Coagulation of Organic Color With Hydrolyzing Coagulants

M surface waters have a charOden," has been adopted widely and is acteristic brown color, which is shown in Table 1. due to the presence of complex organic Various authors 2-4 have demoncompounds of natural origin derived strated the presence of fulvic acids from the water soluble peptizable C0111together with a proportion of hymatoponents of soil humus and peat. The melanic and humic acids in natural organic composition of soil humus has waters. been studied for many years and it is The coagulation of organic color in now generally accepted that a special natural waters has been the subject of category of organic compounds termed numerous investigations. 5-9 Miller 6 "humic substances" is present. Alstated that in the coagulation of color though their precise molecular constituwith aluminum sulfate, the aluminum tion is still uncertain, the available ion was the active coagulant, whereas evidence strongly suggests that humic Ermolenko and Levina' regarded the substances are formed in the soil by a process as one of chemisorption on the polymerization of polyphenolic units surface of precipitated hydroxides. derived from either bacterial synthesis Black and Willems S have concluded or the breakdown of lignin residues. that the process may be regarded as Alcoholic OH-, phenolic OH-, carthe coagulation of a negatively charged boxyl, methoxyl and quinonoid grouporganic colloid by positively charged ings have been demonstrated in addihydrolysis products of iron or alumition to variable proportions of nitrogeI1UI11. Shapiro.!? however, has quesnous compounds such as amino acids tioned the colloidal nature of organic and polypeptides. color that is not in association with The term "humic substances" emiron. Packham 4 has stated that it is braces a very wide range of comlikely that humic substances are in true pounds having an essentially similar solution in water, but that a proportion constitution and many common properof the molecules are sufficiently large to ties, but differing in molecular weight exhibit colloidal properties. and the proportion of the various funcIn the investigation described in this tional groups. A convenient classificaarticle, the coagulation of organic color tion of humic substances, which is was studied using humic substances based on that proposed originally by that had been isolated from river water