Phytotoxicity and cyto-genotoxicity evaluation of organic and inorganic pollutants containing petroleum refinery wastewater using plant bioassay

The present study was aimed to evaluate the pollution load and toxicity of petroleum refinery wastewater (PRW) before and after the biological treatment process. PRW induced phytotoxicity and cyto-genotoxicity in mung bean (Vigna radiata L.) and onion (Allium cepa L.) were investigated. The physico-chemical analysis such as pH, BOD, COD, EC, solids, total phenol, and other pollutants in PRW sample were high and beyond the permissible limits. The GC–MS and FTIR analysis suggest the presence of toxic organic pollutants. In comparison to control, the seeds of V. radiata exposed to 100% PRW sample showed a reduction in seed germination, root length, shoot length, and biomass by 50%, 85.1%, 69.3% and 36.6%, respectively, after 5 days of treatment. A. cepa root exposed to different concentration of wastewater samples indicated the reduction of root length and biomass in concentration dependent manner when compared to untreated solutions, after 5 days of incubation. A. cepa root tip rooted in different concentration (25%–100% v/v) of PRW samples showed a significant reduction in mitotic index (MI%) from 67.7 % to 38.7% compared to control root tip cells (79.3%) exposed to tap water indicating the induction of the cytotoxicity. Besides, wastewater induced genotoxicity as evidenced by the presence of various chromosomal aberrations (CAs) and nuclear abnormalities (NAs) in A. cepa root tip cells. However, after the secondary treatment process, the toxicity of the PRW was reduced compared to untreated. Thus, the present study’s finding reported that PRW generated different types of toxic organic and inorganic pollutants and may act as phytotoxic and cyto-genotoxic agents.