Determining the Mechanism for Low Sludge Yields in the Cannibal Solids Reduction System

Abstract

Extracellular polymeric substances (EPS) and solids concentrations in samples from the Interchange Bioreactor (IBR), and return activated sludge (RAS) from Cannibal facilities having low and high sludge yields, were analyzed to understand the mechanisms behind low sludge production. Low sludge yields correlated to more EPS degradation, higher concentrations of iron, and reducing conditions in the IBR. In the low yield facilities, iron was reduced when the RAS passed through the anaerobic and reducing conditions of the IBR, and this led to more EPS solubilization and degradation. This "futile cycle" of EPS production and degradation appears to may have been most responsible for reducing sludge yields.

Modeling, instrumentation, automation, and optimization of water resource recovery facilities (Review of 2018 Literature) DIRECT

“…The zone settling velocity correlations to MLSS for the three facilities were not similar enough to allow a general conclusion to be drawn on how to design and consistently grow rapidly settling flocculant biomass. Ginkel et al (2018) analyzed extracellular polymeric substances (EPS) and solids concentrations in samples from the interchange bioreactor (IBR), and RAS from Cannibal processes having low and high sludge yields. The trends of volatile suspended solids (VSS), SCOD, EPS, and iron support that, as Fe 3+ was reduced to Fe 2+ in the IBR at a low ORP of −400 mV, EPS was solubilized and returned to the aeration tanks as soluble COD.…”