Department of Civil Engineering, Department of Mining Engineering, Indian Institute of Engineering Science and Techonology, Shibpur, Howrah-711 103, West Bengal, India E-mail: tumpabairagi8@gmail.com, asok@civil.iiests.ac.in, mirajul@mining.iiests.ac.in Manuscript received online 20 December 2019, accepted 23 March 2020 The antibiotic resistant bacteria have been spread from the environment to human through the water and the inactivation processes may be a possible way to reduce this type of threat. The main objective of this work is to investigate inactivation of E. coli present in wastewater employing direct UV andadvanced UV/H2O2 process. Bacterial inactivation both in real wastewater as well as synthetic wastewater was also investigated. Direct photolysis at 253.7 nm showed only 61% inactivation when initial bacterial concentration was 1.7×107 CFU/mL. In case of UV/H2O2 , about 99% bacterial inactivation was observed at 240 min treatment. It is concluded that during the advanced oxidation process, the chemical compound hydrogen peroxide (H2O2 ) absorbs UV light andhydroxyl radicals are produced by photolysis. These hydroxyl radicals are strong oxidizing agents and help to inactivate the bacteria.