8.2 Fate of micropollutants in treatment processes

Micropollutants in wastewater undergo various transformations during treatment. These include adsorption, biodegradation, chemical changes, and volatilization. The fate of these compounds depends on their properties, wastewater composition, and treatment conditions.

Different treatment stages tackle micropollutants differently. Primary treatment offers limited removal through physical processes. Secondary treatment uses biological processes for biodegradation and adsorption. Tertiary treatment employs advanced techniques like activated carbon and membrane filtration for enhanced removal.

Fate of Micropollutants in Conventional Wastewater Treatment

Micropollutants in wastewater treatment

Top images from around the web for Micropollutants in wastewater treatment

• 

  7.4 Water Treatment – Environmental Biology View original

  Is this image relevant?

• 

  Frontiers | Emerging Trends in Biological Treatment of Wastewater From Unconventional Oil and ... View original

  Is this image relevant?

• 

  Frontiers | Biological Approaches Integrating Algae and Bacteria for the Degradation of ... View original

  Is this image relevant?

• 

  7.4 Water Treatment – Environmental Biology View original

  Is this image relevant?

• 

  Frontiers | Emerging Trends in Biological Treatment of Wastewater From Unconventional Oil and ... View original

  Is this image relevant?

1 of 3

Top images from around the web for Micropollutants in wastewater treatment

• 

  7.4 Water Treatment – Environmental Biology View original

  Is this image relevant?

• 

  Frontiers | Emerging Trends in Biological Treatment of Wastewater From Unconventional Oil and ... View original

  Is this image relevant?

• 

  Frontiers | Biological Approaches Integrating Algae and Bacteria for the Degradation of ... View original

  Is this image relevant?

• 

  7.4 Water Treatment – Environmental Biology View original

  Is this image relevant?

• 

  Frontiers | Emerging Trends in Biological Treatment of Wastewater From Unconventional Oil and ... View original

  Is this image relevant?

1 of 3

• Micropollutants undergo various transformations during wastewater treatment processes:
  • Adsorb onto suspended solids and sludge removes micropollutants from the aqueous phase
  • Biodegradation by microorganisms in biological treatment processes breaks down some micropollutants (pharmaceuticals, personal care products)
  • Chemical transformations alter the structure and properties of micropollutants (hydrolysis of esters, oxidation of phenols, reduction of nitro groups)
  • Volatilization removes volatile compounds from wastewater (fragrances, solvents)
• Factors influencing micropollutant behavior in wastewater treatment:
  • Physicochemical properties determine the fate and removal of micropollutants (solubility in water, hydrophobicity, molecular size)
  • Wastewater composition and characteristics affect micropollutant behavior (pH influences ionization, organic matter content impacts adsorption)
  • Treatment process conditions control the extent of micropollutant removal (retention time, redox conditions)

Effectiveness of treatment stages

• Primary treatment removes micropollutants through physical processes:
  • Limited removal of micropollutants due to the nature of the processes
  • Removal mainly occurs through adsorption onto settleable solids (suspended particles, oils, greases)
• Secondary treatment involves biological processes for micropollutant removal:
  • Biodegradation of some biodegradable micropollutants by microorganisms (pharmaceuticals, hormones)
  • Adsorption onto activated sludge flocs removes micropollutants from the aqueous phase
  • Removal efficiency varies depending on the compound and treatment conditions (SRT, temperature)
• Tertiary treatment employs advanced processes for enhanced micropollutant removal:
  • Activated carbon adsorption removes a wide range of micropollutants (pesticides, industrial chemicals)
  • Advanced oxidation processes degrade recalcitrant micropollutants (ozonation, UV/H2O2)
  • Membrane filtration retains micropollutants based on size exclusion (nanofiltration, reverse osmosis)

Factors in micropollutant removal

• Physicochemical properties of micropollutants influence their removal:
  • Hydrophobicity determines the extent of adsorption onto solids and sludge (log Kow)
  • Biodegradability affects the effectiveness of removal during biological treatment (ready biodegradability tests)
  • Molecular size impacts removal through size exclusion mechanisms (molecular weight cut-off)
• Treatment conditions control the removal efficiency of micropollutants:
  • Hydraulic retention time (HRT) allows more time for adsorption and biodegradation (typical HRTs: 6-24 hours)
  • Sludge retention time (SRT) promotes the growth of diverse microbial communities, enhancing biodegradation (typical SRTs: 5-20 days)
  • Redox conditions influence the transformation pathways of micropollutants (aerobic, anoxic, anaerobic)
  • pH affects the ionization state and solubility of micropollutants, impacting their removal (pKa values)

Formation and Implications of Transformation Products

Transformation products and implications

• Transformation products can form during wastewater treatment processes:
  • Incomplete biodegradation of parent compounds leads to the formation of metabolites
  • Chemical reactions alter the structure of micropollutants (oxidation of amines, reduction of azo dyes)
  • Photodegradation by UV disinfection or sunlight exposure forms photoproducts
• Potential environmental implications of transformation products:
  • Transformation products may have different toxicological properties compared to parent compounds (increased toxicity, endocrine disruption)
  • Some transformation products can be more persistent or bioaccumulative in the environment (halogenated compounds)
  • Formation of toxic or endocrine-disrupting transformation products raises ecological concerns (estrogenic effects on aquatic organisms)
  • Incomplete removal of transformation products during treatment leads to their release into the environment (surface waters, groundwater)
• Assessing the environmental impact of transformation products requires:
  1. Identification and characterization of transformation products using analytical techniques (LC-MS/MS, GC-MS)
  2. Toxicity and ecotoxicity studies to evaluate the effects on organisms (in vitro assays, in vivo tests)
  3. Monitoring of transformation products in treated effluents and receiving water bodies to assess environmental exposure (targeted and non-targeted analysis)