Ecotoxicological properties of wastewater treated using tertiary methods

Area of Science:

• Environmental Science
• Water Treatment Technologies
• Ecotoxicology

Background:

• Reclaimed wastewater requires advanced treatment to minimize environmental toxicity.
• Coagulation and ozonation are key processes for wastewater purification.

Purpose of the Study:

• To evaluate the efficiency of coagulation (FeCl3, alum) and ozonation in reducing the toxicity of reclaimed wastewater.
• To assess the ecotoxicological impact of treated effluents on various aquatic organisms.

Main Methods:

• Secondary municipal effluents were treated using ferric chloride (FeCl3), aluminum sulfate (alum), or ozonation.
• Toxicity was evaluated using Vibrio fischeri, Daphnia magna, Daphnia pulex, Thamnocephalus platyurus, and Brachionus calyciflorus.

Main Results:

• Alum reduced Daphnia pulex immobilization toxicity from 90% to 60%.
• Ozonation at 2.5 mg O3/L for 2 min reduced D. pulex toxicity to 25%.
• High ozone concentrations and contact times caused acute toxicity to Vibrio fischeri, but this diminished after 48-hour storage.

Conclusions:

• Both coagulation and ozonation are effective in reducing reclaimed wastewater toxicity.
• Ozonation requires careful control of dosage and contact time to avoid adverse effects on certain organisms.
• Storage of ozonated effluent for 48 hours significantly reduces residual toxicity, potentially enabling safer discharge.