Cheers, i maintain the instrumentation side of things there and several other plants too.
Number 2 is one of the inlets from the reservoir, that is untreated water.
Number 3 are the various filter tanks
Number 4 is the DAF (Dissolved-air flotation) system
Number 5 is the inlet to the 2nd stage filters before its fit to drink
Sorry, never crossed my mind to explain what they were, i see them most days.