Premium
Synthetic sludge: A physical/chemical model in understanding bioflocculation
Author(s) -
Sanin F. Dilek,
Vesilind P. Aarne
Publication year - 1996
Publication title -
water environment research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.356
H-Index - 73
eISSN - 1554-7531
pISSN - 1061-4303
DOI - 10.2175/106143096x127938
Subject(s) - flocculation , calcium , extracellular polymeric substance , chemistry , polymer , chemical engineering , activated sludge , calcium alginate , wastewater , microorganism , polysaccharide , polystyrene , bacteria , environmental engineering , organic chemistry , biofilm , environmental science , geology , paleontology , engineering
We postulate a mechanism for floc formation and demonstrate its feasibility by building synthetic sludge flocs. In this work, polystyrene latex particles of a size similar to bacteria are used to simulate individual bacteria; alginate, a polysaccharide, is used to simulate microbial extracellular polymers; and calcium ions are used as the bridging cations. Calcium and alginate are added at typical concentration ranges relative to the amount of microorganisms existing in wastewater treatment biological sludges. Flocs are formed almost instantly by the addition of calcium ions and are observed to be remarkably similar to the activated sludge flocs in physical appearance. Floc formation is faster at higher calcium concentrations. Higher alginate and calcium concentrations always ensure lower turbidities indicating better floc forming abilities.
The results of this study indicate that formation of metal‐polymer complexes and polymer gelation are important means of flocculation. Because of similar concentration ranges of alginate and calcium in this study to extracellular polymers and calcium in activated sludge, these mechanisms of flocculation are suggested also to be the main mechanism of interaction during bioflocculation in activated sludge systems.