Purified sewage from municipal treatment plants was acidified to pH 2 and treated with ion exchange resins in a lab. column to sep. the humic acids (HA). After desorption with aq. NH3, the HA were concd. under vacuum and studied for mass yield, UV (250 and 300 nm) and visible (465 and 665 nm) light spectra, IR absorption spectra and elementary compn. The concn. of HA in the treated sewage was 2.8 and 3 mg/L as compared with 1-9 mg/L in surface waters in the region. The compn. of the sewage-sepd. HA contained arom. rings and substantially differed from those sepd. from Wista river water.