Process for removing silica and reducing total hardness from water

A process for removing silica and reducing total hardness of a natural or waste water containing silica and scale-forming ions, the process comprising:

• adding (i) magnesium hydroxide or a precursor of magnesium hydroxide and (ii) a soluble aluminate compound or a precursor of aluminate to said water while maintaining the pH of said stream at pH >8 to produce layered double hydroxide in situ, wherein the layered double hydroxide contains the scale-forming ions in a lattice of the layered double hydroxide and silica is incorporated in the lattice of the layered double hydroxide as an interlayer anion and/or bound by the layered double hydroxide via one or more binding modes, wherein the process further comprises a recycling and regeneration step;
• wherein the recycling and regeneration step comprises:
• a) removing layered double hydroxide from the process;
• b) regenerating and/or recycling at least a portion of the layered double hydroxide removed from the process to form regenerated and/or recycled layered double hydroxide;
• and
• c) reintroducing the regenerated and/or recycled layered double hydroxide back into the process.