HYDROPHOBIC HYDROPHILIC PROPERTIES OF ACTIVATED-SLUDGE EXOPOLYMERIC SUBSTANCES/

Hydrophobic interactions may be fundamental in the cohesiveness and ot her properties of bacterial aggregates called flocs. Exopolymeric subs tances (EPS) form a matrix in which bacteria and other particles are e mbedded. However, knowledge about EPS hydrophobic properties is rather scanty. In this study, EPS extracted from activated sludges from diff erent origins were fractionated, exploiting their property of sorbabil ity by non-ionic resins and the formation of precipitates under-acidic environment. In the light of the results obtained with the XAD-8 resi n, at least 7% of the dissolved carbon and 12% of the proteins may be considered as hydrophobic. No carbohydrates were found in the hydropho bic fraction. The precipitable fraction at pH 2 on the other hand cont ained 64% carbohydrates and 76% proteins. This suggests that EPS are h eteropolymers principally made up of carbohydrates and proteins. (C) 1 998 IAWQ. Published by Elsevier Science Ltd.