Analytical Properties of the Soluble, Metal‐complexing Fractions in Sludge‐soil Mixtures: III. Unaltered Anionic Surfactants in Fulvic Acid

Abstract

Abstract A rapid analytical procedure was developed for the quantitative determination of unbiodegraded anionic surfactants in the fulvic acid fraction of sewage sludge. This procedure, which is a modification of the methyl green method of Moore and K olbeson, consists of: (i) hydrolysis in 4 N HCl, (ii) separation on an anion exchange resin, (iii) extraction of a methyl green‐surfactant complex into benzene, and (iv) colorimetric determination of the complex. The modified procedure is free of the negative interferences that occurred when the original methyl green method was applied to a sludge‐derived fulvic acid and does not require specialized reagents or expensive instrumentation. An application of the modified procedure to two representative fulvic acids extracted from anaerobically‐digested sewage sludges indicated that about 5% of the dry mass of a sludge‐derived fulvic acid (water‐ and ash‐free basis) may be attributed to unaltered anionic surfactant compounds. This result suggests that a significant aspect of the chemistry of agricultural soils into which sewage sludge has been incorporated will be reactions involving both unaltered and partially biodegraded anionic surfactants.