The river water source is categorized as ‘hard water’ due to the high concentrations of magnesium and calcium ions. Explain ONE (1) negative effect of water hardness. With the concept of solubility and solubility product, identify the unit process needed to treat this problem and hence, discuss the process by outlining the relevant chemical compounds and chemical equations. 

River water Unit process 1: Aeration Unit process 2: Clark's process Unit process 3: Coagulation & flocculation Treated Unit process 5: water Unit process 4: End-users Disinfection Filtration