Definition: Micropollutants are chemical compounds present in very low concentrations — typically micrograms (µg) per liter or even nanograms (ng) per liter of water. Despite their tiny amounts, they can have big environmental impacts.
Examples: These are substances we use daily — from household products, personal care items, pharmaceuticals, and cleaning agents — each with distinct chemical structures and functions.
When we use these compounds, they enter wastewater systems through household drains or industrial runoff. 🚽 → 💧 → 🏭 (Wastewater Treatment Plant) → 🌊 (Environment)
However, conventional wastewater treatment plants are not designed to remove all micropollutants effectively. As a result, these compounds pass through and end up in rivers, lakes, and groundwater — where they can affect aquatic ecosystems and even return to us through drinking water.
Even at low concentrations, micropollutants can:
They are chemically diverse — from antibiotics and hormones to pesticides and surfactants — which makes their removal especially challenging.
Scientists study how these compounds can be removed or broken down. The main mechanisms include:
Microorganisms like bacteria can metabolize micropollutants, using them as a carbon or energy source. However:
This includes chemical and physical processes like:
Certain materials (like activated carbon) can trap micropollutants, removing them from water without necessarily breaking them down.
Researchers use molecular tools to find which bacteria degrade which compounds:
Each bacterial strain may have unique enzymes that can cleave specific chemical bonds — e.g. aromatic ring cleavage, hydroxylation, or dehalogenation.
Different bacterial species use different metabolic strategies to attack pollutants:
| Compound Type | Example Bacteria | Mechanism |
|---|---|---|
| Phenolic compounds | Pseudomonas spp. | Hydroxylation → Ring cleavage |
| Chlorinated compounds | Dehalococcoides spp. | Reductive dechlorination |
| Pharmaceuticals | Sphingomonas, Rhodococcus | Co-metabolism or enzymatic oxidation |
Each degradation pathway reflects adaptation and specialization — showing how microbial diversity is key to environmental resilience.
| Concept | Key Takeaway |
|---|---|
| Micropollutants | Tiny concentrations, huge effects |
| Main sources | Households, pharmaceuticals, personal care, industry |
| Environmental impact | Toxicity, endocrine disruption, bioaccumulation |
| Removal mechanisms | Biotic (microbial) + abiotic (chemical/physical) |
| Research focus | Identifying bacteria and degradation pathways |
| Bacterial diversity | Different microbes = different enzymatic tools |