Pharmaceutical industry wastewater mainly includes antibiotic production wastewater and synthetic drug production. Pharmaceutical industry wastewater mainly includes four categories: antibiotic production wastewater, synthetic drug production wastewater, Chinese patent medicine production wastewater, and washing water and washing wastewater in various preparation processes. The wastewater is characterized by complex composition, high organic content, high toxicity, deep chroma and high salt content, especially poor biochemical properties, and intermittent discharge, which is an industrial wastewater that is difficult to treat. With the development of China's pharmaceutical industry, pharmaceutical wastewater has gradually become one of the important sources of pollution. How to treat this type of wastewater is a difficult problem in environmental protection today.
1. Treatment method 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 various methods, and various treatment methods have their own advantages and disadvantages.
1.1 Materialized treatment
According to the water quality characteristics of pharmaceutical wastewater, physicochemical treatment is required as a pretreatment or post-treatment process for biochemical treatment. The 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 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 for traditional Chinese medicine wastewater. The key to efficient coagulation treatment is to properly select and add coagulants with excellent performance. In recent years, the development direction of coagulants has evolved from low molecular to polymeric polymers, from single-component to complex-type functional [3]. Liu Minghua et al [4] treated a high-efficiency composite flocculant F-1 with a high-efficiency composite flocculant F-1 to treat COD, SS and chromaticity of waste liquor at pH 6.5 and flocculant dosage of 300 mg/L. The removal rates are 69.7%, 96.4% and 87.5%, respectively, and their performance is significantly better than PAC (powdered activated carbon), polyacrylamide (PAM) and other single flocculants.
1.1.2 Air floatation method
The air floatation method generally includes various forms such as aeration air floatation, dissolved air flotation, chemical air floatation, and electrolysis air floatation. Xinchang Pharmaceutical Factory uses CAF vortex air flotation device to pretreat pharmaceutical wastewater. With the appropriate agent, the average removal rate of COD is about 25%.
1.1.3 Adsorption method
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 show that the adsorption pretreatment has a COD removal rate of 41.1% and an increase in BOD5/COD.
1.1.4 Membrane separation method
Membrane technology includes reverse osmosis, nanofiltration membranes and fiber membranes to recover useful materials and reduce total emissions 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. Juanna and others used a nanofiltration membrane to separate the cinnamycin wastewater. It was found that both the inhibitory effect of lincomycin on the microorganisms in the wastewater was reduced, and the cinnamycin was recovered.
1.1.5 Electrolysis
The method has the advantages of high efficiency, easy operation and the like, and the electrolysis method has a good decolorization effect. Li Ying [8] pretreated the riboflavin supernatant by electrolysis, and the removal rates of COD, SS and chromaticity reached 71%, 83% and 67%, respectively.
1.2 Chemical treatment
When chemical methods are applied, the excessive use of certain reagents may easily lead to secondary pollution of water bodies. Therefore, 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, and the like.
1.2.1 Iron and carbon method
Industrial operation shows that the biodegradability of effluent can be greatly improved by using Fe-C as a pretreatment step of pharmaceutical wastewater. Lou Maoxing used iron-micro-electrolysis-anaerobic-aerobic-air-floating combined treatment to treat wastewater from pharmaceutical intermediates such as erythromycin and ciprofloxacin. The COD removal rate after treatment with iron and carbon was 20%. %, the final effluent meets the national first-class standard of Integrated Wastewater Discharge Standard (GB8978-1996).
1.2.2 Fenton reagent treatment
The combination of ferrous salt and H2O2 is called Fenton's reagent, which can effectively remove the refractory organic matter that cannot be removed by traditional wastewater treatment technology. With the deepening of the research, ultraviolet light (UV), oxalate (C2O42-) and the like are introduced into the Fenton reagent, so that the oxidation capacity is greatly enhanced. Using TiO2 as catalyst and 9 W low-pressure mercury lamp as the light source, the pharmaceutical wastewater was treated with Fenton reagent, and the decolorization rate was 100%, the COD removal rate was 92.3%, and the nitrobenzene compound decreased from 8.05 mg/L. 0.41 mg/L.
1.2.3 Oxidation method
The method can improve the biodegradability of wastewater and has a good removal rate for COD. For example, Balcioglu and other three antibiotic wastewaters were subjected to ozone oxidation treatment. The results showed that the ozone oxidation wastewater not only increased the ratio of BOD5/COD, but also the COD removal rate was above 75%.
1.2.4 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, wet oxidation, supercritical water oxidation, photocatalytic oxidation and Ultrasonic degradation method, etc. Among them, the ultraviolet photocatalytic oxidation technology has the advantages of novelity, high efficiency, no selectivity to wastewater, especially suitable for the degradation of unsaturated hydrocarbons, and the reaction conditions are mild, no secondary pollution, and has a good application prospect. Compared with ultraviolet, heat, pressure and other treatment methods, ultrasonic treatment of organic matter is more direct, and the requirements for equipment are lower. As a new type of treatment method, more and more attention is being paid. Xiao Guangquan et al [13] treated the pharmaceutical wastewater with ultrasonic-aerobic biological contact method. Under ultrasonic treatment for 60 s and power of 200 w, the total COD removal rate of wastewater was 96%.
1.3 Biochemical treatment
Biochemical treatment technology is a widely used treatment technology for pharmaceutical wastewater, including aerobic biological method, anaerobic biological method, aerobic-anaerobic combination method.
1.3.1 Aerobic biological treatment
Since most of the pharmaceutical wastewater is high-concentration organic wastewater, it is generally necessary to dilute the stock solution when performing aerobic biological treatment. Therefore, the power consumption is large, and the wastewater is biodegradable, and it is difficult to directly discharge the standard after biochemical treatment. Therefore, aerobic use alone. There are not many treatments, and general pretreatment is required. Commonly used aerobic biological treatment methods include activated sludge method, deep well aeration method, adsorption biodegradation method (AB method), contact oxidation method, sequencing batch intermittent activated sludge method (SBR method), and circulating activated sludge method. (CASS law) and so on.
(1) Deep well aeration method
Deep well aeration is a high-speed activated sludge system. The method has the advantages of high oxygen utilization rate, small floor space, good treatment effect, low investment, low operating cost, no sludge expansion, and low mud production. In addition, its heat preservation 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 high-concentration organic wastewater from the Northeast Pharmaceutical 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. Play a decisive role.
(2) AB method
The AB method is an ultra-high load activated sludge process. The removal rate of BOD5, COD, SS, phosphorus and ammonia nitrogen by AB process is generally higher than that of conventional activated sludge process. Its outstanding advantages are high load in section A, strong impact load resistance, and 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 and other methods use the hydrolysis 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 kind of wastewater.
(3) Biological contact oxidation method
The technology integrates the advantages of activated sludge and biofilm method, and has the advantages of high volumetric load, low sludge production, strong impact resistance, stable process operation and convenient management. Many projects use a two-stage method, which aims to acclimate the dominant strains at different stages, give full play to the synergy between different microbial populations, and improve biochemical effects and impact resistance. In the engineering, anaerobic digestion and acidification are often used as pretreatment steps, and the contact oxidation process is used to treat pharmaceutical wastewater. Harbin North Pharmaceutical Factory used hydrolysis acidification-two-stage biological contact oxidation process to treat pharmaceutical wastewater. The operation results show that the treatment effect is stable and the process combination is reasonable. With the gradual maturity of the process technology, the application field is also more extensive.
(4) SBR method
The SBR method has the advantages of strong impact load resistance, high sludge activity, simple structure, no need for reflow, flexible operation, small land occupation, low investment, stable operation, high matrix removal rate, good nitrogen and phosphorus removal effect, etc. Fluctuating wastewater. The experiment of treating pharmaceutical wastewater with SBR process shows that the aeration time has a great influence on the treatment effect of the process; setting the anoxic section, especially the repeated design of anoxic and aerobic, can significantly improve the treatment effect; The SBR strengthening treatment process with PAC can significantly improve the removal effect of the system. In recent years, the process has become more and more perfect, and it has been widely used in the treatment of pharmaceutical wastewater. The bio-pharmaceutical wastewater has been treated by hydrolysis acidification-SBR method, and the effluent quality has reached the first-class standard of GB8978-1996.
1.3.2 Anaerobic biological treatment
At present, the treatment of high-concentration organic wastewater at home and abroad is mainly based on anaerobic method, but the effluent COD is still high after treatment by a separate anaerobic method, 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 study of operating conditions. The most successful applications in the treatment of pharmaceutical wastewater are upflow anaerobic sludge blanket (UASB), anaerobic composite bed (UBF), anaerobic baffled reactor (ABR), hydrolysis, and the like.
(1) UASB method
The UASB reactor has the advantages of high anaerobic digestion efficiency, simple structure, short hydraulic retention time, and no need for a separate sludge reflux device. When UASB is used to treat pharmaceutical production wastewater such as kanamycin, chlorin, VC, SD and glucose, the SS content is usually not too high to ensure 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 method
Buying Wenning et al. conducted a comparative test of UASB and UBF. The results show that UBF has the characteristics of good mass transfer and separation effect, large biomass and biological species, high processing efficiency and strong operational stability. Oxygen bioreactor.
(3) Hydrolysis acidification
The hydrolysis tank is referred to as a hydrolyzed upflow sludge bed (HUSB), which is an improved UASB. Compared with the whole process anaerobic tank, the hydrolysis tank has the following advantages: no need for sealing, stirring, no three-phase separator, which reduces the cost and facilitates maintenance; it can degrade large molecules and non-biodegradable organic substances in sewage into small molecules. Organic matter that is easily biodegradable, improves the biodegradability of raw water; rapid reaction, small tank volume, less capital investment, and reduced sludge volume. 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 matter removal effect is remarkable. COD, BOD5 The removal rates of SS and SS 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 can not meet the requirements, anaerobic-aerobic, hydrolysis acidification-aerobic and other combined processes improve the biodegradability, impact resistance, investment cost and treatment effect of wastewater. Out of the performance of a single processing method, it has been widely used in engineering practice. For example, a pharmaceutical factory uses anaerobic-aerobic process to treat pharmaceutical wastewater, BOD5 removal rate is 98%, COD removal rate is 95%, and the treatment effect is stable. Micro-electrolysis-anaerobic hydrolysis acidification-SBR process is used to treat chemical synthesis of pharmaceutical wastewater. The results show that the whole series process has strong impact resistance to the change of wastewater quality and water volume, and the COD removal rate can reach 86%～92%, which is an ideal process choice for treating pharmaceutical wastewater; In the treatment of wastewater, the hydrolytic acidification-A/O-catalytic oxidation-contact oxidation process is adopted. When the influent COD is about 12 000 mg/L, the effluent COD is less than 300 mg/L; the biofilm-SBR method is used to treat the biological The removal rate of COD in pharmaceutical wastewater with refractory can reach 87.5%~98.31%, which is much higher than the treatment effect of biofilm method and SBR method alone.
In addition, with the continuous development of membrane technology, the application research of membrane bioreactor (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 floor space and less residual sludge. The anaerobic-membrane bioreactor process was used to treat the pharmaceutical intermediate acid chloride wastewater with COD of 25 000 mg/L. The COD removal rate of the system was maintained above 90%. The ability to degrade specific organic matter by obligate bacteria was adopted for the first time. The extraction membrane bioreactor was used to treat industrial wastewater containing 3,4-dichloroaniline. The HRT was 2 h, and the removal rate reached 99%, and the ideal treatment effect was obtained. Despite the 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 treatment alone, so necessary pretreatment must be carried out before biochemical treatment. Generally, a regulating tank should be set to adjust the water quality and pH, and according to the actual situation, a physicochemical or chemical method is used as a pretreatment process to reduce the SS, salinity and partial COD in the water, and reduce the biological inhibitory substances in the wastewater, and Improve the degradability of wastewater to facilitate subsequent biochemical treatment of wastewater.
The pretreated wastewater can be treated according to its water quality characteristics by an anaerobic and aerobic process. If the effluent requirements are high, the aerobic treatment process should be continued after the aerobic treatment process. The choice of specific process should take into account the nature of the wastewater, the treatment effect of the process, infrastructure investment and operation and maintenance, etc., so that the technology is feasible and economical. The overall process route is a pretreatment-anaerobic-aerobic- (post-treatment) combination process. The comprehensive pharmaceutical wastewater containing artificial insulin and the like is treated by a hydrolysis adsorption-contact oxidation-filtration combination process, and the treated effluent water quality is superior to the first-class standard of GB8978-1996. Air flotation-hydrolysis-contact oxidation process for chemical pharmaceutical wastewater, composite micro-oxygen hydrolysis-composite aerobic-sand filtration process for antibiotic wastewater, air flotation-UBF-CASS process for treatment of high-concentration Chinese medicine extraction wastewater, etc. effect.
3. Recycling of useful materials in pharmaceutical wastewater
Promote clean production in 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 through reforming processes. Due to the particularity of certain pharmaceutical production processes, the wastewater contains a large amount of recyclable materials. For the treatment of such pharmaceutical wastewater, material recovery and comprehensive utilization should be strengthened first. For the ammonium salt content of the pharmaceutical intermediate wastewater up to 5% to 10%, the fixed scraper film is used for evaporation, concentration, crystallization, and the recovery of (NH4)2SO4 and NH4NO3 with a mass fraction of about 30% is used as a fertilizer or reuse. Obvious economic benefits; a high-tech pharmaceutical company uses blow-off method to treat production wastewater with extremely high formaldehyde content. After recovery, formaldehyde gas can be formulated into formalin reagent or burned as boiler heat source. 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. However, in general, pharmaceutical wastewater has complex composition and is difficult to recycle, and the recycling process is complicated and the cost is high. Therefore, advanced and efficient integrated wastewater treatment technology is the key to completely solve the sewage problem.
4, the conclusion
There have been many reports on the treatment of pharmaceutical wastewater. However, due to the diversity of raw materials and processes in the pharmaceutical industry, the wastewater quality of wastewater is very different. Therefore, pharmaceutical wastewater does not have a mature and unified treatment method. Which process route is selected depends on the wastewater. nature. According to the characteristics of the wastewater, it is generally necessary to pre-treat to improve the biodegradability of the wastewater and to initially remove the pollutants, and then combine biochemical treatment. At present, the development of an economical and effective composite water treatment unit is an urgent problem to be solved. At the same time, research on cleaner production should be strengthened, and the value of waste water recycling and appropriate ways should be considered in the early stage of treatment to achieve the unification of economic and environmental benefits.
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