Applications and limitations of the colloid titration method for measuring activated sludge surface charges.
Surface charge quantification of polymer solutions and sludge suspensions were investigated by the colloid titration technique and compared to charge densities obtained by pH-titration. The colloid titration technique worked well for polymer samples. The charge quantity of humic acid and activated sludge extracellular polymers (EPS) was estimated to be -1.51 and -0.42 meq/g, respectively. These values are reasonable when compared to pH-titration results. The surface charge of activated sludge particles appears to be below the limit of detection. However, surface charge estimates are obtained, when the reactant doses and sample concentration are increased. It is suggested that such estimates are not correct, but artefacts of the non-stoichiometric precipitation of the polymeric reactants at high doses. It appears that the colloid titration method is limited to conditions of low reactant doses and valid for charge determination of extracted sludge polymers, whereas the method is not valid for charge determination of whole sludge.
Department of Environmental Engineering, Aalborg University, Sohngaardsholmsvej 57, Aalborg 9000, Denmark. lhmi@novozymes.com
Lene Haugaard
LH
Mikkelsen
D003102:Colloids; D004784:Environmental Monitoring / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D011108:Polymers / Q000032:analysis* / Q000737:chemistry; D012722:Sewage / Q000737:chemistry*; D017186:Titrimetry
D003102:Colloids; D011108:Polymers; D012722:Sewage