Removal of Suspended Solids
Referring back to Figure and examining the effluent of the softener, they search that both sodium salts and precipitates are present. Those substances result from reactions that classically occur based on the presence of Ca++ and Mg++ salts. The chemicals most generally used for softening are soda ash or sodium carbonate (Na2CO3) and hydrated lime (Ca (OH) 2). Hard water (water holding Ca++ and Mg++ salts) holds calcium and magnesium bicarbonates (Ca (HCO3)2) and (Mg (HCO3)2), as well as calcium sulfate (CaSO4) and magnesium chloride (MgCl2). These impurities generate the subsequent reactions.
Ca(HCO3)2 + Ca(OH)2 → 2CaCO3 + 2H2O (4-18)
Mg(HCO3)2 + 2Ca(OH)2 → Mg(OH)2 + CaSO4 (4-19)
MgSO4 + Ca(OH)2 → Mg(OH)2 + CaSO4 (4-20)
CaSO4 + Na2CO3 → CaCO3 + Na2SO4 (4-21)
MgCl2+ Ca(OH)2 → Mg(OH)2 + CaCl2 (4-22)
CaCl2 + Na2CO3 → CaCO3 + 2NaCl (4-23)
As evident from the above reactions, while Ca++ and Mg++ ions could be removed from solution, soluble sodium salts are formed. As a result the total dissolved solid content is fundamentally unchanged. CaCO3 and Mg (OH) 2 are in precipitate form and must also be erased from the solution. A single method of doing this is through filtration. It is the procedure in that insoluble solids are erased from the water through passing them through a filter medium consisting of some category of porous material. That procedure will remove suspended solids and precipitates, other than has no effect on dissolved solids. Numerous materials are used as filter media and involved sand, anthracite, activated charcoal, diatomaceous earth, and to some extent resin in an ion exchanger. Sand is not generally used in nuclear applications since of the silicate ion (SiO3 =) related. Silicate ions are undesirable because they hydrolyze in water and form a weak acid that tends to increase corrosion. Activated charcoal is frequently used following a chlorinator in a water treatment system since it removes excess residual chlorine as well as suspended matter.