9.1 Occurrence and fate of pharmaceuticals
3 min read•july 19, 2024
Pharmaceuticals in wastewater come from various sources, including human excretion, improper disposal, and industrial discharges. Their concentrations are influenced by consumption patterns, pharmacokinetics, and environmental factors. Understanding these sources and factors is crucial for effective wastewater treatment.
Tracking pharmaceuticals in wastewater is challenging due to their complex fate and transformation processes. , , and affect their removal, while detection difficulties arise from low concentrations and matrix interferences. These challenges highlight the need for advanced analytical techniques in wastewater treatment.
Sources, Pathways, and Occurrence of Pharmaceuticals in Wastewater
Sources of pharmaceuticals in wastewater
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- Human excretion introduces unmetabolized pharmaceuticals () and metabolites into wastewater
- Improper disposal of unused or expired medications by flushing down toilets or sinks and discarding in household waste contributes to pharmaceutical loads
- Hospital and healthcare facility effluents contain high concentrations of various pharmaceuticals (, )
- Veterinary use and animal husbandry practices lead to the release of antibiotics () and growth promoters into wastewater through runoff from animal waste
- Manufacturing and industrial discharges from pharmaceutical production plants and accidental spills or leaks introduce pharmaceuticals into wastewater systems
Factors affecting pharmaceutical concentrations
- Consumption patterns and prescription rates influence pharmaceutical concentrations, with an aging population and increased use of medications leading to higher levels in wastewater
- Pharmacokinetics and excretion rates determine the percentage of unmetabolized drug excreted (10-90%) and the formation and excretion of metabolites
- Water consumption and dilution effects, such as per capita water use and wastewater dilution in sewer systems, impact pharmaceutical concentrations in wastewater
- Seasonal variations lead to higher concentrations during flu and allergy seasons (antihistamines, decongestants)
- Regional and cultural differences in prescription practices and over-the-counter medication use () affect pharmaceutical occurrence in wastewater
Fate, Transformation, and Detection Challenges of Pharmaceuticals in Wastewater
Fate of pharmaceuticals in treatment
- Adsorption to sludge and suspended solids occurs through hydrophobic interactions and electrostatic interactions, removing some pharmaceuticals from the aqueous phase
- Biodegradation by microorganisms in aerobic and anaerobic processes and enzyme-mediated transformations () contribute to pharmaceutical removal
- Abiotic transformations, such as hydrolysis and photolysis, can degrade pharmaceuticals in wastewater treatment and the environment
- Incomplete removal during conventional wastewater treatment, particularly in primary and secondary treatment stages, results in the release of pharmaceuticals into receiving water bodies
- Released pharmaceuticals can accumulate in sediments and be taken up by aquatic organisms (fish, invertebrates)
- Transport and distribution of pharmaceuticals in the environment occur through groundwater infiltration and surface water transport, leading to their presence in various environmental compartments
Challenges in pharmaceutical detection
- Low concentrations in the ng/L to μg/L range require highly sensitive analytical techniques () for accurate quantification
- The complex wastewater matrix, containing interfering substances (organic matter, salts), can cause matrix effects in analysis and complicate pharmaceutical detection
- The wide range of pharmaceutical compounds with diverse chemical structures and properties necessitates the use of multiple analytical methods for comprehensive monitoring
- Identification and quantification of metabolites and transformation products pose challenges due to limited available standards and reference materials
- Sample preparation and extraction techniques, such as (SPE) and (LLE), can be affected by matrix interferences and recovery issues
- Advanced analytical instrumentation, including - (LC-MS), (GC-MS), and tandem mass spectrometry (MS/MS), is required for reliable detection and confirmation of pharmaceuticals in wastewater
Key Terms to Review (25)
Abiotic transformations: Abiotic transformations refer to the chemical changes that occur in substances through non-biological processes, such as hydrolysis, photolysis, and oxidation. These transformations are crucial for understanding the fate of various contaminants, particularly pharmaceuticals, in the environment as they can alter the chemical structure and reactivity of these compounds, influencing their mobility and toxicity in water systems.
Acetaminophen: Acetaminophen is a widely used over-the-counter medication that alleviates pain and reduces fever. It's often found in various pharmaceuticals, making its presence significant in both therapeutic applications and environmental studies related to the occurrence and fate of pharmaceuticals in wastewater systems.
Adsorption: Adsorption is the process by which molecules from a liquid, gas, or dissolved solid adhere to a surface, forming a thin layer. This interaction is crucial in wastewater treatment, particularly in the removal of contaminants and micropollutants, where substances cling to the surface of adsorbents like activated carbon or zeolites, enhancing water quality and safety.
Advanced Oxidation Processes: Advanced oxidation processes (AOPs) are chemical treatment methods that involve the generation of highly reactive species, particularly hydroxyl radicals, to effectively decompose organic pollutants in water and wastewater. These processes address the limitations of conventional treatment methods, especially when dealing with emerging contaminants and micropollutants that are resistant to traditional techniques.
Antibiotics: Antibiotics are chemical substances used to inhibit the growth of or kill bacteria, primarily used in medical treatments to combat infections. Their widespread use has led to significant impacts on both human health and the environment, particularly regarding the treatment of wastewater and the presence of pharmaceutical residues in ecosystems.
Biodegradation: Biodegradation is the process through which organic substances are broken down by microorganisms, such as bacteria and fungi, into simpler compounds. This natural process plays a crucial role in the treatment of wastewater, particularly for micropollutants and pharmaceuticals, as it helps reduce harmful substances in the environment, ensuring safer water for reuse or discharge.
Case of Diclofenac Contamination: The case of diclofenac contamination refers to the environmental pollution caused by the pharmaceutical diclofenac, a nonsteroidal anti-inflammatory drug (NSAID), primarily impacting aquatic ecosystems. This contamination is significant due to the drug's persistence in water bodies, which can lead to harmful effects on aquatic organisms, particularly birds and fish, and raises concerns about public health and environmental safety.
Chemotherapy drugs: Chemotherapy drugs are powerful medications used to treat cancer by killing or slowing the growth of cancer cells. These drugs can target rapidly dividing cells, which is a hallmark of cancer, but they may also affect normal cells, leading to side effects. Understanding the occurrence and fate of these drugs in the environment is crucial for assessing their impact on ecosystems and human health.
Cytochrome P450: Cytochrome P450 refers to a large family of enzymes that play a crucial role in the metabolism of various compounds, including pharmaceuticals, by catalyzing oxidation reactions. These enzymes are involved in the biotransformation of drugs and can affect their efficacy and toxicity. Understanding the activity and fate of cytochrome P450 enzymes is key to comprehending how pharmaceuticals behave in biological systems and their potential environmental impact.
Ecotoxicology: Ecotoxicology is the study of the harmful effects of chemicals on ecosystems, particularly focusing on the interactions between toxic substances and living organisms. This field examines how pollutants, including pharmaceuticals, impact environmental health and biodiversity. By understanding these interactions, ecotoxicology plays a vital role in assessing risks and developing strategies to mitigate the negative effects of contaminants on ecosystems.
EPA Guidelines: EPA guidelines refer to the set of regulations and recommendations established by the Environmental Protection Agency to protect human health and the environment from pollutants. These guidelines provide a framework for managing and reducing contaminants in water, including emerging pollutants and advanced treatment technologies.
Exposure Assessment: Exposure assessment is the process of estimating or measuring the intensity, frequency, and duration of human or ecological contact with environmental contaminants. This concept is critical for understanding how contaminants, including emerging pollutants and pharmaceuticals, may affect health and the environment. It combines information on contaminant sources, pathways of exposure, and populations at risk to determine the potential impacts on human health and ecosystems.
Gas Chromatography-Mass Spectrometry: Gas chromatography-mass spectrometry (GC-MS) is an analytical technique that combines the features of gas chromatography and mass spectrometry to identify and quantify chemical compounds. This method allows for the separation of complex mixtures of volatile substances, followed by the detection and analysis of individual components based on their mass-to-charge ratio. It plays a crucial role in understanding the occurrence and fate of pharmaceuticals in environmental samples, particularly in wastewater treatment processes.
Ibuprofen: Ibuprofen is a widely used nonsteroidal anti-inflammatory drug (NSAID) that helps reduce pain, fever, and inflammation. Its presence in the environment raises concerns about its occurrence and fate in wastewater, as it can enter water systems through various pathways, leading to potential impacts on aquatic life and human health.
Lc-ms/ms: LC-MS/MS, or liquid chromatography-tandem mass spectrometry, is an analytical technique used to separate, identify, and quantify compounds in a sample. This powerful method combines the physical separation capabilities of liquid chromatography with the mass analysis capabilities of mass spectrometry, making it particularly effective for detecting trace levels of pharmaceuticals and their metabolites in complex matrices such as wastewater.
Liquid chromatography: Liquid chromatography is a widely used analytical technique for separating mixtures of compounds dissolved in a liquid. It operates on the principle of partitioning components between a stationary phase and a mobile phase, allowing for the identification and quantification of different substances, including micropollutants and pharmaceuticals, in complex mixtures.
Liquid-liquid extraction: Liquid-liquid extraction is a separation process that involves transferring a solute from one liquid phase to another, typically using a solvent that selectively dissolves the desired compounds. This technique is crucial for isolating and purifying pharmaceuticals from complex mixtures found in wastewater, allowing for better understanding of their occurrence and fate in the environment. The efficiency of this process depends on various factors, including the solubility of the target compounds, the choice of solvent, and the conditions under which the extraction occurs.
Mass Spectrometry: Mass spectrometry is an analytical technique used to measure the mass-to-charge ratio of ions, allowing for the identification and quantification of chemical compounds within a sample. This powerful tool is essential in understanding how micropollutants behave in wastewater treatment, assessing the ecotoxicological effects of pharmaceutical residues, and evaluating advanced methods for pharmaceutical removal.
Membrane Filtration: Membrane filtration is a physical separation process that uses semi-permeable membranes to separate particles and contaminants from liquids. This technology is crucial in advanced wastewater treatment as it effectively removes suspended solids, microorganisms, and various dissolved substances, playing a significant role in addressing emerging contaminants and ensuring water quality.
Persistence: Persistence refers to the ability of a substance, particularly contaminants, to remain in the environment for an extended period without significant degradation or removal. This property is critical when assessing the long-term effects of pollutants, especially in water systems, as persistent substances can accumulate, posing risks to ecosystems and human health.
Solid-Phase Extraction: Solid-phase extraction (SPE) is a sample preparation technique used to isolate specific compounds from a liquid mixture by passing it through a solid adsorbent material. This method is crucial for removing interfering substances and concentrating target analytes, particularly in the context of analyzing pharmaceuticals in wastewater. SPE enhances the detection and quantification of these compounds by effectively separating them from complex matrices, thus revealing their occurrence and fate in the environment.
Studies on wastewater treatment plants: Studies on wastewater treatment plants investigate the processes and technologies used to treat sewage and industrial waste before it is released into the environment. These studies aim to understand the effectiveness of various treatment methods, the removal of contaminants, and the overall impact on water quality, particularly focusing on the occurrence and fate of pharmaceuticals within these systems.
Tetracycline: Tetracycline is a broad-spectrum antibiotic that is commonly used to treat various bacterial infections. It is particularly effective against a wide range of Gram-positive and Gram-negative bacteria, making it significant in both human and veterinary medicine. However, its presence in the environment, especially in wastewater, raises concerns regarding the occurrence and fate of pharmaceuticals, as well as contributing to mechanisms of antibiotic resistance and the survival of antibiotic-resistant bacteria during treatment processes.
Transport Pathways: Transport pathways refer to the routes or mechanisms through which substances, such as pharmaceuticals, move through various environmental compartments, including soil, water, and air. Understanding these pathways is essential for assessing how pharmaceuticals enter different ecosystems, how they are distributed, and ultimately their fate in the environment, impacting both ecological health and human safety.
Water Framework Directive: The Water Framework Directive (WFD) is a European Union legislation that aims to improve and protect the quality of water resources across Europe by establishing a framework for the management of rivers, lakes, groundwater, and coastal waters. This directive plays a crucial role in addressing the occurrence and fate of pharmaceuticals in aquatic environments by setting standards for water quality and requiring member states to assess and manage their water bodies effectively.