Micropollutants are organic or inorganic substances present in trace amounts (µg/L to ng/L) in water. They include 💊 pharmaceuticals, 💅 personal care products, 🌾 pesticides, and ⚙️ industrial chemicals. Even at low concentrations, they can disrupt ecosystems and harm organisms.
Modern wastewater treatment plants (WWTPs) aren’t designed for these trace pollutants. The goal of future treatment is higher effluent water quality and stable operation, with resource recovery (energy, nutrients, materials).
Each year, Denmark produces about 365,000 tonnes of surplus sludge (5–30% dry matter). It’s used in:
Sludge contains energy (15–30 MJ/kg dry matter) and valuable resources, but also micropollutants — making treatment complex.
Studies (Falås et al., 2012) show that pharmaceuticals enter and leave WWTPs largely intact — conventional processes remove only part of them. Each plant varies in efficiency depending on design, operation, and hydraulic retention time.
Micropollutants often combine in cocktails, causing additive, antagonistic, or synergistic effects on organisms. ☠️
A mass balance shows:
10% forms bound residues
🧩 Bound residues = chemicals attached to solids (plastics, fibers, etc.), often hidden from standard tests.
| Method | Advantages | Disadvantages |
|---|---|---|
| Activated Carbon | Treats many MPs; low cost | Poor removal of some (BAM/DMS); maintenance; disinfection needed |
| Chemical Oxidation (Ozone) | Effective on many MPs | Toxic byproducts; costly |
| Filtration (NF/RO) | High efficiency; no byproducts | Very expensive; high maintenance; water loss; MP upconcentration |
Different WWTPs (Aalborg East, West, Aabybro, Hirtshals) show varying rates due to:
When pathways are unknown, scientists combine molecular and ecological tools:
Example: Only 0.1‰ of biomass degraded EE2 (a hormone pollutant). Tiny but significant!
Biometer flasks detect degradation by measuring radioactive CO₂ production. GC-MS/MS and toxicology assays confirm compound disappearance and transformation. Some pollutants (like Prozac) can alter animal behavior — e.g., make fish aggressive! 🐟💢
Adding biofilm carriers (MBBR systems) improves removal of slowly degradable compounds 8–10× compared to conventional activated sludge. Biofilms provide:
Introducing specialized microbes or nutrients can enhance degradation. However, exogenous strains often fail due to:
Effectiveness is usually short-lived. Still, it’s useful for targeted removal or resilience boosting.
Workflow:
Metagenome-Assembled Genomes (MAGs) reconstruct genomes from complex communities — sometimes representing <0.1% of the total population.
👉 COMBREX helps bridge computational predictions with experimental validation.
Genome mining can identify degradation-related genes, but expression (epigenetics) matters too. Tools like EAWAG-BBD Pathway Prediction System (PPS) simulate microbial degradation routes based on known reactions.
By combining:
→ Researchers can reveal complete degradation pathways.
Gemfibrozil (a lipid-lowering drug) undergoes:
Each response helps the cell survive and transform the compound.
Exposure to EE2 (synthetic estrogen) changes expression of many molecular functions (membrane transport, oxidoreductases, etc.). Ibuprofen degradation involves enzymes:
🧬 Together, they break down ibuprofen through aromatic ring cleavage and oxidation.
By identifying marker genes and pathways, we can:
Goal: Move from describe → predict → control microbial behavior.
Steps for sustainable bioremediation:
→ Outcome: a bioreactor with predictable, stable, and effective pollutant degradation.