Correlation of physicochemical properties and sludge dewaterability under chemical conditioning using inorganic coagulants

• Published in: Bioresource technology 2013-09, Vol.144, p.337-343
• Main Authors: Niu, Meiqing, Zhang, Weijun, Wang, Dongsheng, Chen, Yu, Chen, Ronglai
• Format: Article
• Language: English
• Subjects: Applied sciences; Biological and medical sciences; Biopolymers - chemistry; Chemical conditioning; Chemical Phenomena; Chlorides; Coagulants; Conditioning; Correlation; Dewatering (separation process); EPS; Exact sciences and technology; Filtration; Flocculation; Fractal analysis; Fundamental and applied biological sciences. Psychology; Inorganic Chemicals - chemistry; Inorganic coagulants; Kinetics; Molecular Weight; Particle Size; Physicochemical properties; Pollution; Sewage - chemistry; Sludge; Sludge dewaterability; Solubility; Viscosity; Wastes; Water - chemistry
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2013.06.126

•Waste sludge conditioned with inorganic coagulants.•Change in physicochemical properties of sludge floc was investigated.•Chemical conditioning process included rapid aggregation and floc densification.•SRF correlated well with the change in content of soluble EPS, LB-EPS and TB-EPS.•Compression of EPS structure was a major mechanism of dewaterability improvement. This study investigated the effects of chemical conditioning with three representative inorganic coagulants (FeCl3, polyaluminum chloride (PACl) and high performance PACl (HPAC) on sludge dewaterability. We monitored the particle size, kinetic viscosity (KV), fractal dimension (DF) and extracellular polymeric substances (EPS) located in different layers of sludge floc (soluble, loosely-bound (LB), tightly-bound (TB)) to understand the correlation of dewaterability and physicochemical properties of sludge under chemical conditioning. The conditioning process included the rapid aggregation of sludge particles induced by charge neutralization and bridging followed by floc densification caused by double electric layer compression. The floc size and DF were increased after chemical conditioning, indicating that larger and more compact floc formed. The floc conditioned with FeCl3 was smaller but denser than that of PACl and HPAC. Furthermore, sludge dewaterability correlated well with the change in concentration of soluble EPS, LB-EPS and TB-EPS, but not with KV, DF, floc size.