Influence of organic and inorganic flocculants on sludge treated by electroosmotic vacuum preloading

The application of electrokinetic geosynthetics in electroosmotic vacuum preloading treatment of dredged sludge suffers the problems of severe clogging and uneven reinforcement effects. The effects of organic flocculant anionic polyacrylamide (APAM) and inorganic flocculant ferric chloride (FeCl3) on the electrical conductivity and permeability coefficient of dredged sludge were obtained in tests, and the optimal flocculant dosage was determined accordingly. A series of electroosmotic vacuum preloading model tests were performed by adding organic and inorganic flocculants to dredged sludge. Slight variations of the discharge rate and settlement amount were noticed between the sludge samples mixed with FeCl3 and APAM at the vacuum preloading stage, but after electroosmosis initiation, the discharge rate of the sludge with APAM became higher, as well as the final settlement. The shear strength and uniformity of sludge with APAM after treatment were better than those of sludge with FeCl3. Compared to FeCl3, electroosmotic vacuum preloading with APAM help increase the effective electric potential of sludge and benefit the discharging of heavy metals.