The Guwahati Refinery (GR), the first public sector refining unit in the country, is all set to manufacture lead-free petrol after completion of the Isosiv project, according to its general manager, C K Raja. Speaking to media persons , Mr Raja said the work on the project has already commenced. The step has been taken as part of their commitment to reduce level of ambient air pollution, he said. He said the refinery has embarked on modernization of effluent treatment plant (ETP) to augment the quality of treated water further.