NH4+ ad-/desorption in sequencing batch reactors: simulation, laboratory and full-scale studies

Abstract

Significant NH4-N balance deficits were found during the measurement campaigns for the data collection for dynamic simulation studies at five full-scale sequencing batch reactor (SBR) waste water treatment plants (WWTPs), as well as during subsequent calibrations at the investigated plants. Subsequent lab scale investigations showed high evidence for dynamic, cycle-specific NH4+ ad-/desorption to the activated flocs as one reason for this balance deficit. This specific dynamic was investigated at five full-scale SBR plants for the search of the general causing mechanisms. The general mechanism found was a NH4+ desorption from the activated flocs at the end of the nitrification phase with subsequent nitrification and a chemical NH4+ adsorption at the flocs in the course of the filling phases. This NH4+ ad-/desorption corresponds to an antiparallel K+ ad/-desorption.One reasonable full-scale application was investigated at three SBR plants, a controlled filling phase at the beginning of the sedimentation phase. The results indicate that this kind of filling event must be specifically hydraulic controlled and optimised in order to prevent too high waste water break through into the clear water phase, which will subsequently be discarded.

Nitrogen Removal From Municipal Wastewater Using a Two‐Sludge Denitrification/Nitrification Batch Reactor: Performance and Mechanisms

“…Moreover, according to the previous studies, the sorption amount of NH 4 + ‐N (mass of the adsorbed NH 4 + ‐N to 1 g MLSS) onto the sludge flocs was only 0.07–0.2 mg g −1 suspended solids (SS) . In that case, based on the results of other studies, only 0.21–0.6 mg L −1 of NH 4 + ‐N was adsorbed onto the sludge flocs in this study, which further proved the steady variation of NH 4 + ‐N (Figure a). Higher NH 4 + ‐N concentration showed no promotion for adsorption.…”

“…In the sorption assays, the concentration of NH 4 + ‐N remained almost constant during the whole period of experimentation (Figure a), demonstrating that the anoxic sludge had low or no adsorption of NH 4 + ‐N. It was previously reported that the sorption of NH 4 + ‐N was based on ion‐exchange, which was significantly influenced by other cations (e.g., Ca 2+ , Na + , K + , Fe 2+ , and Fe 3+ ) adsorbed onto the negatively charged bacterial cell walls . In the sorption assays, the content of these cations in the supernatant indeed decreased (Figure S1 and S2, Supporting Information), indicating the sorption of these ions onto the sludge.…”

Lag phase, dynamic alpha factor and ammonium adsorption behaviour: introduction of special activated sludge characteristics in the ASM3 + EAWAG-BioP-model

“…Based on a series of lab-tests a cycle-specific NH þ 4 ad-and desorption processes in SBR activated sludge samples could be found within the range of 1.0-2.5 mg NH þ 4 per 10 g MLSS (Schwitalla et al 2008). To describe the cycle-specific NH þ 4 ad-and desorption processes in SBR activated sludge systems, two fractions SNHs (free NH þ 4 ions) and XNH (floc adsorbed NH þ 4 ions) are introduced replacing the original SNH fraction.…”

“…However, Nielsen (1996) had found a purely chemical NH þ 4 ad-and desorption to activated sludge flocs at conventional activated sludge plants. Subsequent lab-scale analysis revealed cycle-specific NH þ 4 ad-and desorption processes in SBR activated sludge samples within the range of 1.0-2.5 mg NH þ 4 per 10 g MLSS (Schwitalla et al 2008).…”

“…Performing further lab-scale analysis as described , Scharfscheer et al (2008) and Schwitalla et al (2008), the following mechanisms were identified to be responsible for these discrepancies: † the activity of biomass shows a significant lag phase after long anoxic/anaerobic phases † after filling phases, during the first few minutes after switching the aeration on a reduced oxygen transfer rate was observed, which was caused by a variable alpha factor † a third effect, which might be of interest, is a moderate ammonium adsorption Several studies showed that the activated sludge has a lag phase mainly during the transition from oxic to anoxic or under purely oxic or anoxic growth conditions given sudden substrate concentration changes (Vanrolleghem et al 2004;Casasus et al 2005). Full-scale SBR simulations doi: 10.2166/wst.2009.588 and recent OUR batch experiments revealed that a lag phase occurs even during the switch between the anoxic/anaerobic phase to the following oxic phase (Rö nner- Holm et al 2006;Scharfscheer et al 2008).…”