68e07683_SAHRA___Home_Water_Testing__Likely_source
[Lab result] TDS [Treatment options] Reverse osmosis or distillation (POU) [Likely source] 
"Total dissolved solids" refers to any minerals, salts, metals, cations, or anions dissolved in water and usually naturally occurring. Excessive dissolved solids make water brackish or otherwise unsuitable for drinking or industrial uses. More discussion of TDS in Arizona municipalities is available here.
SAHRA - Home Water Testing
Likely source