Complex sentence: In lime softening, there is a substantial reduction in total dissolved solids (TDS) whereas in ion exchange softening (sometimes referred to as zeolite softening), there is no significant change in the level of TDS.
Split into simpler sentences: In lime softening, there is a substantial reduction in total dissolved solids (TDS). In ion exchange softening (sometimes referred to as zeolite softening), there is no significant change in the level of TDS.