Treatment method of high-salt high-concentration degradation-resistant organic wastewater

Abstract

The invention discloses a method for treating high-salt and high-concentration refractory organic wastewater, which comprises the following steps: carrying out advanced oxidation on the high-salt and high-concentration refractory organic wastewater, and mixing in an adjusting tank; carrying out softening reaction on the biochemical treatment effluent, and filtering through a tubular membrane to remove calcium ions, magnesium ions and suspended solids; performing concentration electrodialysis on the effluent of the tubular membrane; the biochemical treatment salinity is reduced through electrodialysis fresh water internal reflux, the problem of growth inhibition of a high-salt environment on microorganisms is solved, the salt concentration rate is improved through electrodialysis, the problems that traditional reverse osmosis concentration is low in COD tolerance and serious in membrane pollution are solved, and finally efficient treatment of high-salt and high-concentration refractory organic wastewater is achieved. The method has the advantages of low treatment cost and high treatment efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of industrial wastewater treatment and resource utilization, and in particular relates to a method for treating high-salt, high-concentration, and difficult-to-degrade organic wastewater. Background Art

[0002] High-salt, high-concentration, and difficult-to-degrade organic wastewater is widely found in the pharmaceutical, papermaking, coal chemical and other industries. The salt content and COD of the wastewater can generally reach tens of thousands of mg / L, and the COD is mostly difficult-to-degrade organic matter. The high salt content inhibits and toxicizes microorganisms, making biochemical treatment difficult to operate. Existing treatment technologies generally use the "advanced oxidation + reverse osmosis concentration" process to remove organic matter and salt step by step. This process consumes a huge amount of strong oxidants, causes serious pollution of the reverse osmosis membrane, and has a high treatment cost. Chinese patent CN105347584A discloses a method for treating high-salt, high-concentration, difficult-to-degrade organic wastewater. The method adopts the "iron-carbon micro-electrolysis + electrodialysis + UASB reactor + BSBR reactor + H iron-carbon micro-electrolysis" treatment process. First, iron-carbon micro-electrolysis is used to degrade some organic matter and improve biodegradability. Then, electrodialysis is used to separate organic matter and inorganic salts. Finally, the organic matter is biochemically treated. This method uses electrodialysis to separate organic matter and inorganic salts. Although the step-by-step removal of organic matter and inorganic salts is achieved, the high-concentration organic matter seriously pollutes the electrodialysis ion exchange membrane, which requires frequent cleaning, ultimately resulting in a high service life and operating cost of the electrodialysis. Summary of the invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a low-cost method for treating high-salt, high-concentration, difficult-to-degrade organic wastewater.

[0004] The technical solution of the present invention is summarized as follows:

[0005] A method for treating high-salt, high-concentration, difficult-to-degrade organic wastewater comprises the following steps:

[0006] 1) subjecting high-salt, high-concentration, and difficult-to-degrade organic wastewater to advanced oxidation to improve the biodegradability of the wastewater and remove part of the COD to obtain advanced oxidation effluent;

[0007] 2) the effluent from the advanced oxidation and the fresh water reflux obtained from the concentrated electrodialysis in step 5) are introduced into a regulating tank for mixing;

[0008] 3) The effluent from the regulating pond is biochemically treated to remove COD from the wastewater;

[0009] 4) After the water from the biochemical treatment is softened, it is filtered through a tubular membrane to remove calcium, magnesium ions and suspended solids;

[0010] 5) The effluent from the tubular membrane is concentrated by electrodialysis to obtain concentrated brine and fresh water; the fresh water is divided into a fresh water return stream and a qualified discharge stream;

[0011] 6) The concentrated brine is evaporated and crystallized to obtain salt and high-quality fresh water, and the high-quality fresh water is reused in the production system.

[0012] Preferably, the high-salt, high-concentration, difficult-to-degrade organic wastewater in step 1) has a salt content of less than 35,000 mg / L and a COD of less than 50,000 mg / L.

[0013] The advanced oxidation is preferably Fenton oxidation or iron-carbon micro-electrolysis.

[0014] In step 5), the salt content of the concentrated brine is in the range of 130000 mg / L-180000 mg / L.

[0015] The advantages of the present invention are:

[0016] (1) The present invention dilutes the advanced oxidation effluent by concentrating the freshwater reflux obtained by electrodialysis to reduce salinity without adding external water sources, effectively solving the salt tolerance problem of microorganisms in biochemical treatment and giving full play to the advantage of low cost per ton of water treatment in the biochemical treatment process. In addition, the "advanced oxidation + biochemical treatment" combined process significantly reduces the amount of oxidant used in degrading organic matter compared with the conventional direct advanced oxidation process. Although the processing volume of the biochemical treatment is increased, the operating cost of the method of the present invention is significantly reduced.

[0017] (2) The combined process of "advanced oxidation + biochemical treatment" is used to degrade organic matter, allowing the concentrated electrodialysis to operate under low COD conditions, solving the serious membrane fouling problem that exists in traditional electrodialysis in the separation of organic matter and inorganic salts, thereby increasing the service life of the ion exchange membrane in the concentrated electrodialysis device and reducing operating costs.

[0018] (3) The use of concentrated electrodialysis for desalination / concentration significantly improves the concentration ratio compared with the traditional reverse osmosis process. The concentrated water produced by the concentrated electrodialysis enters the evaporation crystallization, and the evaporation crystallization processing volume is significantly reduced. In addition, the use of concentrated electrodialysis can solve the problems of low COD tolerance and severe membrane pollution in the traditional reverse osmosis process. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of a method for treating high-salt, high-concentration, difficult-to-degrade organic wastewater according to the present invention. DETAILED DESCRIPTION

[0020] The present invention will be further described below through specific embodiments and accompanying drawings.

[0021] Example 1

[0022] A method for treating high-salt, high-concentration, difficult-to-degrade organic wastewater, see Figure 1 , including the following steps:

[0023] 1) High-salt, high-concentration, refractory organic wastewater is fed into an advanced oxidation device (Fenton equipment) for advanced oxidation (Fenton oxidation) to improve the biodegradability of the wastewater and remove part of the COD to obtain advanced oxidation effluent;

[0024] Specific operation: Fenton oxidation process is used, with a treatment flow of 10m 3 / h, adding hydrogen peroxide and ferrous sulfate to high-salt, high-concentration, difficult-to-degrade organic wastewater to control the mass ratio of COD to H2O2 to 1:1, Fe 2+ The molar ratio of H2O2 was 1:4, the pH value was adjusted to 3-4, and advanced oxidation (Fenton oxidation) was carried out for 3 hours to obtain advanced oxidation effluent, see Table 1.

[0025] Note: B / C refers to the ratio of BOD to COD. Generally, biological treatment can be carried out when it is greater than 0.3.

[0026] Table 1

[0027] Detection indicators Calcium ion (mg / L) Salt content (mg / L) <![CDATA[COD cr (mg / L)]]> B / C Influent (high-salt, high-concentration, difficult-to-degrade organic wastewater) 680 28260 48540 0.2 Effluent (Advanced Oxidation Effluent) 680 30850 26210 0.45

[0028] 2) The effluent from the advanced oxidation and the freshwater return stream obtained by the concentrated electrodialysis in step 5) are introduced into the regulating tank for mixing; low-salt and low-concentration biodegradable organic wastewater (the effluent from the regulating tank) is obtained; the flow rates of the effluent from the advanced oxidation and the freshwater return stream obtained by the concentrated electrodialysis are 10m 3 / h、23.5m 3 / h, other indicators are shown in Table 2.

[0029] Table 2

[0030] Detection indicators Calcium ion (mg / L) Salt content (mg / L) <![CDATA[COD cr (mg / L)]]> Influent 1 (Advanced Oxidation Effluent) 680 30850 26210 Inlet 2 (fresh water return) 0.1 963 195 Outlet water (outlet water from regulating tank) 202 9868 7960

[0031] 3) The effluent from the regulating pond is biochemically treated (UASB+AO process) to remove COD in the wastewater; the UASB reaction time is 24 hours, the AO reaction time is 16 hours, and the treatment flow rate is 33.5m 3 / h, other indicators are shown in Table 3.

[0032] Table 3

[0033] Detection indicators Calcium ion (mg / L) Salt content (mg / L) <![CDATA[COD cr (mg / L)]]> Inlet (outlet from regulating tank) 202 9868 7960 Effluent (biochemical treatment effluent) 202 9868 237

[0034] 4) After the water from the biochemical treatment is softened, it is filtered through a tubular membrane to remove calcium, magnesium ions and suspended solids;

[0035] The softening reaction is to add sodium hydroxide and sodium carbonate to the biochemical treatment effluent, the sodium hydroxide dosage is 15mg / L, the sodium carbonate dosage is 610mg / L, the reaction time is 40min, the tubular membrane is operated in large flow cross-flow, the water inlet pressure is 6bar, and the treatment flow is 33.5m 3 / h, effluent turbidity 0.2NTU, other indicators see Table 4.

[0036] Table 4

[0037] Detection indicators Calcium ion (mg / L) Salt content (mg / L) <![CDATA[COD cr (mg / L)]]> Influent (biochemical treatment effluent) 202 9868 237 Outlet water (tubular membrane outlet water) 20 9868 195

[0038] 5) The effluent from the tubular membrane is concentrated by electrodialysis to obtain concentrated brine and fresh water;

[0039] Concentrated electrodialysis adopts two stages, in which the first stage electrodialysis adopts concentrated electrodialysis and the second stage electrodialysis adopts desalination electrodialysis. The fresh water from the first stage electrodialysis enters the second stage electrodialysis for secondary desalination. The total water inlet flow is 33.5m 3 / h, concentrated water flow rate 2.0m 3 / h, fresh water return flow 23.5m 3 / h, fresh water discharge flow rate 8.0m 3 / h, other indicators are shown in Table 5.

[0040] Table 5

[0041] Detection indicators Calcium ion (mg / L) Salt content (mg / L) <![CDATA[COD cr (mg / L)]]> Influent (tubular membrane effluent) 20 9868 195 Concentrated salt water 319.2 158370 195 freshwater 0.1 940 195

[0042] The fresh water is divided into fresh water return shares or qualified discharge shares;

[0043] The fresh water return stream is returned to the regulating tank in step 2), and the water that meets the discharge standards is implemented in accordance with the "Integrated Wastewater Discharge Standard" GB 8978-1996.

[0044] 6) The concentrated brine is evaporated and crystallized to obtain salt and high-quality fresh water, which is then reused in the production system. Processing flow rate: 1.9m 3 / h, high quality fresh water flow rate 1.9m 3 / h, other indicators are shown in Table 6.

[0045] Table 6

[0046] Detection indicators Calcium ion (mg / L) Salt content (mg / L) <![CDATA[COD cr (mg / L)]]> Influent (Brine) 319.2 158370 195 High quality fresh water 0.05 5 ＜1

[0047] Iron-carbon micro-electrolysis is used to replace the Fenton oxidation in this embodiment, and a high-salt, high-concentration, difficult-to-degrade organic wastewater is treated according to the steps of this embodiment.

Claims

1. A method for treating high-salt, high-concentration, difficult-to-degrade organic wastewater, characterized in that The following steps are involved: 1) subjecting high-salt, high-concentration, and difficult-to-degrade organic wastewater to advanced oxidation to improve the biodegradability of the wastewater and remove part of the COD to obtain advanced oxidation effluent; 2) the effluent from the advanced oxidation and the fresh water reflux obtained from the concentrated electrodialysis in step 5) are introduced into a regulating tank for mixing; 3) The effluent from the regulating pond is biochemically treated to remove COD from the wastewater; 4) After the water from the biochemical treatment is softened, it is filtered through a tubular membrane to remove calcium, magnesium ions and suspended solids; 5) The effluent from the tubular membrane is concentrated by electrodialysis to obtain concentrated brine and fresh water; the fresh water is divided into a fresh water return stream and a qualified discharge stream; 6) The concentrated brine is evaporated and crystallized to obtain salt and high-quality fresh water, and the high-quality fresh water is reused in the production system.

2. The processing method according to claim 1, characterized in that In the step 1), the high-salt, high-concentration, difficult-to-degrade organic wastewater has a salt content of less than 35,000 mg / L and a COD of less than 50,000 mg / L.

3. The processing method according to claim 1, characterized in that The advanced oxidation is Fenton oxidation or iron-carbon micro-electrolysis.

4. The processing method according to claim 1, characterized in that In step 5), the salt content of the concentrated brine is in the range of 130000 mg / L-180000 mg / L.

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