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Updated: May 7, 2026
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Mesocosm-Scale Constructed Wetland Design for Wastewater Treatment
Published on: May 2, 2025
High salinity wastewater treatment
1Faculty of Chemical Engineering and Technology, Marko Marulić Square 19, Zagreb, Croatia
Summary
Activated sludge microorganisms can acclimatize to low salt concentrations (below 10 g/L NaCl) over several weeks. Higher salinity levels (above 30 g/L NaCl) severely inhibit or prevent microbial activity and acclimatization in wastewater treatment.
Area of Science:
- Environmental Science
- Microbiology
- Wastewater Treatment
Background:
- Seawater intrusion into sewage systems can occur due to storm surge flooding.
- Salinity poses a significant challenge to the efficiency of biological wastewater treatment processes.
Purpose of the Study:
- To investigate the shock effect, survival, and acclimatization capacity of activated sludge exposed to varying NaCl and Na2SO4 concentrations.
- To simulate and assess the impact of potential seawater contamination on activated sludge performance.
Main Methods:
- Activated sludge from a communal wastewater treatment plant was used.
- Experiments involved adding NaCl (up to 40 g/L) and Na2SO4 (up to 4.33 g/L) to simulate saline conditions.
- Monitoring of activated sludge parameters (pH, DO, TSS, VSS, SVI, etc.) and microbial activity over five weeks.
Main Results:
- High salt concentrations (above 30 g/L NaCl) significantly inhibited or completely halted microbial activity.
- Activated sludge demonstrated acclimatization capabilities at NaCl concentrations below 10 g/L, regaining initial activity within weeks.
- Acclimatization was slow or impossible at NaCl concentrations exceeding 30 g/L.
Conclusions:
- Activated sludge exhibits limited tolerance to high salinity, with significant impacts on microbial activity and treatment efficiency.
- Wastewater treatment plants may face operational challenges following significant saline intrusion events.
- Understanding microbial acclimatization limits is crucial for managing wastewater treatment under varying salinity conditions.
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