CN104445812A - Treatment method of waste liquor obtained after alcohol mother liquor purifying in doxycycline hydrochloride production - Google Patents

Abstract

The invention discloses a treatment method of waste liquor obtained after alcohol mother liquor purifying in doxycycline hydrochloride production. The treatment method comprises the following steps: (1) cooling: stirring and cooling the waste liquor to 40-45 DEG C in a regulating reservoir; (2) performing primary flocculation and sedimentation: adding a flocculating agent into cooled wastewater, and adding alkaline to neutralize after performing the flocculation and sedimentation, and mud-water separation; (3) performing secondary flocculation and sedimentation: performing filter-pressing on the liquid neutralized in the step (2) by virtue of a filter press, performing flocculation and sedimentation on filtrate again, and separating mud from water; (4) performing biochemical treatment: performing biochemical reaction on liquid supernatant obtained by mud-water separation through an ozone oxidation decoloration unit, an anaerobic treatment unit and an aerobic biochemical unit; (5) filtering and performing membrane separation: treating the liquid treated in the step (4) through a membrane bioreactor, a nanofiltration membrane and a reverse osmosis membrane. Compared with the prior art, the treatment method has the beneficial effects of high treatment efficiency, stable operation and capacity of eliminating the pollution of wastewater on the environment.

Description

Treatment method of waste liquid after purification of ethanol mother liquor in the production of doxycycline hydrochloride

technical field

The invention relates to a method for treating waste liquid in the chemical production process, in particular to a method for treating waste liquid after purification of ethanol mother liquor in the production of acid doxycycline.

Background technique

Doxycycline hydrochloride is a broad-spectrum antibiotic made from oxytetracycline as raw material through multi-step chemical reactions of chlorination, dehydration, hydrogenation into salt, and replacement, followed by purification, decolorization, filtration, crystallization, and drying. There are many kinds of raw materials for its production, and the process is complicated. Ethanol is an important raw material of this product, and a large amount of waste water containing ethanol will be discharged during the production process. In the process of distillation and recovery of ethanol in wastewater, a large amount of purified waste liquid cannot be processed. The chemical oxygen demand (COD) of the waste liquid is as high as hundreds of thousands of milligrams per liter, with poor biodegradability, large chroma, dark brown appearance, high acidity and high content of inorganic salts. The main components in the waste liquid are degradation products of oxytetracycline, p-toluenesulfonic acid, sulfosalicylic acid and fluoride, hydrochloric acid, degradation products of doxycycline and residues of acetanilide, etc. Due to the characteristics of this waste liquid, it is very difficult to treat, and there are not many published research results so far, and there is no suitable treatment process that can make it discharge up to the standard after treatment.

Contents of the invention

In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for treating waste liquid after purification of ethanol mother liquor in the production of high-concentration and difficult-to-handle doxycycline hydrochloride. The method has the advantages of thorough treatment, high efficiency and stable operation. Features.

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

A method for treating waste liquid after purification of ethanol mother liquor in the production of doxycycline hydrochloride, comprising the following steps: (1) Cooling: Stir the waste liquid in a regulating tank and cool it naturally to 40-45°C; (2) Primary flocculation and precipitation : add flocculant to wastewater, and then add alkali for neutralization after flocculation and sedimentation; (3) secondary flocculation and precipitation: filter the liquid after step (2) through a filter press, and the filtrate Flocculation and sedimentation again and separation of mud and water; (4) Biochemical treatment: the supernatant obtained in step (3) of mud and water separation is sequentially passed through ozone oxidation decolorization, anaerobic, and aerobic biochemical units for biochemical reactions; (5) Filtration and membrane separation: The liquid treated in step (4) is sequentially treated by membrane bioreactor, nanofiltration and reverse osmosis membrane.

The flocculant added in the step (2) is polyaluminum chloride, and the dosage is 1000-3000mg/L.

The alkali added in the step (2) is quicklime, and the dosage of quicklime is 8g/L; the quicklime is neutralized with the supernatant obtained from the first flocculation precipitation, so that the pH value of the wastewater is adjusted to 6.5-7.5.

The flocculant added during the second flocculation and sedimentation in the step (3) is polyaluminum chloride, and the dosage is 500-1000mg/L.

The dosage of ozone in the step (4) is 100-200g/h, and the ozone contact reaction time is 1.5-3 hours.

In the step (4), the completely mixed anaerobic digester is used to perform anaerobic biochemical reaction on the wastewater after ozone decolorization, and the residence time of the wastewater in the anaerobic digester is 6 hours.

In the step (4), a biological contact oxidation tank is used to perform aerobic biochemical reaction on the wastewater after the anaerobic biochemical reaction, and the residence time of the wastewater in the biological contact oxidation tank is 10 hours.

The elastic biological filler is used in the biological contact oxidation tank, the height of the filler is 2 meters, and the length of the filler wire is 200 mm.

The biological contact oxidation tank is divided into four compartments, elastic biological fillers are installed in the first three compartments, and a submerged membrane bioreactor is installed in the fourth compartment; the submerged membrane bioreactor adopts a curtain ultrafiltration membrane, and the membrane flux It is 4-7 liters/square meter. Hours.

In the step (5), a two-stage reverse osmosis process is used to filter and membrane-separate the biochemically treated wastewater; the first stage of the membrane separation uses a nanofiltration membrane, and the second stage uses a reverse osmosis membrane.

Compared with the prior art, the beneficial effects of the present invention are: the present invention has the characteristics of thorough treatment, high treatment efficiency, stable operation, etc. After being treated by the method of the present invention, the doxycycline hydrochloride production wastewater can be discharged to meet the wastewater discharge standard GB8978 -Class I standard in 1996, while eliminating the pollution caused by waste water to the environment.

Description of drawings

Fig. 1 is a process flow diagram of the present invention.

Detailed ways

In conjunction with the accompanying drawings of the description, the specific embodiments of the present invention are as follows:

Example 1

A method for treating waste liquid after purification of ethanol mother liquor in the production of doxycycline hydrochloride, comprising the following steps: (1) Cooling: homogenizing the water quality and quantity of the waste liquid in a regulating tank and stirring, so that the water temperature is naturally cooled from 90°C to 40°C; (2) primary flocculation and sedimentation: the waste liquid in step (1) is pumped to the flocculation reaction tank, and the flocculant polyaluminium chloride is added to the waste water through the metering pump, and the dosage is 1000mg/L After flocculation and sedimentation, the supernatant liquid after separation of sludge and water is added with quicklime for neutralization. The dosage of quicklime is 8g/L. Adjust from 0.5 to 6.5 to precipitate the dissolved salts in the waste water and initially remove the suspended matter in the waste liquid; (3) Secondary flocculation and sedimentation: the waste liquid neutralized in step (2) is then pumped to the plate frame The filter press performs solid-liquid separation by pressing, and the solid matter obtained can be used as brick-making materials. The filtered liquid flows into the second flocculation sedimentation by gravity, and the flocculant polyaluminium chloride is added to the filtrate again, and the dosage is (4) Ozone oxidation, anaerobic and aerobic biochemical treatment: the effluent of the second flocculation sedimentation tank in step (3) is self-flowing Entering the ozone oxidation tank, ozone is generated by the ozone generator, and then diffused into the wastewater through the microporous aeration device. The dosage of ozone is 100g/h, and the ozone contact reaction time is 2 hours. The pump is transported to the anaerobic digestion tank. The anaerobic tank adopts a completely mixed tank type. The macromolecular organic matter in the wastewater is degraded by the action of anaerobic microorganisms. The residence time is 6 hours. The effluent from the anaerobic digestion tank flows into the biological contact oxidation tank. Carry out aerobic biochemical reaction on the wastewater after the anaerobic biochemical reaction, the wastewater stays in the biological contact oxidation tank for 10 hours, and is aerated with oxygen to completely decompose the organic matter in the wastewater through the action of aerobic microorganisms; (5) Activated carbon filtration and membrane separation: The liquid treated in step (4) is passed through the ultrafiltration membrane bioreactor, and the effluent from the ultrafiltration membrane bioreactor is filtered through activated carbon to further remove color and organic pollutants, and then transported to Two-stage reverse osmosis system, the first stage adopts nanofiltration membrane, and the second stage adopts reverse osmosis membrane to treat the effluent and discharge it up to standard.

In this embodiment, the biological contact oxidation tank is divided into four grids. Elastic biological fillers are installed in the first three grids. The filter membrane bioreactor adopts curtain ultrafiltration membrane, and the membrane flux is 4 liters/square meter. Hour.

The discharge value of the effluent in this embodiment: various index values when the water enters, and the various index values of the effluent after treatment are shown in Table 1:

Table 1

the COD (mg/L) BOD5 (mg/L) SS (mg/L) Chroma (times) pH flooded 340000 22000 9000 10000 1.0 out of water 95 20 5.0 - 6.6 Emission Standards ≤100 ≤30 ≤70 50 6.0－9.0

Example 2

A method for treating waste liquid after purification of ethanol mother liquor in the production of doxycycline hydrochloride, comprising the following steps: (1) Cooling: homogenizing the water quality and quantity of the waste liquid in a regulating tank and stirring, so that the water temperature is naturally cooled from 90°C to 42°C; (2) primary flocculation and sedimentation: the waste liquid in step (1) is pumped to the flocculation reaction tank, and the flocculant polyaluminum chloride is added to the waste water through the metering pump, and the dosage is 2500mg/L After flocculation and sedimentation, the supernatant liquid after separation of sludge and water is added with quicklime for neutralization. The dosage of quicklime is 8g/L. Adjust from 0.7 to 6.9 to precipitate dissolved salts in the wastewater and initially remove suspended solids in the waste liquid; (3) Secondary flocculation and sedimentation: the waste liquid neutralized in step (2) is then pumped to the plate frame The filter press performs solid-liquid separation by pressing, and the solid matter obtained can be used as brick-making materials. The filtered liquid flows into the second flocculation sedimentation by gravity, and the flocculant polyaluminium chloride is added to the filtrate again, and the dosage is 800mg/L, after re-flocculation and sedimentation and separation of mud and water, further removal of suspended solids in the waste liquid; (4) Ozone oxidation, anaerobic and aerobic biochemical treatment: the effluent of the second flocculation sedimentation tank in step (3) is self-flowing Entering the ozone oxidation pool, ozone is generated by the ozone generator, and then diffused into the wastewater through the microporous aeration device. The dosage of ozone is 150g/h, and the ozone contact reaction time is 2.5 hours. The pump is transported to the anaerobic digestion tank. The anaerobic tank adopts a completely mixed tank type. The macromolecular organic matter in the wastewater is degraded by the action of anaerobic microorganisms. The residence time is 6 hours. The effluent from the anaerobic digestion tank flows into the biological contact oxidation tank. Carry out aerobic biochemical reaction on the wastewater after the anaerobic biochemical reaction, the wastewater stays in the biological contact oxidation tank for 10 hours, and is aerated with oxygen to completely decompose the organic matter in the wastewater through the action of aerobic microorganisms; (5) Activated carbon filtration and membrane separation: The liquid treated in step (4) is passed through the ultrafiltration membrane bioreactor, and the effluent from the ultrafiltration membrane bioreactor is filtered through activated carbon to further remove color and organic pollutants, and then transported to Two-stage reverse osmosis system, the first stage adopts nanofiltration membrane, and the second stage adopts reverse osmosis membrane to treat the effluent and discharge it up to standard.

In this embodiment, the biological contact oxidation tank is divided into four grids. Elastic biological fillers are installed in the first three grids. The membrane bioreactor adopts curtain ultrafiltration membrane, and the membrane flux is 5 liters/square meter.hour.

The discharge value of the effluent in this embodiment: the values of various indicators when the water enters, and the values of the various indicators of the effluent after treatment are shown in Table 2:

Table 2

the COD (mg/L) BOD5 (mg/L) SS (mg/L) Chroma (times) pH flooded 340000 22000 9000 10000 1.0 out of water 83 twenty two 7.0 - 6.5 Emission Standards ≤100 ≤30 ≤70 50 6.0－9.0

Example 3

A method for treating waste liquid after purification of ethanol mother liquor in the production of doxycycline hydrochloride, comprising the following steps: (1) Cooling: homogenizing the water quality and quantity of the waste liquid in a regulating tank and stirring, so that the water temperature is naturally cooled from 90°C to 44°C; (2) primary flocculation and sedimentation: the waste liquid in step (1) is pumped to the flocculation reaction tank, and the flocculant polyaluminium chloride is added to the waste water through the metering pump, and the dosage is 1500mg/L After flocculation and sedimentation, the supernatant liquid after separation of sludge and water is added with quicklime for neutralization. The dosage of quicklime is 8g/L. Adjust from 0.8 to 7.0 to precipitate dissolved salts in the waste water and initially remove suspended solids in the waste liquid; (3) Secondary flocculation and sedimentation: the waste liquid neutralized in step (2) is then pumped to the plate frame The filter press performs solid-liquid separation by pressing, and the solid matter obtained can be used as brick-making materials. The filtered liquid flows into the second flocculation sedimentation by gravity, and the flocculant polyaluminium chloride is added to the filtrate again, and the dosage is 1000mg/L, after re-flocculation and sedimentation and separation of mud and water, the suspended solids in the waste liquid are further removed; (4) Ozone oxidation, anaerobic and aerobic biochemical treatment: the effluent of the second flocculation sedimentation tank in step (3) is self-flowing Enter the ozone oxidation tank, the ozone is generated by the ozone generator, and then diffused into the wastewater through the microporous aeration device. The dosage of ozone is 200g/h, and the ozone contact reaction time is 3 hours. The pump is transported to the anaerobic digestion tank. The anaerobic tank adopts a completely mixed tank type. The macromolecular organic matter in the wastewater is degraded by the action of anaerobic microorganisms. The residence time is 6 hours. The effluent from the anaerobic digestion tank flows into the biological contact oxidation tank. Carry out aerobic biochemical reaction on the wastewater after the anaerobic biochemical reaction, the wastewater stays in the biological contact oxidation tank for 10 hours, and is aerated with oxygen to completely decompose the organic matter in the wastewater through the action of aerobic microorganisms; (5) Activated carbon filtration and membrane separation: The liquid treated in step (4) is passed through the ultrafiltration membrane bioreactor, and the effluent from the ultrafiltration membrane bioreactor is filtered through activated carbon to further remove color and organic pollutants, and then transported to Two-stage reverse osmosis system, the first stage adopts nanofiltration membrane, and the second stage adopts reverse osmosis membrane to treat the effluent and discharge it up to standard.

In this embodiment, the biological contact oxidation tank is divided into four grids. Elastic biological fillers are installed in the first three grids. The membrane bioreactor adopts curtain ultrafiltration membrane, and the membrane flux is 5 liters/square meter.hour.

The discharge value of the effluent in this embodiment: the values of various indicators when the water enters, and the values of the various indicators of the effluent after treatment are shown in Table 3:

table 3

the COD (mg/L) BOD5 (mg/L) SS (mg/L) Chroma (times) pH flooded 340000 22000 9000 10000 1.0 out of water 75 18 8.0 - 6.8 Emission Standards ≤100 ≤30 ≤70 50 6.0－9.0

Example 4

A method for treating waste liquid after purification of ethanol mother liquor in the production of doxycycline hydrochloride, comprising the following steps: (1) Cooling: homogenizing the water quality and quantity of the waste liquid in a regulating tank and stirring, so that the water temperature is naturally cooled from 90°C to 45°C; (2) primary flocculation and sedimentation: the waste liquid in step (1) is pumped to the flocculation reaction tank, and the flocculant polyaluminum chloride is added to the waste water through the metering pump, and the dosage is 3000mg/L After flocculation and sedimentation, the supernatant liquid after separation of sludge and water is added with quicklime for neutralization. The dosage of quicklime is 8g/L. 1 is adjusted to 7.5, so that the dissolved salts in the wastewater are precipitated, and the suspended solids in the waste liquid are initially removed; (3) Secondary flocculation and sedimentation: the waste liquid neutralized in step (2) is then pumped to the plate frame The filter press performs solid-liquid separation by pressing, and the solid matter obtained can be used as brick-making materials. The filtered liquid flows into the second flocculation sedimentation by gravity, and the flocculant polyaluminium chloride is added to the filtrate again, and the dosage is 1000mg/L, after re-flocculation and sedimentation and separation of mud and water, the suspended solids in the waste liquid are further removed; (4) Ozone oxidation, anaerobic and aerobic biochemical treatment: the effluent of the second flocculation sedimentation tank in step (3) is self-flowing Entering the ozone oxidation pool, ozone is generated by the ozone generator, and then diffused into the wastewater through the microporous aeration device. The dosage of ozone is 200g/h, and the ozone contact reaction time is 3 hours. The pump is transported to the anaerobic digestion tank. The anaerobic tank adopts a completely mixed tank type. The macromolecular organic matter in the wastewater is degraded through the action of anaerobic microorganisms. The residence time is 6 hours. The effluent from the anaerobic digestion tank flows into the biological contact oxidation tank by itself. Carry out aerobic biochemical reaction on the wastewater after the anaerobic biochemical reaction, the wastewater stays in the biological contact oxidation tank for 10 hours, and is aerated with oxygen to completely decompose the organic matter in the wastewater through the action of aerobic microorganisms; (5) Activated carbon filtration and membrane separation: The liquid treated in step (4) is passed through the ultrafiltration membrane bioreactor, and the effluent from the ultrafiltration membrane bioreactor is filtered through activated carbon to further remove color and organic pollutants, and then transported to Two-stage reverse osmosis system, the first stage adopts nanofiltration membrane, and the second stage adopts reverse osmosis membrane to treat the effluent and discharge it up to standard.

In this embodiment, the biological contact oxidation tank is divided into four grids. Elastic biological fillers are installed in the first three grids. The filter membrane bioreactor adopts curtain ultrafiltration membrane, and the membrane flux is 7 liters/square meter. Hour.

The discharge value of the effluent in this embodiment: the values of various indicators when the water enters, and the values of the various indicators of the effluent after treatment are shown in Table 4:

Table 4

the COD (mg/L) BOD5 (mg/L) SS (mg/L) Chroma (times) pH flooded 340000 22000 9000 10000 1.0 out of water 78 12 9.6 - 6.8 Emission Standards ≤100 ≤30 ≤70 50 6.0－9.0

Example 5

A method for treating waste liquid after purification of ethanol mother liquor in the production of doxycycline hydrochloride, comprising the following steps: (1) Cooling: homogenizing the water quality and quantity of the waste liquid in a regulating tank and stirring, so that the water temperature is naturally cooled from 90°C to 40-45°C; (2) primary flocculation and sedimentation: the waste liquid in step (1) is pumped to the flocculation reaction tank, and the flocculant polyaluminum chloride is added to the waste water through the metering pump, and the dosage is 2800mg /L, quicklime is added to the supernatant after flocculation and sedimentation for neutralization. The dosage of quicklime is 8g/L. The value is adjusted from 0.8 to 7.5, so that the dissolved salts in the wastewater are precipitated, and the suspended solids in the waste liquid are initially removed; (3) Secondary flocculation and sedimentation: the waste liquid neutralized in step (2) is then pumped to The plate and frame filter press performs solid-liquid separation by pressure filtration, and the obtained solid matter can be used as brick-making materials. The amount is 1000mg/L, and the suspended solids in the waste liquid are further removed after re-flocculation and sedimentation and the separation of mud and water; (4) Ozone oxidation, anaerobic and aerobic biochemical treatment: the second flocculation sedimentation tank in step (3) The effluent flows into the ozone oxidation pool by itself. The ozone is generated by the ozone generator, and then diffused into the wastewater through the microporous aeration device. The dosage of ozone is 180g/h, and the ozone contact reaction time is 1.8 hours. The wastewater oxidized by ozone Then it is transported to the anaerobic digestion tank by the pump. The anaerobic tank adopts a completely mixed tank type, and the macromolecular organic matter in the wastewater is degraded through the action of anaerobic microorganisms. The residence time is 6 hours. The effluent of the anaerobic digestion tank flows into the biological contact oxidation aerobic biochemical reaction to the wastewater after the anaerobic biochemical reaction, the residence time of the wastewater in the biological contact oxidation tank is 10 hours, and it is aerated with oxygen to completely decompose the organic matter in the wastewater through the action of aerobic microorganisms; ( 5) Activated carbon filtration and membrane separation: pass the liquid treated in step (4) through the ultrafiltration membrane bioreactor, and the effluent from the ultrafiltration membrane bioreactor is then filtered through activated carbon to further remove color and organic pollutants, and then pass through the high-pressure pump It is transported to a two-stage reverse osmosis system, the first stage adopts nanofiltration membrane, and the second stage adopts reverse osmosis membrane to treat the effluent and discharge it up to standard.

In this embodiment, the biological contact oxidation tank is divided into four grids. Elastic biological fillers are installed in the first three grids. The filter membrane bioreactor adopts curtain ultrafiltration membrane, and the membrane flux is 6 liters/square meter. Hour.

The discharge value of the effluent in this embodiment: the values of various indicators when the water enters, and the values of the various indicators of the effluent after treatment are shown in Table 5:

table 5

the COD (mg/L) BOD5 (mg/L) SS (mg/L) Chroma (times) pH flooded 340000 22000 9000 10000 1.0 out of water 86 10 11 - 7.1 Emission Standards ≤100 ≤30 ≤70 50 6.0－9.0

Example 6

A method for treating waste liquid after purification of ethanol mother liquor in the production of doxycycline hydrochloride, comprising the following steps: (1) Cooling: homogenizing the water quality and quantity of the waste liquid in a regulating tank and stirring, so that the water temperature is naturally cooled from 90°C to 42°C; (2) primary flocculation and sedimentation: the waste liquid in step (1) is pumped to the flocculation reaction tank, and the flocculant polyaluminum chloride is added to the waste water through the metering pump, and the dosage is 2800mg/L After flocculation and sedimentation, the supernatant liquid after separation of sludge and water is added with quicklime for neutralization. The dosage of quicklime is 8g/L. Adjust from 0.5 to 6.8 to precipitate the dissolved salts in the waste water and initially remove the suspended matter in the waste liquid; (3) Secondary flocculation and sedimentation: the waste liquid neutralized in step (2) is then pumped to the plate frame The filter press performs solid-liquid separation by pressing, and the solid matter obtained can be used as brick-making materials. The filtered liquid flows into the second flocculation sedimentation by gravity, and the flocculant polyaluminium chloride is added to the filtrate again, and the dosage is 500mg/L, after re-flocculation and sedimentation and separation of mud and water, the suspended solids in the waste liquid are further removed; (4) Ozone oxidation, anaerobic and aerobic biochemical treatment: the effluent of the second flocculation sedimentation tank in step (3) is self-flowing Entering the ozone oxidation tank, ozone is generated by the ozone generator, and then diffused into the wastewater through the microporous aeration device. The dosage of ozone is 100g/h, and the ozone contact reaction time is 1.5 hours. The pump is transported to the anaerobic digestion tank. The anaerobic tank adopts a completely mixed tank type. The macromolecular organic matter in the wastewater is degraded by the action of anaerobic microorganisms. The residence time is 6 hours. The effluent from the anaerobic digestion tank flows into the biological contact oxidation tank. Carry out aerobic biochemical reaction on the wastewater after the anaerobic biochemical reaction, the wastewater stays in the biological contact oxidation tank for 10 hours, and is aerated with oxygen to completely decompose the organic matter in the wastewater through the action of aerobic microorganisms; (5) Activated carbon filtration and membrane separation: The liquid treated in step (4) is passed through the ultrafiltration membrane bioreactor, and the effluent from the ultrafiltration membrane bioreactor is filtered through activated carbon to further remove color and organic pollutants, and then transported to Two-stage reverse osmosis system, the first stage adopts nanofiltration membrane, and the second stage adopts reverse osmosis membrane to treat the effluent and discharge it up to standard.

In this embodiment, the biological contact oxidation tank is divided into four grids. Elastic biological fillers are installed in the first three grids. The filter membrane bioreactor adopts curtain ultrafiltration membrane, and the membrane flux is 6 liters/square meter. Hour.

The discharge value of the effluent in this embodiment: various index values when the water enters, and the various index values of the effluent after treatment are shown in Table 6:

Table 6

the COD (mg/L) BOD5 (mg/L) SS (mg/L) Chroma (times) pH flooded 340000 22000 9000 10000 1.0 out of water 72 11 4.5 - 6.5 Emission Standards ≤100 ≤30 ≤70 50 6.0－9.0

Claims (10)

1. A method for treating waste liquid after purification of ethanol mother liquor in the production of doxycycline hydrochloride, which is characterized in that it comprises the following steps: (1) Cooling: stirring and cooling the waste liquid to 40-45°C in a regulating tank; (2) Primary flocculation and sedimentation: add flocculant to the cooled wastewater, and then add alkali for neutralization after flocculation and sedimentation and mud-water separation; (3) Secondary flocculation and sedimentation: pressurize the neutralized liquid in step (2) The filter is pressed, the filtrate is flocculated and precipitated again, and the mud and water are separated; (4) Biochemical treatment: the supernatant obtained in step (3) of mud and water separation is sequentially subjected to ozone oxidation decolorization, anaerobic treatment, and aerobic biochemical unit for biochemical reaction (5) Filtration and membrane separation: the liquid treated in step (4) is sequentially treated by membrane bioreactor, nanofiltration and reverse osmosis membrane. 2. The method for treating waste liquid after purification of ethanol mother liquor in the production of doxycycline hydrochloride according to claim 1, characterized in that: the flocculant added in the step (2) is polyaluminum chloride, and the dosage It is 1000-3000mg/L. 3. The method for treating waste liquid after purification of ethanol mother liquor in the production of doxycycline hydrochloride according to claim 1, characterized in that: the alkali added in the step (2) is quicklime, and the dosage of quicklime is 8g/ L; Quicklime is neutralized with the supernatant obtained from the first flocculation precipitation, so that the pH value of the wastewater is adjusted to 6.5-7.5. 4. The method for treating waste liquid after purification of ethanol mother liquor in the production of doxycycline hydrochloride according to claim 1, characterized in that: the flocculant added during the secondary flocculation and precipitation in the step (3) is polychlorination Aluminum, the dosage is 500-1000mg/L. 5. The method for treating waste liquid after purification of ethanol mother liquor in the production of doxycycline hydrochloride according to claim 1, characterized in that: the dosage of ozone in the step (4) is 100-200g/h, and the ozone contact The reaction time is 1.5-3 hours. 6. The method for treating waste liquid after purification of ethanol mother liquor in the production of doxycycline hydrochloride according to claim 1, characterized in that: in the step (4), the waste water after ozone decolorization is adopted in the complete mixed anaerobic digester The anaerobic biochemical reaction is carried out, and the residence time of the wastewater in the anaerobic digester is 6 hours. 7. The method for treating waste liquid after purification of ethanol mother liquor in the production of doxycycline hydrochloride according to claim 1, characterized in that: in the step (4), the waste water after the anaerobic biochemical reaction is treated with a biological contact oxidation tank Aerobic biochemical reaction, the residence time of wastewater in the biological contact oxidation tank is 10 hours. 8. the processing method of waste liquid after ethanol mother liquor purification in the production of doxycycline hydrochloride according to claim 7, is characterized in that: adopt elastic biological filler in the described biological contact oxidation tank, described filler height is 2 meters, and filler wire The length is 200mm. 9. the treatment method of waste liquid after ethanol mother liquor purification in the production of doxycycline hydrochloride according to claim 8, it is characterized in that: described biological contact oxidation tank is divided into four grids, elastic biological filler is installed in the first three grid pools, the second A submerged membrane bioreactor is installed in the four-grid pool; the submerged membrane bioreactor adopts a curtain ultrafiltration membrane, and the membrane flux is 4-7 liters/square meter.hour. 10. The method for treating waste liquid after purification of ethanol mother liquor in the production of doxycycline hydrochloride according to any one of claims 1-9, characterized in that: in the step (5), a two-stage reverse osmosis process is used to treat the waste liquid after biochemical treatment The final waste water is filtered and membrane separated; the first stage of the membrane separation adopts nanofiltration membrane, and the second stage adopts reverse osmosis membrane.