Modified silica fume powder with oleic acid through coupling agent was prepared based on the in situ utilizing long-chain fatty acids (LCFA) properties of Microthrix parvicella (M. parvicella) in the activated sludge system. The modification was confirmed by XRD and infrared spectrum. The contact angle analysis showed that the modification gave the silica fume powder a hydrophobic surface. The modified silica fume powder had a good combination with M. parvicella from the SEM and Gram staining measurements. The addition of modified silica powder has a certain effect on the settling capacity of sludge, but has little effect on the sludge treatment capacity, while the SVI dropped from 400.1 to 100.0 mL/g. These suggested that the modified silica fume powder could be used as an excellent weight-increasing agent to inhibit sludge bulking.
Keywords: Silica fume; filamentous sludge bulking; hydrophobic modification; oleic acid; settleability.