BIODEGRADABILITY AND AQUATIC TOXICITY OF GLYCOSIDE SURFACTANTS AND A NONIONIC ALCOHOL ETHOXYLATE

The environmental properties of three glycoside surfactants and one al cohol ethoxylate were examined by standardized laboratory methods. All of the surfactants biodegraded extensively in aerobic screening tests and may be assumed to approach 100% removal in aerobic wastewater tre atment plants, except in cases of high loadings or otherwise exception al conditions. Anaerobic biodegradability tests showed that an ethyl g lycoside monoester (EGE) and a linear alkyl polyglycoside (APG) were b oth mineralized (>70%) under methanogenic conditions. In contrast, a b ranched APG resisted anaerobic degradation, while the alcohol ethoxyla te was partially mineralized by anaerobic bacteria. The EGE surfactant was most rapidly mineralized in aerobic and anaerobic biodegradabilit y tests. None of the surfactants inhibited respiration in activated sl udge at the highest concentration tested (200 mg/L). Tests with aquati c organisms showed increasing toxicity in the following order: branche d APG < EGE < linear APG < alcohol ethoxylate. Negligible aquatic toxi city was observed for the branched APG, while the alcohol ethoxylate w as highly toxic to examined organisms. This evaluation demonstrates th at considerable variation in biodegradability and toxicity responses c an be seen within structurally related glucose-based surfactants.