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Views: 222 Author: Carie Publish Time: 2025-05-31 Origin: Site
Content Menu
● Understanding Sewage Treatment and Pharmaceuticals
>> What Happens in a Sewage Treatment Plant?
>> Pharmaceuticals in Wastewater
● Why Are Pharmaceuticals Difficult to Remove?
>> Chemical Complexity and Diversity
>> Limitations of Conventional Treatment Processes
>> Adsorption and Sludge Issues
>> Biological Treatment Challenges
>> Persistence of Pharmaceuticals in the Environment
● Advanced Treatment Technologies and Their Potential
>> Advanced Oxidation Processes (AOPs)
>> Adsorption on Activated Carbon or Biochar
>> Enzyme Immobilization and Biofilters
● Environmental and Health Implications
● Strategies to Improve Pharmaceutical Removal
>> Source Control and Proper Disposal
● FAQ
>> 1. Why do some pharmaceuticals pass through sewage treatment plants unchanged?
>> 2. Can sludge reuse spread pharmaceutical contamination?
>> 3. Are there treatment methods that can remove all pharmaceuticals?
>> 4. How do pharmaceuticals affect aquatic ecosystems?
>> 5. What future research is needed to improve pharmaceutical removal?
Pharmaceuticals in the environment have become a growing concern worldwide. Despite the advanced processes used in sewage treatment plants (STPs), many pharmaceutical compounds persist through treatment and enter waterways, posing risks to ecosystems and human health. This article explores why conventional sewage treatment struggles to fully remove pharmaceuticals, the challenges involved, and emerging solutions to address this complex issue.
Sewage treatment plants process wastewater through several stages to remove contaminants before releasing treated water back into the environment. The main stages include:
1. Movement of sludge: Wastewater is collected and transported to the treatment plant.
2. Pre-screening: Removal of large debris such as plastics, diapers, and wipes.
3. Primary settlement: Separation of suspended solids by sedimentation, forming sludge.
4. Secondary treatment: Biological processes degrade organic matter using microorganisms.
5. Tertiary treatment and disinfection: Further polishing of water and killing of pathogens, often using UV light or chemicals.
Pharmaceuticals enter sewage systems primarily through human excretion (unmetabolized drugs), disposal of unused medicines, industrial discharges, and hospital wastewater. Common drugs found include antibiotics, painkillers, antidepressants, anti-inflammatory drugs, and more.
Pharmaceuticals are a diverse group of compounds with varying chemical properties such as solubility, molecular size, and stability. Some are hydrophilic (water-soluble), others hydrophobic; some are neutral, others ionic. This diversity affects how they interact with treatment processes.
For example, carbamazepine, a widely used antiepileptic drug, is highly persistent due to its chemical stability and low biodegradability. On the other hand, ibuprofen, a common painkiller, is more biodegradable and easier to remove.
- Primary and secondary treatments focus on removing suspended solids and biodegradable organic matter but are not designed specifically to target pharmaceuticals.
- Many pharmaceuticals, such as carbamazepine, pass through conventional activated sludge (CAS) systems largely untransformed.
- Some drugs like ibuprofen and naproxen can be reduced by up to 90% during treatment, but others like diclofenac and carbamazepine show poor removal.
While some pharmaceuticals are partially removed from water by adsorbing onto sludge, this transfers the pollutants rather than eliminating them. The sludge, often used as fertilizer, can reintroduce pharmaceuticals into the environment, creating a cycle of contamination.
- Microorganisms in biological treatment can degrade some pharmaceuticals, but many drugs resist biodegradation.
- Enzymatic and fungal degradation methods show promise but face challenges like bacterial contamination, enzyme instability, and operational difficulties in continuous treatment systems.
Pharmaceuticals are designed to be biologically active and stable to exert therapeutic effects in the human body. This stability means they often resist breakdown in natural environments and treatment plants. Their persistence leads to continuous contamination of surface waters, groundwater, and even drinking water sources.
MBRs combine biological treatment with membrane filtration, offering better removal of pharmaceuticals than conventional systems. The membrane acts as a physical barrier, retaining suspended solids and some micropollutants.
- Studies show MBRs can achieve over 80% removal for many drugs.
- However, some persistent compounds like carbamazepine remain largely unaffected.
- MBRs require higher energy input and maintenance costs compared to conventional treatment.
Ligninolytic fungi such as Trametes versicolor and Phanerochaete chrysosporium produce enzymes capable of degrading complex organic molecules, including pharmaceuticals.
- Fungal bioreactors have demonstrated high removal efficiencies for drugs like diclofenac and fluoxetine.
- Maintaining fungal activity in real wastewater is challenging due to bacterial competition and variable wastewater composition.
- Scaling fungal bioreactors for full-scale treatment plants remains under research.
AOPs generate highly reactive species such as hydroxyl radicals that can non-selectively oxidize and break down pharmaceuticals.
- Common AOPs include ozonation, UV/H₂O₂ treatment, and Fenton reactions.
- These processes can degrade a wide range of pharmaceuticals effectively.
- Challenges include high operational costs, formation of potentially toxic by-products, and the need for careful process control.
Adsorption onto activated carbon is a widely used tertiary treatment method to remove micropollutants.
- It is effective for many hydrophobic pharmaceuticals.
- Spent activated carbon requires regeneration or disposal, adding to treatment costs.
- Biochar, a carbon-rich material from biomass, is emerging as a sustainable alternative adsorbent.
Immobilizing enzymes on solid supports can enhance stability and reusability for pharmaceutical degradation.
- Enzyme biofilters integrate immobilized enzymes into treatment systems.
- This approach is still experimental and faces challenges like enzyme deactivation and cost.
Pharmaceutical residues in water bodies can disrupt aquatic ecosystems by affecting reproduction, growth, and behavior of organisms. For instance:
- Endocrine disruptors such as synthetic hormones can cause reproductive abnormalities in fish.
- Antibiotics in the environment promote the development of antimicrobial resistance (AMR), a major global health threat.
- Psychotropic drugs can alter the behavior of aquatic species, impacting predator-prey dynamics.
Human exposure to trace pharmaceuticals through drinking water is an emerging concern, though current levels are generally low. Long-term effects of chronic exposure to pharmaceutical mixtures remain poorly understood.
- Educating the public on proper disposal of unused medicines can reduce pharmaceutical loads entering wastewater.
- Take-back programs and safe disposal sites help prevent flushing drugs down toilets or drains.
- Incorporating advanced treatment stages such as MBRs, AOPs, or activated carbon adsorption can significantly improve removal.
- Retrofitting existing plants requires investment but is crucial for reducing pharmaceutical pollution.
- Improved monitoring of pharmaceuticals in wastewater and surface waters helps identify hotspots and track removal efficiencies.
- Regulatory frameworks are evolving to set limits and guidelines for pharmaceutical discharges.
- Developing microbial consortia or genetically engineered organisms capable of degrading pharmaceuticals.
- Exploring hybrid systems combining biological and chemical treatments.
- Investigating the fate and transformation products of pharmaceuticals during treatment.
Sewage treatment plants are not currently equipped to fully remove pharmaceutical compounds due to the chemical diversity, persistence, and complexity of these substances. Conventional biological and physical treatments can reduce some drugs but often fail to eliminate more resilient pharmaceuticals. Advanced techniques like membrane bioreactors, fungal treatments, and advanced oxidation processes show promise but require further development and optimization. Addressing pharmaceutical pollution demands integrated approaches, improved treatment technologies, source control, and regulatory oversight to protect environmental and human health.
Many pharmaceuticals have chemical structures that resist biodegradation and adsorption in conventional treatment processes, allowing them to persist through the system.
Yes, pharmaceuticals adsorbed onto sludge can enter the environment when sludge is used as fertilizer, creating secondary pollution pathways.
No single method currently removes all pharmaceuticals completely. Combining advanced treatments like membrane bioreactors, fungal degradation, and oxidation processes improves removal but does not guarantee total elimination.
Even low concentrations can disrupt aquatic life by altering reproduction, growth, and behavior, and contribute to antibiotic resistance in bacteria.
Research is needed to optimize membrane materials, microbial populations, enzymatic treatments, and to understand pharmaceuticals' environmental fate and effects better.
