Toxicity of chlorinated and ozonated wastewater effluents probed by genetically modified bioluminescent bacteria and cyanobacteria Spirulina sp

• Published in: Water research (Oxford) 2019-11, Vol.164, p.114910, Article 114910
• Main Authors: Bhuvaneshwari, M., Eltzov, Evgeni, Veltman, Boris, Shapiro, Orr, Sadhasivam, Giji, Borisover, Mikhail
• Format: Article
• Language: English
• Subjects: bacteria; bioluminescence; Chlorination; chlorine; Cytotoxicity; disinfection; effluents; fluorescence; genetically engineered microorganisms; Genetically modified bioluminescent bacteria; Genotoxicity; humans; monitoring; mutagens; Ozonation; ozone; reactive oxygen species; risk; ROS; sodium hypochlorite; spectral analysis; Spirulina; wastewater
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2019.114910

Chlorination and ozonation of various waters may be associated with the formation of toxic disinfection byproducts (DBPs) and cause health risks to humans. Monitoring the toxicity of chlorinated and ozonated water and identification of different toxicity mechanisms are therefore required. This study is one of its kind to examine the toxic effects of chlorinated and ozonated wastewater effluents on three genetically modified bioluminescent bacteria, in comparison to the naturally isolated cyanobacteria, Spirulina strains as test systems. Three different secondary wastewater effluents were collected from treatment plants, chlorinated using sodium hypochlorite (at 1 and 10 mg L−1 of chlorine) or treated using 3–4 mg L−1 of ozone at different contact times. As compared to cyanobacterial Spirulina sp., the genetically modified bacteria enhancing bioluminescence at the presence of stress agents demonstrated greater sensitivity to the toxicity induction and have also provided mechanism-specific responses associated with genotoxicity, cytotoxicity and reactive oxygen species (ROS) generation in wastewater effluents. Effects of effluent chlorination time and chlorine concentration revealed by means of bioluminescent bacteria suggest the formation of genotoxic and cytotoxic DBPs followed with their possible disappearance at longer times. Ozonation could degrade genotoxic compounds in some effluents, but the cytotoxic potential of wastewater effluents may certainly increase with ozonation time. No induction of ROS-related toxicity was detected in either chlorinated or ozonated wastewater effluents. UV absorbance- and fluorescence emission-based spectroscopic characteristics may be variously correlated with changes in genotoxicity in ozonated effluents, however, no associations were obtained in chlorinated wastewater effluents. The bacterial response to the developed mechanism-specific toxicity differs among wastewater effluents, reflecting variability in effluent compositions. [Display omitted] •Chlorinated effluents showed strong genotoxicity and cytotoxicity potential.•Formation of genotoxic DBPs during chlorination is followed with their disappearance.•Ozonation may strongly suppress genotoxicity in some effluents.•Spectroscopic characteristics correlate with genotoxicity of ozonated effluents.•Spirulina sp. was less sensitive to DBP formation than bioluminescent bacteria.