This can be a rather broad ...

This can be a rather broad reply as the type of process to be contemplated is not disclosed

you have biological removal processes that can reduce N and P through organic biological activity under specific applied conditions and you can source chemical and physical treatment process for inorganic water treatment streams, this may be chemical precipitation, membranes, ion exchange to mention a few

both have numerous references in the market, as mentioned previously Metcalf and Eddy is a good printed version

you can find other references through the IWA publications and others as well

bottom line, you need to understand the characteristics of the incoming water and quality and quantity, then select your target treated water quality objectives and then identify the type of process to deploy and design it accordingly