Settling velocity of sludge in coagulation flocculation treatment of leachate using ferric chloride and chitosan

Abstract

Leachate is a highly contaminated wastewater which needs to be treated before being discharged to the environment. This is due to the concern that it may cause severe impacts on the environment. One of the well-known treatments that have been adapted for decades for treating leachate is the coagulation and flocculation processes. Coagulation and flocculation processes involve the addition of chemical or natural coagulant in order to destabilize the particles and remove the contaminants present. The rate or performance of chemical/natural coagulant use can be evaluated by determining the sludge settling rate during the flocculation process. This study emphasizes on the effect of Chitosan as natural coagulant aid/polymer in improving the settling rate of flocs after the flocculation process. After a series of experiments, Chitosan as a polymer showed a potential and gave a satisfying results as it improved the sludge settling velocity from 0.57 cm/min, when FeCl3 (chemical coagulant) was used independently to 0.69 cm/min when Chitosan was applied as a coagulant aid. Moreover, Chitosan also increased the floc size to 198. 5 µm compared to 83.3 μm when FeCl3 was used alone. The improvement in terms of settling velocity and size of flocs was due higher molecular weight of Chitosan which provides a long chain for particle attachments. With this ability, Chitosan had a greater potential in increasing the performance of flocculation.