Wastewater treatment plant design, get the plan and then cad draw the floor plan, how should I start? Seeking ideas from the experts! Thank you very much!

1 to get the program should be the first process calculations, to determine the parameters of each structure

2 general layout

3 to the civil engineering professionals to propose civil conditions

4 in the civil construction drawings on the design of the process, the civil engineering drawings do not need to be deleted, and ultimately complete the process construction drawings and piping construction drawings