Application of Advanced Oxidation Technology in Pharmaceutical Wastewater Treatment

Application of Advanced Oxidation Technology in Pharmaceutical Wastewater Treatment

Pharmaceutical wastewater contains high concentrations of organic matter and toxic substances. If discharged without effective treatment, it poses a serious threat to the natural environment and public health. Traditional treatment methods have certain limitations, while the emerging advanced oxidation technology offers new solutions for the treatment of pharmaceutical wastewater.

Overview of Pharmaceutical Wastewater

Pharmaceutical wastewater mainly comes from various stages of pharmaceutical production, and its composition and properties vary due to different production processes and raw materials. According to production types, it can be classified into wastewater from antibiotic production, traditional Chinese medicine production, chemical synthesis drug production, and biopharmaceutical production, etc. Antibiotic production wastewater contains high levels of antibiotic residues, fermentation products, and organic solvents; wastewater from traditional Chinese medicine production is rich in plant extraction residues, pigments, and other organic substances; chemical synthesis drug wastewater has a complex composition with a large amount of organic compounds, acids, and bases; biopharmaceutical wastewater mainly consists of fermentation waste liquid and culture medium residues. These different types of wastewater pose a high risk of pollution to the environment.

Common pollutants in pharmaceutical wastewater include high-concentration organic matter, antibiotics, heavy metals, acid-base compounds, and suspended solids, etc. These pollutants have high COD, high color intensity, and biological toxicity, making them difficult to effectively remove through conventional treatment methods. Antibiotics and other drug components entering the environment can easily lead to the generation and spread of antibiotic-resistant strains, threatening the balance of the ecosystem. The accumulation of heavy metals and toxic organic substances can cause long-term pollution to water bodies and soil, seriously affecting the health of animals, plants, and humans. The effective treatment of pharmaceutical wastewater has significant environmental and social significance.

Conventional treatment methods

Physical treatment methods are the primary approaches for pharmaceutical wastewater treatment, mainly including filtration, sedimentation, and flotation processes. Filtration can remove solid particles from the wastewater, sedimentation separates larger particles by gravity, and flotation uses bubbles to float suspended solids to the surface. This method is simple and cost-effective, but it has limited effectiveness in removing dissolved organic matter and fine particles, and can only be used as a preliminary treatment to reduce the burden on subsequent processes.

Chemical treatment methods involve adding chemical agents to treat wastewater, covering oxidation-reduction reactions, neutralization reactions, and precipitation reactions. Common techniques include chemical precipitation, oxidation-reduction reactions, and coagulation and flocculation. It can effectively remove dissolved pollutants and toxic substances from wastewater, but it may cause secondary pollution, has a relatively high treatment cost, and requires professional personnel for appropriate selection and management of chemicals.

Biological treatment methods utilize microorganisms to degrade organic matter in wastewater, such as the activated sludge process, biological filters, and stabilization ponds. The activated sludge process cultivates activated sludge to degrade organic matter; biological filters use microorganisms attached to filter media to decompose pollutants; and stabilization ponds utilize natural conditions and microorganisms for treatment. This method is highly effective in removing organic matter but has limited effectiveness in treating refractory substances and requires strict control of the operating environment.

The principle of advanced oxidation technology

Advanced Oxidation Processes (AOPs) are treatment technologies that use strong oxidants to remove organic pollutants from wastewater. They effectively decompose refractory organic pollutants by generating intermediate products with strong oxidation capabilities, such as hydroxyl radicals (·OH). The main feature of this technology is its ability to efficiently remove pollutants from pharmaceutical wastewater under restricted reaction conditions, making it suitable for treating wastewater that is difficult to handle with traditional methods.

The core principle of advanced oxidation technology is to oxidize and degrade pollutants in wastewater using highly reactive oxidants. Among them, hydroxyl radicals are strong oxidants with an oxidation capacity far exceeding that of conventional oxidants, capable of effectively decomposing complex organic pollutants. AOPs include ozone oxidation, Fenton oxidation, and photocatalytic oxidation, among others. Each method has a slightly different generation principle and reaction mechanism. Ozone oxidation uses ozone as the main oxidant to generate hydroxyl radicals; Fenton oxidation utilizes the reaction between hydrogen peroxide and iron ions to generate hydroxyl radicals; photocatalytic oxidation generates hydroxyl radicals under ultraviolet light irradiation with the help of a photocatalyst. These methods have their own advantages and disadvantages and need to be comprehensively considered in practical applications.

Advanced oxidation processes (AOPs) have significant advantages in treating highly refractory organic compounds. Due to their ability to generate powerful oxidants such as hydroxyl radicals (·OH), they can effectively break down the complex structures of organic molecules, achieving efficient degradation. Compared with traditional treatment methods, AOPs can handle refractory organic substances, such as drug residues and high-molecular-weight organic compounds, which are often limited in their removal by biological treatment methods, within a shorter reaction time. The strong oxidation capacity of hydroxyl radicals enables them to attack and break carbon-hydrogen and carbon-oxygen bonds in organic molecules, significantly reducing the pollution load of wastewater and improving treatment efficiency to meet stricter discharge standards.

AOPs also demonstrate outstanding performance in removing toxic and harmful substances. They can effectively decompose antibiotics, heavy metals, and other toxic chemicals in pharmaceutical wastewater, which are difficult to remove by conventional methods. By generating hydroxyl radicals, AOPs can oxidize these toxic substances into harmless intermediate products or ultimately degrade them into simple inorganic substances, significantly reducing their environmental risks. For instance, the Fenton oxidation method can effectively remove drug residues and refractory harmful compounds through the hydroxyl radicals generated in the reaction, while ozone oxidation has a highly efficient degradation capacity for certain difficult-to-treat toxic and harmful substances. These advantages make AOPs an important technical choice for treating wastewater with high pollution loads.

Practical Application Analysis

The ozone oxidation method has demonstrated significant practical application effects in the treatment of pharmaceutical wastewater. This technology utilizes ozone to generate hydroxyl radicals, effectively degrading organic pollutants and toxic substances in the wastewater. When analyzing the effect of ozone oxidation in treating pharmaceutical wastewater, the "organic matter removal rate" is generally the key indicator to be detected and calculated. As the dosage of ozone increases and the treatment time extends, the COD concentration after treatment gradually decreases, and the removal rate gradually increases. For instance, when the treatment time is 50 minutes and the ozone dosage is 60 mg/L, the removal rate reaches 75%, indicating that this method has a significant advantage in treating high-concentration organic pollutants. In practical applications, by optimizing the ozone dosage and reaction time, the treatment effect of wastewater can be significantly improved, meeting higher discharge standards.

The process of treating pharmaceutical wastewater using the Fenton method includes pretreatment, Fenton reaction, and post-treatment stages. The wastewater first undergoes pretreatment to remove large suspended particles and some easily degradable substances, reducing interference with the Fenton reaction. Common pretreatment methods include sedimentation, filtration, and chemical flocculation. After pretreatment, the wastewater enters the Fenton reaction stage, where hydrogen peroxide and ferrous ions are added to the wastewater in a certain proportion, and the pH of the wastewater is adjusted to acidic. Hydrogen peroxide reacts with ferrous ions to generate hydroxyl radicals, attacking organic pollutants in the wastewater. After the reaction, the reaction products need to be treated to remove precipitates and residual chemicals. Common post-treatment methods include sedimentation, filtration, and neutralization. This stage may also involve further water quality adjustment to ensure that the treated pharmaceutical wastewater meets discharge standards. Water quality needs to be tested during and after the treatment process to evaluate the treatment effect and guide process optimization.

Conclusion and Outlook

In summary, the treatment of pharmaceutical wastewater poses numerous challenges, and continuous technological innovation is needed to enhance treatment efficiency. Advanced oxidation technologies, with their highly efficient degradation capabilities, have demonstrated significant advantages in treating wastewater with high COD and high toxicity. Through practical analysis of ozone oxidation and Fenton methods, it can be seen that these technologies have achieved good results in actual applications. However, the application of advanced oxidation technologies still faces certain cost and operational complexity issues, which require further optimization and improvement.