Emerging pollutants characterization, mitigation and toxicity assessment of sewage wastewater treatment plant- India: A case study

India faces major challenges related to fresh water supply and the reuse of treated wastewater is an important strategy to combat water scarcity. Wastewater in Gorakhpur, India, is treated by a decentralised wastewater treatment system (DEWATS) and the treated wastewater is reused in the rural area. This research provides important scientific data that ascertain the safety of wastewater reuse in this region. The physicochemical characteristics, including pigment, ionic strength, BOD, COD, TDS, TSS, salinity, total N, ammonium N, phenolics, heavy metals, and sulphate, of the inlet and outlet sewage water samples (SWWs) from a wastewater treatment facility was conducted. These parameters were found to be significantly over the national limit. The inlet and outlet samples were further characterised by using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR) and gas chromatography–mass spectrometry (GC–MS). SEM showed microstructure and the presence of various metals, polymers, and other co-pollutants in the samples and FT-IR confirmed the presence of aldehyde, hard liquor, and nitrogen molecules in the SWW's discharge. Many endocrine disruptors and potentially mutagenic chemical substances (e.g., Dodecane, Hexadecane, Octadecane etc.) were identified in the outlet SWW by the GC–MS analysis. Toxicity of the SWW was assessed via phytotoxicity assessment using Phaseolus mungo L. and histological and biochemical analyses of Heteropneustes fossilis in a 24-h exposure study. Results confirmed the wastewater was harmful and inhibited germination of P. mungo L. by >80% compared to the control, destroyed gill laminae and significantly increased oxidative stress (above 5% increase in catalase production) in H. fossilis. This work clearly demonstrated that the quality of the treated wastewater in Gorakhpur was poor and immediate action is needed before it can be discharged or reused.