title: Influence of cations on activated-sludge effluent quality.
abstract: Laboratory experiments and field tests were conducted to determine the effect of inorganic cations on effluent from activated-sludge systems. Laboratory experiments showed that monovalent cations tend to increase the concentration of solution biological polymers (biopolymers), whereas divalent cations tend to retain the biopolymers in the floc. Biopolymers in solution affect effluent chemical oxygen demand (COD). Coagulation tests were performed on the effluent with ferric chloride. Ferric hydroxide can coagulate protein through possible adsorptive interactions and may be responsible for some biopolymer retention in the flocs. In the field study, it was found that sodium ions in the influent wastewater caused an increase in proteins and polysaccharides in solution, thereby increasing the effluent COD concentration of the treated municipal wastewater. The attachment or release of these microbially derived organic biopolymers and recalcitrant influent substrate may depend on the monovalent-to-divalent cation ratio and the concentration of iron. Modeling of effluent organics in the activated-sludge process can be enhanced through incorporation of concepts that take into account the partitioning (between floc and solution) of microbial biopolymers and influent recalcitrant substrate.
authors.affiliation: Department of Civil Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA. smurthy@ch2m.com
authors.forename: S N
authors.initials: SN
authors.lastname: Murthy
authors.forename: J T
authors.initials: JT
authors.lastname: Novak
mesh_terms: D001704:Biopolymers; D002412:Cations; D004787:Environmental Pollution / Q000517:prevention & control*; D009930:Organic Chemicals / Q000378:metabolism; D011134:Polysaccharides / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D012722:Sewage / Q000737:chemistry*; D012988:Soil Microbiology
chemical_list: D001704:Biopolymers; D002412:Cations; D009930:Organic Chemicals; D011134:Polysaccharides; D011506:Proteins; D012722:Sewage