Does high concentration pharmaceutical wastewater need to be diluted before it can enter the biochemical system?

Study on pharmaceutical wastewater treatment technology Pharmaceutical industrial wastewater mainly includes four categories: wastewater from antibiotic production, wastewater from synthetic drug production, wastewater from Chinese patent medicine production, and washing water and washing wastewater from the production of various preparations. Its wastewater has the characteristics of complex composition, high organic content, high toxicity, deep chroma and high salt content, especially poor biodegradability, and intermittent discharge, which is difficult to treat. With the development of China's pharmaceutical industry, pharmaceutical wastewater has gradually become one of the important pollution sources. How to treat this kind of wastewater is a difficult problem in environmental protection today. 1 treatment methods of pharmaceutical wastewater The treatment methods of pharmaceutical wastewater can be summarized as: physical and chemical treatment, chemical treatment, biochemical treatment and the combination of various methods. Each treatment has its own advantages and disadvantages. 1. 1 Physical and chemical treatment According to the water quality characteristics of pharmaceutical wastewater, it is necessary to adopt physical and chemical treatment as the pretreatment or post-treatment process of biochemical treatment. At present, physical and chemical treatment methods mainly include coagulation, air flotation, adsorption, ammonia stripping, electrolysis, ion exchange, membrane separation and so on. Coagulation (1. 1) This technology is a widely used water quality treatment method at home and abroad, which is widely used in the pretreatment and post-treatment of pharmaceutical wastewater, such as aluminum sulfate and polymeric ferric sulfate used in traditional Chinese medicine wastewater. The key to efficient coagulation treatment lies in the selection and addition of coagulant with excellent performance. In recent years, the development direction of coagulant is from low molecular to high molecular polymer, from single component and function to compound development. Liu Minghua et al. used his high-efficient composite flocculant F- 1 to treat the wastewater from the production of fast syrup. When the pH is 6.5 and the dosage of flocculant is 300 mg/L, the removal rates of COD, SS and chromaticity of wastewater reach 69.7%, 96.4% and 87.5% respectively, and its performance is obviously better than that of single flocculant such as powdered activated carbon (PAC) and polyacrylamide (PAM). 1. 1.2 flotation usually includes aerated flotation, solution flotation, chemical flotation and electrolytic flotation. Xinchang Pharmaceutical Factory used CAF vortex-concave air flotation device to pretreat pharmaceutical wastewater, and added appropriate chemicals, the average removal rate of COD could reach about 25%. 1. 1.3 adsorbents commonly used in adsorption method include activated carbon, activated coal, humic acid, adsorption resin, etc. Wuhan Jianmin Pharmaceutical Factory used fly ash adsorption-two-stage aerobic biological treatment process to treat its wastewater. The results showed that the removal rate of COD in wastewater by adsorption pretreatment reached 4 1. 1%, and the BOD5/COD value was improved. 1. 1.4 membrane separation technology includes reverse osmosis, nanofiltration membrane and fiber membrane, which can recover useful substances and reduce the total discharge of organic matter. The main characteristics of this technology are simple equipment, convenient operation, no phase change and chemical change, high treatment efficiency and energy saving. Juana et al. used nanofiltration membrane to separate lincomycin wastewater, and found that it not only reduced the inhibition of lincomycin on microorganisms in wastewater, but also recovered lincomycin. 1. 1.5 electrolysis has been paid attention to because of its high efficiency and easy operation, and the decoloration effect of electrolysis is good. Mars pretreated the supernatant of riboflavin by electrolysis, and the removal rates of COD, SS and chromaticity reached 765, 438+0%, 83% and 67% respectively. When chemical methods are used in the chemical treatment of 1.2, excessive use of some reagents will easily lead to secondary pollution of water, so relevant experimental research work should be done well before design. Chemical methods include iron-carbon method, chemical oxidation-reduction method (Fenton reagent, H2O2, O3) and advanced oxidation technology. The industrial operation of 1.2. 1 iron-carbon process shows that the biodegradability of the effluent can be greatly improved by using iron-carbon as the pretreatment step of pharmaceutical wastewater. Lou Maoxing et al. [9] used the combined treatment process of iron-carbon-micro-electrolysis-anaerobic-aerobic-air flotation to treat the wastewater from pharmaceutical intermediates such as erythromycin and ciprofloxacin hydrochloride. After iron-carbon treatment, the removal rate of COD reached 20%, and the final effluent reached the first-class standard of the national integrated wastewater discharge standard (GB 8978- 1996). 1.2.2 Fenton reagent treatment method ferrous salt combined with H2O2 is called Fenton reagent, which can effectively remove refractory organic substances that cannot be removed by traditional wastewater treatment technology. With the development of research, ultraviolet (UV) and oxalate (C2O42-) were introduced into Fenton reagent, which greatly enhanced its oxidation ability. Cheng Cangcang et al. [10] used TiO2 _ 2 as catalyst and 9 W low-pressure mercury lamp as light source to treat pharmaceutical wastewater with Fenton reagent. The decolorization rate was 100% and the COD removal rate was 92.3%. The nitrobenzene compounds decreased from 8.05 mg/L to 0.41mg/L. For example, Balcioglu used ozone oxidation to treat three kinds of antibiotic wastewater. The results show that not only the ratio of BOD5/COD is increased, but also the removal rate of COD is over 75%. 1.2.4 oxidation technology, also known as advanced oxidation technology, brings together the latest research results of modern optics, electricity, sound, magnetism, materials and other related disciplines, mainly including electrochemical oxidation, wet oxidation, supercritical water oxidation, photocatalytic oxidation, ultrasonic degradation and so on. Among them, ultraviolet catalytic oxidation technology has the advantages of novelty, high efficiency and no selectivity to wastewater, and is especially suitable for the degradation of unsaturated hydrocarbons. The reaction conditions are mild and there is no secondary pollution, so it has a good application prospect. Compared with ultraviolet, heat and pressure treatment methods, ultrasonic treatment of organic matter is more direct and requires less equipment. As a new treatment, it is attracting 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 wastewater reached 96%. 1.3 biochemical treatment biochemical treatment technology is a widely used pharmaceutical wastewater treatment technology at present, including aerobic biological method, anaerobic biological method, aerobic-anaerobic combined method and so on. 1.3. 1 aerobic biological treatment Because pharmaceutical wastewater is mostly high-concentration organic wastewater, it is usually necessary to dilute the original solution during aerobic biological treatment, so the power consumption is high, the biodegradability of wastewater is poor, and it is difficult to discharge directly after biochemical treatment. Therefore, aerobic treatment alone is not much, and pretreatment is generally needed. Commonly used aerobic biological treatment methods include activated sludge method, deep well aeration method, adsorption biodegradation method (AB method), contact oxidation method, sequencing batch batch batch activated sludge method (SBR method), circulating activated sludge method (CASS method) and so on. (1) Deep well aeration is a high-speed activated sludge system, which has the advantages of high oxygen utilization rate, small floor space, good treatment effect, low investment, low operating cost, no sludge bulking and low sludge output. In addition, the heat preservation effect is good, and the treatment is not affected by climatic conditions, which can ensure the effect of sewage treatment in northern winter. After biochemical treatment, the removal rate of COD in high-concentration organic wastewater from Northeast Pharmaceutical Factory reached 92.7%, which indicated that the treatment efficiency was high, which was extremely beneficial to the next treatment and played a decisive role in the effluent standard of process treatment. (2)AB process AB process belongs to ultra-high load activated sludge process. The removal rate of BOD5, COD, SS, phosphorus and ammonia nitrogen by AB method is generally higher than that by conventional activated sludge method. Its outstanding advantages are high class A load, strong impact load resistance, and great buffering effect on pH and toxic substances, and it is especially suitable for treating sewage with high concentration and great changes in water quality and quantity. Yang Junshi and others used hydrolytic acidification -AB biological process to treat antibiotic wastewater. The process is short, energy-saving and the treatment cost is lower than that of chemical flocculation-biological treatment of similar wastewater. (3) Biological contact oxidation combines the advantages of activated sludge process and biofilm process, and has the advantages of high volume load, low sludge output, strong impact resistance, stable process operation and convenient management. Many projects adopt two-stage method, aiming at domesticating dominant strains in different stages, giving full play to the synergy between different microbial populations, and improving biochemical effects and impact resistance. Anaerobic digestion and acidification are commonly used as pretreatment processes in engineering, and pharmaceutical wastewater is treated by contact oxidation. Harbin North Pharmaceutical Factory used hydrolytic 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. With the gradual maturity of this technology, the application field is more extensive. (4)SBR process SBR process has the advantages of strong impact load resistance, high sludge activity, simple structure, no need for backflow, flexible operation, less land occupation, low investment, stable operation, high substrate removal rate and good nitrogen and phosphorus removal effect, and is suitable for treating wastewater with large fluctuation in water quantity and quality. Wang Zhong's experiment of treating pharmaceutical wastewater by SBR method shows that aeration time has great influence on the treatment effect of this process. Setting the anoxic section, especially the alternating design of anoxic and aerobic, can obviously improve the treatment effect; The SBR enhanced treatment process with PAC in the reaction tank can obviously improve the removal effect of the system. In recent years, the process has become increasingly perfect and has been widely used in pharmaceutical wastewater treatment. Qiu Lijun et al. used hydrolytic acidification-SBR process to treat biopharmaceutical wastewater, and the effluent quality reached the first-class standard of GB 8978- 1996. 1.3.2 Anaerobic biological treatment At present, the main method for treating high-concentration organic wastewater at home and abroad is anaerobic treatment, but the effluent COD is still high after anaerobic treatment alone, and post-treatment (such as aerobic biological treatment) is generally needed. 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. Upflow anaerobic sludge bed (UASB), anaerobic composite bed (UBF), anaerobic baffled reactor (ABR) and hydrolysis method have been successfully applied to the treatment of pharmaceutical wastewater. (1)UASB reactor has the advantages of high anaerobic digestion efficiency, simple structure, short hydraulic retention time and no need for additional sludge reflux device. When using UASB method to treat pharmaceutical wastewater such as kanamycin, chlorophyllase, VC, SD, glucose, etc., it is usually required that SS content should not be too high to ensure the removal rate of COD is above 85% ~ 90%. The COD removal rate of two-stage series UASB can reach above 90%. (2) UBF Famaiwenning and others made a comparative experiment between UASB and UBF. The results show that UBF is a practical and efficient anaerobic bioreactor, which has the characteristics of good mass transfer and separation effect, large biomass, many kinds of organisms, high treatment efficiency and strong operation stability. (3) Hydrolysis acidification 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 is beneficial to maintenance; It can degrade macromolecules and refractory organics in sewage into micromolecules and biodegradable organics, and improve the biodegradability of raw water. Rapid reaction, small pool, less capital investment and less sludge. In recent years, hydrolysis-aerobic process has been widely used in pharmaceutical wastewater treatment. For example, a biopharmaceutical factory uses hydrolytic acidification-two-stage biological contact oxidation process to treat pharmaceutical wastewater, which runs stably and has obvious organic matter removal effect. The removal rates of COD, BOD5 and SS are 90.7%, 92.4% and 87.6% respectively. 1.3.3 Combined treatment processes such as anaerobic-aerobic are often unable to meet the requirements due to aerobic treatment or anaerobic treatment alone, while combined processes such as anaerobic-aerobic and hydrolytic acidification-aerobic have obvious advantages over single treatment methods in improving the biodegradability, impact resistance, investment cost and treatment effect of wastewater, so they have been widely used in engineering practice. For example, when Limin Pharmaceutical Factory adopts anaerobic-aerobic process to treat pharmaceutical wastewater, the removal rate of BOD5 reaches 98% and the removal rate of COD reaches 95%, and the treatment effect is stable. Xiao Liping used micro-electrolysis-anaerobic hydrolysis acidification-SBR process to treat chemical synthesis of pharmaceuticals wastewater. The results show that the whole series process has strong impact resistance to the change of wastewater quality and quantity, and the COD removal rate can reach 86% ~ 92%, which is an ideal process choice for pharmaceutical wastewater treatment. Hu Daqiang and others used hydrolytic acidification -A/O- catalytic oxidation-contact oxidation process to treat pharmaceutical intermediate wastewater. When the influent COD is about 12 000 mg/L, the effluent COD is less than 300 mg/L; Xu Meiying et al. used biofilm -SBR process to treat pharmaceutical wastewater containing biodegradable substances, and the COD removal rate can reach 87.5% ~ 98.35438+0%, which is much higher than that of biofilm process and SBR process alone. In addition, with the continuous development of membrane technology, the application research of membrane bioreactor in pharmaceutical wastewater treatment has 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 floor space and less excess sludge. Bai Xiaohui and others used anaerobic-membrane bioreactor process to treat pharmaceutical intermediate acyl chloride wastewater with COD of 25 000 mg/L, and chose ZKM-W0.5T membrane module produced by Hanghua Membrane Engineering Company. The removal rate of COD in the system remains above 90%. Livinggston et al. first used the ability of specialized bacteria to degrade specific organic matter to treat industrial wastewater containing 3,4-dichloroaniline. The hydraulic retention time was 2 h, and the removal rate reached 99%, which achieved the ideal treatment effect. Although membrane pollution still exists, with the continuous development of membrane technology, MBR will be widely used in the field of pharmaceutical wastewater treatment. The choice of treatment technology and water quality characteristics of pharmaceutical wastewater makes most pharmaceutical wastewater unable to meet the standard by biochemical treatment alone, so necessary pretreatment must be carried out before biochemical treatment. Generally, regulating tanks should be set up to regulate water quality, water quantity and pH, and some physicochemical or chemical methods should be adopted as pretreatment processes according to the actual situation, so as to reduce ss, salinity and partial COD in the water, reduce biological inhibitory substances in the wastewater, improve the biodegradability of the wastewater, and be beneficial to the subsequent biochemical treatment of the wastewater. The pretreated wastewater can be treated by anaerobic and aerobic processes according to its water quality characteristics. If the requirements for wastewater are high, post-treatment should be continued after aerobic treatment. The selection of specific process should comprehensively consider the nature of wastewater, treatment effect of process, capital construction investment, operation and maintenance and other factors, so as to make it technically feasible, economical and reasonable. The overall process route is pretreatment-anaerobic-aerobic-(post-treatment) combined process. For example, Chen Minghui et al. used the combined process of hydrolytic adsorption-contact oxidation-filtration to treat the comprehensive pharmaceutical wastewater containing artificial insulin, and the treated effluent quality was better than the first-class standard of GB 8978- 1996. Chemical pharmaceutical wastewater was treated by air flotation-hydrolysis-contact oxidation process, antibiotic wastewater was treated by composite micro-oxygen hydrolysis-composite aerobic-sand filtration process, and high-concentration Chinese medicine extraction wastewater was treated by air flotation-UBF-CASS process, all of which achieved good treatment results. The recycling of useful substances in pharmaceutical wastewater promotes the clean production of pharmaceutical industry, improves the utilization rate of raw materials and the comprehensive recovery rate of intermediate products and by-products, and reduces or eliminates the pollution in the production process through process transformation. Due to the particularity of some pharmaceutical production processes, their wastewater contains a lot of recyclable substances. To treat this kind of pharmaceutical wastewater, we must first strengthen the material recovery and comprehensive utilization. For example, Zhejiang Yiwu Huayi Pharmaceutical Co., Ltd. recovered about 30% of (NH4)2SO4 and NH4NO3 by fixed scraping film evaporation, concentration and crystallization as fertilizers or ammonium salts in its pharmaceutical intermediate wastewater, which had obvious economic benefits. A high-tech pharmaceutical enterprise uses stripping method to treat production wastewater with high formaldehyde content. Formaldehyde gas can be made into formalin reagent after recovery, and can also be used as boiler heat source for incineration. By recycling formaldehyde, resources can be continuously utilized, and the investment cost of the treatment station can be recovered within 4 ~ 5 years [33], realizing the unification of environmental benefits and economic benefits. But generally speaking, pharmaceutical wastewater has complex components, difficult recovery, complex recovery process and high cost. Therefore, advanced and efficient comprehensive treatment technology of pharmaceutical wastewater is the key to completely solve the sewage problem. Conclusion There have been many reports on the treatment of pharmaceutical wastewater, but because of the diversity of raw materials and processes in pharmaceutical industry, the quality of discharged wastewater is very different, so there is no mature and unified treatment method for pharmaceutical wastewater, and the specific process route chosen depends on the nature of wastewater. According to the characteristics of wastewater, pretreatment should be generally used to improve the biodegradability of wastewater and remove pollutants initially, and then combined with biochemical treatment. At present, it is an urgent problem to develop an economical and effective composite water treatment device. At the same time, we should strengthen the research on cleaner production, and consider whether the wastewater has the value of recycling and appropriate ways in the early stage of treatment, so as to achieve the unity of economic benefits and environmental benefits.