Sewage produced by pharmaceutical companies are mostly organic substances with complex structure, toxic, harmful and biologically difficult to degrade, causing serious pollution to water bodies. At the same time, industrial sewage also shows obvious acidity and alkalinity, and some sewage contains too high salt. These characteristics make pharmaceutical sewage become a kind of sewage that is more difficult to treat in the water treatment industry.
The pharmaceutical industry wastewater mainly includes four categories of antibiotic production wastewater, synthetic drug production wastewater, Chinese patent medicine production wastewater, and washing water and washing wastewater of various preparation production processes. Its wastewater is characterized by complex components, high organic content, high toxicity, deep color and high salt content, especially poor biochemical properties, and intermittent discharge, it is difficult to handle industrial wastewater. With the development of China’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 problem for environmental protection today.
Pharmaceutical wastewater treatment process and selection
The water quality characteristics of pharmaceutical wastewater make most of the pharmaceutical wastewater alone unable to meet the standard by biochemical treatment, so the necessary pretreatment must be carried out before biochemical treatment. Generally, a regulating tank should be set up to regulate the water quantity and pH, and a physical-chemical or chemical method should be used as a pretreatment process according to the actual situation to reduce SS, salinity and part of COD in the water, and reduce the biological inhibitory substances in the wastewater, and Improve the degradability of wastewater to facilitate the subsequent biochemical treatment of wastewater.
The pre-treated wastewater can be treated by an anaerobic and aerobic process according to its water quality characteristics. If the effluent requirements are high, the post-treatment needs to be continued after the aerobic process. The selection of specific processes should take into account factors such as the nature of the wastewater, the treatment effect of the process, capital investment, operation and maintenance, etc., so that the technology is feasible and economically reasonable. The overall process route is a combined pretreatment-anaerobic-aerobic- (post-treatment) process. For example, Chen Minghui, etc. used the combined process of hydrolysis, adsorption, contact oxidation and filtration to treat synthetic pharmaceutical wastewater containing artificial insulin. The quality of the effluent after treatment was better than the first-class standard of GB8978-1996. Air floatation-hydrolysis-contact oxidation process for chemical and pharmaceutical wastewater treatment, composite microaerolysis-composite aerobic-sand filtration process for antibiotic wastewater treatment, and air floatation-UBF-CASS process for high-concentration Chinese medicine extraction wastewater have all achieved good treatment. effect.
1 Treatment method of pharmaceutical wastewater
The treatment methods of pharmaceutical wastewater can be summarized as the following: physical and chemical treatment, chemical treatment, biochemical treatment, and combination treatment of various 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 is required as a pre-treatment or post-treatment process of biochemical treatment in the treatment process. The current physical and chemical treatment methods mainly include coagulation, air floatation, adsorption, ammonia stripping, electrolysis, ion exchange and membrane separation methods.
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 of pharmaceutical wastewater, such as aluminum sulfate and polyferric sulfate, etc., used in traditional Chinese medicine wastewater. The key to efficient coagulation is to properly select and add coagulants with excellent performance. In recent years, the development direction of coagulants is from low-molecular to polymeric polymers, from a single type of component function to a composite type. Liu Minghua et al. Used its high-efficiency composite flocculant F-1 to treat the acute syrup production wastewater. At a pH of 6.5 and a flocculant dosage of 300 mg / L, the removal rates of COD, SS and color of the waste liquid Respectively reached 69.7%, 96.4% and 87.5%, its performance is significantly better than PAC (powder activated carbon), polyacrylamide (PAM) and other single flocculants.
1.1.2 Air floatation method
The air floatation method generally includes various forms such as inflatable air floatation, dissolved air floatation, chemical air floatation and electrolytic air floatation. Xinchang Pharmaceutical Factory uses the CAF vortex concave air floatation device to pretreat pharmaceutical wastewater. With the appropriate reagents, the average removal rate of COD is about 25%.
Commonly used adsorbents include activated carbon, activated coal, humic acids, and adsorption resins. Wuhan Jianmin Pharmaceutical Factory uses coal ash adsorption-two-stage aerobic biological treatment process to treat its wastewater. The results showed that the COD removal rate of wastewater by adsorption pretreatment reached 41.1%, and the BOD5 / COD value was increased.
1.1.4 Membrane separation method
Membrane technologies include reverse osmosis, nanofiltration membranes and fiber membranes, which can recover useful substances and reduce the total amount of organic emissions. The main features of this technology are simple equipment, easy operation, no phase change and chemical change, high processing efficiency and energy saving. Juanna et al. Used nanofiltration membranes to conduct a separation experiment on zeomycin wastewater, and found that it not only reduced the inhibitory effect of lincomycin on microorganisms in the wastewater, but also recovered lincomycin.
The treatment of wastewater by this method has the advantages of high efficiency and easy operation, which has been paid attention to by people. At the same time, the electrolytic method has a good decolorization effect. The riboflavin supernatant was pretreated by electrolytic method, and the removal rates of COD, SS and chroma reached 71%, 83% and 67%, respectively.
2 Recycling of useful substances in pharmaceutical wastewater
Promote the clean production of the pharmaceutical industry, improve the utilization rate of raw materials and the comprehensive recovery rate of intermediate products and by-products, and reduce or eliminate pollution in the production process by reforming the process. Due to the particularity of certain pharmaceutical production processes, their wastewater contains a large amount of recyclable materials. For the treatment of this type of pharmaceutical wastewater, material recovery and comprehensive utilization should be strengthened first. A high-tech pharmaceutical company uses the blow-off method to treat the production wastewater with extremely high formaldehyde content. After the formaldehyde gas is recovered, it can be used as a formalin reagent or as a boiler heat source for incineration. Through the recovery of formaldehyde, the resources can be used sustainably, and the investment cost of the treatment station can be recovered within 4 to 5 years , achieving the unification of environmental and economic benefits. But generally speaking, the composition of pharmaceutical wastewater is complex and difficult to recycle, and the recycling process is complicated and the cost is high. Therefore, advanced and efficient pharmaceutical wastewater comprehensive treatment technology is the key to completely solve the wastewater problem.
When applying chemical methods to chemical treatment, excessive use of certain reagents may easily lead to secondary pollution of water bodies, so relevant experimental research work should be done before design. Chemical methods include iron-carbon method, chemical redox method (fenton reagent, H2O2, O3), deep oxidation technology, etc.
2.1 Iron-carbon method
Industrial operation shows that the Fe-C as a pretreatment step of pharmaceutical wastewater, the biodegradability of the effluent can be greatly improved. Lou Maoxing et al  used iron-carbon-microelectrolysis-anaerobic-aerobic-air floatation combined treatment process to treat methrubicin, ciprofloxacin hydrochloride and other pharmaceutical intermediate production wastewater, and the COD removal after iron-carbon treatment The rate reaches 20%, and the final effluent reaches the first-level standard of the National Comprehensive Wastewater Discharge Standard (GB8978-1996).
2.2 Fenton reagent treatment method
The combination of ferrous salt and H2O2 is called Fenton’s reagent, which can effectively remove refractory organics that cannot be removed by traditional wastewater treatment technology. With the deepening of research, ultraviolet light (UV), oxalate (C2O42-), etc. were introduced into Fenton reagent to greatly enhance its oxidizing ability. Cheng Cangcang et al.  used TiO2 as a catalyst and 9 W low-pressure mercury lamp as a light source to treat pharmaceutical wastewater with Fenton reagent, and achieved the effects of 100% decolorization rate and 92.3% COD removal rate, and the nitrobenzene compounds from 8.05 mg / L decreased to 0.41 mg / L.
2.3 Using this method can improve the biodegradability of wastewater, and at the same time has a better removal rate of COD.
For example, Balcioglu et al. Carried out ozone oxidation treatment on the three kinds of antibiotic wastewater. The results show that not only the BOD5 / COD ratio has been increased, but also the COD removal rate is more than 75%.
2.4 Oxidation technology
Also known as advanced oxidation technology, it brings together the latest research results of modern optical, electrical, acoustic, magnetic, materials and other similar disciplines, including electrochemical oxidation method, wet oxidation method, supercritical water oxidation method, photocatalytic oxidation method and Ultrasonic degradation method, etc. Among them, UV photocatalytic oxidation technology has the advantages of novelty, high efficiency, and no selectivity to waste water. 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 less equipment. As a new treatment method, it is receiving more and more attention. Xiao Guangquan et al  used the 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 wastewater reached 96%.
2.5 Biochemical treatment
Biochemical treatment technology is currently widely used in pharmaceutical wastewater treatment technology, including aerobic biological method, anaerobic biological method, aerobic-anaerobic combination methods.
2.6 Aerobic biological treatment
Since pharmaceutical wastewater is mostly high-concentration organic wastewater, the original liquid needs to be diluted during aerobic biological treatment, so the power consumption is large, and the biodegradability of the wastewater is poor, so it is difficult to directly discharge after biochemical treatment. There is not much processing, 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), circulating activated sludge method (CASS method) etc.
2.6.1 Deep well aeration method
Deep well aeration is a high-speed activated sludge system. This method has the advantages of high oxygen utilization rate, small footprint, good treatment effect, low investment, low operating cost, no sludge expansion, and low sludge production. In addition, its thermal insulation effect is good, and the treatment is not affected by climatic conditions, which can ensure the effect of winter wastewater treatment in the northern region. After the biochemical treatment of high-concentration organic wastewater from the Northeast Pharmaceutical General Plant in the deep well aeration tank, the COD removal rate reached 92.7%, which shows that the treatment efficiency is very high, and it is extremely beneficial to the next step of treatment, and the effluent of the process treatment reaches the standard Plays a decisive role.
2.6.2 AB method
The AB method is an ultra-high-load activated sludge method. The removal rate of BOD5, COD, SS, phosphorus and ammonia nitrogen by the AB process is generally higher than that of the conventional activated sludge method. Its outstanding advantages are high load in section A, strong resistance to impact load, and a large buffering effect on pH and toxic substances. It is especially suitable for the treatment of wastewater with high concentration and large changes in water quality and water quantity. Yang Junshi et al. Adopted the hydrolytic acidification-AB biological process to treat antibiotic wastewater. The process is short, energy-saving, and the treatment cost is also lower than the chemical flocculation-biological process of the same kind of wastewater.
2.6.3 Biological contact oxidation method
The technology combines the advantages of activated sludge and biofilm method, and has the advantages of high volume load, low sludge output, strong impact resistance, stable process operation, and convenient management. Many projects use a two-stage method, the purpose of which is to domesticate the dominant strains at different stages, to give full play to the synergy between different microbial populations, and to improve biochemical effects and impact resistance. In the project, anaerobic digestion and acidification are often used as pretreatment steps, and the contact oxidation method is used to treat pharmaceutical wastewater. Harbin North Pharmaceutical Factory adopts hydrolysis acidification-two-stage biological contact oxidation process to treat pharmaceutical wastewater. The operation results show that the process has stable treatment effect and reasonable process combination. With the gradual maturity of the process technology, the application field is also more extensive.
2.6.4 SBR method
The SBR method has the advantages of strong impact load resistance, high sludge activity, simple structure, no need for backflow, flexible operation, small footprint, low investment, stable operation, high substrate removal rate, and good nitrogen and phosphorus removal effects. It is suitable for treating water volume and water quality. Fluctuating wastewater. Wang Zhong ’s experiment with the SBR process to treat pharmaceutical wastewater showed that: the aeration time has a great influence on the treatment effect of the process; the setting of anoxic section, especially the repeated design of anoxic and aerobic, can significantly improve the treatment effect; reaction tank The SBR enhanced treatment process of CIC and PAC can significantly improve the removal effect of the system. In recent years, the process has become more and more perfect, and it is also widely used in the treatment of pharmaceutical wastewater. Qiu Lijun et al. Used hydrolytic acidification-SBR method to treat biological pharmaceutical wastewater, and the effluent quality reached GB8978-1996 first-class standard.
2.7 Anaerobic biological treatment
At present, the treatment of high-concentration organic wastewater at home and abroad is mainly based on the anaerobic method, but the COD of the effluent after treatment by the separate anaerobic method is still high, and generally requires post-treatment (such as aerobic biological treatment). At present, it is still necessary to strengthen the development and design of high-efficiency anaerobic reactors and conduct in-depth research on operating conditions. Successful applications in the treatment of pharmaceutical wastewater include upflow anaerobic sludge bed (UASB), anaerobic composite bed (UBF), anaerobic baffled reactor (ABR), hydrolysis method, etc.
2.7.1 UASB method
The UASB reactor has the advantages of high anaerobic digestion efficiency, simple structure, short hydraulic retention time, and no need for additional sludge return device. When the UASB method is used to treat pharmaceutical production wastewater such as kanamycin, chloramphenicol, VC, SD and glucose, it is usually required that the SS content should not be too high to ensure that the COD removal rate is above 85% to 90%. The COD removal rate of two-stage series UASB can reach more than 90%.
2.7.2 UBF method
The comparison test between UASB and UBF shows that UBF has the characteristics of good reaction mass transfer and separation effect, large biomass and many biological types, high processing efficiency and strong operating stability, and is a practical and efficient anaerobic bioreactor .
2.7.3 Hydrolysis and acidification
The hydrolysis tank 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 need to be sealed and stirred, and there is no three-phase separator, which reduces the cost and facilitates maintenance; it can degrade large molecules in wastewater and organic substances that are not easily biodegradable into small molecules 1. Organic substances that are easily biodegradable, improve the biodegradability of raw water; rapid reaction, small pond volume, less capital investment, and can reduce the amount of sludge. In recent years, the hydrolysis-aerobic process has been widely used in the treatment of pharmaceutical wastewater. For example, a biopharmaceutical plant uses a hydrolysis acidification-two-stage biological contact oxidation process to treat pharmaceutical wastewater. The operation is stable and the organic substance removal effect is significant. COD, BOD5 The removal rates of SS and SS were 90.7%, 92.4% and 87.6%, respectively.
2.8 Anaerobic-aerobic and other combined treatment processes
Because separate aerobic treatment or anaerobic treatment often fails to meet the requirements, the combined processes of anaerobic-aerobic, hydrolytic acidification-aerobic, etc. improve the performance of wastewater biodegradability, impact resistance, investment cost, treatment effect, etc. The performance is obviously superior to the single processing method, so it is widely used in engineering practice. For example, Limin Pharmaceutical Factory adopts anaerobic-aerobic process to treat pharmaceutical wastewater, BOD5 removal rate reaches 98%, COD removal rate reaches 95%, and the treatment effect is stable; Xiao Liping uses micro-electrolysis-anaerobic hydrolysis acidification-SBR process to treat chemistry Synthesizing pharmaceutical wastewater, the results show that the entire series process has strong impact resistance to changes in wastewater water quality and quantity, and the COD removal rate can reach 86% to 92%. It is an ideal process choice for treating pharmaceutical wastewater; Hu Daqiang, etc. In the treatment of pharmaceutical intermediates and pharmaceutical wastewater, the hydrolysis acidification-A / O-catalytic oxidation-contact oxidation process is used. When the COD of the influent is about 12 000 mg / L, the COD of the effluent is less than 300 mg / L; Xu Meiying et al. Biofilm-SBR process for the treatment of pharmaceutical wastewater containing bio-refractory substances, the removal rate of COD can reach 87.5% to 98.31%, much higher than the treatment effect of the biofilm and SBR process alone.
In addition, with the continuous development of membrane technology, the application research of membrane bioreactor (MBR) in the treatment of pharmaceutical wastewater is also gradually deepened. MBR combines the characteristics of membrane separation technology and biological treatment, and has the advantages of high volume load, strong impact resistance, small footprint, and small amount of residual sludge. Bai Xiaohui et al. Adopted the anaerobic-membrane bioreactor process to treat the pharmaceutical intermediate acid chloride wastewater with COD of 25 000 mg / L, and selected the ZKM-W0.5T membrane module produced by Hangzhou Chemical Filtration Membrane Engineering Co., Ltd. for the removal rate of COD by the system Both are maintained at more than 90%; Livinggston and others use the ability of specific bacteria to degrade specific organic substances, and for the first time used an extractive membrane bioreactor to treat industrial wastewater containing 3,4-dichloroaniline, with an HRT of 2 h and a removal rate of 99 %, The ideal treatment effect is obtained. 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.
There have been many reports on the research on the treatment of pharmaceutical wastewater, but due to the diversity of raw materials and processes in the pharmaceutical industry, the quality of wastewater discharged varies widely, so there is no mature and unified treatment method for pharmaceutical wastewater. The specific choice of process route depends on the wastewater. nature. According to the characteristics of the waste water, pretreatment should generally be used to improve the biodegradability of the waste water and the preliminary removal of pollutants, and then combined with 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 consideration should be given to whether the waste water has recycling value and appropriate means in the early stage of treatment to achieve the unity of economic and environmental benefits.