of complex treatment process, large consumption of chemical agents, high cost, backflow of treated concentrated solution and the like in the existing garbage percolation treatment technology, and the biochemical effluent purification device and the deep purification method thereof for the garbage percolation liquid are formed by combining catalytic electrolytic denitrification, biological aerated filter and denitrification of biochemical effluent to make up for deficiencies of each other.

The biochemical effluent purification device of the landfill leachate comprises a hardness removal device, a catalytic electrolysis denitrification device, a filter biochemical treatment device and a coagulating sedimentation device, wherein the purification method comprises the steps of sequentially carrying out hardness removal, catalytic electrolysis denitrification, filter biochemical treatment and coagulating sedimentation treatment on the biochemical effluent purification device of the landfill leachate, and the inlet and outlet water obtained by purifying the biochemical effluent of the landfill leachate by adopting the device and the method completely meet the requirements of 'pollutant control standard of domestic refuse landfill' (GB16889-2008) in Table 2, and the specific indexes are shown in Table 1:

TABLE 1 Biochemical effluent indexes of landfill leachate purified by the present invention

Compared with the prior art, the invention has the following obvious advantages:

1. effluent after the biochemical treatment of the landfill leachate completely meets the index requirements of table 2 of the pollutant control standard of domestic refuse landfill (GB16889-2008), and no concentrated solution exists, so that the treatment problem of 35-40% membrane concentrated solution in the existing landfill leachate treatment technology is solved;

2. the treated effluent indexes all meet the requirements of table 2 of the domestic garbage landfill pollutant control standard (GB16889-2008), and the problem that the ammonia nitrogen of the effluent in winter exceeds the standard in the existing landfill leachate treatment technology is solved;

3. the effluent treatment process of biochemical treatment of the landfill leachate is shortened from the prior 'UF + NF + RO' into 'hardness removal + electrolytic denitrification + filter tank biochemical treatment + coagulation', so that the process flow is greatly shortened, and the investment is reduced to a certain extent.

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 biochemical effluent purification device for landfill leachate of the present invention.

Fig. 2 is a schematic view of a hardness removal apparatus of the present invention.

FIG. 3 is a schematic view of the catalytic electrolytic denitrification apparatus of the present invention.

FIG. 4 is a schematic view of a biochemical apparatus for a filter according to the present invention.

FIG. 5 is a schematic view of the structure of a biological aerated filter or a denitrification deep-bed filter according to the invention.

FIG. 6 is a schematic view of a coagulating sedimentation device 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 biochemical effluent purification device for landfill leachate includes: the device comprises a biochemical water outlet device 10, a hardness removal device (100), a catalytic electrolysis denitrification device (200), a filter biochemical treatment device (300) and a coagulating sedimentation device (400), and specifically comprises the following components:

(1) hardness removing device (100) (double alkali method hardness removing device)

The hardness removal device (100) consists of a sodium carbonate solution storage tank (112), a lime storage tank (113), a hardness removal reaction tank (110), a precipitation tank (120), an intermediate water tank (130) and a solid-liquid separator (126), and is used for removing the hardness of effluent of the biochemical treatment of the landfill leachate; the hardness removing reaction tank (110) is provided with a stirrer, a sodium carbonate solution storage tank (112) and a lime storage tank (113), a water inlet of the hardness removing reaction tank (110) is connected with a middle water tank of the biochemical water outlet device (10), a water outlet of the hardness removing reaction tank (110) is connected with a water inlet of the sedimentation tank (120), a water outlet of the sedimentation tank (120) is connected with a middle water tank (130), and a sludge outlet of the sedimentation tank (120) is connected with an inlet of the solid-liquid separator (126). The solid-liquid separator is one of a plate-and-frame filter press, a centrifugal machine and a vacuum filter.

(2) Catalytic electrolytic denitrification device (200)

The catalytic electrolysis purification device (200) comprises an electrolysis machine (210), a direct current power supply (220), a degassing tank (230), a catalyst feeding device (240), an electrode cleaning device (250) and a reduction device (260), wherein a water inlet of the electrolysis machine (210) is connected with a water outlet of a secondary sedimentation tank or MBR of the biochemical water outlet device through a lift pump (211), a valve (212), a flow meter (213) and a valve (215), a water outlet of the electrolysis machine (210) is connected with a water inlet (231) of the degassing tank (230), a water outlet of the degassing tank (230) is connected with a water inlet of the reduction device (260), a water outlet of the reduction device (260) is connected with a water inlet pipe of the filter biochemical device (300), a circulation port is further arranged at a position 1-1.5 m or two-thirds below the water outlet of the degassing tank (230), and is connected with the water inlet pipe of the electrolysis machine (210) through a circulation pipe and a circulation water pump (270), the catalyst adding device 240 is composed of a catalyst solution storage tank and a solution delivery pump and is used for adding denitrification catalyst solution into the garbage infiltration; the electrode cleaning device (250) is composed of an acid cleaning solution storage tank (252) and an acid cleaning solution delivery pump (251), wherein the acid cleaning solution adopts 2% -3% hydrochloric acid solution or 4% -5% citric acid solution.

The water inlet of the degassing tank (230) is connected with a water distributor (232) positioned at the bottom of the degassing tank (230), the water outlet at the upper part of the degassing tank (230) is connected with the water inlet pipe of the reduction device (260), and the top of the degassing tank (230) is also provided with a slag scraper and a bubble collecting tank. And a drain outlet is arranged at the bottom of the degassing tank and is connected with a water inlet of the coagulating sedimentation device.

The reduction device (260) comprises a reduction pool (261) and a reducing agent solution storage tank (262), wherein the reducing agent solution storage tank is connected with the reduction pool through a metering dosing pump (263), a stirrer (264) is further installed on the reduction pool, a water inlet of the reduction pool is connected with a water outlet of the degassing tank (230), and a water outlet of the reduction pool (261) is connected with a water inlet of the filter biochemical device (300).

Specifically, a pH adjusting tank is arranged before water enters the catalytic electrolytic denitrification device and is used for adding 5-20% of alkali liquor to adjust the pH of the water body to 8.5-10.

(3) Biochemical treatment device of filter (300)

The filter biochemical treatment device is a combination of an aeration biological filter and a denitrification deep bed filter.

The filter biochemical treatment device (300) consists of an aeration biological filter (310), a denitrification deep bed filter (320) and an intermediate water tank (330).

The water outlet of the reduction tank (261) of the catalytic electrolytic denitrification device (200) is connected with the water inlet of the filter biochemical treatment device (300) and sequentially passes through the aeration biological tank (310), the denitrification deep bed filter (320) and the middle water tank (330), and the water outlet of the middle water tank (330) is connected with the water inlet of the coagulating sedimentation device (400).

More specifically, referring to fig. 5, the biological aerated filter (310) or the denitrification deep-bed filter (320) comprises a filter main body and a backwashing system, wherein the filter main body comprises a filter body (311), filter bricks (312), an air pipe (313) and filter materials (314) which are arranged in the filter body, an aeration fan (315) and an air pipe (313) are arranged outside the filter main body, and the air pipe is arranged between the filter bricks and the bottom of the filter main body; the backwashing system consists of a clean water storage tank (317), a clean water pump (318) and a backwashing water storage tank (319); a clear water storage tank (317) of the backwashing system is connected with a cleaning water inlet (321) at the bottom of the filter body, a backwashing water outlet (322) at the top of the filter body is connected with an inlet of a backwashing water storage tank (319), and a water outlet of the backwashing water storage tank (319) is connected with a landfill leachate raw water tank (323). The denitrification deep bed filter is a filter body in an anaerobic environment, and when the denitrification deep bed filter works, sewage overflows into the filter body from a water inlet channel a1 at the periphery of the filter body, and flows out from a water outlet channel a2 after biochemical reaction is carried out in the filter body after passing through filter materials and filter bricks; if the backwashing is needed, the aeration fan and the air pipe are started, meanwhile, water flow enters the filter tank main body from the clear water storage tank through the cleaning water inlet at the bottom of the tank, the filter material in the filter tank main body is washed, then flows out of the backwashing water storage tank, and then flows into the landfill leachate raw water tank for subsequent treatment. Similarly, the aeration biological filter is designed by adopting a similar structure, and the difference is that because the aeration biological filter is a pool body in an aerobic environment, an air pipe and an aeration fan of the aeration biological filter are always in an open state in the biochemical reaction process, oxygen is continuously conveyed to the water body in the pool, and the dissolved oxygen concentration of the water body in the pool is maintained.

(4) Coagulating sedimentation device (400)

Referring to the attached figure 6, the coagulating sedimentation device (400) comprises a pH adjusting tank (410), a coagulating basin (420), a coagulation aiding basin (430) and a sedimentation basin (440) which are sequentially connected, wherein a supernatant outlet is arranged at the top of the sedimentation basin and is connected with a drainage system, a sludge outlet is arranged at the bottom of the sedimentation basin and is connected with a sludge pump.

The coagulation tank (420) comprises a coagulant dosing device and a coagulation mixer, wherein 1-20% by mass of a coagulant, such as one of PAC (poly aluminum chloride) solution, ferric sulfate solution or ferric trichloride solution, is stored in the coagulant dosing device; 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.

The biochemical effluent of the landfill leachate is effluent after being treated by primary anaerobic treatment, primary aerobic treatment, secondary anaerobic treatment, secondary aerobic treatment and MBR treatment, or being treated by primary anaerobic treatment, primary aerobic treatment, secondary anaerobic treatment, secondary aerobic treatment and coagulating sedimentation treatment, or being treated by primary anaerobic treatment, primary anoxic treatment, primary aerobic treatment, secondary anaerobic treatment, secondary aerobic treatment and coagulating sedimentation, or being treated by one of primary anaerobic treatment, primary anoxic treatment, primary aerobic treatment, secondary anaerobic treatment, secondary aerobic treatment and MBR treatment, and the biochemical effluent of the landfill leachate has the main pollutant indexes: COD_Cr≤1200mg/L，BOD₅Less than or equal to 500mg/L, less than or equal to 900mg/L of ammonia nitrogen, less than or equal to 1000mg/L of total nitrogen, less than or equal to 30mg/L of total phosphorus and 50-6000 mg/L of chloride ion concentration, and the method comprises the following steps:

(1) hardness removal (hardness removal by double alkali method):

pumping the garbage leachate after biochemical treatment into a hardness removal reaction tank, starting a stirrer, and driving the stirrer to weigh 1-3 kg/m³Adding lime to react for 5-10 minutes, and then reacting according to the proportion of 300-900 g/m³And adding sodium carbonate to react for 10-15 minutes, pumping into a precipitation tank for precipitation separation to obtain supernatant and bottom sludge, storing the supernatant in a storage tank of an intermediate water tank, separating the bottom sludge by using a stationary liquid to obtain sludge blocks and filtrate, and feeding the filtrate into the intermediate water tank.

2Ca(HCO₃)₂+Ca(OH)₂→2CaCO₃+2H₂O

2Mg(HCO₃)₂+Ca(OH)₂→CaCO₃+MgCO₃+2H₂O

CaSO₄+Na2CO₃→CaCO₃+Na₂SO₄

(2) Catalytic electrolytic denitrification:

the biochemical effluent of the landfill leachate is subjected to hardness removal treatment and then pumped into an electrolysis machine for catalytic electrolysis denitrification, wherein the working voltage of the electrolysis machine is 5-50V, and the current is 10-5000A; after the biochemical treatmentAnd the indexes of main pollutants of the effluent of the landfill leachate after hardness removal are as follows: COD_Cr≤1200mg/L，BOD₅Less than or equal to 500mg/L, ammonia nitrogen less than or equal to 900mg/L, total nitrogen less than or equal to 1000mg/L, total phosphorus less than or equal to 30mg/L, and chloride ion concentration of 50-6000 mg/L; when the chloride ion concentration of the landfill leachate is less than 500mg/L, a sodium chloride adding device is started to supplement sodium chloride until the chloride ion concentration is more than or equal to 500mg/L, the electrolyzed biochemical effluent enters a degassing tank for gas-liquid separation, bubbles at the upper part are scraped into a bubble collecting tank through a residue scraping machine, and the lower clear liquid is pumped into an electrolysis machine again through a circulating water pump for further electrolysis and denitrification until the ammonia nitrogen is less than or equal to 100 mg/L; and (3) feeding the water discharged from the degassing tank after electrolytic denitrification into a reduction device, and adding 5-20% of reducing agent solution to neutralize and eliminate excessive sodium hypochlorite until the residual chlorine is less than or equal to 0.2 mg/L.

(3) Biochemical treatment of the filter tank:

pumping the effluent water after the catalytic electrolytic denitrification in the step (2) into a filter biochemical treatment device, and respectively performing biochemical treatment and precipitation separation by an aeration biological filter and a denitrification deep bed filter until the chroma of the effluent water is less than 5 and the COD is_Cr≤150mg/L、BOD₅Less than or equal to 20mg/L, ammonia nitrogen less than or equal to 15mg/L, total nitrogen less than or equal to 30mg/L, total phosphorus less than or equal to 5mg/L, fecal coliform less than or equal to 100/L, total mercury less than or equal to 0.001mg/L, total chromium less than or equal to 0.1mg/L, hexavalent chromium less than or equal to 0.05mg/L, total cadmium less than or equal to 0.01mg/L, total lead less than or equal to 0.1mg/L and total arsenic less than or equal to 0.1mg/L enter a coagulating sedimentation device (400).

(4) Coagulating sedimentation:

pumping effluent subjected to biochemical treatment in the filter tank in the step (3) into a pH adjusting tank of a coagulating sedimentation device, adding a sodium hydroxide solution to adjust the pH to 8.5-9.5 under the condition of continuous stirring, then flowing into the coagulating tank, adding a 2% coagulant solution according to 6-30 ml/L under the condition of continuous stirring, then flowing into a coagulation aiding tank, adding a 2% PAM solution according to 1-1.5 ml/L under the condition of continuous stirring for coagulation aiding, then entering the precipitating tank for solid-liquid separation to obtain supernatant and lower sludge, measuring ammonia nitrogen of the supernatant on line to be less than or equal to 10mg/L, total nitrogen to be less than or equal to 30mg/L, total phosphorus to be less than or equal to 2mg/L, and detecting the supernatant in a qualified drainage system; the sludge at the lower part enters a sludge dewatering system to be dewatered into sludge blocks and sewage, and the sewage returns to a biochemical effluent storage tank after electrolytic purification. The coagulant solution is one of polyaluminium chloride, polyferric, ferric sulfate, ferrous sulfate or a mixture of polyaluminium chloride and polyferric.

The descaling method of the electrolytic purification device after scaling in the electrolytic process is to wash the electrolytic purification device for 40-90 minutes by adopting 2-3% hydrochloric acid solution or 4-6% citric acid to remove the scale.

The water inlet and outlet after the biochemical effluent of the landfill leachate is treated by adopting the device and the method completely meet the requirements of table 2 of the pollutant control standard of a domestic garbage landfill (GB 16889-2008).

Example 1

The biochemical effluent purifying device for treating the landfill leachate of a certain municipal refuse landfill built by adopting the production process comprises a biochemical effluent device 10, a hardness removal device (100), a catalytic electrolysis denitrification device (200) and a filter biochemical treatment device (300) and a coagulating sedimentation device (400).

TABLE 2 Biochemical effluent design Water quality index for landfill leachate treatment in certain landfill

Serial number	Item	Biochemical effluent index	Treated effluent index	Removal Rate (%)
					1	Color intensity	280	5	98.21
2	COD_Cr(mg/L)	1100	90	91.82
					3	Total nitrogen (mg/L)	1000	30	97
4	Ammonia nitrogen (mg/L)	950	25	97.37
					5	Total phosphorus (mg/L)	8.5	3	64.70
6	Hardness (mg/L)	1020	3	99.71

The biochemical effluent purifying device for treating the landfill leachate purifies the biochemical effluent treated by the landfill leachate in the table 1 according to the following steps:

degree of hardness removal

Pumping the garbage leachate after biochemical treatment into a hardness removal reaction tank, measuring the hardness of the garbage leachate to be 1020mg/L, starting a stirrer, and driving the stirrer to weigh 1 to 1.2 kg/m³Adding lime to react for 5-10 minutes, and then reacting according to the proportion of 300g/m³And adding sodium carbonate to react for 10-15 minutes, pumping into a precipitation tank for precipitation separation to obtain supernatant and bottom sludge, storing the supernatant in a storage tank of an intermediate water tank, separating the bottom sludge by using a stationary liquid to obtain sludge blocks and filtrate, and feeding the filtrate into the intermediate water tank.

TABLE 3 indexes of main pollutants in biochemical effluent of landfill leachate after hardness removal by two-alkali method

Serial number	Item	Biochemical effluent index	Index of water discharge	Removal Rate (%)
					1	Color intensity	280	230	17.86
2	COD_Cr(mg/L)	1100	800	27.27
					3	Total nitrogen (mg/L)	1000	910	9.00
4	Ammonia nitrogen (mg/L)	950	912	4.00
					5	Total phosphorus (mg/L)	8.5	4.3	49.41
6	Hardness (mg/L)	1020	3	99.58
					7	Chloride ion (mg/L)	410

As can be seen from Table 3, after the biochemical effluent of landfill leachate treatment is subjected to hardness removal, the hardness of the biochemical effluent is reduced from 1020mg/L to 3mg/L, the removal rate reaches 99.58%, the hardness removal effect is obvious, COD is reduced by 27%, total nitrogen is reduced by 9.00%, ammonia nitrogen is removed by 4.00%, the effluent does not meet the discharge standard, and electrolytic purification needs to be further adopted.

And (3) pumping the carbonate precipitate in the precipitation tank (120) subjected to hardness removal into a centrifuge for centrifugal separation to obtain carbonate solid with 10% of water and effluent, wherein the effluent enters an intermediate water tank (130) and then enters a water inlet of the catalytic electrolytic denitrification device (200).

Secondly, catalyzing the electrolytic denitrification

Delivering the supernatant in the intermediate water tank (130) obtained by hardness removal to an electrolytic machine (210) for electrolysis through a lift pump (211), a valve (212) and a flowmeter (213), and simultaneously starting an electrolyte adding device to perform electrolysis according to the volume of 6L/m³Adding 20% sodium chloride solution to supplement chloride ions, feeding electrolyzed direct current power supply with working voltage of 26.5V and current of 590A into degassing tank (230), discharging electrolyzed effluent into degassing tank (230), and releasing nitrogen generated by reaction of sodium hypochlorite and residual ammonia in biochemical effluent during electrolytic purification and CO generated by reaction of oxygen generated by electrolysis and organic matters in degassing tank (230)₂And the hydrogen generated by electrolysis reacts with the nitrate radical in the biochemical effluent to generate nitrogen gas, a large amount of bubbles are formed, and the bubbles are discharged through a slag scraper. And pumping the water in the degassing tank (230) into an electrolysis machine (210) through a circulating water pump (270) for electrolysis, and taking a water sample for detection when a monitoring instrument shows that the ammonia nitrogen in the water is less than or equal to 20mg/L, wherein the result is shown in Table 4.

TABLE 4 effluent indexes of biochemical hardness-removed effluent after catalytic electrolytic denitrification for landfill leachate treatment

Serial number	Item	Index of water outlet of hardness removal	Index of electrolytic effluent	Removal Rate (%)
					1	Color intensity	230	30	86.96
2	COD_Cr(mg/L)	800	620	22.50
					3	Total nitrogen (mg/L)	910	105	88.46
4	Ammonia nitrogen (mg/L)	912	90.3	90.10
					5	Total phosphorus (mg/L)	4.3	3.3	23.26
6	Hardness (mg/L)	3	-	-
					7	Residual chlorine (mg/L)	-	0.1	-

As can be seen from Table 4, after the biochemical effluent of landfill leachate treatment is subjected to hardness removal and catalytic electrolytic denitrification, the indexes of pollutants such as COD, BOD, total nitrogen, ammonia nitrogen and the like are all close to the indexes of the pollutant control Standard for municipal solid waste landfill (GB16889-2008) in Table 2.

Biochemical treatment in filter tank

The biochemical effluent obtained by denitrification treatment of the catalytic electrolytic denitrification device (200) flows into an aeration biological filter (310), a denitrification deep bed tank (320) and an intermediate water tank (330) of the filter biochemical treatment device (300) in sequence for secondary biochemical treatment, and the effluent indexes are shown in Table 5.

TABLE 5 effluent indexes of biochemical electrolytic denitrification effluent treated by landfill leachate after biochemical treatment in filter

Fourthly, coagulating sedimentation

Biochemical effluent of landfill leachate treatment obtained by biochemical treatment of a filter tank enters a pH adjusting tank (410) of a coagulating sedimentation device (400), a stirrer is started, the rotating speed is adjusted to be 60 revolutions per minute, 10% of sodium hydroxide solution is quantitatively added, the pH of water is adjusted to be 9, the water enters a coagulating tank (420), the stirrer is started, the rotating speed is adjusted to be 100 revolutions per minute, 2% of PAC solution is metered from a PAC storage tank according to 6 liters per ton, the mixture reacts for 10 minutes and enters a coagulation aiding tank (430), the stirrer is started, the rotating speed is adjusted to be 20 revolutions per minute, 0.1% of PAM solution is metered from a PAM storage tank according to 1 liter per ton, the mixture reacts for 2 minutes and enters a sedimentation tank (440) for sedimentation for 30 minutes, and clear purified water of the biochemical effluent of the landfill leachate is obtained through solid-liquid separation, and the specific pollutant indexes are shown in Table 6.

TABLE 6 effluent indexes of biochemical effluent treated by landfill leachate after biochemical and coagulating sedimentation in filter tank

As can be seen from Table 6, after the biochemical effluent from landfill leachate treatment is purified by the procedures of hardness removal, catalytic electrolytic denitrification, secondary biochemical treatment, coagulation and the like, the main pollutants of the biochemical effluent completely meet the indexes of Table 2 in the Standard for controlling pollutants for municipal solid waste landfill (GB 16889-2008).

Example 2

The MBR effluent purification device for landfill leachate treatment of a certain municipal refuse landfill built by the production process comprises a biochemical effluent device 10, a hardness removal device (100), a catalytic electrolysis denitrification device (200), a filter biochemical treatment device (300) and a coagulating sedimentation device (400).

The filter biochemical treatment device consists of a biological aerated filter (310), a denitrification deep bed filter (320) and an intermediate water tank (330).

TABLE 7 Biochemical effluent design Water quality index for landfill leachate treatment in certain landfill

The biochemical effluent purifying device for treating the landfill leachate of the invention purifies the biochemical effluent treated by the landfill leachate of the table 7 according to the following steps, and the result is as follows:

single and double alkali method for removing hardness

Pumping the garbage percolate subjected to biochemical treatment into a hardness removal reaction tank, measuring the hardness of the garbage percolate to be 2000mg/L, starting a stirrer, and driving the stirrer to weigh 3 kg/m³Adding lime to react for 5-10 minutes, and then reacting according to the proportion of 900g/m³And adding sodium carbonate to react for 10-15 minutes, pumping into a precipitation tank for precipitation separation to obtain supernatant and bottom sludge, storing the supernatant in an intermediate water tank, separating the bottom sludge by using a stationary liquid to obtain mud blocks and filtrate, and introducing the filtrate into the intermediate water tank, wherein the indexes of main pollutants are shown in table 8.

TABLE 8 indexes of main pollutants in biochemical effluent from hardness removal by double-alkali precipitation

Secondly, the supernatant in the intermediate water tank (130) obtained by double-alkali precipitation and hardness removal is conveyed to an electrolysis machine (210) for electrolysis through a lift pump (211), a valve (212) and a flowmeter (213), the working voltage of an electrolyzed direct-current power supply is 50V, the current is 20000A, the electrolyzed effluent enters a degassing tank (230), nitrogen generated by the reaction of sodium hypochlorite and residual ammonia in MBR effluent during electrolytic purification and CO generated by the reaction of oxygen generated by electrolysis and organic matters are released in the degassing tank (230)₂And the hydrogen generated by electrolysis reacts with the nitrate radical in the biochemical effluent to generate nitrogen gas, a large amount of bubbles are formed, and the bubbles are discharged through a slag scraper. And repeatedly pumping the water in the degassing tank (230) into an electrolysis machine (210) through a circulating water pump for electrolysis, directly displaying indexes such as ammonia nitrogen, total nitrogen and COD (chemical oxygen demand) in the water by a monitoring instrument to be close to indexes in table 2 of the control standard of pollutants for domestic waste landfill (GB16889-2008), and taking a water sample for detection, wherein the result is shown in table 9.

TABLE 9 effluent index of biochemical effluent from landfill leachate treatment after electrolytic denitrification

Serial number	Item	Index of water outlet of hardness removal	Effluent index of electrolytic denitrification	Removal Rate (%)
					1	Color intensity	160	35	78.13
2	COD_Cr(mg/L)	930	689	25.91
					3	BOD₅(mg/L)	490	384	21.63
3	Total nitrogen (mg/L)	910	132	85.49
					4	Ammonia nitrogen (mg/L)	885	95	89.26
5	Total phosphorus (mg/L)	9	8.9	1.11
					6	Hardness (mg/L)	17	-
7	SS(mg/L)	35	-

Biochemical treatment in filter tank

The biochemical effluent obtained by denitrification treatment of the catalytic electrolytic denitrification device (200) flows into the aeration biological filter (310), the denitrification deep bed filter (320) and the middle water pool (330) of the filter biochemical treatment device (300) in sequence, and the effluent indexes are shown in the table 10.

TABLE 10 effluent indexes of biochemical effluent from landfill leachate treatment after electrolytic denitrification and filter tank

Serial number	Item	Effluent of electrolytic denitrification	Biochemical effluent of filter pool	Removal Rate (%)
					1	Color intensity	35	35	-
2	COD_Cr(mg/L)	689	143	79.25
					3	BOD₅(mg/L)	384	16	95.83
3	Total nitrogen (mg/L)	132	22.5	82.95
					4	Ammonia nitrogen (mg/L)	95	5	94.74
5	Total phosphorus (mg/L)	8.9	8.1	8.99
					6	Hardness (mg/L)	-	-
7	SS(mg/L)	-	-

Fourthly, coagulating sedimentation

The method comprises the steps of enabling biochemical effluent treated by landfill leachate to pass through hardness removal, catalytic electrolytic denitrification and secondary biochemical treatment, enabling the effluent to enter a pH adjusting tank (410) of a coagulating sedimentation device (400), starting a stirrer, adjusting the rotating speed to be 20 revolutions per minute, quantitatively adding 10% sodium hydroxide solution, adjusting the pH of water to be 9, enabling the effluent to enter a coagulating basin (420), starting the stirrer, adjusting the rotating speed to be 90 revolutions per minute, adding 15% ferric sulfate solution into a ferric sulfate storage tank according to 30 liters per ton, reacting for 5 minutes, enabling the effluent to enter a coagulation assisting basin (430), starting the stirrer, adjusting the rotating speed to be 20 revolutions per minute, adding 0.1% PAM solution into a PAM storage tank according to 1 liter per ton, reacting for 1 minute, enabling the effluent to enter a sedimentation basin (440) for sedimentation for 30 minutes, and performing solid-liquid separation to obtain purified water of clarified effluent, wherein specific pollutant indexes are shown in a table 11.

TABLE 11 effluent indexes of biochemical effluent from landfill leachate treatment after biochemical filtration and coagulating sedimentation

Serial number	Item	Biochemical effluent index	Index of coagulating sedimentation water outlet	Removal Rate (%)
					1	Color intensity	35	4	86.67
2	COD_Cr(mg/L)	143	85	86.15
					3	BOD₅(mg/L)	16	15	-
4	Total nitrogen (mg/L)	22.5	20	78.78
					5	Ammonia nitrogen (mg/L)	5	4.5	94.70
6	Total phosphorus (mg/L)	8.1	0.9	68.57
					7	Hardness (mg/L)		3.5	-
8	Residual chlorine (mg/L)	0.1	0.1	-
					9	Faecal coliform (per/L)		1000	-
10	Fecal coliform (per/L)		3	-
					11	Total mercury (mg/L)	-	0.001	-
12	Total cadmium (mg/L)	-	0.01	-
					13	Total chromium (mg/L)	-	0.1	-
14	Hexavalent chromium (mg/L)	-	0.05	-
					15	Total arsenic (mg/L)	-	0.1	-
16	Total lead (mg/L)		0.1	-

From table 11, it can be seen that the indexes of the main pollutants of the biochemical effluent of the landfill leachate after the biochemical effluent is purified by the procedures of hardness removal by a double alkali method, catalytic electrolysis denitrification, biochemical treatment in a filter tank and coagulation all meet the indexes of table 2 of the control standard of pollutants for domestic refuse landfill (GB 16889-2008).

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 biochemical effluent purification device of landfill leachate is characterized by comprising a biochemical effluent device, a hardness removal device, a catalytic electrolysis denitrification device, a filter biochemical treatment device and a coagulating sedimentation device,

the hardness removal device consists of a sodium carbonate solution storage tank, a lime storage tank, a hardness removal reaction tank, a sedimentation tank, an intermediate water tank and a solid-liquid separator, wherein a stirrer, the sodium carbonate solution storage tank and the lime storage tank are installed on the hardness removal reaction tank;

the catalytic electrolytic denitrification device is composed of an electrolytic machine, a degassing tank, a catalyst feeding device, an electrode cleaning device and a reduction device, wherein a water inlet of the electrolytic machine is connected with a water outlet of the intermediate water tank, a water outlet of the electrolytic machine is connected with a water inlet of the degassing tank, a water outlet of the degassing tank is connected with a water inlet of the reduction device, and a water outlet of the reduction device is connected with the secondary biochemical treatment device; the degassing tank is also provided with a circulation port, and the circulation port is connected with a water inlet pipe of the electrolysis machine through a circulation pipe and a circulation water pump; the reducing device comprises a reducing pool and a reducing agent solution storage tank, wherein the reducing agent solution storage tank is connected with the reducing pool through a metering dosing pump;

the biochemical treatment device of the filter tank is a combined device of an aeration biological filter tank and a denitrification deep-bed filter tank, the aeration biological filter tank or the denitrification deep-bed filter tank consists of a filter tank main body and a backwashing system, the filter tank main body consists of a tank body and filter bricks, air pipes and filter materials which are arranged in the tank body, the backwashing system consists of a clear water storage tank, a clear water pump and a backwashing water storage tank, the clear water storage tank of the backwashing system is connected with a cleaning water inlet at the bottom of the filter tank main body, a backwashing water outlet at the top of the filter tank main body is connected with an inlet of the backwashing water storage tank, and a water outlet of the backwashing water storage tank is connected with a raw garbage percolate tank;

the coagulating sedimentation purification device comprises a pH adjusting tank, a coagulating basin, a coagulation assisting tank and a sedimentation tank which are sequentially connected, wherein a supernatant outlet is arranged at the top of the sedimentation tank and is connected with a drainage system, a sludge outlet is arranged at the bottom of the sedimentation tank, and the sludge outlet is connected with a sludge pump.

2. The biochemical effluent purification device for landfill leachate according to claim 1, wherein the circulation port is disposed at a height of two thirds of the degassing tank or 1-1.5 meters below the water outlet of the degassing tank.

3. The biochemical effluent purification device for landfill leachate according to any one of claims 1 or 2, wherein a water inlet of the degassing tank is connected with a water distributor at the bottom of the degassing tank, a water outlet at the upper part of the degassing tank is connected with a water inlet pipe of the reduction device, and a slag scraper and a bubble collecting tank are further arranged at the top of the degassing tank.

4. The biochemical effluent purification device for landfill leachate according to claim 1, wherein a pH adjusting tank is further disposed in front of the water inlet of the catalytic electrolytic denitrification device.

5. The biochemical effluent purification device for landfill leachate according to claim 1, wherein the solid-liquid separator is one of a plate and frame filter press, a centrifuge, and a vacuum filter.

6. The biochemical effluent purification device for the landfill leachate as claimed in claim 1, wherein the coagulation tank comprises a coagulant dosing device and a coagulation mixer, and the coagulant dosing device stores 1-20% by mass of coagulant; 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.

7. The biochemical effluent purification device for landfill leachate according to claim 1, wherein an aeration fan is further installed outside the filter tank main body, and the aeration fan is connected with the air pipe.

8. The deep purification method of biochemical effluent of landfill leachate is characterized by comprising the following steps:

step (1): hardness of removal

Pumping biochemical effluent of the landfill leachate into a hardness removing reaction tank, starting a stirrer, and keeping the density at 1-3 kg/m³Adding lime to react for 5-10 minutes, and then reacting according to the proportion of 300-900 g/m³Adding sodium carbonate to react for 10-15 minutes, pumping into a precipitation tank for precipitation separation to obtain supernatant and bottom sludge, storing the supernatant in an intermediate water tank, performing solid-liquid separation on the bottom sludge to obtain sludge blocks and filtrate, and allowing the filtrate to enterPutting into an intermediate water tank;

step (2): catalytic electrolytic denitrification

The biochemical effluent of the landfill leachate is subjected to hardness removal treatment and then pumped into an electrolysis machine for catalytic electrolysis denitrification, wherein the working voltage of the electrolysis machine is 5-50V, and the current is 10-20000A; when the chloride ion concentration of the landfill leachate is less than 500mg/L, a sodium chloride adding device is started to supplement sodium chloride until the chloride ion concentration is more than or equal to 500mg/L, the electrolyzed biochemical effluent enters a degassing tank for gas-liquid separation, bubbles at the upper part are scraped into a bubble collecting tank through a residue scraping machine, and the lower clear liquid is pumped into an electrolysis machine again through a circulating water pump for further electrolysis and denitrification until the ammonia nitrogen is less than or equal to 100 mg/L; and (3) feeding the water discharged from the degassing tank after electrolytic denitrification into a reduction device, and adding 5-20% of reducing agent solution to neutralize and eliminate excessive sodium hypochlorite until the residual chlorine is less than or equal to 0.2 mg/L.

And (3): biochemical treatment in filter tank

Pumping the effluent water after the catalytic electrolytic denitrification in the step (2) into a filter biochemical treatment device, respectively performing biochemical treatment and intermediate water tank precipitation separation by an aeration biological filter and a denitrification deep bed filter until the chroma of the effluent water is less than 5 and the COD is_Cr≤150mg/L、BOD₅Less than or equal to 20mg/L, ammonia nitrogen less than or equal to 20mg/L, total nitrogen less than or equal to 35mg/L, total phosphorus less than or equal to 5mg/L, fecal coliform less than or equal to 100/L, total mercury less than or equal to 0.001mg/L, total chromium less than or equal to 0.1mg/L, hexavalent chromium less than or equal to 0.05mg/L, total cadmium less than or equal to 0.01mg/L, total lead less than or equal to 0.1mg/L and total arsenic less than or equal to 0.1mg/L enter a coagulating sedimentation device (400);

and (4): coagulating sedimentation

Pumping effluent subjected to biochemical treatment in the filter tank in the step (3) into a pH adjusting tank of a coagulating sedimentation device, adding a sodium hydroxide solution to adjust the pH to 8.5-9.5 under the condition of continuous stirring, then flowing into the coagulating tank, adding a 2% coagulant solution according to 6-30 ml/L under the condition of continuous stirring, then flowing into a coagulation aiding tank, adding a 2% PAM solution according to 1-1.5 ml/L under the condition of continuous stirring for coagulation aiding, then entering the precipitating tank for solid-liquid separation to obtain supernatant and lower sludge, measuring ammonia nitrogen of the supernatant on line to be less than or equal to 20mg/L, total nitrogen to be less than or equal to 35mg/L, total phosphorus to be less than or equal to 2mg/L, and detecting the supernatant in a qualified drainage system; the sludge at the lower part enters a sludge dewatering system to be dewatered into sludge blocks and sewage, and the sewage returns to a biochemical effluent storage tank after electrolytic purification.

9. The method for deeply purifying biochemical effluent of landfill leachate according to claim 8, wherein a pH adjusting tank is further disposed before the catalytic electrolytic denitrification device is fed with water, and is used for adding 5-20% of alkali liquor to adjust the pH of the water body to 8.5-10.

10. The method of claim 8, wherein the biochemical effluent of the landfill leachate is effluent of the landfill leachate after being sequentially treated by a first-stage anaerobic treatment, a first-stage aerobic treatment, a second-stage anaerobic treatment, a second-stage aerobic treatment and an MBR treatment, or sequentially treated by a first-stage anaerobic treatment, a first-stage aerobic treatment, a second-stage anaerobic treatment, a second-stage aerobic treatment and a coagulating sedimentation treatment, or sequentially treated by one of a first-stage anaerobic treatment, a first-stage anoxic treatment, a first-stage aerobic treatment, a second-stage anaerobic treatment, a second-stage aerobic treatment and an MBR treatment, and the biochemical effluent of the landfill leachate has a pollutant index: COD_Cr≤1200mg/L，BOD₅Less than or equal to 500mg/L, less than or equal to 900mg/L of ammonia nitrogen, less than or equal to 1000mg/L of total nitrogen, less than or equal to 30mg/L of total phosphorus, and 50-6000 mg/L of chloride ion concentration.