Disentangling urban wastewater sources using isotopic tracers and CEC-based diagnostic indicators

Area of Science:

• Environmental Chemistry
• Water Quality Monitoring
• Wastewater Treatment

Background:

• Urban rivers face complex nitrogen pollution from multiple wastewater sources.
• Distinguishing between human and animal wastewater inputs is crucial for effective management.
• Existing diagnostic tools often struggle with overlapping pollution signals.

Purpose of the Study:

• To develop and validate a novel approach for wastewater source attribution in urban rivers.
• To integrate isotopic tracers with contaminants of emerging concern (CECs) for improved accuracy.
• To assess the ecological risk posed by detected contaminants.

Main Methods:

• Collected monthly water samples over two years from five urban river stations.
• Analyzed nitrate isotopes (δ¹⁵N-NO₃^-), conventional hydrochemistry, and a suite of CECs.
• Employed a Bayesian mixing model with CEC-derived indices (HWI, HI) and source signatures.

Main Results:

• Nitrate concentrations and δ¹⁵N-NO₃^- values indicated increasing wastewater influence downstream.
• Isotopic data alone could not differentiate human from animal wastewater sources.
• The integrated method revealed human wastewater contributions >60% at all sites; elevated HI identified hospital wastewater.

Conclusions:

• Combining nitrate isotopes with CEC-based diagnostic indicators significantly enhances wastewater source attribution in complex urban systems.
• CECs provide complementary information to isotopes, revealing sources like hospital wastewater.
• The approach has direct implications for urban water quality monitoring and management, highlighting high ecological risks.