CN116535054A - Treatment method of high-salt wastewater - Google Patents

Abstract

The invention provides a treatment method for high-salt wastewater, the treatment method comprising the following steps: (1) mixing wastewater with a pH value ≥ 7 with an oxidant to obtain a mixture; (2) mixing the mixture obtained in step (1) with ozone The mixed gas is oxidized sequentially through the micro-nano bubble generating device and the oxidation reaction device to obtain the first pretreated water; (3) the first pretreated water obtained in step (2) is treated with a phosphorus removal agent, and the water is discharged to complete the waste water processing. The invention realizes efficient and low-cost removal of organic matter and organic phosphine in high-salt wastewater through combined treatment processes such as pH adjustment, oxidation treatment, and precipitation flocculation in the presence of phosphorus removal agents, and has the advantages of simple operation, low dosage of agents, and secondary The advantage of less pollution.

Description

A method for treating high-salt wastewater

Technical Field

The invention belongs to the technical field of water treatment, and in particular relates to a method for treating high-salt wastewater.

Background Art

With the rapid development of industry, a large amount of difficult-to-treat industrial organic wastewater has been generated, posing a threat to the entire ecosystem and human health; especially in recent years, the new demand for zero wastewater discharge has generated a large amount of complex organic wastewater containing high concentrations of inorganic salts, further increasing the difficulty of wastewater treatment. At present, the treatment technologies for complex organic wastewater in the industry include biodegradation, chemical oxidation, adsorption, etc.; among them, the cost of biodegradation is relatively low, but the activity of biological bacteria is greatly inhibited by high concentrations of inorganic salts, and it is not suitable for the treatment of high-salt organic wastewater; chemical oxidation and adsorption can partially remove organic matter in wastewater, but their treatment efficiency is low and the treatment effect is poor. Generally, it is necessary to improve the efficiency of a single treatment technology, or to use a combination of treatment technologies to achieve the purpose of deep treatment.

In complex organic wastewater containing high concentrations of inorganic salts, the treatment of organophosphine pollutants is particularly problematic. Organophosphine is widely found in pesticide wastewater, fine chemical wastewater, electroplating wastewater, and metallurgical wastewater, and is very difficult to remove. Treatment methods using chemical oxidation or adsorption methods are usually inefficient and less economical. Specifically, the adsorption method can remove a certain amount of organophosphine, but it is very easy to become saturated when treating high concentrations of organophosphine, and requires a large amount of adsorbent and frequent regeneration; the chemical oxidation method can convert organophosphine into inorganic phosphorus, but it cannot be removed directly, so it is necessary to use a combination of different treatment technologies to optimize, improve treatment efficiency, and reduce treatment costs.

At present, there are few studies on the deep removal of organic matter and organophosphorus in high-salt wastewater, and it is still in the exploratory stage. For example, CN102198989A discloses a method for treating bis(glyphosate) wastewater, which specifically includes: first adjusting the pH of the wastewater to 2.5-4, then irradiating with ultraviolet light and adding Fenton reagent (hydrogen peroxide and ferrous ions) for oxidation treatment, adjusting the alkaline pH after oxidation for a period of time for precipitation, and filtering the water to enter the biochemical treatment system. Although this method can reduce the total phosphorus and formaldehyde in bis(glyphosate) wastewater, since high-salt wastewater cannot adopt biochemical treatment technology, this method is not suitable for high-salt wastewater treatment.

CN114275937A discloses a deep treatment process for high-concentration organic phosphine wastewater. The device used in the process includes wastewater treatment equipment and a pretreatment box, wherein the pretreatment box includes a feed pipe, a filter screen, a rotating pipe, a baffle and multiple feeding barrels, a dephosphorization metal salt is added to one feeding barrel, and a wastewater flocculant is added to another feeding barrel. The baffle is used to block the wastewater so that the wastewater added to the pretreatment box will not directly contact the filter screen, avoiding direct contact and causing the impurities adsorbed by the flocculant during pretreatment to be partially under the filter screen. The core treatment means of the device is to add dephosphorization metal salts and wastewater flocculants, generate insoluble precipitates through the reaction of metal ions and organic phosphine, and adsorb impurities in the wastewater through the flocculant to preliminarily treat the wastewater; however, the composition of the dephosphorization metal salt and the wastewater flocculant is not disclosed in the treatment process, and the metal salt is more suitable for removing inorganic phosphorus, and the degree of its reaction with organic phosphine is not high, so the treatment effect of this method on organic phosphine is obviously insufficient.

CN106745613A discloses a method for treating wastewater containing high concentration of organic phosphine. The specific method comprises: firstly adjusting the pH value of the wastewater to 2-3, then adding an organic phosphine precipitant containing ferrous sulfate, magnesium oxide, silicon dioxide and manganese oxide, then adding hydrogen peroxide for reaction, and finally adjusting the pH value of the wastewater to above 10. The method can destroy organic acids and organic amine complexing agents in the wastewater, and can capture hypophosphite to form precipitation, thereby reducing the total phosphorus content in the wastewater. However, the method has the following defects: (1) the process of first adjusting the strong acid and then adjusting the strong alkali consumes a large amount of chemical reagents, thereby increasing the treatment cost and the salinity of the treated water; (2) the added organic phosphine precipitant contains a large amount of solids, which greatly improves the quality of the generated insoluble solids. These insoluble solids contain a large amount of organic phosphine, which will be treated as hazardous waste or as hazardous waste in the future, thereby increasing the treatment cost; (3) the amount of the added organic phosphine precipitant and hydrogen peroxide is too high, which is 10-30 times that of the organic phosphine, so the treatment cost is relatively high.

It can be seen that the current methods for removing organic phosphine and inorganic phosphorus from wastewater still have various problems. They are either not suitable for high-salinity wastewater treatment, or suitable for removing inorganic phosphorus, but have limited treatment capacity for organic phosphine, or consume a large amount of reagents and produce a large amount of precipitation, resulting in very high treatment costs. Therefore, how to develop a treatment method for deeply removing refractory organic matter and organic phosphine from high-salinity wastewater is a great challenge and a technical problem that needs to be solved urgently in the field of industrial wastewater treatment.

Summary of the invention

In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for treating high-salt wastewater, which is a method for deeply removing organic matter and organic phosphine in high-salt wastewater. It can effectively remove organic pollutants and convert organic phosphine into inorganic phosphorus through the synergistic effect of oxidant, ozone mixed gas and ozone micro-nano bubbles generated in situ by a micro-nano bubble generating device, and further remove inorganic phosphorus and organic matter through a phosphorus removal agent. The treatment method has the advantages of simple operation, low dosage of reagents, and less secondary pollution, can match different water quality characteristics, optimize treatment costs, and meet different treatment needs.

To achieve this object, the present invention adopts the following technical solutions:

The present invention provides a method for treating high-salt wastewater, which comprises the following steps:

(1) mixing wastewater having a pH value of ≥7 with an oxidant to obtain a mixture;

(2) subjecting the mixture obtained in step (1) and the ozone mixed gas to oxidation treatment through a micro-nano bubble generating device and an oxidation reaction device in sequence to obtain first pretreated water;

(3) The first pretreated water obtained in step (2) is treated with a phosphorus removal agent, and the water is discharged to complete the wastewater treatment.

The present invention has been found in the research that the treatment technologies of organic wastewater in the prior art mainly include biodegradation, chemical oxidation and adsorption, etc.; among them, the adsorption method is widely used and simple in design, but has the disadvantages of being easily saturated and requiring frequent regeneration, requiring a large amount of adsorbent, and producing a large amount of difficult-to-treat concentrated water; the biodegradation method has a low cost, but because the biological bacteria are intolerant to high concentrations of inorganic salts and have extremely low activity in a high-salt environment, it is not suitable for high-salt organic wastewater treatment; the chemical oxidation method is suitable for low-concentration organic wastewater treatment, but the direct oxidation efficiency is low, and an external catalyst, energy field or coupling with other oxidants is required to produce oxidative free radicals to achieve deep oxidation of organic matter.

At present, it is extremely difficult to treat high-salinity wastewater containing refractory organic matter and organophosphorus. In addition to efficiently removing organic matter, it is also necessary to deeply remove organophosphorus and total phosphorus. Conventional unit technologies such as adsorption and flocculation sedimentation have very low treatment efficiencies and are difficult to achieve the ultimate treatment goals; moreover, existing conventional treatment technologies cannot meet the requirements after simple combination.

Based on the above research findings, the method for treating high-salt wastewater provided by the present invention combines oxidants, ozone, micro-nano bubbles generated by a micro-nano bubble generator, and a phosphorus removal agent, etc., and achieves deep treatment of organic matter, organic phosphine and total phosphorus through the mutual coordination between materials and process steps. The specific analysis is as follows:

On the one hand, the oxidation potential of ozone molecules is high, and the decomposition products have no secondary pollution, and can achieve oxidative degradation of organic matter; however, ozone oxidation has reaction selectivity, so the degradation of organic matter is not thorough, and the solubility of ozone in water is low, and there are problems such as poor mass transfer effect. In steps (1) and (2) of the present invention, on the one hand, the oxidation of the ozone mixture and the oxidant is combined, and on the other hand, the mixture containing the oxidant and the ozone mixed gas are passed into the micro-nano bubble generating device to generate ozone micro-nano bubbles in situ, and the gas-liquid mass transfer process is synchronously enhanced, the cavitation effect of the ozone micro-nano bubble fragmentation, and the composite synergistic effect between the ozone molecules and the oxidant are combined, and multiple effects are coordinated with each other to jointly improve the efficiency of the conversion of ozone molecules into free radicals, thereby deeply degrading organic matter, and converting the difficult-to-remove organic phosphine into inorganic phosphorus to obtain the first pretreated water.

Steps (1) and (2) of the present invention are oxidation steps, wherein the pH value of the wastewater in step (1) is ≥7, that is, a neutral or alkaline water environment, which can improve the oxidation and degradation efficiency of organic matter/organophosphine. The oxidation process of the present invention has multiple advantages: first, a micro-nano bubble generating device is used to fully mix the ozone mixed gas with a mixture containing an oxidant and wastewater, which can increase the ozone concentration in the wastewater, promote the full contact between ozone and organic matter in the wastewater, and improve the utilization efficiency of ozone; second, ozone micro-nano bubbles are generated in the micro-nano bubble generating device, and a part of the ozone nano-micro bubbles are self-decomposed to generate free radicals under the action of hydraulic cavitation, degrade organic matter in the wastewater, and convert part of the organic phosphine into inorganic phosphorus; third, the ozone nano-micro bubbles react with the oxidant, promote the decomposition of ozone molecules and the oxidant to generate various free radicals, oxidize and remove organic matter in the wastewater, and convert the organic phosphine into inorganic phosphorus; fourth, the oxidation process of the present invention does not need to use a solid catalyst, will not be affected by the scaling of high-concentration inorganic salts during the reaction process to produce problems such as catalyst deactivation, the treatment effect is stable, and the first pretreated water with good treatment effect is obtained.

Secondly, it is difficult to remove organic phosphine by precipitation and flocculation in the presence of a phosphorus removal agent. The present invention removes a large amount of organic matter through steps (1) and (2), and converts organic phosphine into inorganic phosphorus to obtain a first pretreated water. The first pretreated water is then treated with a phosphorus removal agent to remove inorganic phosphorus and some residual organic matter through precipitation and flocculation, thereby achieving an excellent treatment effect.

Therefore, in the treatment method of the present invention, through the design and mutual coordination of materials and process steps, deep treatment of organic matter, organic phosphine and total phosphorus in high-salt wastewater can be achieved, and it has the advantages of simple operation, low dosage of reagents, and less secondary pollution. The dosage of reagents and process parameters can be adjusted according to different water quality characteristics, the treatment cost can be optimized, and different treatment needs can be met.

The following are preferred technical solutions of the present invention, but should not be used as limitations on the technical solutions provided by the present invention. Through the following preferred technical solutions, the purpose of the present invention can be better achieved and the beneficial effects of the present invention can be better realized.

The treatment method provided by the present invention is particularly suitable for high-salt wastewater containing organic matter and organic phosphine, wherein the mass percentage of inorganic salt in the high-salt wastewater is 10%-15%, the chemical oxygen demand (COD) is 700-1200 mg/L, and the total phosphorus (mainly organic phosphine) content is 15-30 mg/L.

Preferably, an alkaline substance is used to adjust the pH value of the wastewater to be treated to obtain wastewater with a pH value ≥ 7.

Preferably, the pH value of the wastewater is 7-13, for example, it can be 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 10.8, 11, 11.5, 12 or 12.5, as well as specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values included in the range, and 8-13 is further preferred, and 11-13 is further preferred.

As a preferred technical solution of the present invention, the pH value of the wastewater is adjusted to neutral or alkaline, more preferably alkaline, which can improve the degradation efficiency of organic matter and organic phosphine in the oxidation treatment.

Preferably, the alkaline substance comprises NaOH solution and/or KOH solution.

Preferably, the oxidant comprises any one of hydrogen peroxide, monopersulfate, peroxydisulfate, peracetic acid, chlorine dioxide, hypochlorite, or a combination of at least two thereof.

Preferably, the oxidant comprises any one of hydrogen peroxide, monopersulfate, peroxydisulfate, or a combination of at least two thereof.

Preferably, the monopersulfate includes any one of potassium monopersulfate, sodium monopersulfate, ammonium monopersulfate, or a combination of at least two of them.

Preferably, the peroxodisulfate includes any one of potassium persulfate, sodium persulfate, and ammonium persulfate, or a combination of at least two of them.

As a preferred technical solution of the present invention, the oxidant includes any one of monopersulfate and peroxydisulfate or a combination of at least two thereof; on the one hand, the oxidant has a strong oxidizing ability, and the decomposition products are water and/or sulfate, and no secondary pollution is generated; on the other hand, under neutral or alkaline conditions, the oxidant and ozone cooperate with each other, which is not only conducive to the decomposition of ozone and the oxidant, but also the reaction between ozone and the oxidant produces free radicals, thereby improving the degradation efficiency of organic matter, and being able to efficiently and completely convert organic phosphine into inorganic phosphorus.

Preferably, the ozone mixed gas comprises a combination of ozone and oxygen.

Preferably, the mass concentration of ozone in the ozone mixture is 50-200 mg/L, for example, it can be 60 mg/L, 80 mg/L, 100 mg/L, 110 mg/L, 120 mg/L, 130 mg/L, 140 mg/L, 150 mg/L, 160 mg/L, 170 mg/L, 180 mg/L or 190 mg/L, as well as specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values included in the range.

Preferably, the ozone mixed gas is a mixed gas containing ozone and oxygen generated by an ozone generating device (ozone generator) using oxygen as a gas source.

Exemplarily, the method for preparing the ozone mixed gas includes: introducing oxygen (of different purities) into an ozone generating device (ozone generator), converting part of the oxygen into ozone by high-voltage discharge, and obtaining the ozone mixed gas containing ozone and oxygen.

It should be noted that the ozone concentration in the ozone mixture is measured using an ozone concentration analyzer. The ozone concentration in the ozone mixture can be adjusted by adjusting the power of the ozone generator, or the amount of ozone produced can be adjusted by changing the flow rate of oxygen passing into the ozone generator to obtain ozone mixtures with different ozone concentrations.

Preferably, the molar ratio of ozone to the oxidant in the ozone mixture is (1-5):1, for example, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1 or 4.5:1, and more preferably (1-3):1.

In the present invention, the ozone mixed gas and the mixture containing the oxidant and the wastewater enter the micro-nano bubble generating device together. In addition to the direct oxidation degradation of organic pollutants by the ozone molecules and the oxidant, ozone micro-nano bubbles are generated in situ in the system, and the ozone nano-micro bubbles cavitation generates free radicals to degrade the pollutants. Through the synergistic effect of ozone, the oxidant and the ozone nano-micro bubbles, free radicals are generated to degrade the pollutants.

As a preferred technical solution of the present invention, through the reasonable compatibility and mutual cooperation of ozone and oxidant in the ozone mixed gas, a relatively high concentration of active free radicals can be quickly generated, and the rapid and sufficient degradation of organic pollutants and organic phosphine can be achieved, thereby obtaining a better pollutant degradation effect. If the proportion of the oxidant is low, the concentration of the generated free radicals is low, and it is difficult to play the role of strengthening the degradation of organic pollutants; if the proportion of the oxidant is too high, the generated free radicals will have an ineffective annihilation reaction with each other, which not only wastes the oxidant, but also reduces the degradation efficiency.

Preferably, the mass ratio of ozone in the ozone mixture to the COD of the wastewater is (1-10):1, for example, it can be 1.5:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1 or 9:1, and more preferably (1-3):1.

In the present invention, ozone mixed gas and oxidant are used to cooperate with each other to oxidize and degrade organic matter in wastewater, and degrade organic phosphine into inorganic phosphorus; excessive addition of ozone can improve the treatment effect, but at the same time it will increase the treatment cost, and inorganic phosphorus is difficult to remove by oxidation, and phosphorus removal agents and other technologies are required for combined treatment. Selecting an appropriate ratio of ozone to COD in wastewater can achieve the purpose of pollutant removal and reduce the treatment cost.

Preferably, the ozone mixed gas is passed through a micro-nano bubble generating device to generate a mixture of nano bubbles and micron bubbles.

Preferably, the diameter of the nanobubbles is 100-500 nm, for example, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm or 450 nm, as well as specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values included in the range.

Preferably, the diameter of the microbubble is 15-50 μm, for example, it can be 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm or 45 μm, as well as specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values included in the range.

Preferably, the ratio of the total volume of nanobubbles generated by the ozone mixture through the micro-nano bubble generating device to the total volume of micron bubbles is (3-9):1, for example, it can be 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1 or 8.5:1, etc.

It should be noted that the ozone mixed gas passes through the micro-nano bubble generating device to generate a combination of nanobubbles and micron bubbles; "total volume of nanobubbles" means the sum of the volumes of all nanobubbles within a unit volume, and "total volume of micron bubbles" means the sum of the volumes of all micron bubbles within a unit volume.

As a preferred technical solution of the present invention, by setting parameters such as power and gas-water mixing ratio in the micro-nano bubble generating device, the volume ratio of nanobubbles to micron bubbles per unit volume is (3-9):1. Thus, by increasing the ratio of nanobubbles, the efficiency of degrading organic matter in wastewater and converting organic phosphine into inorganic phosphorus is higher, achieving more thorough oxidative degradation.

Preferably, the oxidation reaction device comprises an oxidation tower.

Preferably, the residence time in the oxidation reaction device is 15-60 min, for example, it can be 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min or 55 min, as well as specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values included in the range.

Preferably, the outlet water of the oxidation reaction device flows back to the inlet of the micro-nano bubble generating device, and is mixed with ozone and sequentially passes through the micro-nano bubble generating device and the oxidation reaction device for oxidation treatment.

Preferably, the reflux ratio of the outlet water of the oxidation reaction device is 5%-100%, for example, it can be 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% or 90%, as well as specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values included in the said range, and it is further preferably 20%-70%.

Since ozone has a low solubility in water, as a preferred technical solution of the present invention, a portion of the effluent from the oxidation reaction device flows back to the inlet of the micro-nano bubble generating device and re-enters the micro-nano bubble generating device together with the ozone mixed gas, so that the organic pollutants and organic phosphine in the wastewater can fully contact and react with more ozone, oxidants and free radicals, thereby improving the oxidation treatment efficiency.

Preferably, the phosphorus removal agent includes any one of aluminum sulfate, aluminum chloride, polyaluminum chloride, ferrous sulfate, ferric chloride, polyferric chloride sulfate, polyferric chloride, polyacrylamide, calcium hydroxide, and modified diatomaceous earth, or a combination of at least two thereof.

Preferably, the phosphorus removal agent includes any one of ferrous sulfate, polyferric chloride, polyacrylamide, and modified diatomaceous earth, or a combination of at least two thereof.

Preferably, the ratio of the mass of the phosphorus removal agent to the total phosphorus content in the first pretreated water is (3-8):1, for example, it can be 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1 or 7.5:1, etc., and more preferably (3-6):1.

Preferably, the treatment time with the phosphorus removal agent is 30-60 minutes, for example, it can be 35 minutes, 40 minutes, 45 minutes, 50 minutes or 55 minutes, as well as specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values included in the range.

As a preferred technical solution of the present invention, the total phosphorus content in the first pretreated water obtained in the test step (2) is used as a benchmark to control the added mass of the phosphorus removal agent to be 3-8 times, preferably 3-6 times, of the total phosphorus content, and the action time of the phosphorus removal agent with the first pretreated water (the time for treatment with the phosphorus removal agent) is set to 30-60 minutes, so that sufficient precipitation and flocculation can occur and a good phosphorus removal effect can be achieved.

The first pretreated water obtained in step (2) of the present invention contains inorganic phosphorus converted by oxidation of organic phosphine. After adding a phosphorus removal agent thereto, the inorganic phosphorus is fully removed by precipitation and flocculation, and part of the soluble organic matter and residual trace organic phosphine can also be removed at the same time.

Preferably, the effluent in step (3) is also subjected to adsorption treatment.

As a preferred technical solution of the present invention, after filtering the effluent obtained by the phosphorus removal agent treatment, adsorption treatment is performed according to different treatment requirements for total phosphorus and organic matter to further remove residual organic phosphine and refractory organic matter in the water, so that the effluent meets higher treatment requirements and achieves higher treatment goals. In actual operation, different adsorption units can be selected according to different influent water quality and treatment requirements.

Preferably, the adsorption treatment method comprises: filtering the effluent of step (3) to obtain second pretreated water; and subjecting the second pretreated water to adsorption treatment by an adsorbent to complete the treatment of the wastewater.

Preferably, the adsorbent used in the adsorption treatment includes any one of cation exchange resin, anion exchange resin, activated carbon, and metal-loaded activated carbon, or a combination of at least two of them.

Preferably, the adsorbent comprises anion exchange resin and/or metal-loaded activated carbon.

Preferably, the adsorbent is loaded in an adsorption column; the second pretreated water is passed through the adsorption column loaded with the adsorbent to complete the adsorption treatment, and the obtained effluent is the treated water.

Preferably, the processing method specifically comprises the following steps:

(1) mixing wastewater having a pH value of 7-13 with an oxidant to obtain a mixture;

(2) subjecting the mixture obtained in step (1) and the ozone mixed gas to oxidation treatment through a micro-nano bubble generating device and an oxidation reaction device in sequence to obtain first pretreated water;

Wherein, the mass ratio of ozone in the ozone mixed gas to the COD of the wastewater is (1-10):1, and the molar ratio of ozone in the ozone mixed gas to the oxidant is (1-5):1;

The ratio of the total volume of nanobubbles generated by the ozone mixed gas through the micro-nano bubble generating device to the total volume of micron bubbles is (3-9):1;

The residence time in the oxidation reaction device is 15-60 minutes; the effluent of the oxidation reaction device is refluxed to the inlet of the micro-nano bubble generating device at a reflux ratio of 20%-70%, and is mixed with ozone gas and then passed through the micro-nano bubble generating device and the oxidation reaction device in sequence for oxidation treatment;

(3) treating the first pretreated water obtained in step (2) with a phosphorus removal agent, filtering the effluent, and obtaining a second pretreated water; wherein the ratio of the mass of the phosphorus removal agent to the total phosphorus content in the first pretreated water is (3-8):1; and the treatment time is 30-60 min;

The second pretreated water is subjected to adsorption treatment using an adsorbent to complete the treatment of the wastewater.

As a preferred technical solution of the present invention, the treatment method includes multiple links of pH adjustment, oxidation, precipitation flocculation, and adsorption. The materials/agents, steps, and parameters in each link are combined and coordinated with each other, which can achieve deep treatment of high-salt wastewater containing organic matter and organic phosphine, and fully remove the organic matter, organic phosphine, and total phosphorus therein.

Preferably, the COD of the effluent from the treatment method is ≤300 mg/L, preferably ≤200 mg/L, further preferably <180 mg/L, and further preferably <150 mg/L; the COD removal rate is ≥80%, for example, 80-85%.

Preferably, the total phosphorus content of the effluent from the treatment method is ≤5 mg/L, more preferably <2 mg/L, and even more preferably <0.5 mg/L; the total phosphorus removal rate is >90%, even more preferably >93.5%, for example, it can be 93.8-98.9%.

Compared with the prior art, the present invention has the following beneficial effects:

In the treatment method provided by the present invention, a combined treatment process of pH adjustment, oxidation treatment, precipitation flocculation in the presence of a phosphorus removal agent, and optional adsorption is used to achieve efficient and low-cost removal of organic matter and organic phosphine in high-salinity wastewater, and has the advantages of simple operation, low dosage of agents, and less secondary pollution. The specific effects include:

(1) No solid catalyst is used in the entire treatment process, and the problem of reduced treatment efficiency due to catalyst clogging and scaling caused by high concentration of inorganic salts will not occur;

(2) Through the synergy of ozone micro-nano bubbles and oxidants, the efficiency of free radical generation can be improved, the utilization efficiency of ozone can be improved, the treatment cost can be reduced, and an excellent oxidation effect can be achieved, thereby efficiently removing organic matter in wastewater and converting organic phosphine into inorganic phosphorus;

(3) The first pretreated water obtained by oxidation treatment interacts with the phosphorus removal agent, and while removing inorganic phosphorus by precipitation and flocculation, some organic matter can also be removed simultaneously; the combined treatment technology of oxidation-precipitation and flocculation in the present invention not only has a good treatment effect, but also has a low treatment cost;

(4) For wastewater with higher treatment requirements or difficult to treat, the treatment method may also include adsorption treatment with an adsorbent, which has higher overall operational flexibility and better treatment effects.

The treatment method of the present invention is used to treat high-salt wastewater with an inorganic salt mass content of 10%-15%, a COD of 700-1200 mg/L, and a total phosphorus (mainly organic phosphine) concentration of 15-30 mg/L, and the COD of the treated water is less than 200 mg/L and the total phosphorus content is less than 2 mg/L.

DETAILED DESCRIPTION

The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only used to help understand the present invention and should not be regarded as specific limitations of the present invention.

In the following specific implementation of the present invention, the treatment object is high-salt wastewater containing organic matter and organic phosphine from a metallurgical enterprise, wherein the mass percentage of inorganic salt is 10%-15%, the chemical oxygen demand (COD) is 700-1200 mg/L, and the total phosphorus (mainly organic phosphine) concentration is 15-30 mg/L.

In the following specific embodiments of the present invention, the ozone mixed gas used is a mixed gas containing ozone and oxygen produced by an ozone generator using industrial oxygen as a gas source.

In the following specific embodiments of the present invention, an ozone mixed gas and a mixture containing wastewater are introduced into a micro-nano bubble generator to generate a combination of nanobubbles and micrometer bubbles; the total volume of nanobubbles and the total volume of micrometer bubbles generated per unit time are determined by using a laser particle size analyzer to determine the number and average size of nanobubbles per unit volume of wastewater, and the total volume of nanobubbles is calculated; the number and average size of micrometer bubbles per unit volume are determined by taking pictures with a high-speed camera, and the total volume of micrometer bubbles is calculated; and the ratio of the total volume of nanobubbles to the total volume of micrometer bubbles is calculated based on the ratio of the total volume of nanobubbles per unit volume to the total volume of micrometer bubbles.

Example 1

A method for treating high-salt wastewater specifically comprises the following steps:

(1) The pH value of the wastewater to be treated is 6.7, the mass percentage of inorganic salt is 13.5%, the COD is 873 mg/L, and the total phosphorus concentration is 27.5 mg/L; the pH value of the wastewater is adjusted to 12.0 using a NaOH solution, and a sodium monopersulfate solution is added thereto to obtain a mixture;

(2) introducing the mixture obtained in step (1) and an ozone mixed gas with an ozone concentration of 120 mg/L into a micro-nano bubble generator, and then entering an oxidation tower for oxidation treatment, wherein the residence time in the oxidation tower is 60 min, and the effluent from the oxidation tower is refluxed to the inlet of the micro-nano bubble generator at a reflux ratio of 70% for further treatment to obtain first pretreated water;

In steps (1) and (2), the molar ratio of sodium monopersulfate to ozone in the ozone mixture is 1:1, and the mass ratio of ozone to COD is 3:1; the diameter of the nanobubbles generated in the micro-nano bubble generator is 100-500nm, the diameter of the micron bubbles is 15-50μm, and the ratio of the total volume of nanobubbles to the total volume of micron bubbles per unit volume is 9:1;

(3) the first pretreated water obtained in step (2) is introduced into a precipitation flocculation reactor, ferrous sulfate is added for precipitation flocculation treatment, and the effluent is filtered to obtain a second pretreated water; wherein the amount of ferrous sulfate added is 5.5 times the total phosphorus content in the first pretreated water, and the precipitation flocculation treatment time is 40 min;

The second pretreated water enters an adsorption column loaded with anion exchange resin for adsorption treatment to complete the treatment of the wastewater and obtain final effluent.

Example 2

A method for treating high-salt wastewater specifically comprises the following steps:

(1) The pH value of the wastewater to be treated is 6.7, the mass percentage of inorganic salt is 13.5%, the COD is 873 mg/L, and the total phosphorus concentration is 27.5 mg/L; the pH value of the wastewater is adjusted to 12.0 using a NaOH solution, and a potassium monopersulfate solution is added thereto to obtain a mixture;

(2) introducing the mixture obtained in step (1) and an ozone mixed gas with an ozone concentration of 180 mg/L into a micro-nano bubble generator, and then entering an oxidation tower for oxidation treatment, wherein the residence time in the oxidation tower is 30 min, and the effluent from the oxidation tower is refluxed to the inlet of the micro-nano bubble generator at a reflux ratio of 50% for further treatment to obtain a first pretreated water;

In steps (1) and (2), the molar ratio of potassium monopersulfate to ozone in the ozone mixture is 1:3, and the mass ratio of ozone to COD is 1:1; the diameter of the nanobubbles generated in the micro-nano bubble generator is 100-500nm, the diameter of the micron bubbles is 15-50μm, and the ratio of the total volume of nanobubbles to the total volume of micron bubbles per unit volume is 8:1;

(3) the first pretreated water obtained in step (2) is placed in a precipitation flocculation reactor, ferrous sulfate is added for precipitation flocculation treatment, and the effluent is filtered to obtain a second pretreated water; wherein the amount of ferrous sulfate added is 3.5 times the total phosphorus content in the first pretreated water, and the precipitation flocculation treatment time is 50 min;

The second pretreated water enters an adsorption column loaded with anion exchange resin for adsorption treatment to complete the treatment of the wastewater and obtain final effluent.

Example 3

A method for treating high-salt wastewater specifically comprises the following steps:

(1) The wastewater to be treated is the same as that in Example 1, and the pH value of the wastewater is adjusted to 12.8 using a NaOH solution, and potassium monopersulfate is added thereto to obtain a mixture;

(2) introducing the mixture obtained in step (1) and an ozone mixed gas with an ozone concentration of 120 mg/L into a micro-nano bubble generator, and then entering an oxidation tower for oxidation treatment, wherein the residence time in the oxidation tower is 15 min, and the effluent from the oxidation tower is refluxed to the inlet of the micro-nano bubble generator at a reflux ratio of 70% for further treatment to obtain first pretreated water;

In steps (1) and (2), the molar ratio of potassium monopersulfate to ozone in the ozone mixture is 1:2, and the mass ratio of ozone to COD is 2.5:1; the diameter of the nanobubbles generated in the micro-nano bubble generator is 100-500nm, the diameter of the micron bubbles is 15-50μm, and the ratio of the total volume of nanobubbles to the total volume of micron bubbles per unit volume is 7:1;

(3) the first pretreated water obtained in step (2) is introduced into a precipitation flocculation reactor, ferrous sulfate is added for precipitation flocculation treatment, and the effluent is filtered to obtain a second pretreated water; wherein the amount of ferrous sulfate added is 3.0 times the total phosphorus content in the first pretreated water, and the precipitation flocculation treatment time is 60 min;

The second pretreated water enters an adsorption column loaded with activated carbon for adsorption treatment to complete the treatment of the wastewater and obtain final effluent.

Example 4

A method for treating high-salt wastewater, which differs from Example 1 only in that the sodium monopersulfate solution in step (1) is replaced by a sodium hypochlorite solution, and the molar ratio of sodium hypochlorite to ozone in the ozone mixture is 1:1; other conditions are the same as those in Example 1.

Example 5

A method for treating high-salt wastewater, which differs from Example 1 only in that the sodium monopersulfate solution in step (1) is replaced by hydrogen _peroxide with a _H2O2 mass concentration of 30%, and the molar ratio of ozone in the _{H2O2 to} ozone mixed gas is 1:1; other conditions are the same as in Example 1.

Example 6

A method for treating high-salt wastewater, which differs from Example 1 only in that the ferrous sulfate in step (3) is replaced by an equal mass of polyaluminium chloride; other conditions are the same as those in Example 1.

Example 7

A method for treating high-salt wastewater, which differs from Example 1 only in that the ferrous sulfate in step (3) is replaced by an equal mass of calcium hydroxide; other conditions are the same as in Example 1.

Example 8

A method for treating high-salt wastewater, which differs from Example 1 only in that an adsorption column loaded with a cation exchange resin is used for adsorption treatment in step (3); other conditions are the same as those in Example 1.

Example 9

A method for treating high-salt wastewater, which differs from Example 1 only in that the molar ratio of ozone in the sodium monopersulfate and ozone mixed gas is 1:5; other conditions are the same as those in Example 1.

Example 10

A method for treating high-salt wastewater, which differs from Example 1 only in that the molar ratio of ozone in the sodium monopersulfate and ozone mixed gas is 1:6; other conditions are the same as those in Example 1.

Embodiment 11

A method for treating high-salt wastewater, which differs from Example 1 only in that the molar ratio of ozone in the sodium monopersulfate and ozone mixed gas is 2:1; other conditions are the same as those in Example 1.

Example 12

A method for treating high-salt wastewater, which differs from Example 1 only in that the ratio of the total volume of nanobubbles to the total volume of microbubbles per unit volume is 3:1; other conditions are the same as those in Example 1.

Example 13

A method for treating high-salt wastewater, which differs from Example 1 only in that the ratio of the total volume of nanobubbles to the total volume of microbubbles per unit volume is 2:1; other conditions are the same as those in Example 1.

Embodiment 14

A method for treating high-salt wastewater, which differs from Example 1 only in that the ratio of the total volume of nanobubbles to the total volume of microbubbles per unit volume is 1:5; other conditions are the same as those in Example 1.

Comparative Example 1

A method for treating high-salt wastewater, which differs from Example 1 only in that a micro-nano bubble generator is not used in step (2), and the mixture obtained in step (1) and an ozone mixed gas with an ozone concentration of 120 mg/L (using ordinary aeration method) are directly introduced into an oxidation tower for oxidation treatment, the residence time in the oxidation tower is 60 minutes, and the effluent from the oxidation tower is refluxed to the oxidation tower inlet at a reflux ratio of 70% for further treatment; other conditions are the same as those in Example 1.

Comparative Example 2

A method for treating high-salt wastewater, which differs from Example 1 only in that ferrous sulfate is not used for precipitation and flocculation treatment, that is, the first pretreated water obtained in step (2) directly enters an adsorption column loaded with anion exchange resin for adsorption treatment to obtain final effluent; other conditions are the same as those in Example 1.

Comparative Example 3

A method for treating high-salt wastewater, which differs from Example 1 only in that no adsorption treatment is performed and the second pretreated water is the final effluent; other conditions are the same as those in Example 1.

Comparative Example 4

A method for treating high-salt wastewater, which differs from Example 1 only in that no oxidant sodium monopersulfate is added, and the wastewater with a pH value of 12.0 directly enters step (2), is introduced into a micro-nano bubble generator together with an ozone mixed gas with an ozone concentration of 120 mg/L, and then enters an oxidation tower filled with activated carbon for oxidation treatment, wherein the volume of the activated carbon is 50% of the effective volume of the oxidation tower, and the reaction residence time is 60 minutes; other conditions are the same as those in Example 1.

The final effluent obtained in Examples 1-14 and Comparative Examples 1-4 was tested, and the specific method is as follows:

(1) COD concentration determination: Test according to the method in "Determination of Chemical Oxygen Demand of Water Quality - Potassium Dichromate Method" (GB/T11914-1989). Dilute the water sample by a certain multiple, add a certain amount of potassium dichromate solution, digest at 165℃ for 10 minutes, and measure the sample absorbance with a COD detector.

(2) Determination of total phosphorus content: A series of standard solutions with known phosphate concentrations were prepared and measured using an inductively coupled plasma atomic emission spectrometer (ICP-OES) to develop a standard curve. The samples were then measured using ICP-OES and the total phosphorus content was calculated based on the standard curve.

The test results are shown in Table 1:

Table 1

Combined with the performance test data in Table 1, it can be seen that in the treatment method provided by the present invention, the organic matter and organic phosphine in the high-salinity wastewater can be efficiently degraded through the mutual cooperation of ozone micro-nano bubbles and oxidants, and the treatment efficiency of organic matter, organic phosphine and total phosphorus can be further improved by combining pH adjustment, precipitation flocculation and adsorption treatment. As can be seen from Table 1, under the optimized treatment conditions, the effluent COD after combined treatment is 132-179 mg/L, the total phosphorus content is 0.4-1.7 mg/L, the COD removal rate is ≥80%, which can reach about 85%, and the total phosphorus removal rate is >93.5%, which can reach 3.8-98.9%. For high-salinity wastewater that cannot be treated biochemically, the treatment effect is very good, which is higher than the conventional treatment method.

In the present invention, through the synergistic effect of ozone micro-nano bubbles and oxidants, the organic matter in the high-salt wastewater is fully oxidized and decomposed, and the organic phosphine is converted into inorganic phosphorus as completely as possible. The type of oxidant and the ratio of the oxidant to ozone are designed to further optimize the oxidation treatment effect. Combining the test data of Examples 1-3 and 4-5, it can be seen that when the oxidant is monopersulfate, its synergistic effect with ozone micro-nano bubbles is better; at the same time, combining the data of Examples 1 and 9-11, it can be seen that by controlling the molar ratio of ozone to oxidant to 1:1-5:1, the two work together to promote the generation of free radicals, further improve the oxidative degradation efficiency of organic matter and the efficiency of converting organic phosphine into inorganic phosphorus.

In the present invention, by controlling the ratio of the total volume of nanobubbles to the total volume of micron bubbles in ozone micro-nano bubbles, the removal efficiency of organic matter in high-salinity wastewater and the conversion efficiency of organic phosphine to inorganic phosphorus can be improved. Because the size of nanobubbles is 1-2 orders of magnitude smaller than that of micron bubbles, if the same volume of gas exists in the form of nanobubbles, the specific surface area will be 100-10000 times higher than that of micron bubbles, thus significantly improving the contact reaction probability of ozone and organic pollutants. In addition, nanobubbles are small in size and have a large internal gas pressure, making them more prone to cavitation and fragmentation than micron bubbles, forming oxidative free radicals to degrade pollutants. Comparing the test data of Example 1 with that of Example 12-14, it can be seen that controlling the ratio of the total volume of nanobubbles to the total volume of microbubbles to be 3:1-9:1 can obtain better oxidation treatment effects, improve COD removal rate and total phosphorus removal rate; if there are fewer nanobubbles (Examples 13-14), the oxidation removal effect of organic matter and the conversion effect of organic phosphine to inorganic phosphorus will be reduced; but limited by the current micro-nano bubble generation technology, it is difficult to form a system that is all nanobubbles.

Compared with Example 1, in Comparative Example 1, no micro-nano bubble generator is used, and ozone micro-nano bubbles cannot be generated. Only conventional aeration method is used to mix ozone with a combined oxidant to treat high-salt wastewater. The oxidation efficiency of organic matter and organic phosphine is low, the COD and total phosphorus contents of the effluent are high, and the treatment effect is not good.

Compared with Example 1, in Comparative Example 2, no phosphorus removal agent was used for precipitation and flocculation treatment, resulting in the inability to remove inorganic phosphorus produced by oxidation and incomplete removal of organic matter, resulting in high COD and total phosphorus contents in the final effluent.

Compared with Example 1, in Comparative Example 3, no adsorption treatment was performed, and only oxidation and precipitation flocculation treatment methods were used, so the removal rate of organic phosphine and total phosphorus was reduced.

Compared with Example 1, no oxidant was added in Comparative Example 4, and the removal rates of COD and total phosphorus were both reduced through the reaction of activated carbon catalyst and ozone micro-nano bubbles.

The applicant declares that the present invention illustrates the method for treating high-salt wastewater of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned embodiments, that is, it does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims (10)

1. a treatment method for high-salt wastewater, characterized in that, said treatment method may further comprise the steps: (1) mixing wastewater with a pH value of ≥7 and an oxidizing agent to obtain a mixture; (2) The mixture obtained in step (1) and the ozone mixed gas are oxidized successively through the micro-nano bubble generating device and the oxidation reaction device to obtain the first pretreated water; (3) The first pretreatment water obtained in step (2) is treated with a phosphorus removal agent, and the water is discharged to complete the treatment of waste water. 2. The treatment method according to claim 1, characterized in that, the pH value of the waste water to be treated is adjusted by an alkaline substance to obtain waste water with a pH value of ≥7; Preferably, the pH value of the wastewater is 7-13, more preferably 8-13, even more preferably 11-13. 3. according to claim 1 and 2 described processing methods, it is characterized in that, described oxygenant comprises hydrogen peroxide, monopersulfate, peroxodisulfate, peracetic acid, chlorine dioxide, hypochlorite Any one or a combination of at least two, more preferably any one of monopersulfate and peroxodisulfate or a combination of at least two. 4. according to the processing method described in any one of claim 1-3, it is characterized in that, described ozone gas mixture comprises the combination of ozone and oxygen; Preferably, the mass concentration of ozone in the ozone mixture is 50-200mg/L; Preferably, the molar ratio of the ozone in the ozone mixture to the oxidant is (1-5):1, more preferably (1-3):1; Preferably, the mass ratio of the ozone in the ozone mixture to the COD of the wastewater is (1-10):1, more preferably (1-3):1. 5. according to the processing method described in any one of claim 1-4, it is characterized in that, described ozone gas mixture generates the mixture of nano-bubble and micro-bubble by micro-nano bubble generating device; Preferably, the nanobubbles have a diameter of 100-500nm; Preferably, the microbubbles have a diameter of 15-50 μm; Preferably, the ratio of the total volume of the nanobubbles generated by the ozone mixture to the total volume of the microbubbles generated by the micronanobubble generator is (3-9):1. 6. according to the processing method described in any one of claim 1-5, it is characterized in that, the residence time in the described oxidation reaction device is 15-60min; Preferably, the effluent from the oxidation reaction device flows back to the inlet of the micro-nano bubble generating device, and the mixed gas with ozone passes through the micro-nano bubble generating device and the oxidation reaction device for oxidation treatment; Preferably, the reflux ratio of the effluent of the oxidation reaction device is 5%-100%, more preferably 20%-70%. 7. The treatment method according to any one of claims 1-6, wherein the phosphorus removal agent comprises aluminum sulfate, aluminum chloride, polyaluminum chloride, ferrous sulfate, ferric chloride, polychlorinated Any one or a combination of at least two of ferric sulfate, polyferric chloride, polyacrylamide, calcium hydroxide, modified diatomite, preferably ferrous sulfate, polyferric chloride, polyacrylamide, modified silicon Any one or a combination of at least two of algae; Preferably, the ratio of the quality of the phosphorus removal agent to the total phosphorus content in the first pretreatment water is (3-8):1; Preferably, the treatment time with the phosphorus removal agent is 30-60 minutes. 8. according to the treatment method described in any one of claim 1-7, it is characterized in that, the described effluent of step (3) also carries out adsorption treatment; Preferably, the adsorption treatment method includes: filtering the effluent in step (3) to obtain second pretreated water; performing adsorption treatment on the second pretreated water through an adsorbent to complete the treatment of wastewater; Preferably, the adsorbent used in the adsorption treatment includes any one or a combination of at least two of cation exchange resin, anion exchange resin, activated carbon, and metal-loaded activated carbon. 9. The processing method according to any one of claims 1-8, wherein the processing method specifically comprises the steps of: (1) mixing wastewater with a pH value of 7-13 and an oxidizing agent to obtain a mixture; (2) The mixture obtained in step (1) and the ozone mixed gas are oxidized successively through the micro-nano bubble generating device and the oxidation reaction device to obtain the first pretreated water; Wherein, the mass ratio of the ozone in the ozone mixed gas to the COD of the waste water is (1-10): 1, and the mol ratio of the ozone in the ozone mixed gas to the oxidant is (1-5): 1; The ratio of the total volume of the nano-bubbles generated by the ozone gas mixture to the total volume of the micro-bubbles generated by the micro-nano bubble generating device is (3-9): 1; The residence time in the oxidation reaction device is 15-60min; the outlet water of the oxidation reaction device is refluxed to the inlet of the micro-nano bubble generating device with a reflux ratio of 20%-70%, and the mixed gas with ozone passes through the micro-nano bubbles in turn The generating device and the oxidation reaction device are used for oxidation treatment; (3) The first pretreated water obtained in step (2) is treated with a phosphorus removal agent, and the effluent is filtered to obtain the second pretreatment water; wherein, the quality of the phosphorus removal agent is the same as the total phosphorus in the first pretreatment water The ratio of content is (3-8): 1; The time of described treatment is 30-60min; The second pretreated water is subjected to adsorption treatment with an adsorbent to complete the treatment of waste water. 10. The treatment method according to any one of claims 1-9, characterized in that, the COD of the effluent from the treatment method is <180 mg/L, preferably COD <150 mg/L; Preferably, the total phosphorus content of the effluent from the treatment method is less than 2 mg/L, more preferably the total phosphorus content is less than 0.5 mg/L.