Research on Pharmaceutical Wastewater Treatment Technology Pharmaceutical industry wastewater mainly includes four categories: antibiotic production wastewater, synthetic drug production wastewater, Chinese patent medicine production wastewater, as well as washing water and flushing wastewater from various preparation production processes. The wastewater is characterized by complex composition, high organic matter content, high toxicity, deep color and high salt content. In particular, it has poor biochemical properties and is discharged intermittently. It is an industrial wastewater that is difficult to treat. With the development of my country's pharmaceutical industry, pharmaceutical wastewater has gradually become one of the important sources of pollution. How to deal with this type of wastewater is a difficult problem in today's environmental protection. 1 Treatment methods of pharmaceutical wastewater The treatment methods of pharmaceutical wastewater can be summarized as follows: physical and chemical treatment, chemical treatment, biochemical treatment and combination treatment of multiple methods. Each treatment method has its own advantages and disadvantages. 1.1 Physical and chemical treatment According to the water quality characteristics of pharmaceutical wastewater, physical and chemical treatment needs to be used as a pretreatment or post-treatment process for biochemical treatment during its treatment process. Currently applied physical and chemical treatment methods mainly include coagulation, air flotation, adsorption, ammonia stripping, electrolysis, ion exchange and membrane separation. 1.1.1 Coagulation method This technology is a water quality treatment method commonly used at home and abroad. It is widely used in the pretreatment and post-treatment processes of pharmaceutical wastewater, such as aluminum sulfate and polymerized ferric sulfate for traditional Chinese medicine wastewater. The key to efficient coagulation treatment lies in the appropriate selection and addition of coagulants with excellent performance. In recent years, the development direction of coagulants is from low molecules to polymeric polymers, and from single-component and functional types to composite types. Liu Minghua et al. used a high-efficiency composite flocculant F-1 developed by Liu Minghua to treat emergency syrup production wastewater. When the pH was 6.5 and the flocculant dosage was 300 mg/L, the removal rate of COD, SS and chroma of the waste liquid was Reaching 69.7, 96.4 and 87.5 respectively, their performance is significantly better than single flocculants such as PAC (powder activated carbon) and polyacrylamide (PAM). 1.1.2 Air flotation method Air flotation method usually includes various forms such as inflatable air flotation, dissolved air flotation, chemical air flotation and electrolytic air flotation. Xinchang Pharmaceutical Factory uses CAF vortex concave air flotation device to pretreat pharmaceutical wastewater. With appropriate chemicals, the average removal rate of COD is about 25. 1.1.3 Commonly used adsorbents in adsorption methods include activated carbon, activated coal, humic acids, adsorption resins, etc. Wuhan Jianmin Pharmaceutical Factory uses coal ash adsorption-two-stage aerobic biological treatment process to treat its wastewater. The results show that the COD removal rate of wastewater by adsorption pretreatment reaches 41.1 and increases the BOD5/COD value. 1.1.4 Membrane separation method Membrane technology includes reverse osmosis, nanofiltration membrane and fiber membrane, which can recover useful substances and reduce the total emission of organic matter. The main features of this technology are simple equipment, easy operation, no phase change and chemical change, high processing efficiency and energy saving. Zhu Anna et al. used nanofiltration membranes to conduct separation experiments on chloramphenicol wastewater, and found that it not only reduced the inhibitory effect of chloramphenicol on microorganisms in the wastewater, but also recovered chloramphenicol. 1.1.5 Electrolysis method This method has attracted people's attention because of its high efficiency and easy operation in treating wastewater. At the same time, electrolysis method has a good decolorization effect. Li Ying used electrolysis to pretreat riboflavin supernatant, and the removal rates of COD, SS and chroma reached 71%, 83% and 67% respectively. 1.2 Chemical treatment When applying chemical methods, the excessive use of certain reagents can easily lead to secondary pollution of the water body. Therefore, relevant experimental research should be done before design. Chemical methods include iron-carbon method, chemical redox method (fenton reagent, H2O2, O3), deep oxidation technology, etc. 1.2.1 The industrial operation of the iron-carbon method shows that using Fe-C as a pretreatment step for pharmaceutical wastewater can greatly improve the biodegradability of the effluent. Lou Maoxing et al. [9] used iron-carbon-microelectrolysis-anaerobic-aerobic-air flotation combined treatment process to treat pharmaceutical intermediate production wastewater such as erythromycin and ciprofloxacin hydrochloride. COD was removed after iron-carbon treatment. The rate reaches 20, and the final effluent reaches the first-level standard of the national "Integrated Wastewater Discharge Standard" (GB8978-1996).
1.2.2 Fenton reagent treatment method The combination of ferrous salt and H2O2 is called Fenton reagent, which can effectively remove refractory organic matter that cannot be removed by traditional wastewater treatment technology. With the deepening of research, ultraviolet light (UV), oxalate (C2O42-), etc. were introduced into Fenton's reagent to greatly enhance its oxidation ability. Cheng Cangcang et al. [10] used TiO2 as the catalyst and a 9 W low-pressure mercury lamp as the light source to treat pharmaceutical wastewater with Fenton's reagent. They achieved a decolorization rate of 100 and a COD removal rate of 92.3, and the nitrobenzene compounds were reduced from 8.05 mg/ L dropped to 0.41 mg/L. 1.2.3 Using this method can improve the biodegradability of wastewater and have a better removal rate of COD. For example, Balcioglu et al. conducted ozone oxidation treatment on three types of antibiotic wastewater. The results showed that not only the BOD5/COD ratio of the ozonated wastewater increased, but also the COD removal rate was more than 75%. 1.2.4 Oxidation technology is also called advanced oxidation technology. It brings together the latest research results of modern light, electricity, sound, magnetism, materials and other related disciplines. It mainly includes electrochemical oxidation method, wet oxidation method, supercritical water oxidation method, Photocatalytic oxidation method and ultrasonic degradation method, etc. Among them, ultraviolet photocatalytic oxidation technology has the advantages of novelty, high efficiency, and non-selectivity for wastewater. It is especially suitable for the degradation of unsaturated hydrocarbons, and the reaction conditions are relatively mild, without secondary pollution, and has good application prospects. Compared with ultraviolet, heat, pressure and other treatment methods, ultrasonic treatment of organic matter is more direct and requires lower equipment. As a new treatment method, it is receiving more and more attention. Xiao Guangquan et al. [13] used ultrasonic-aerobic biological contact method to treat pharmaceutical wastewater. Under the condition of ultrasonic treatment for 60 s and power of 200 W, the total COD removal rate of the wastewater reached 96%. 1.3 Biochemical treatment Biochemical treatment technology is currently a widely used treatment technology for pharmaceutical wastewater, including aerobic biological methods, anaerobic biological methods, aerobic-anaerobic and other combined methods. 1.3.1 Aerobic biological treatment Since most pharmaceutical wastewater is high-concentration organic wastewater, the original solution generally needs to be diluted during aerobic biological treatment. Therefore, power consumption is large, and the biodegradability of the wastewater is poor, making it difficult to meet the standards after direct biochemical treatment. Emissions, so aerobic treatment alone is not often used, and pretreatment is generally required. Commonly used aerobic biological treatment methods include activated sludge method, deep well aeration method, adsorption biodegradation method (AB method), contact oxidation method, sequential batch intermittent activated sludge method (SBR method), and circulating activated sludge method. (CASS method) etc. (1) Deep well aeration method Deep well aeration is a high-speed activated sludge system. This method has high oxygen utilization rate, small footprint, good treatment effect, low investment, low operating cost, no sludge expansion, and no production. Advantages include low mud volume. In addition, its thermal insulation effect is good, and the treatment is not affected by climate conditions, which can ensure the effect of wastewater treatment in northern areas in winter. After the high-concentration organic wastewater from the Northeast Pharmaceutical General Plant was biochemically treated in the deep well aeration tank, the COD removal rate reached 92.7. It can be seen that the treatment efficiency is very high, and it is extremely beneficial to the next step of treatment. It will help the effluent of the process treatment to meet the standards. plays a decisive role. (2) AB method AB method is an ultra-high load activated sludge method. The removal rates of BOD5, COD, SS, phosphorus and ammonia nitrogen by the AB process are generally higher than those of the conventional activated sludge process. Its outstanding advantages are that the A section has a high load, strong impact load resistance, and a large buffering effect on pH and toxic substances. It is especially suitable for treating sewage with high concentration and large changes in water quality and quantity. Yang Junshi et al. used hydrolysis and acidification-AB biological process to treat antibiotic wastewater. The process is short, energy-saving, and the treatment cost is lower than the chemical flocculation-biological treatment method of the same type of wastewater. (3) Biological contact oxidation method This technology combines the advantages of activated sludge and biofilm methods. It has the advantages of high volume load, low sludge production, strong impact resistance, stable process operation, and convenient management. Many projects adopt a two-stage method, which aims to domesticate dominant strains at different stages, give full play to the synergy between different microbial populations, and improve biochemical effects and impact resistance. In projects, anaerobic digestion and acidification are often used as pretreatment processes, and contact oxidation method is used to treat pharmaceutical wastewater.
Harbin Northern Pharmaceutical Factory uses a hydrolysis acidification-two-stage biological contact oxidation process to treat pharmaceutical wastewater. The operation results show that the treatment effect of this process is stable and the process combination is reasonable. As the process technology gradually matures, its application fields become more extensive. (4) SBR method The SBR method has the advantages of strong impact load resistance, high sludge activity, simple structure, no need for reflux, flexible operation, small footprint, low investment, stable operation, high matrix removal rate, and good denitrification and phosphorus removal effects. , suitable for treating wastewater with large fluctuations in water quantity and quality. Wang Zhong’s experiment using SBR process to treat pharmaceutical wastewater showed that the aeration time has a great influence on the treatment effect of the process; setting up anoxic section, especially the repeated design of anoxic and aerobic alternating, can significantly improve the treatment effect; reaction tank CIC's SBR enhanced treatment process with PAC can significantly improve the removal effect of the system. In recent years, this process has become increasingly perfect and has been widely used in pharmaceutical wastewater treatment. Qiu Lijun and others used the hydrolysis and acidification-SBR method to treat biopharmaceutical wastewater, and the effluent water quality reached the first-level standard of GB8978-1996. 1.3.2 Anaerobic biological treatment At present, the anaerobic method is mainly used to treat high-concentration organic wastewater at home and abroad. However, the effluent COD is still high after being treated by a separate anaerobic method, and post-treatment (such as aerobic biological treatment) is generally required. ). At present, it is still necessary to strengthen the development and design of efficient anaerobic reactors and conduct in-depth research on operating conditions. The more successful applications in treating pharmaceutical wastewater include upflow anaerobic sludge bed (UASB), anaerobic compound bed (UBF), anaerobic baffle reactor (ABR), hydrolysis method, etc. (1) UASB method The UASB reactor has the advantages of high anaerobic digestion efficiency, simple structure, short hydraulic retention time, and no need for an additional sludge return device. When using the UASB method to treat pharmaceutical production wastewater such as kanamycin, chlorenzyme, VC, SD and glucose, the SS content is usually required not to be too high to ensure that the COD removal rate is above 85 to 90. The COD removal rate of the two-stage series UASB can reach more than 90%. (2) UBF Famai Wenning and others conducted a comparative test between UASB and UBF. The results showed that UBF has the characteristics of good mass transfer and separation effect of the reaction liquid, large biomass and various biological species, high processing efficiency, and strong operational stability. It is a practical and efficient anaerobic bioreactor. (3) The hydrolysis tank of hydrolysis and acidification method is called hydrolysis upflow sludge bed (HUSB), which is an improved UASB. Compared with the full-process anaerobic tank, the hydrolysis tank has the following advantages: it does not require sealing, stirring, and three-phase separators, which reduces the cost and facilitates maintenance; it can degrade macromolecules and non-biodegradable organic matter in sewage into small molecules , easily biodegradable organic matter, improves the biodegradability of raw water; has rapid response, small pool size, low infrastructure investment, and can reduce the amount of sludge. In recent years, hydrolysis-aerobic process has been widely used in pharmaceutical wastewater treatment. For example, a biopharmaceutical factory uses hydrolysis acidification-two-stage biological contact oxidation process to treat pharmaceutical wastewater. The operation is stable and the organic matter removal effect is remarkable. COD and BOD5 and SS removal rates were 90.7%, 92.4% and 87.6% respectively. 1.3.3 Anaerobic-aerobic and other combined treatment processes Because aerobic treatment or anaerobic treatment alone often cannot meet the requirements, combined processes such as anaerobic-aerobic, hydrolysis acidification-aerobic, etc. can improve the biodegradability of wastewater. , impact resistance, investment cost, treatment effect and other aspects have shown significantly better performance than a single treatment method, so it has been widely used in engineering practice.
For example, Limin Pharmaceutical Factory uses anaerobic-aerobic process to treat pharmaceutical wastewater, with a BOD5 removal rate of 98% and a COD removal rate of 95%. The treatment effect is stable; Xiao Liping uses micro-electrolysis-anaerobic hydrolysis acidification-SBR process to treat chemical Synthetic pharmaceutical wastewater, the results show that the entire series process has strong impact resistance to changes in wastewater quality and quantity, and the COD removal rate can reach 86-92, which is an ideal process choice for treating pharmaceutical wastewater; Hu Daqiang et al. The hydrolysis-acidification-A/O-catalytic oxidation-contact oxidation process is used in the treatment of pharmaceutical intermediate pharmaceutical wastewater. When the inlet water COD is about 12 000 mg/L, the effluent COD reaches less than 300 mg/L; Xu Meiying et al. use biofilm - When the SBR method treats pharmaceutical wastewater containing refractory biodegradable substances, the COD removal rate can reach 87.5% to 98.31%, which is much higher than the treatment effects of the biofilm method and the SBR method alone. In addition, with the continuous development of membrane technology, research on the application of membrane bioreactors (MBR) in pharmaceutical wastewater treatment has gradually deepened. MBR combines the characteristics of membrane separation technology and biological treatment, and has the advantages of high volumetric load, strong impact resistance, small footprint, and small amount of remaining sludge. Bai Xiaohui et al. used an anaerobic-membrane bioreactor process to treat pharmaceutical intermediate acid chloride wastewater with a COD of 25 000 mg/L. They selected the ZKM-W0.5T membrane module produced by Hangzhou Chemical Filtration Membrane Engineering Company. The system’s removal rate of COD All remained above 90%; Livinggston et al. used the ability of specialized bacteria to degrade specific organic matter and used an extraction membrane bioreactor for the first time to treat industrial wastewater containing 3,4-dichloroaniline. The HRT was 2 h, and the removal rate reached 99 %, achieving ideal processing results. Although there are still problems in membrane fouling, with the continuous development of membrane technology, MBR will be more widely used in the field of pharmaceutical wastewater treatment. 2. Treatment process and selection of pharmaceutical wastewater. The water quality characteristics of pharmaceutical wastewater make it impossible for most pharmaceutical wastewater to be treated by biochemical methods alone. Therefore, necessary pretreatment must be carried out before biochemical treatment. Generally, a regulating tank should be set up to adjust the water quality, quantity and pH, and a certain physicochemical or chemical method should be used as a pretreatment process according to the actual situation to reduce SS, salinity and some COD in the water, reduce bioinhibitory substances in the wastewater, and Improve the degradability of wastewater to facilitate subsequent biochemical treatment of wastewater. The pretreated wastewater can be treated by certain anaerobic and aerobic processes according to its water quality characteristics. If the effluent requirements are higher, post-treatment must be continued after the aerobic treatment process. The selection of specific processes should comprehensively consider factors such as the nature of the wastewater, the treatment effect of the process, infrastructure investment, operation and maintenance, etc., to ensure that it is technically feasible and economically reasonable. The overall process route is pretreatment-anaerobic-aerobic-(post-treatment) combined process. For example, Chen Minghui et al. used a combined process of hydrolysis adsorption-contact oxidation-filtration to treat comprehensive pharmaceutical wastewater containing artificial insulin, etc., and the effluent quality after treatment was better than the first-level standard of GB8978-1996. The air flotation-hydrolysis-contact oxidation process treats chemical pharmaceutical wastewater, the compound microaerobic hydrolysis-compound aerobic-sand filtration process treats antibiotic wastewater, and the air flotation-UBF-CASS process treats high-concentration traditional Chinese medicine extraction wastewater, etc. have all achieved good results. Effect. 3. The recycling of useful substances in pharmaceutical wastewater promotes clean production in the pharmaceutical industry, improves the utilization rate of raw materials and the comprehensive recovery rate of intermediate products and by-products, and reduces or eliminates pollution in the production process by reforming the process. Due to the particularity of some pharmaceutical production processes, their wastewater contains a large number of recyclable substances. To treat this type of pharmaceutical wastewater, material recovery and comprehensive utilization should first be strengthened. For example, Zhejiang Yiwu Huayi Pharmaceutical Co., Ltd. uses fixed scraper film evaporation, concentration, crystallization, and recovery of (NH4) 2SO4 with a mass fraction of about 30% for the ammonium salt content in its pharmaceutical intermediate wastewater as high as 5% to 10%. NH4NO3 is used as fertilizer or reused, which has obvious economic benefits; a high-tech pharmaceutical company uses stripping method to treat production wastewater with extremely high formaldehyde content. After the formaldehyde gas is recovered, it can be formulated into formalin reagent, and can also be used as a boiler heat source for incineration. .
By recycling formaldehyde, resources can be used sustainably, and the investment cost of the treatment station can be recovered within 4 to 5 years [33], achieving the unification of environmental benefits and economic benefits. But generally speaking, pharmaceutical wastewater has complex components and is difficult to recycle. The recycling process is complex and the cost is high. Therefore, advanced and efficient pharmaceutical wastewater comprehensive treatment technology is the key to completely solving the sewage problem. 4 Conclusion There have been many reports on the research on the treatment of pharmaceutical wastewater. However, due to the diversity of raw materials and processes in the pharmaceutical industry, the quality of wastewater discharged varies widely. Therefore, there is no mature and unified treatment method for pharmaceutical wastewater. The specific process route chosen depends on Nature of wastewater. According to the characteristics of the wastewater, pretreatment should generally be used to improve the biodegradability of the wastewater and initially remove pollutants, followed by biochemical treatment. At present, the development of economical and effective composite water treatment units is an urgent problem to be solved. At the same time, research on cleaner production should be strengthened, and whether wastewater has recycling value and appropriate channels should be considered in the early stage of treatment to achieve the unity of economic and environmental benefits.