Efect of Magnesium and Calcium Precipitation on Coagulation-Flocculation With Lime

Coagulation-flocculation studies were carried out to identify and quantify the organic matter (TOC) fraction removed by Mg (OH) sub(2) precipitation and the fraction removed due to CaCO sub(3) precipitation in lime treatment of wastewater. Most experiments were carried out with domestic sewage and some with a tannic acid solution simulating coagulable organics in wastewater. The experiments showed a clear relation between the amount of TOC removed and the amount of Mg (OH) sub(2) formed. This relation between TOC removal and Mg(OH) sub(2) precipitation can be expressed in terms of an adsorption isotherm. The coagulation-flocculation tests of sewage with lime as a coagulant indicated that about 26% of the removable TOC in sewage is eliminated by Mg(OH) sub(2).