I have calculated AQI, WQI, Solid Waste collection efficiency of the concerned city now I want to show all of these in the form of a risk factor or an index
in addition to Michael J. Lynch suggestions you can also look into the environmental performance index (EPI; https://en.wikipedia.org/wiki/Environmental_Performance_Index) to see how they combine the various indices (health impact, air quality, water and sanitation, ...) using weightage factors.
I did not ask you to calculate the EPI using your data. What I meant was to have a look how they do it (and from there come up with your own index). The challenge for you will be to find the suitable weightage factor.