The endotoxin content and pyrogenic response of granular activated carbon (GAC) filtered waters were studied. GAC-filtered secondary effluent from an activated sludge pilot plant contained free endotoxins in the range 6-250 micrograms/l yielding positive pyrogenic responses in 18 of 20 trials. Samples obtained from 27 different water supplies in the U.S. that utilize GAC adsorption contained free endotoxin ranging from 1.2-25 micrograms/l but none gave a pyrogenic response. No relationship was discernible between endotoxin content and pyrogenic response. Small removals of total organic carbon (TOC) by GAC beds which had been in operation in water treatment plants without regeneration for as long as 110 months were observed. However, 5 of 28 samples showed an increase in TOC through GAC and 8 of 28 samples showed an increase in standard plate count. One of 25 samples yielded pseudomonads, but none of the 28 samples contained coliforms. Good correlations were observed on non-disinfected AWT effluent samples between standard plate count and total endotoxin (r = 0.945), standard plate count and free endotoxin (r = 0.932), and total coliforms and free endotoxin (r = 0.939). Lack of good correlations, however, were observed in assaying AWT samples that had been subject to the disinfecting procedures of chlorination, ozonation, pH or UV irradiation.

Grant no. R-804420. Feb. 1979. Includes bibliographical references.