Is A/A/O process effective in toxicity removal? Case study with coking wastewater

Area of Science:

• Environmental Science
• Environmental Chemistry
• Toxicology

Background:

• The anaerobic-anoxic-oxic (A/A/O) process is widely used for biological wastewater treatment, particularly for coking wastewater.
• Limited data exists on the A/A/O process's efficacy in removing various bio-toxicological parameters from wastewater.

Purpose of the Study:

• To evaluate the performance of the A/A/O process in removing acute toxicity, oxidative damage, and genotoxicity from coking wastewater.
• To assess the impact of A/A/O treatment on test species Daphnia magna and Danio rerio.

Main Methods:

• Assessing acute toxicity using Daphnia magna and zebra fish (Danio rerio).
• Measuring reactive oxygen species (ROS) levels to evaluate oxidative damage.
• Employing comet assays to determine genotoxicity in zebra fish.

Main Results:

• A/A/O process significantly reduced acute toxicity, with no observed toxicity in the final effluent for either test species.
• Effluent from A/A/O tanks induced ROS, indicating oxidative damage, which was mitigated differently in oxic (D. magna) and anoxic (zebra fish) tanks.
• Genotoxicity was reduced stepwise, but the final effluent still exhibited genotoxicity to zebra fish.

Conclusions:

• The A/A/O process is effective for acute toxicity removal from coking wastewater but less so for oxidative damage and genotoxicity.
• Further advanced technologies are recommended for comprehensive toxicity mitigation.
• Incorporating toxicity indices into wastewater discharge regulations is advised.