Abstract
A bioflocculant-producing bacterium, named N-10, was isolated from activated sludge and was identified as Klebsiella sp. The bioflocculant (named MBF10) produced by Klebsiella sp. had a good flocculating capability and could achieve a flocculating rate of 86.5% to kaolin suspension at the dosage of 0.034?g/L. Compared with chemical flocculants, such as Al2(SO4)3, polyaluminum chloride (PAC) and cationic polyacrylamide (PAM) at their optimal dosages, MBF10 showed a similar performance for sludge dewatering. After preconditioning, dry solids (DS) and specific resistance to filtration (SRF) of the sludge were 17.5% and 3.36 x 1012 m/kg, respectively. The combined use of MBF10 and Al2(SO4)3 resulted in optimum sludge dewatering properties, SRF reduced from 10.87 x 1012 m/kg to 1.72 x 1012 m/kg, and DS increased from 13.1% to 21.3%. Charge neutralisation and interparticle bridging were proposed as the reasons for the enhanced performance based upon the experimental observations.