COAGULATION - ITS EFFECT ON ORGANIC-MATTER

Removal of natural aquatic dissolved organic matter (DOM) by conventio nal coagulation using ferric chloride was investigated. Reverse osmosi s was used to isolate DOM from the Suwannee River in southern Georgia and from Lake Allatoona in northwestern Georgia. The two most signific ant differences between the source water are pH and organic carbon con centration. Extensive jar-testing identified regions of removal based on initial concentration of DOM, coagulant dosage, and pH conditions. Fast atom bombardment mass spectrometry was used to characterize the m olecular-weight distributions of DOM before and after coagulation. Tre nds in the shape of the mass spectra correlated well with data for DOM removal and suggested that the mechanism for DOM removal varies with the pH and coagulant dosage. At higher pH conditions and lower coagula nt dosages, masses up to 1,000 daltons (D) were detected in the mass s pectra after coagulation. At lower pH conditions and higher coagulant dosages, no masses above 750 D appeared in the mass spectra.