Can anyone give me some guidance on some online research I have to do?

Obviously there's no one way to this. I can think of the following steps.

1) go to scholar.google.com and use the keywords 'state of the art in electric public transportation' or state of the art in *insert field name*.

2) If you're lucky you'll find an exact state of the art review paper. If not, then go to whatever you do find.

3) Contact the author(s) and ask them about the latest technology in the field and who is doing the leading research.

4) Using that info as lead you'll find useful stuff.

OR

1) find out the latest research topics on that stuff yourself. Also, find out the mega projects related to those field (like construction of the tallest tower or something). And find out the researchers involved in the company that has taken the project or the authors.

Ultimately, you probably have to find someone who is doing research on that field and ask them who are the leading researchers on that field.

There will be a ranking for universities around the word. Just follow it and see who is leading in research go through the departments.

sustainability technologies !

Recycled Water

https://iwaponline.com/wst/search-results?page=1&q=%22advanced%20wastewater%20treatment%22&fl_SiteID=28

https://twitter.com/IWAP_OA

https://www.sciencedirect.com/science/article/abs/pii/S0273122397001790

https://books.google.com.au/books?hl=en&lr=&id=HbR0BgAAQBAJ&oi=fnd&pg=PP1&dq=sustainability++technologies+water+recycle&ots=8-aPlAe109&sig=WF2FXmpnbZHrelsebpWtIL7HbvM#v=onepage&q=sustainability%20%20technologies%20water%20recycle&f=false

https://iwaponline.com/ws/article-abstract/3/4/21/25821/Some-examples-of-water-recycling-in-Australian

https://lmgtfy.app/?q=leading+research+institutions+in+sustainability+technology