The process depends on which department you apply for. Each has its own unique method of interviewing candidates. Some are the more traditional, others have you meet multiple people at once, and a few wing it.
I applied through university. I interviewed at Philadelphia Water Department in Jan 2019
Interview
Went over my resume and expanded on most points in it. I spoke a lot about my leadership experience in school organizations. I also spoke about what I was doing in class.
Interview questions [1]
Question 1
I was asked about my leadership and community service.