Two surface active agents were prepd. by using waste glycerol and waste fat (stearic acid) and tested for biodegradability by activated sludge microorganisms for 28 days and toxicity against the microorganisms. The agent based on glycerol showed higher biodegradability degree (87-100%) than that based on fat (70-81%). This agent inhibited the activity of nitrifying bacteria (by 15%) but was not toxic.