Sludge conditioning by using alumina nanoparticles and polyelectrolyte

• Published in: Water science and technology Vol. 56; no. 8; pp. 125 - 132
• Main Authors: Wang, Z.S, Hung, M.T, Liu, J.C
• Format: Journal Article
• Language: English
• Published: England IWA Publishing 01.01.2007
• Subjects: Activated sludge; aluminum; Aluminum oxide; Aluminum Oxide - chemistry; Anions; capillarity; Cations; Cations - chemistry; Charge density; Conditioning; Dewatering; Electrical resistivity; electrolytes; Electrolytes - chemistry; filtration; Flocculation; fractal dimensions; Industrial Waste; Metal Nanoparticles - chemistry; Molecular Weight; Nanoparticles; nanotechnology; Nucleotide sequence; particle size; Polyelectrolytes; Pulp; Pulp & paper industry; Retention; Sewage - chemistry; Silica; Silicon dioxide; Sludge; Sludge conditioning; Suction; Waste Disposal, Fluid - methods; Waste Management - methods; wastewater treatment; Water Purification - methods
• ISSN: 0273-1223; 1996-9732
• DOI: 10.2166/wst.2007.708

The combined use of nanoparticle and polyelectrolyte as retention aids in pulp and paper industry tend to give better flocculation (retention) and drainage (dewatering) than conventional polyelectrolyte flocculation. The combined use of alumina nanoparticle and polyelectrolyte in conditioning waste activated sludge was investigated in the current study. Alumina with three different sizes (139.5, 241.7, and 326.4 nm) was utilized in combination with a cationic polyelectrolyte (T3052) of molecular weight of 1.1 x 10(7) and charge density of 2.1 meq/g. It was found from capillary suction time (CST) and specific resistance to filtration (SRF) measurement that sludge conditioned with alumina/polyelectrolyte showed a better dewaterability than polyelectrolyte alone. In addition, it was found that the better dewaterability was obtained as alumina became smaller. Floc size and fractal dimension of flocs were examined as well. The mechanism of enhanced dewaterability was proposed that alumina nanoparticles became adsorbed onto sludge and positive patches were formed. The electrostatic repulsion made the polyelectrolyte more stretched, and resulted in more effective flocculation and bridging as polyelectrolyte was added. Dosing sequence also affected the conditioning effectiveness. However, the combined use of silica nanoparticles and a cationic polelectrolyte, KP-201C, or alumina nanoparticles and an anionic polyelectrolyte, AP410, did not result in improved dewaterability of waste activated sludge. Possible explanation was discussed. Preliminary results show that some in-depth work is needed regarding the introduction of nanoparticles in sludge conditioning.