HOW TO REDUCE HARDNESS AND TDS?

By adding corrosion inhibitor & blow down the cycle.

By using softener followed by RO.

If you have a hard water problem, your solution could be through a water filtration system such as Reverse Osmosis (RO) (which will remove most minerals), Distillation (which will remove all minerals) or a Water Softener.  For a whole house, reverse osmosis or other types of filtration are typically more costly options than a water softener.  

Water softeners do not remove TDS.  Instead, water softeners work through a process of ion exchange.  As water flow through the water softener, it will pass through a resin, bed of small plastic beads or chemical matrix (called Zeolite) that will exchange the calcium and magnesium ions with sodium ions (salt).  Therefore, the TDS level will remain virtually constant (there may be minor differences).

Water softeners are designed to "soften" water so that it washes brighter, rinses cleaner and feels much better.

Since a water softener does not lower the TDS level of your water, an additional filter may be necessary for your drinking water.  The need for an additional filtration system is entirely dependent upon your source water.  Always test your water to determine your needs prior to investing in a filtration or purification system.

If you want to reduce you hardness and TDS level together in industrial scale, you can use one of the following devices:

1- RO

2- MED RO (steam plant is required) 

3- Cationic and Anionic resins column (If you just use cationic alone your TDS would not change, just hardness will reduce)

4-Finally you can use lime and soda as traiditional method

For hardness which causes scaling can be subsided by adopting softners, which also depends on use like domestic or industrial. For removal of TDS from wastewater the most effective method is RO. One can achieve90-95% salt rejection. 

You can reduce hardness & TDS with different ways depends on application and your requirement. You can redcuce through pracipitation method, soulblization method, filtration method and ion exchange method.

1. If you go with pracipitation method, you have to add lime in the water and go with lime softening and reduce the hardness , if you reduce the hardness , TDS will also reduce with it.

2.If you add EDTA in water, it will make a soluble complex with hardness and reduce hardness, thats caled solubalization.

3. If you pass water through RO plant with reduce all dislove ions up to98 % with hardness.

4. Cation exchanger will reduce hardness up to99 %. Hardness ions replace with H ions in this pcocess.

in All above process, TDS will also decrease.

Water hardness can be treated with water filtration systems such as Reverse Osmosis and Distillation, which are two effective methods in removing minarls from the water.