I made such a spread sheet years ago on Lotus 123. It was based on use of a series of deep wells with varying water composition. Since the well operation was changed only infrequently, the spread sheet worked fine. It included use of MgO for silica removal along with hydrated lime. The natural alkalinity was such that soda ash was not required at this location. I based the chemical feeds on water flow to the HLS, the particular wells in operation and the desired 2P-M. Chemical concentration in the feed tanks had to be constant, ie #/" of solution made.
Operation of a HLS can be a nightmare in addition to the maintenance. I devised a plan to take this single unit out of service for cleaning every 6 months. Cleaning time was scheduled for approximately 24 hours. Basically it was a wash down to remove accumulated sludge in all compartments and sight glasses. It is also necessary to limit flow swings to no more than 50 gpm per hour to prevent serious upsets. Perhaps I'm preaching to the choir here.
I'll search my computer discs and will let you know if I found the spread sheet. Give me a few days and I'll get back to you.