The invention provides compositions comprising bauxite refinery residues that have been reacted with sufficient calcium and magnesium ions that they have a reaction pH of less than 10.5, and one or more water treating additives. The invention also provides processes for treatment of water containing dissolved inorganic substances involving stepwise treatment of the water in which the reacted bauxite refinery residues are added after the addition of a pH-raising additive. The invention also provides processes for treatment of water containing dissolved inorganic substances in which the reacted bauxite refinery residues are added stepwise, with one or more water treating additives also being added in at least one of the steps. The invention also provides a process for the neutralisation of bauxite refinery residue by reacting it with a base amount and a treating amount of calcium ions and a base amount and a treating amount of magnesium ions for a time sufficient to produce an at least partially-neutralized residue exhibiting a reaction pH of less than 10.5.