Toxicity-based assessment of the treatment performance of wastewater
treatment and reclamation processes
The reclamation and reuse of wastewater is one of the possible ways to relieve the serious fresh water resource crisis in China.
Efficient reclamation treatment technologies ensure the safe reuse of reclaimed water. In order to screen out and evaluate technologies
appropriate for reclamation treatment, a great deal of efforts have been brought to bear. In the present study, a toxicity-based
method including a Photobacterium phosphoreum test for acute toxicity and SOS/umu test for genotoxicity, accompanied by the
traditional physicochemical parameters DOC (dissolved organic carbon) and UV254 (absorbance at 254 nm), was used to measure the
treatment performance of different reclamation processes, including the anaerobic-anoxic-oxic biological process (A2O) and subsequent
physical/chemical reclamation processes (ultrafiltration, ozonation, chlorination). It was found that for the secondary effluent after the
A2O process, both the toxicity and physicochemical indices had greatly decreased compared with those of the influent. However,
chemical reclamation processes such as ozonation and chlorination could possibly raise toxicity levels again. Fortunately, the toxicity
elevation could be avoided by optimizing the ozone dosage and using activated carbon after ozonation. It was noted that by increasing
the ozone dosage to 10 mg/L and employing activated carbon with more than 10 min hydraulic retention time, toxicity elevation
was controlled. Furthermore, it was shown that pre-ozonation before activated carbon and chlorination played an important role in
removing organic compounds and reducing the toxicity formation potential. The toxicity test could serve as a valuable tool to evaluate
the performance of reclamation processes.