Although there is some information on the total amounts of proteins in wastewater and sludges1"3 and on the amino acids in them,4-11 especially in activated sludge,12 there is almost no evidence on the nature of the proteins in these materials. A knowledge of the nature of proteins in wastewater, sludges, and similar substances would be useful not only for determining the pollutional effects on the environment and the changes in the protein structures during decomposition or treatment, but also for determining the possible usage of the resulting materials in agriculture,13 includ ing animal nutrition.