our country is a major producer of chemical APIs, and the chemical pharmaceutical industry is a manufacturing industry that combines the decomposition and synthesis technology of chemical APIs with modern clinical diagnostic medicine, and is also one of the main indicators to measure the pharmaceutical capacity and level of a country.
   However, with the continuous development of our country's pharmaceutical industry, the pollution caused by chemical pharmaceutical wastewater to the natural environment is becoming more and more serious, seriously threatening people's health. The chemical pharmaceutical industry generally has the characteristics of large changes in production scale, a wide variety of products, and very complex production processes. At this stage, the output value of our country's chemical and pharmaceutical industry accounts for about 1.7% of the total industrial output value, but the proportion of sewage discharge is as high as 2.0%, and the chemical pharmaceutical industry has become one of the main objects of environmental governance.
01 Characteristics and composition of pharmaceutical wastewater
   Pharmaceutical wastewater has the characteristics of large composition differences, complex components, large amount of pollutants, high COD, low and fluctuating ratio of BOD5 to CODcr, poor biodegradability, many refractory substances, strong toxicity, intermittent discharge, and large fluctuations in water quantity and quality and pollutants.

02 Chemical pharmaceutical wastewater is very harmful
   Most of the chemically synthesized wastewater is organic wastewater with high concentration, high salt content, and large pH changes, and some raw materials or products are biotoxic and generally difficult to be biodegraded, such as phenolic compounds, aniline compounds, heavy metals, benzene and halogenated hydrocarbon solvents. Water pollutants include conventional and characteristic pollutants, including TOC, COD, BOD5, SS, pH, ammonia nitrogen, total nitrogen, total phosphorus, chromaticity, acute toxicity, total copper, volatile phenols, sulfides, nitrobenzene, aniline, methylene chloride, total zinc, total cyanide and total mercury, total cadmium, amino mercury, hexavalent chromium, total arsenic, total lead and total nickel.
   Pharmaceutical wastewater may contain residual drugs, drug intermediates, reaction unknowns, unreactants, and resistant bacteria that may be produced by microorganisms involved in biological treatment, which are all challenges in wastewater treatment. Most of these pollutants are highly toxic, carcinogenic, teratogenic and mutagenic. If left untreated or improperly handled, they will stay in the water for a long time, accumulate and enrich through the food chain, and all enter the animal or human body, posing a huge threat to the health of animals and humans.
03 Policies are forced to promote the green development of the pharmaceutical industry
   Strengthening pharmaceutical wastewater treatment to meet the requirements of the "Comprehensive Sewage Discharge Standard", so as to reduce the pollution of pharmaceutical wastewater to the environment and the waste of water resources, is our country's dual goal of environmental protection and enterprise efficiency. How to treat pharmaceutical wastewater up to standard, or even reuse, and achieve near-zero discharge, has become the responsibility and obligation of contemporary enterprises. In recent years, our country's policies on pharmaceutical wastewater treatment have been frequently increased, which has also prompted breakthroughs and progress in related wastewater treatment technologies.
  The data shows that the output value of the sewage treatment industry in 2020 will be about 84 billion yuan, and it will reach 130 billion yuan in 2025, and the development space of the sewage treatment equipment industry will be very broad. As the main producer of wastewater, the development prospects of the pharmaceutical wastewater treatment equipment industry are even greater. Attracted by the huge market, many equipment companies have laid out. With the rise of wastewater treatment and membrane treatment equipment manufacturers in the pharmaceutical industry at home and abroad, this will surely bring new technologies or solutions to the industry and further promote the pharmaceutical industry towards green development.
04 There are many technologies, and achieving zero wastewater discharge is the key
   Different pharmaceutical companies choose different treatment methods due to different raw materials, processes, wastewater volume, and treatment degrees. According to the principles of each method, it is generally summarized into physical method, chemical method, and biological method. In the process of pharmaceutical wastewater treatment, the wastewater treated by biological methods cannot be discharged directly, usually first pretreatment by physical and chemical methods to improve its biodegradability and reduce toxicity, and then continue to carry out biological treatment, so that the wastewater can meet the discharge requirements.
1. Physical law
   1. Adsorption method
   The adsorption method relies on the porous polymer material itself to have high adsorption performance for pollutants and toxic substances, and forms a precipitation under the action of gravity, reducing the content of pollutants in water, and then achieving the purpose of purification. Commonly used adsorbents are activated carbon, activated coal, humic acid, adsorption resin, etc., of which activated carbon mainly includes powder activated carbon (PAC), granular activated carbon (GAC) and biological activated carbon (BAC) three categories, its adsorption belongs to physical adsorption, not affected by water quality, water quantity and water temperature, not only can remove organic matter and heavy metals with molecular weight in the aqueous phase of 500~3000, but also can effectively remove odor, color, etc., with a wide application prospect. Zhang Xin et al. used non-styrene skeleton adsorption resin to deeply treat sulfonamide-metrimethoprim wastewater precipitated by CaO flocculation, and the COD removal rate of wastewater could reach 81.66%, and the resin could be repeated many times, and the adsorption performance was still good.
 2. Membrane filtration method
   Membrane filtration method uses the selective filtration of semi-permeable membranes with different properties and pore sizes to separate pollutants and toxic substances in wastewater. Commonly used membrane filtration methods mainly include ultrafiltration, microfiltration and fine filtration. Although this method has a significant treatment effect and can remove most of the pollutants, due to the defects of the semi-permeable membrane itself, such as relatively thin, long-term use is easy to corrode and damage and blockage, the efficiency of the semi-permeable membrane gradually decreases with the extension of working time, and the cost of the membrane filtration method is high, and finally directly leads to the inability to completely remove some pollutants in the filtrate. Zhang Chunhui et al. used the ceramic filtration-ceramic membrane combination process to deeply treat the cough syrup wastewater that had been treated with biological contact oxidation and could not meet the discharge standards, and the final treated wastewater BOD, COD, solid suspended solids (SS) and ammonia nitrogen index (NH3-N) could meet the discharge standards.
 3. Air flotation method
   The air flotation method is mainly used in the pretreatment process of pharmaceutical wastewater, and the chemical air flotation is only suitable for the pretreatment of wastewater with high suspended solids content, but it cannot effectively remove soluble organic matter in the waste liquid, which has advantages in terms of investment cost, energy consumption, process accuracy, and maintenance. For example, Xinchang Pharmaceutical Plant chose CAF vortex air flotation device for wastewater treatment, and after adding other specific chemicals, the average removal rate of CODcr in wastewater was about 25%. Li Hongyun et al. used the self-priming shear flow microporous microbubble generator air flotation experimental device and the electrocoagulation air flotation experimental device to study the wastewater, and the COD removal rate of the water samples reached 46.23% and 54.24%, respectively.
2. Chemical method
   1. Precipitation method
   The sedimentation method refers to the addition of certain chemical substances that can react with pollutants and toxic substances in wastewater treatment, through precipitation and filtration, and finally achieve the purpose of purification. Unlike the adsorption method, this process has a chemical reaction and is a chemical method. Wang Xinqi used ammonium magnesium phosphate precipitation method to treat wastewater, and found that under the optimal pH conditions, the removal rate of PO43- and NH4+ reached 15%, which could increase the removal rate by about 20% when adding crystal seeds. This method is low-cost, but it introduces new substances, and the amount of addition will cause secondary pollution.

2. Advanced oxidation method
   Advanced oxidation is an environmentally friendly treatment method that uses some highly active free radicals to degrade organic pollutants, convert them into easily degradable small molecules, or even completely oxidize them to CO2 and H2O. Due to its excellent treatment effect, it has been favored by researchers at home and abroad.
  At present, the Fenton method mainly includes ultrasonic Fenton method, electric Fenton method, optical Fenton method, and microwave Fenton method, which has been applied in practical production and has a significant effect on the treatment of organic wastewater. Badawy et al. investigated the treatment of pharmaceutical wastewater with BOD/COD of 0.25~0.30 by Fenton and biotechnology, and Zhu Rongshu et al. investigated the removal rate of other components such as CH2Cl2, tetrahydrofuran, DMF, nitrobenzene, and o-toluidine in the wastewater with Fenton pretreatment wastewater with a low removal rate of about 53.3%, and the removal rate of other components such as CH2Cl2, tetrahydrofuran, DMF, nitrobenzene, and o-toluidine was more than 92%.
  A common method among advanced oxidation methods is ozone oxidation method, based on ozone's own strong oxidation performance, some organic molecules and chromophensic groups in pharmaceutical wastewater are oxidized into small molecule compounds or directly oxidized to CO2 and H2O, and most of the bacteria are removed to achieve the purpose of wastewater treatment. This method is more environmentally friendly, generally does not pollute the environment, and the biodegradability is greatly improved, so the ozone oxidation method and its combined technology are widely used in wastewater. Wang Shaojun et al. used the combined process of Fe/C pretreatment + biochemistry + ozone biochar to treat high-concentration vitamin B2 production wastewater, and the treated wastewater has met the discharge requirements of the "Comprehensive Sewage Discharge Standard" (GB8978-1996).
3. Biological method
   Biological method is a method to use the metabolism of microorganisms to remove organic pollutants in wastewater and achieve the purpose of water purification. Biological treatment technology is the most mature sewage treatment technology at present, and the treatment cost is low and the effect is good.
 1. Aerobic biological treatment
    Aerobic biological treatment is a method that relies on aerobic microorganisms and facultative microorganisms to carry out metabolic activities under aerobic conditions to convert organic compounds in wastewater into H2O and CO2, etc., to achieve the purpose of degrading pollutants in wastewater. Aerobic treatment can remove most of the organic matter, and the COD removal rate is generally more than 80%. At present, the most effective aerobic treatment methods are traditional activated sludge method, biological contact oxidation method, sequential batch activated sludge method (SBR), deep well aeration method, etc. In recent years, pharmaceutical companies have adopted a variety of combined processes, which can significantly improve the treatment effect of wastewater, such as hydrolytic acidification-aerobic catalytic oxidation and SBR treatment of pharmaceutical wastewater.
  (1) Traditional activated sludge method. Therefore, in recent years, in order to improve the treatment effect of wastewater, the change of microbial fixation method has become one of the most important directions of the traditional activated sludge method.
  (2) Contact oxidation method. Biological contact oxidation method is an efficient sewage treatment method that adds fillers covered with biofilm, and the wastewater contacts the biofilm to remove organic matter by using the metabolism of microorganisms to achieve water purification. This method has a high treatment load, a relatively small footprint, can be used intermittently, will not cause sludge expansion problems, and the operation cost of the whole process is very low. Due to the advantages of biological contact oxidation method, this method is often combined with other physical and chemical technologies to become a new combination process, which can enhance the treatment effect. Zhu Xinfeng and Zhang optimistic treated oxytetracycline wastewater by Fe/C microelectrolysis-Fenton-biocontact oxidation method, and when the CODcr concentration in the influent was 1000~1200mg/L, the CODcr removal rate reached more than 90%, reaching the direct discharge standard.
   (3) Sequential batch intermittent activated sludge method (SBR). SBR method is a kind of activated sludge method operated according to the intermittent aeration mode, which is widely used in pharmaceutical wastewater treatment, and has the advantages of strong purification capacity, no sludge backflow, uniform effluent quality, strong impact load resistance, simple process structure, convenient operation, good operation stability of the whole process, and less overall investment. She Zonglian et al. used the SBR method to treat wastewater containing a variety of antibiotics, and if the COD of the influent was 911~3280mg/L, the removal rate could reach 84.6%~90.6%, and the effluent BOD and SS both met the national industry discharge standards. 
   (4) Hydrolytic acidification-aerobic catalytic oxidation method. Hydrolytic acidification, also known as uplifted sludge bed (HUSB), is an improved version of UASB. The hydrolysis-aerobic process has two advantages:
   (1) With the replacement of the traditional primary sedimentation tank by the hydrolysis tank, the removal rate of organic matter is greatly improved, which not only changes the total amount of organic matter, but also changes the physical and chemical properties, shortening the subsequent treatment time.
   (2) The process also completes the treatment of sludge, so that the treatment of sewage and sludge is unified, and the traditional digester is abandoned, reducing the total residence time and energy consumption. our country has successively developed hydrolysis-activated sludge treatment, hydrolysis-oxidation ditch treatment, hydrolysis-contact oxidation treatment and other processes, these combined treatment processes improve the treatment effect of wastewater, shorten the total hydraulic residence time of pharmaceutical enterprises during production by at least 30%, reduce the aeration by 50%, and reduce the total investment and operating costs.
2. Anaerobic biological treatment
    At this stage, aerobic biological treatment is not suitable for high-concentration organic wastewater, and pharmaceutical factories often use anaerobic biological treatment technology to treat high-concentration pharmaceutical organic wastewater. Anaerobic biological treatment is a method of using organic matter as raw materials to carry out life metabolism activities through anaerobic bacteria under oxygen-free conditions, and finally convert them into inorganic substances, CO2, H2, CH4 and other non-toxic substances. The wastewater treated by this method alone cannot meet the requirements of direct discharge due to the high COD content, and needs to be treated with aerobic treatment to meet the discharge target. Due to the long time required for anaerobic bacteria to metabolize, the whole process is difficult to control artificially, and if a large amount of biomass is lost in the effluent, it will seriously affect the treatment efficiency and cannot ensure the stability of the treatment efficiency. At present, the commonly used anaerobic treatment processes mainly include upstream anaerobic sludge bed reactors, anaerobic belder reactors, etc.
    Rising anaerobic sludge bed (UASB): The equipment has a simple structure, strong treatment capacity, stable operation, and the treatment efficiency can reach more than 85%~90% when suitable microorganisms have been formed in the equipment. The key part of UASB is the three-phase separator, which effectively separates the solid, liquid and gas phases, and finally makes the sludge and gas reasonably removed and collected, so as to achieve the purpose of treating sewage. Due to the high efficiency of anaerobic digestion, there is no need to use sludge reflux devices, but usually when treating pharmaceutical wastewater such as erythromycin, chloramphenicol, oxytetracycline, etc., it is often required that the concentration of suspended solids should not be too high when the wastewater is influent.
    Anaerobic baffle plate reactor (ABR): ABR is the third generation of new anaerobic reactors, which have many advantages, mainly including high system operation stability, easy operation, low total asset investment, the most significant is good sludge sedimentation performance, can achieve a good solid-liquid separation effect, so the effluent volume is uniform, the water quality is good, especially to toxic substances, difficult to degrade substances has strong adaptability.
3. Anaerobic-aerobic biological treatment
    Due to different raw materials, many reaction by-products, different production processes, etc., the pharmaceutical wastewater produced by pharmaceutical wastewater has complex composition, high concentration, deep color, high toxicity, and high content of difficult-to-degrade substances. The combination of the two processes can improve its biodegradability, improve the treatment effect of wastewater, and reduce the investment cost of the entire combined process.
    The overall COD removal rate of the entire process system can reach 86%, the COD removal rate of the anaerobic section (UASB) is about 70%, and the COD removal rate of the aerobic section is 59%. Li et al. used a combination of ABR, membrane bioreactor (MBR) and mobile biofilm reactor (MBBR) to treat pharmaceutical wastewater, and experiments showed that when the solid suspended solids content in the original wastewater was 1000mg/L, COD was 10000mg/L, and the nitrogen and ammonia content was 500mg/L, the turbidity, COD and nitrogen and ammonia were less than 3NTU, 500mg/L and 10mg/L, respectively, and the removal rates before and after treatment were as high as 98%, 95% and 98%, respectively.
    To sum up, to solve the environmental problems restricting the development of the pharmaceutical industry, we must not only have governance ideas to solve the problems, but also explore the deep-seated causes of pollution. Green manufacturing and green development are a strategic choice. Green pharmaceuticals and green development are the fundamental way out for the development of pharmaceutical enterprises and industries.