CN114538689A

CN114538689A - High-salt high-organic matter gas field bubble drainage treatment method

Info

Publication number: CN114538689A
Application number: CN202210165707.2A
Authority: CN
Inventors: 杨平; 杨红梅; 黄文凤; 刘同远; 曾文懿
Original assignee: Sichuan Entech Environment Technology Co ltd; Sichuan University
Current assignee: Sichuan Entech Environment Technology Co ltd; Sichuan University
Priority date: 2022-02-23
Filing date: 2022-02-23
Publication date: 2022-05-27
Anticipated expiration: 2042-02-23
Also published as: CN114538689B

Abstract

The invention discloses a high-salinity high-organic matter gas field bubble drainage treatment method, and aims to solve the problem that a subsequent evaporation system cannot operate due to the fact that bubble drainage contains a large amount of organic matters and foam when the gas field bubble drainage is treated by the existing method, greatly reduce the amount of sludge and reduce the emission of pollutants. Which comprises the following steps: primary coagulating sedimentation, primary de-hardening treatment, advanced oxidation treatment, secondary de-hardening flocculation sedimentation, sludge treatment and catalyst regeneration. By adopting the method, organic matters in the foam drainage can be effectively reduced, foams are eliminated, and the stable operation of the subsequent MVR evaporation process is ensured, so that the water quality after the foam drainage treatment of the gas field is ensured to be stable and reach the standard, the sludge yield is reduced, the pollutant emission is reduced, and the ecological environment is protected.

Description

High-salt high-organic matter gas field bubble drainage treatment method

Technical Field

The application relates to the field of gas field well maintenance, in particular to the field of oxidation of high-salt high-organic matter gas field bubble drainage organic matters, and specifically relates to a high-salt high-organic matter gas field bubble drainage treatment method.

Background

In the middle and later periods of exploitation of the gas field well, because the formation pressure is reduced, namely the lifting energy is reduced, the critical liquid carrying flow rate cannot be reached, so that accumulated liquid at the bottom of the gas well cannot be discharged in time, and the gas well is flooded.

In order to solve the problem that accumulated liquid at the bottom of a gas well cannot be removed in time, a foaming agent (the foaming agent is a surfactant which can generate stable foam when meeting water) is generally injected at the bottom of the gas well. When the foaming agent is mixed with accumulated water at the bottom of a well, a large amount of low-density water-containing foam is generated under the stirring of the airflow, so that the gas-water flow state in the well is changed. Once a proper amount of foaming agent is added into a gas well in a bubble flow, slug flow or transition flow state, the surface tension is reduced, so that a water phase is dispersed and becomes a circular fog flow with strong liquid carrying capacity. Thus, the gravity and the slippage loss of the lifting liquid column are reduced; under the condition that the formation energy is not changed, the critical liquid carrying flow rate is reduced, and the water carrying capacity of the gas recovery well is improved, so that the formation water is lifted to the ground. At present, the foam drainage process is widely used for the production of the recovery of a water flooded well and the drainage of an unstable gas-water well, and achieves good effects.

However, the foam drainage process discharges foam drainage (abbreviated as foam drainage) from the stratum, which contains a large amount of organic matters, dissolved salts, suspended matters, chloride ions, and has high hardness and odor, and typical raw water quality is shown in table 1 and fig. 1. If discharged directly, it will cause great harm to local environment.

TABLE 1 typical raw Water quality

At present, the commonly used treatment process of foam drainage comprises flocculation precipitation, hardness removal, organic matter removal, MVR evaporation, flocculation precipitation, hardness removal, electric flocculation (electro-Fenton), filtration, ultrafiltration sodium filtration reverse osmosis, MVR evaporation, flocculation precipitation, hardness removal, anaerobic and aerobic, ultrafiltration sodium filtration reverse osmosis and MVR evaporation. The MVR evaporative crystallization is one of key processes for desalting, coping with water quality change and ensuring the effluent to reach the standard stably. However, when the bubble drainage is treated by adopting the process, a large amount of organic matters can be intercepted by the MVR evaporator, and the organic matters are accumulated continuously along with the increase of the concentration multiple, so that the MVR circulating liquid is viscous, the heat transfer coefficient and the stable operation of a compressor are influenced, and the crystallized salt is not easy to dehydrate. In addition, the foam drainage contains a large amount of surfactant, a large amount of bubbles can be generated in the MVR system after hydraulic circulation of the circulating pump, the bubbles can enter the steam pipe and enter the compressor, so that the MVR system cannot stably run, and the stable standard of the effluent of the whole process is influenced. Therefore, removal of organics and foam before entering MVR for evaporation is critical.

At present, the removal method of the organic matters in the foam drainage mainly comprises an anaerobic and aerobic biochemical method, an adsorption method, an ion exchange method, an electrolytic oxidation method, a Fenton oxidation method, an ozone oxidation method, iron-carbon micro-electrolysis and the like. Because the quality of the high-salinity foam drainage water is changed greatly, the salinity is as high as 40000mg/L, and the direct biochemical treatment method is not stable. As COD of the high organic matter foam drainage water is up to 3000-6000 mg/L (see table 1), an adsorption method and an ion exchange method are directly adopted, the using amount of an adsorbent and an ion exchanger is too large, the operation cost is high, and a large amount of dangerous waste products can be generated. When the ozone oxidation and iron-carbon micro-electrolysis process is adopted to carry out advanced oxidation treatment on the foam drainage, a large amount of foam is generated by aeration (as shown in figure 2 d). The bubble drainage is oxidized by adopting advanced oxidation methods such as an electrolytic oxidation method, a Fenton oxidation method, iron-carbon micro-electrolysis and the like, the organic matter oxidation efficiency is low, a large amount of foam can still be generated after RO membrane concentration or MVR concentration (figure 8a), and the membrane can be polluted and blocked. When Fenton is adopted to carry out advanced oxidation treatment on the foam drainage, the chemical adding amount is not well controlled due to large change of the water quality of the foam drainage. On the other hand, if excessive hydrogen peroxide is added in fenton oxidation, hydroxyl radicals can be quenched, advanced oxidation effect is affected, bubbles can be generated, sludge floats upwards, the floating sludge enters an MVR system, an MVR evaporator can be polluted and blocked, the amount of fenton sludge is large, and sludge disposal cost is high (shown in fig. 2a, fig. 2b and fig. 2 c).

Therefore, in order to meet the increasingly strict requirements of environmental protection management and ensure that the foam drainage treatment stably reaches the standard and is discharged, the application provides the gas field foam drainage treatment method for the high-salinity and high-organic matters, which can solve the problem that the subsequent evaporation system cannot operate due to the fact that a large amount of organic matters and foams are contained in the foam drainage when the gas field foam drainage is treated by the existing method, reduce the sludge amount and reduce the pollutant discharge amount.

Disclosure of Invention

The invention of the present application aims to: in order to solve the problems, the method for treating the bubble drainage of the gas field with high salinity and high organic matters is provided. By adopting the method and the device, organic matters in the foam drainage can be effectively reduced, foams are eliminated, and the stable operation of a subsequent MVR evaporation process is guaranteed, so that the water quality after the foam drainage treatment of the gas field is guaranteed to be stable and reach the standard, the sludge yield is reduced, the emission of pollutants is reduced, and the ecological environment is protected.

In order to achieve the purpose, the following technical scheme is adopted in the application:

a gas field bubble drainage treatment method with high salt content and high organic matter content comprises the following steps:

(1) primary coagulation sedimentation

Sending the foam drainage water after water quality and water quantity adjustment into a primary flocculation sedimentation tank, sequentially adding PAC and PAM into the primary flocculation sedimentation tank, performing primary coagulation sedimentation pretreatment, and removing suspended matters and COD through sedimentation;

(2) one-time de-hardening treatment

Feeding the wastewater subjected to the primary coagulating sedimentation treatment into a primary de-hardening tank, and adding hydroxide to adjust the pH value of the wastewater in the primary de-hardening tank to 9-13 so as to complete primary de-hardening treatment;

after the primary hardening treatment is finished, carrying out precipitation treatment, and obtaining supernatant as primary hardening treatment liquid;

(3) advanced oxidation treatment

Sending the primary hardening removal treatment liquid into an advanced oxidation reaction tank, adding an oxidant persulfate into the advanced oxidation reaction tank to obtain oxidized intermediate wastewater, wherein the ratio of the added persulfate to COD is 1-4: 1;

arranging persulfate activator activated carbon in the packing pool to form an activated carbon packing pool; feeding the oxidized intermediate wastewater into an activated carbon filler tank, wherein the volume ratio of activated carbon to the oxidized intermediate wastewater is 0.2-1.5: 1, and the reaction retention time is 2-10 h, so as to obtain advanced oxidation treatment wastewater;

(4) secondary de-hardening flocculation precipitation

Sending the advanced oxidation treatment wastewater into a secondary de-hardening flocculation and precipitation tank, adding sodium carbonate, PAC and PAM into the secondary de-hardening flocculation and precipitation tank in sequence to finish flocculation and precipitation treatment, and enabling the wastewater after flocculation and precipitation to enter a subsequent evaporation system for evaporation and crystallization.

In the step (1), the high-salt and high-organic-matter foam drainage water to be treated is firstly sent into a regulating tank, and then sent into a primary flocculation sedimentation tank after the water quality and the water quantity are regulated.

In the step (1), the adding amount of PAC is 800-1200 mg/L and the adding amount of PAM is 8-10 mg/L based on the volume of the wastewater.

And (3) adding hydroxide into the primary de-hardening tank in the step (2), and adjusting the pH value of the wastewater in the primary de-hardening tank to 10-11.5 to complete primary de-hardening treatment.

In the step (2), the hydroxide is one or more of sodium hydroxide and potassium hydroxide.

In the step (3), the added oxidant is persulfate, and the ratio of persulfate to COD is 1.5-2.5: 1.

in the step (3), the persulfate activator arranged in the filler pool is granular activated carbon;

the volume ratio of the activated carbon to the oxidized intermediate wastewater is 0.4-0.6: 1, the reaction residence time is 4 h.

In the step (4), sodium carbonate, PAC and PAM are added into the secondary de-hardening flocculation sedimentation tank added with the advanced oxidation treatment wastewater in sequence, the hardness of the wastewater in the secondary de-hardening flocculation sedimentation tank is controlled within the range of 150-200 mg/L, the PAC adding amount is 150-300 mg/L, and the PAM adding amount is 1-3 mg/L.

In the step (4), the dosage of PAC is 200mg/L, and the dosage of PAM is 2 mg/L.

Also comprises the following steps:

(5) sludge treatment

Collecting the sludge generated by the primary coagulation sedimentation, the sludge generated by the primary de-hardening treatment, the sludge generated by the advanced oxidation treatment and the sludge generated by the secondary flocculation sedimentation.

And (5) discharging the collected sludge into a subsequent sludge dewatering system.

Also comprises the following steps:

(6) catalyst regeneration

When the COD removal rate of the advanced oxidation treatment is reduced to a set range, the activated carbon of the catalyst is regenerated; the regeneration operation is as follows:

closing a water inlet valve of the packing pool, opening an emptying valve of the packing pool, discharging wastewater in the packing pool into a regulating pool, closing the emptying valve of the packing pool after emptying, discharging MVR condensate with the temperature of 80-90 ℃ into the packing pool filled with activated carbon, adding persulfate into the packing pool, activating the persulfate by using high temperature and activated carbon, carrying out in-situ oxidation on an activated carbon catalyst, aerating by using air or ozone, oxidizing organic matters adsorbed in the activated carbon into small molecules, and forming regenerated water in the packing pool; after the aeration is finished, because the salt content of the reclaimed water is less, the reclaimed water can be directly discharged into an MVR subsequent treatment device. And after the regeneration water in the filler tank is emptied, introducing steam into the activated carbon in the filler tank, heating, washing and desorbing to complete the regeneration of the activated carbon. The aeration intensity of air or ozone is 15L/m²S, aerating for 4 h; the steam temperature is 100 ℃, the pressure is more than or equal to 0.4MPa, the flushing is carried out for 30min, and the adding amount of the persulfate is 2 times of the normal concentration of the oxidant.

Also comprises the following steps:

(7) advanced oxidation switching

Arranging 3-4 advanced oxidation modules, wherein the advanced oxidation modules are arranged in parallel;

when one or more advanced oxidation modules carry out advanced oxidation treatment, the rest advanced oxidation modules are regenerated to complete advanced oxidation switching and realize continuous operation.

The persulfate is sodium persulfate.

Apparatus for use in the foregoing method, comprising:

the adjusting tank is used for adjusting the water quality and the water quantity of the high-salinity high-organic-matter foam drainage water to be treated;

the primary flocculation sedimentation tank is connected with the regulating tank, and the wastewater after the water quality and the water quantity are regulated in the regulating tank can be lifted to the primary flocculation sedimentation tank through a lifting pump for treatment;

the primary agent adding device is connected with the primary flocculation sedimentation tank and can add PAC and PAM into the primary flocculation sedimentation tank to precipitate and remove suspended matters and COD in the wastewater;

the primary hardening removal tank is connected with the primary flocculation sedimentation tank, and the wastewater after primary coagulating sedimentation treatment can be sent into the primary hardening removal tank for primary hardening removal treatment;

the secondary agent adding device is connected with the primary de-hardening tank and can add hydroxide into the primary de-hardening tank to adjust the pH value of wastewater in the primary de-hardening tank to 9-13 so as to complete primary de-hardening treatment;

the advanced oxidation module is connected with the primary de-hardening tank, and primary de-hardening treatment liquid obtained by precipitating the wastewater subjected to primary de-hardening treatment can enter the advanced oxidation module for oxidation treatment to obtain advanced oxidation treatment wastewater;

the secondary de-hardening flocculation sedimentation tank is connected with the advanced oxidation module, the advanced oxidation treatment wastewater obtained by the treatment of the advanced oxidation module can enter the secondary de-hardening flocculation sedimentation tank for secondary de-hardening flocculation sedimentation treatment, and the wastewater after the secondary de-hardening flocculation sedimentation treatment can enter an evaporation system;

the third-stage medicament adding device is connected with the second-stage de-hardening flocculation sedimentation tank and can sequentially add sodium carbonate, PAC (polyaluminium chloride) and PAM (polyacrylamide) into the second-stage de-hardening flocculation sedimentation tank so as to achieve the purposes of de-hardening and flocculation;

the advanced oxidation module includes:

the advanced oxidation reaction tank is connected with the primary de-hardening tank, and primary de-hardening treatment liquid obtained by precipitating the wastewater subjected to primary de-hardening treatment can enter the advanced oxidation reaction tank and is mixed with persulfate to obtain oxidized intermediate wastewater;

the oxidation agent adding device is connected with the advanced oxidation reaction tank and can add persulfate into the advanced oxidation reaction tank;

the filler pond is respectively connected with the advanced oxidation reaction pond and the secondary de-hardening flocculation sedimentation pond, activated carbon filler is arranged in the filler pond, oxidation intermediate waste water entering the filler pond from the advanced oxidation reaction pond can be subjected to advanced oxidation treatment in the filler pond to obtain advanced oxidation treatment waste water, and the advanced oxidation treatment waste water obtained by treatment in the filler pond can be subjected to secondary flocculation sedimentation treatment in the secondary de-hardening flocculation sedimentation pond.

Still include the mud pond of keeping in, the mud pond of keeping in links to each other and the mud that once coagulates precipitation production, the mud that once takes off the hard processing production, the mud that advanced oxidation treatment produced, the mud that the secondary flocculation and precipitation produced with one-level flocculation and precipitation pond, one-level unhardening pond, second grade unhardening flocculation and precipitation pond respectively can get into the mud and keep in the pond and collect.

The number of the advanced oxidation modules is 2-10, and the advanced oxidation modules are arranged in parallel.

Drawings

The invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 shows a raw foam-drainage water produced in a foam-drainage process.

Fig. 2 is a graph showing the results of removing organic substances in the foam drainage by the conventional method. Wherein, FIG. 2a is a floating diagram of sludge after removing organic substances by Fenton; FIG. 2b is a graph of filter fouling and plugging; FIG. 2c is a graph of sludge produced by Fenton's oxidation; FIG. 2d is a graph showing the results of ozone oxidation and aeration of iron-carbon micro-electrolysis process to generate a large amount of foam.

FIG. 3 is a process flow diagram of example 1.

FIG. 4 is a graph showing a comparison between before and after the flocculation in example 1.

Fig. 5 is a graph showing the results of calcium deposition on the catalyst.

FIG. 6 is a graph showing the results of de-hardening precipitation under different pH conditions (pH values 9, 10, and 11 in the order of FIGS. 6a, b, and c).

FIG. 7 is a graph showing the results of evaporation of wastewater after one-time de-hardening treatment and precipitation.

FIG. 8 is a graph showing the effects of aeration after Fenton oxidation and aeration after oxidation of activated carbon activated persulfate.

FIG. 9 is a GCMS analysis of raw water, after advanced oxidation and evaporative condensate.

Detailed Description

All of the features disclosed in this specification, or all of the steps in any method or process so disclosed, may be combined in any combination, except combinations of features and/or steps that are mutually exclusive.

Any feature disclosed in this specification may be replaced by alternative features serving equivalent or similar purposes, unless expressly stated otherwise. That is, unless expressly stated otherwise, each feature is only an example of a generic series of equivalent or similar features.

Example 1

The device that this embodiment adopted includes equalizing basin, one-level flocculation and precipitation pond, one-level medicament throwing device, one-level unhairing pond, second grade medicament throwing device, senior oxidation module, second grade unhairing flocculation and precipitation pond, tertiary medicament throwing device. In the embodiment, the number of the advanced oxidation modules is preferably 3-4, and the advanced oxidation modules are connected in parallel.

Wherein, the primary flocculation sedimentation tank is connected with the adjusting tank; firstly, high-salt and high-organic matter foam drainage water to be treated enters an adjusting tank, is subjected to water quality and water quantity adjustment, and is lifted to a primary flocculation sedimentation tank through a lifting pump for treatment; the primary medicament adding device is connected with the primary flocculation sedimentation tank and used for adding PAC and PAM into the primary flocculation sedimentation tank and removing suspended matters and COD in the wastewater through precipitation. The primary flocculation sedimentation tank and the secondary medicament adding device are respectively connected with the primary de-hardening tank; and (3) feeding the wastewater subjected to the primary coagulating sedimentation treatment into a primary de-hardening tank, and adding hydroxide into the primary de-hardening tank through a secondary medicament adding device to adjust the pH value of the wastewater in the primary de-hardening tank to 9-13 so as to finish primary de-hardening treatment.

In this embodiment, the advanced oxidation module includes an advanced oxidation reaction tank, an oxidizing agent feeding device, and a filler tank. Wherein, the primary de-hardening tank, the oxidizing agent feeding device and the filling tank are respectively connected with the advanced oxidation reaction tank; precipitating the wastewater subjected to primary de-hardening treatment to obtain supernatant as primary de-hardening treatment liquid; feeding the primary de-hardening treatment liquid into an advanced oxidation reaction tank, and mixing the primary de-hardening treatment liquid with persulfate added by an oxidizing agent adding device to obtain oxidized intermediate wastewater; the filler pond is internally provided with an activated carbon filler, persulfate in the oxidized intermediate wastewater can be activated in the filler pond to generate sulfate radicals for advanced oxidation treatment, and advanced oxidation treatment wastewater is obtained. Meanwhile, the filling tank and the third-level medicament adding device are connected with the second-level de-hardening flocculation sedimentation tank; the wastewater after the advanced oxidation treatment is sent into a secondary de-hardening flocculation sedimentation tank for secondary flocculation sedimentation treatment; and the tertiary agent adding device is used for sequentially adding sodium carbonate, PAC and PAM into the secondary de-hardening flocculation sedimentation tank so as to achieve the purposes of de-hardening and flocculation, and the wastewater after secondary flocculation sedimentation treatment can be sent into an MVR evaporation system for treatment.

Preferably, the device of the embodiment further comprises a sludge temporary storage tank, wherein the sludge temporary storage tank is respectively connected with the primary flocculation sedimentation tank, the primary de-hardening tank and the secondary de-hardening flocculation sedimentation tank; the sludge generated by the primary coagulation sedimentation, the sludge generated by the primary de-hardening treatment, the sludge generated by the advanced oxidation treatment and the sludge generated by the secondary de-hardening flocculation sedimentation can be sent into a temporary sludge storage tank for collection. And (4) the collected sludge enters a subsequent sludge dewatering system for treatment.

In this embodiment, the method for treating bubble drainage of a high-salinity high-organic matter gas field comprises the following steps.

1 one-time coagulating sedimentation

The water quality and the water quantity of the high-salt and high-organic-matter foam drainage water have large variation and need to firstly enter an adjusting tank for adjusting the water quality and the water quantity. Since the suspended matter in the wastewater is too high and black, the pre-treatment of coagulation sedimentation is performed first (as shown in fig. 4, wherein fig. 4a is a raw water diagram of the primary coagulation sedimentation without treatment, and fig. 4b is a wastewater diagram of the primary coagulation sedimentation after treatment). Lifting the waste water subjected to water quality and water quantity regulation in the regulating tank to a primary flocculation sedimentation tank by a lifting pump; PAC and PAM are added into the primary flocculation sedimentation tank in sequence, a large amount of suspended matters (the removal rate is 97.79%) and COD (the removal rate is 49.53%) are removed through sedimentation, and the removal results are shown in Table 2. Wherein the adding amount of PAC is 800-1200 mg/L, the adding amount of PAM is 8-10 mg/L, and the longer the waste water is placed, the lower the required flocculating agent is.

TABLE 2 preprocessing parameters Table

2 one-shot unhairing treatment

The wastewater treated by the primary coagulating sedimentation becomes thorough, but the hardness of the wastewater is higher, a large amount of sediment can be generated along with the increase of the pH value, the water quality becomes muddy and settles on a subsequent advanced oxidation catalyst (as shown in figure 5), the advanced oxidation effect is influenced, a large amount of calcium and magnesium ions can form scale in the MVR heat exchanger, the heat exchange coefficient is influenced, and therefore, the unhardening treatment is required after the flocculating sedimentation. The test result shows that: the total hardness of the wastewater was shown in Table 3, in which the precipitation amounts at pH values 9, 10 and 11 were different from each other (as shown in FIG. 6; in FIG. 6, FIG. 6a, FIG. 6b and FIG. 6c are graphs showing precipitation results at pH values 9, 10 and 11 in this order). As can be seen from fig. 5, 6 and table 3, a large amount of precipitate is generated at pH 11, pH rises again, the amount of alkali increases greatly, but the total hardness decreases little, so pH is controlled at 11, and the remaining hardness is removed by adding sodium carbonate.

Meanwhile, studies show that: the carbonate quenches free radicals of advanced oxidation, so that the secondary hardness removal treatment is arranged after the advanced oxidation treatment, and the hardness is controlled within the range of 150-200 mg/L.

TABLE 3 Total hardness at different pH values

pH value	7	9	10	11
					Numerical value mg/L	16800	10746	10272	8968

3 advanced oxidation treatment

The wastewater after primary de-hardening treatment is precipitated, the obtained supernatant is primary de-hardening treatment liquid, the pH value of the primary de-hardening treatment liquid is reduced to about 9.7 (namely, after the primary de-hardening treatment is completed, the pH value of the wastewater is reduced to about 9.7), the COD is high, and a large amount of foam is generated in the evaporator if directly entering the MVR evaporator (see figure 7), and the foam enters the steam pipe and enters the compressor, so that the MVR evaporator cannot operate. Advanced oxidation is also required to remove a large amount of organic matter and foam.

Advanced oxidation is a process for degrading high-stability organic matters in water by utilizing intermediate state components OH with strong oxidizing property formed in the reaction process. At present, the advanced oxidation method mainly comprises a Fenton method, a Fenton-like method, an ozone oxidation method, an electrocatalytic oxidation method, iron-carbon micro-electrolysis and the like. Among them, the fenton oxidation and ozone oxidation methods are most widely used because of their technical convenience in use and easy control of process conditions.

At present, the treatment of organic industrial wastewater not only needs to consider the removal effect of pollutants, but also needs to consider the problem of disposal cost caused by solid waste, especially the yield of dangerous waste. OH in the advanced oxidation has great defects, such as short existence time and disappearance of the reaction with pollutants in time; simultaneously, carbonate, nitrate, phosphate radical, chloride ion and Fe in the water body²⁺、H₂O₂These substances quench OH, and affect the oxidation effect. Therefore, it is necessary to select an advanced oxidation method having a good oxidation effect and a small sludge production amount. In the application, the oxidation of foam drainage organic matters and foams is carried out by adopting an advanced oxidation method of activating persulfate.

Studies show that, SO₄ ^-SO compared with OH₄ ^-More stable, longer half-life period and wider pH value range of reaction; organic substances with stronger oxidizability and some OH can not be degraded, SO₄ ^-It can be degraded. The persulfate includes Peroxodisulfate (PDS) and Peroxomonosulfate (PMS), which have strong oxidizability, but have stable structure at room temperature and are not easily decomposed. Therefore, persulfate alone has no obvious effect on the oxidation of organic matters, and needs to generate intermediate sulfate radicals & SO after the persulfate is activated by an activating agent₄ ^-And OH, with highly active SO₄ ^-OH and OH can enhance the oxidation effect on organic matters.

The activated carbon is used as one of carbon-based catalysts, is a green catalytic material, and can effectively prevent leaching and secondary pollution of toxic metal ions. It has been found that activated carbon can also act as an activator of electron transfer mediators, generating sulfate radicals in the activation of persulfate salts. The active carbon forms comprise powdered active carbon, granular active carbon and honeycomb active carbon, and in consideration of the problem of structural stability of the active carbon, the granular active carbon is adopted to activate persulfate to carry out advanced oxidation, and the active carbon is used for adsorbing and synergistically activating the advanced oxidation of the persulfate to oxidize and remove organic matters and foam matters, so that the organic matters and the foam matters are reduced.

Sending the primary hardening treatment liquid into an advanced oxidation reaction tank, adding sodium persulfate into the advanced oxidation reaction tank, wherein the ratio of the added sodium persulfate to COD is 2: 1, adding the wastewater with the concentration of 20 percent to obtain the oxidized intermediate wastewater. Then feeding the oxidized intermediate wastewater into a granular activated carbon filling tank, wherein granular activated carbon is arranged in the filling tank; the volume ratio of the activated carbon to the oxidized intermediate wastewater is 0.5: 1, the reaction retention time is 4 hours, and advanced oxidation treatment wastewater is obtained; the COD removal rate is 68.8% (see table 4), the pH value of the advanced oxidation treatment wastewater is 8-9, and the pH value does not need to be adjusted back. At the same time, the foam disappeared after the reaction, as shown in FIG. 8. Fig. 8 is a graph showing the aeration effect after fenton oxidation and the aeration effect after oxidation of activated carbon activated persulfate, fig. 8a is a graph showing the aeration effect after fenton oxidation, and fig. 8b is a graph showing the aeration effect after oxidation of activated carbon activated persulfate according to the present application.

TABLE 4 activated carbon persulfate Oxidation data

4 secondary de-hardening flocculation precipitation

After the persulfate advanced oxidation wastewater is activated by the activated carbon, the pH value of the obtained wastewater (namely the advanced oxidation wastewater) is about 7, the pH value does not need to be adjusted back, a small amount of activated carbon residues exist in effluent, and a large amount of calcium exists in water. Therefore, sodium carbonate, PAC and PAM are added in sequence, the hardness is controlled within the range of 150-200 mg/L, the adding amount of the sodium carbonate is determined according to the hardness of water, the adding amount of the PAC is 200mg/L, and the adding amount of the PAM is 2 mg/L. And (3) the wastewater after the secondary de-hardening flocculation precipitation enters an evaporation system for evaporation and crystallization, and as the evaporation condensate contains a small amount of COD and ammonia nitrogen (see table 4), a biochemical treatment system is arranged according to local discharge standards.

5 sludge treatment

Collecting the sludge generated by the primary coagulating sedimentation, the sludge generated by the primary de-hardening treatment, the sludge generated by the advanced oxidation treatment and the sludge generated by the secondary de-hardening flocculation sedimentation, and then pumping the collected sludge into a subsequent sludge dewatering system for treatment.

6 catalyst regeneration

Activated free radicals of activated carbon generally occur on the outer surface of activated carbon. Meanwhile, activated carbon is also a good adsorbent. When the activated carbon is fully adsorbed in the gaps, the activation function of the activated carbon is attenuated, and the activated carbon needs to be regenerated.

The catalyst regeneration operation is as follows: closing a water inlet valve of the packing pool, opening an emptying valve of the packing pool, discharging wastewater in the packing pool into a regulating pool, closing the emptying valve of the packing pool after emptying, discharging MVR condensate with the temperature of 80-90 ℃ into the packing pool filled with activated carbon, adding persulfate into the packing pool, activating the persulfate by using high temperature and activated carbon, carrying out in-situ oxidation on an activated carbon catalyst, aerating by using air or ozone, oxidizing organic matters adsorbed in the activated carbon into small molecules, and forming regenerated water in the packing pool; after the aeration is finished, the salt content of the regenerated water is less, and the regenerated water can be directly discharged into an MVR subsequent treatment device; and after the regeneration water in the filler tank is emptied, introducing steam into the activated carbon in the filler tank, heating, washing and desorbing to complete the regeneration of the activated carbon.

The active carbon mainly adsorbs organic matters with molecular weight more than 100, and has little adsorption effect on small molecular organic matters. Therefore, the activated persulfate is adopted to carry out in-situ oxidation on the activated carbon catalyst, and the high-temperature activation of the persulfate is carried out by utilizing the temperature (80-90 ℃) of MVR condensate, so that the oxidation effect is improved. At the same time, air is adopted for aeration (ozone can be introduced if necessary) to adsorb organic matters in the active carbonOxidized into small molecules and then heated by steam to flush and desorb. In this example, the aeration intensity was 15L/m²S, the aeration time is 4h, the steam temperature is 100 ℃, and the adding amount of persulfate is 2 times of that of normal oxidation. In this application, the waste water salt content that produces after the normal position oxidation is less, can arrange into the follow-up biochemical treatment device of MVR can.

Because the activated carbon needs to be regenerated, 3-4 advanced oxidation modules connected in parallel are arranged (a single advanced oxidation module is formed by an advanced oxidation reaction tank, an oxidation medicament feeding device and a filler tank), and the continuous operation of the system is facilitated. The COD removal efficiency is less than 30 percent, and the catalyst can be regenerated, or the catalyst can be regenerated periodically according to the debugging effect.

With reference to table 4, GCMS analysis is performed on raw water, advanced oxidation treatment wastewater, and evaporation condensate of advanced oxidation treatment wastewater (i.e., condensate generated by subsequent MVR evaporation) (see fig. 9a, 9b, and 9c, where fig. 9a is a raw water chromatogram, fig. 9b is a advanced oxidation treatment wastewater chromatogram, and fig. 9c is an MVR condensate chromatogram), and 93.03% of organic matters in the raw water are alkanes with a molecular weight of 150 to 300 and also contain a small amount of organic nitrogen. After persulfate is activated and oxidized, all the macromolecular alkanes are oxidized into organic matters such as alcohol, ketone, aldehyde and the like with the molecular weight of 50-100, and organic nitrogen is oxidized into ammonia nitrogen; after MVR evaporation, alcohol, ketone, aldehyde and ammonia nitrogen with the molecular weight of 50-100 can enter condensate, biodegradability is good, and subsequent biochemical treatment can reach the standard.

Compared with the prior art, the method has the following beneficial effects.

(1) The application simultaneously utilizes the sulfate radicals generated by persulfate and the catalytic adsorption effect of activated carbon to treat the organic matters, and strengthens the decomposition of organic pollutants while widening the pollutant removal range. The method and the device can effectively remove foam substances and improve the removal rate of organic matters. By adopting the method and the device, the influence of gas field bubble drainage organic matters and foam substances on subsequent evaporation crystallization can be effectively eliminated, and the stable operation of an evaporation system is ensured, so that the quality of effluent water is ensured to reach the standard, and the local ecological environment is protected.

(2) The activated carbon that this application used is green catalyst, and it can adsorb organic matter and activation persulfate simultaneously, produces strong oxidation free radical, and does not produce mud (remove a small amount of activated carbon dust) among the reaction process, just in time can solve the big and advanced oxidation inefficiency series of problems that produce of mud output that current gas field bubble drainage treatment method exists, guarantees gas field bubble drainage treatment system's steady operation and discharge to reach standard. Meanwhile, the invention can reduce the discharge amount of pollutants and play an important role in protecting the ecological environment of shale gas mining areas.

(3) The invention can be provided with 3-4 groups of advanced oxidation modules, and the active carbon catalyst of each group of advanced oxidation modules is subjected to in-situ oxidation regeneration by utilizing ozone, persulfate, MVR high-temperature condensate and steam, so that the utilization rate of the active carbon catalyst is improved, and the treatment cost is reduced.

(4) Before advanced oxidation, the pH value is adjusted to 11 for hardness removal; after advanced oxidation, sodium carbonate is added to remove hardness, so that the influence of carbonate on free radicals can be effectively avoided, and the addition amount of a medicament is reduced; meanwhile, the hardness requirement before evaporation is effectively ensured.

(5) According to the method, the active carbon activated persulfate is adopted to treat the organic matter and the foam matter in the gas field foam drainage, the pH value can be automatically adjusted in the reaction process, the reaction is carried out under the acid-base condition, the pH value of the final effluent tends to be neutral, the pH value does not need to be adjusted back, and the addition amount of the medicament and the operation cost are reduced.

The invention is not limited to the foregoing embodiments. The invention extends to any novel feature or any novel combination of features disclosed in this specification and any novel method or process steps or any novel combination of features disclosed.

Claims

1. A high-salt high-organic matter gas field bubble drainage treatment method is characterized by comprising the following steps:

(1) primary coagulation sedimentation

(2) one-time de-hardening treatment

(3) advanced oxidation treatment

(4) secondary de-hardening flocculation precipitation

2. The method according to claim 1, wherein in the step (1), the high-salt and high-organic-matter foam drainage water to be treated is firstly sent into a regulating tank, and is sent into a primary flocculation sedimentation tank after the water quality and the water quantity are regulated.

3. The method according to claim 1, wherein in the step (1), the PAC is added in an amount of 800-1200 mg/L and the PAM is added in an amount of 8-10 mg/L based on the volume of the wastewater.

4. The method according to any one of claims 1 to 3, wherein in the step (2), hydroxide is added into the primary de-hardening tank, and the pH value of the wastewater in the primary de-hardening tank is adjusted to 10 to 11.5, so that primary de-hardening treatment is completed.

5. The method according to any one of claims 1 to 4, wherein in the step (3), the oxidant added is persulfate, and the ratio of persulfate to COD is 1.5-2.5: 1.

6. the method as claimed in claim 1, wherein in the step (3), the persulfate activator provided in the filler pond is granular activated carbon.

7. The method according to any one of claims 1 to 6, characterized in that in the step (4), sodium carbonate, PAC and PAM are sequentially added into a secondary de-hardening flocculation sedimentation tank added with the wastewater subjected to the advanced oxidation treatment, the hardness of the wastewater in the secondary de-hardening flocculation sedimentation tank is controlled to be within the range of 150-200 mg/L, the PAC adding amount is 150-300 mg/L, and the PAM adding amount is 1-3 mg/L.

8. The method of claim 1, further comprising the steps of:

(5) sludge treatment

Collecting sludge generated by primary coagulation sedimentation, sludge generated by primary de-hardening treatment, sludge generated by advanced oxidation treatment and sludge generated by secondary flocculation sedimentation, and then discharging the collected sludge into a subsequent dehydration treatment system.

9. The method according to any one of claims 1 to 8, further comprising the steps of:

(6) catalyst regeneration

closing a water inlet valve of the packing pool, opening an emptying valve of the packing pool, discharging wastewater in the packing pool into a regulating pool, closing the emptying valve of the packing pool after emptying, discharging MVR condensate with the temperature of 80-90 ℃ into the packing pool filled with activated carbon, adding persulfate into the packing pool, activating persulfate by utilizing high temperature and the activated carbon, carrying out in-situ oxidation on an activated carbon catalyst, aerating by adopting air or ozone, oxidizing organic matters adsorbed in the activated carbon into small molecules, and forming regenerated water in the packing pool; after aeration is finished, because the salt content of the regenerated water is less, the regenerated water can be directly discharged into an MVR subsequent treatment device; after the regeneration water in the filler tank is emptied, introducing steam into the activated carbon in the filler tank, and heating, washing and desorbing to complete the regeneration of the activated carbon;

the aeration intensity of air or ozone is 15L/m²S, aeration time 4 h; the steam temperature is 100 ℃, the pressure is more than or equal to 0.4MPa, the flushing is carried out for 30min, and the adding amount of the persulfate is 2 times of the normal concentration of the oxidant.

10. The method according to any one of claims 1 to 9, further comprising the steps of:

(7) advanced oxidation switching