Simultaneous removal of Ca and Mg Salts using chemical precipitation with lime

One of the major problems of mineral industries wastewater is high concentration of minerals like Ca and Mg salts that cause some difficulties in disposal of effluent into the environment. The aim of the present work was to investigate the optimal conditions and effect of the amount of lime dosage, temperature, detention time and settling time for removal of Ca and Mg salts of a mineral industry wastewater using lime processing. The amount of lime required for the process was determined using bar diagram. Full factorial design was used to experiment works. So the factor of temperature in three levels (25, 50 and 75°C), detention time (5, 10 and 15 min), settling time (5, 15 and 25 min) and factor of lime dosage in four levels (0, 10, 20 and30 g/l) were considered for evaluation of separation percentage of salt ions. The results showed that the amount of lime is the key parameter on the separation percentage and the amount of lime needed for removal of Ca and Mg salts are 20 and 30 g/L respectively. The optimal temperature for removal of these salts was found 75°C, which showed that the precipitation of CaCO3 and Mg(OH)2 is exothermic. Detention time and settling time for the process were determined 15 and 20 minutes respectively.