Quick take
Test first, then build the treatment train in stages: coarse/fine sediment as needed, contaminant-specific treatment, and UV only when microbiological control is justified.
Start with particle load
Sand and grit call for coarse protection; finer turbidity may need staged cartridge filtration.
Add chemistry-specific treatment
Iron, manganese, sulfur and hardness each require different media or processes.
UV is not a sediment filter
UV disinfects but requires clear water and does not remove dirt, metals or hardness. Pretreatment usually comes first.
Do not oversize blindly
Every unnecessary stage adds pressure drop and maintenance. Use testing to keep the treatment train targeted.