Monovalent cations and their influence on activated sludge floc chemistry, structure, and physical characteristics

Abstract

Multivalent cations have been known to be important components of activated sludge floc structure due to their bridging ability of the negatively charged sites on the biopolymer network. Recently in batch systems it was found that excess concentration of monovalent cations led to the deterioration in settleability, dewaterability of sludges and effluent quality of the system. In this study, effect of influent monovalent cations (potassium and sodium) on activated sludge floc structure was investigated in semi-continuous reactors. Results revealed that the increase in concentration of both ions correlated to the general increase in total EPS concentration. The zeta potential values were affected by the cation type and dose in such a way that sludge from sodium reactors had always higher zeta potential values (higher negative charge) than the sludges from potassium reactors. Flocs from sodium reactors were more fragile and weak and the capillary suction time values of these sludges were higher compared to those from potassium reactors. The findings of this research conclude that the floc structure is significantly weakened with the increase of monovalent cations. Even though EPS is produced, it is unable to bind the floc components together. With this, the physical properties of sludge deteriorate for both cations.

Preconditioning with Cations Increases the Attachment of Anoxybacillus flavithermus and Geobacillus Species to Stainless Steel

“…The second effect that cations have on biofilm formation is an indirect effect, such that bacteria may respond to changes in concentrations of cations in their surroundings and adjust their metabolism and physiology (8)(9)(10)(11). These bacterial responses may indirectly influence their ability to transition from a planktonic form to an irreversibly attached form and prosper as a biofilm (8)(9)(10).…”

“…These bacterial responses may indirectly influence their ability to transition from a planktonic form to an irreversibly attached form and prosper as a biofilm (8)(9)(10). Ca 2ϩ and Mg 2ϩ have been shown to stimulate exopolysaccharide (8,12,13) and extracellular protein (9,14,15) production by bacteria and often have physiological roles in assisting the initial reversible association of bacteria with a surface or enhancing the cohesion of a biofilm (9,11,16).…”

“…Ca 2ϩ and Mg 2ϩ have been shown to stimulate exopolysaccharide (8,12,13) and extracellular protein (9,14,15) production by bacteria and often have physiological roles in assisting the initial reversible association of bacteria with a surface or enhancing the cohesion of a biofilm (9,11,16). Na ϩ has been shown to stimulate bacteria to increase the proportion of negatively charged, hydrophilic polymers in a wastewater sludge and, therefore, have a detrimental effect on its cohesion (10).…”

Dynamics of the microfauna community in a full-scale municipal wastewater treatment plant experiencing sludge bulking

“…In this study, besides the annual cyclic changes, we observed significant differences in the community structures at different SVI levels, as shown in Figs (Fig. S1), suggesting that ion exchange of bivalent cations Ca 2+ and Mg 2+ for monovalent Na + and K + ions (especially Na + ), which could influence sludge aggregation, did not occur (Higgins and Novak 1997;Kara et al 2008;Sobeck and Higgins 2002). Microscopic observations showed that Microthrix parvicella-like filaments were abundant when the SVI value was high (Fig.…”

Experimental and Theoretical Approaches for the Surface Interaction between Copper and Activated Sludge Microorganisms at Molecular Scale

“…AS has a negative surface charge, indicated by the negative value of zeta potential (Kara et al 2008). The zeta potential of Stanley AS and Shatin AS was −22.5 and −12.5 mV, respectively.…”