Pharmaceutical wastewater treatment methods

Treatment methods for pharmaceutical wastewater can be summarized as follows: physicochemical treatment, chemical treatment, biochemical treatment, and combined treatment of multiple methods.

1. Physicochemical Treatment According to the characteristics of pharmaceutical wastewater, physicochemical treatment needs to be used as a pretreatment or post-treatment process for biochemical treatment. Currently, the applied physicochemical treatment methods mainly include coagulation, flotation, adsorption, ammonia stripping, electrolysis, ion exchange, and membrane separation.

(1) Coagulation This technology is a commonly used water treatment method 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 lies in the appropriate selection and addition of high-performance coagulants. In recent years, the development direction of coagulants has been from low molecular weight to polymeric high molecular weight, and from single-component and single-function to composite type.

(2) Flotation Flotation generally includes various forms such as air flotation, dissolved air flotation, chemical flotation, and electrolytic flotation. Xinchang Pharmaceutical Factory uses a CAF vortex air flotation device for the pretreatment of pharmaceutical wastewater. With appropriate chemical agents, the average removal rate of COD is about 25%.

(3) Adsorption Commonly used adsorbents include activated carbon, activated coke, humic acid, and adsorption resins. A pharmaceutical factory uses coal ash adsorption-two-stage aerobic biological treatment process to treat its wastewater. The results show that the adsorption pretreatment achieves a COD removal rate of 41.1% and improves the BOD5/COD value.

(4) Membrane Separation Membrane technology includes reverse osmosis, nanofiltration membranes, and fiber membranes, which can recover useful substances and reduce the total amount of organic matter discharged. The main characteristics of this technology are simple equipment, convenient operation, no phase change or chemical change, high processing efficiency, and energy saving. Zhu Anna et al. used nanofiltration membranes to conduct separation experiments on jiamycin wastewater and found that it not only reduced the inhibitory effect of jiamycin on microorganisms in wastewater but also recovered jiamycin.

(5) Electrolysis This method has attracted attention for its high efficiency and ease of operation in wastewater treatment, and it also 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.

2. Chemical Treatment Chemical methods include iron-carbon method, chemical oxidation-reduction method (Fenton reagent, H2O2, O3), and advanced oxidation technology.

(1) Iron-Carbon Method Industrial operation shows that using Fe-C as a pretreatment step for pharmaceutical wastewater can greatly improve the biodegradability of the effluent. Using iron-carbon-microelectrolysis-anaerobic-aerobic-flotation combined treatment process to treat pharmaceutical intermediate production wastewater, the COD removal rate reaches 20% after iron-carbon treatment.

(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 (C2O4-), etc. are introduced into the Fenton reagent, greatly enhancing its oxidation ability. Using TiO2 as a catalyst and a 9W low-pressure mercury lamp as a light source, the Fenton reagent was used to treat pharmaceutical wastewater, achieving complete decolorization, a COD removal rate of 92.3%, and the compound concentration decreased from 8.05 mg/L to 0.41 mg/L. This method can improve the biodegradability of wastewater and has a good COD removal rate.

(3) Oxidation Technology Also known as advanced oxidation technology, it mainly includes electrochemical oxidation, wet oxidation, supercritical water oxidation, photocatalytic oxidation, and ultrasonic degradation. Among them, ultraviolet photocatalytic oxidation technology has the advantages of being novel, efficient, and non-selective for wastewater, especially suitable for the degradation of unsaturated hydrocarbons, and the reaction conditions are relatively mild, with no secondary pollution, and has good application prospects. Compared with ultraviolet light, heat, and pressure treatment methods, ultrasound is more direct in treating organic matter and has lower equipment requirements. As a new treatment method, it is receiving more and more attention.

3. Biochemical Treatment Biochemical treatment technology is a widely used treatment technology for pharmaceutical wastewater, including aerobic biological methods, anaerobic biological methods, and aerobic-anaerobic combined methods.

(1) Aerobic Biological Treatment Since most pharmaceutical wastewater is high-concentration organic wastewater, dilution is generally required when performing aerobic biological treatment, resulting in high energy consumption and poor biodegradability of wastewater. It is difficult to directly achieve discharge standards after biochemical treatment, so aerobic treatment alone is rarely 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, sequencing batch reactor (SBR method), and completely mixed activated sludge process (CASS method).

(2) Anaerobic Biological Treatment Currently, the main method for treating high-concentration organic wastewater at home and abroad is anaerobic treatment, but the COD of the effluent after anaerobic treatment alone is still high, and post-treatment (such as aerobic biological treatment) is generally required. Further development and design of high-efficiency anaerobic reactors and in-depth research on operating conditions are still needed. Anaerobic sludge bed (UASB), anaerobic composite bed (UBF), anaerobic baffle reactor (ABR), and hydrolysis methods have been successfully applied in pharmaceutical wastewater treatment.

(3) Anaerobic-Aerobic and Other Combined Treatment Processes Since single aerobic or anaerobic treatment often cannot meet the requirements, anaerobic-aerobic, hydrolysis-acidification-aerobic, and other combined processes have shown significantly better performance than single treatment methods in terms of improving wastewater biodegradability, shock resistance, investment cost, and treatment effect, and have been widely used in engineering practice.