Anaerobic effluent disinfection using ozone: byproducts formation

Area of Science:

• Environmental Science
• Water Treatment Technologies
• Microbiology

Background:

• Wastewater disinfection is crucial for public health and environmental protection.
• Ozone (O3) is a powerful oxidant used for water disinfection.
• Understanding ozone's efficacy and byproduct formation in wastewater is essential.

Purpose of the Study:

• To evaluate the effectiveness of ozone disinfection on coliform inactivation in anaerobic sanitary wastewater effluent.
• To investigate the impact of varying ozone doses and contact times on disinfection byproducts (DBPs).
• To assess the oxidation of organic matter, measured by chemical oxygen demand (COD) reduction.

Main Methods:

• Anaerobic sanitary wastewater effluent from the University of São Paulo's wastewater treatment plant was used.
• Ozone was applied at doses of 5.0, 8.0, and 10.0 mg O3/L for contact times of 5, 10, and 15 minutes.
• Total coliform and Escherichia coli inactivation, COD reduction, and aldehyde formation (acetaldehyde, glyoxal) were measured.

Main Results:

• Total coliform inactivation ranged from 2.00-4.06 log(10).
• Escherichia coli inactivation ranged from 2.41-4.65 log(10).
• Mean COD reductions were 37.6%, 48.8%, and 42.4% for ozone doses of 5.0, 8.0, and 10.0 mg O3/L, respectively.
• Aldehyde formation varied with ozone dosage, with significant increases observed for acetaldehyde and glyoxal at higher doses.

Conclusions:

• Ozone disinfection is effective in reducing coliforms and E. coli in wastewater.
• Optimal ozone dosage is necessary to balance microbial inactivation with the minimization of disinfection byproduct formation.
• Further research is needed to optimize ozone application for comprehensive wastewater treatment.