Nitrous oxide from moving bed based integrated fixed film activated sludge membrane bioreactors

Abstract

a b s t r a c tThe present paper reports the results of a nitrous oxide (N 2 O) production investigation in a moving bed based integrated fixed film activated sludge (IFAS) membrane bioreactor (MBR) pilot plant designed in accordance with the University of Cape Town layout for biological phosphorous removal. Gaseous and liquid samples were collected in order to measure the gaseous as well as the dissolved concentration of N 2 O. Furthermore, the gas flow rate from each reactor was measured and the gas flux was estimated. The results confirmed that the anoxic reactor represents the main source of nitrous oxide production. A significant production of N 2 O was, however, also found in the anaerobic reactor, thus indicating a probable occurrence of the denitrifying phosphate accumulating organism activity. The highest N 2 O fluxes were emitted from the aerated reactors (3.09 g N 2 OeN m À2 h À1 and 9.87 g N 2 OeN m À2 h À1 , aerobic and MBR tank, respectively). The emission factor highlighted that only 1% of the total treated nitrogen was emitted from the pilot plant. Furthermore, the measured N 2 O concentrations in the permeate flow were comparable with other reactors. Nitrous oxide mass balances outlined a moderate production also in the MBR reactor despite the low hydraulic retention time. On the other hand, the mass balance showed that in the aerobic reactor a constant consumption of nitrous oxide (up to almost 15 mg N 2 O h À1 ) took place, due to the high amount of stripped gas.

Bacterial community structure and removal performances in IFAS-MBRs: A pilot plant case study

“…The anoxic and aerobic compartments were filled with suspended plastic carriers (courtesy of Amitec Co. Ltd, carriers density ¼ 0.95 g cm À3 ; carriers specific surface ¼ 500 m 2 m À3 ), with a 15 and 40% filling fraction, corresponding to a net surface area of 75 and 200 m 2 m À3 in the anoxic and aerobic reactor, respectively. For the schematic layout of the UCT-IFAS-MBR pilot plant, the reader is referred to the literature (Mannina et al, 2017).…”

“…An alternative to managing this problem is to couple a MBR system with a moving bed biofilm reactor (MBBR) in an IFAS mode (Integrated Fixed Film Activated Sludge). In this way, it enhances the simultaneous growth of suspended biomass and biofilm inside the system (Mannina et al, 2011), realizing a socalled moving bed membrane bioreactor (MBMBR) or MBBR-based integrated IFAS membrane bioreactor (IFAS-MBR) (Leyva-Díaz et al, 2013;Yang et al, 2014;Mannina et al, 2017). In particular, MBBR processes rely on the use of small plastic carrier elements that are kept in constant motion throughout the entire volume of the reactor, for biofilm growth (Ødegaard, 2006;Di Trapani et al, 2008.…”

Greenhouse gas emissions and the links to plant performance in a fixed-film activated sludge membrane bioreactor – Pilot plant experimental evidence

“…A UCT-IFAS-MBR pilot plant has been designed and set up at the Laboratory of Sanitary and Environmental Engineering of Palermo University (Mannina et al, 2017a). The pilot plant consists of one anaerobic (volume 62 L), one anoxic (volume 102 L) and one aerobic (volume 211 L) tank according to the UCT scheme.…”

“…Among these the performance of membrane bioreactors (MBRs) and moving bed biofilm reactors (MBBRs) have been thoroughly analysed in the past years and have demonstrated several advantages compared to conventional treatment methods (Ødegaard, 2006;Judd, 2011). Recently, the combination of MBR and MBBR in the Integrated Fixed Film Activated Sludge (IFAS) configuration has been proposed with the aim to further improve the treatment efficiency (Mannina et al, 2017a). During the last few years, the environmenhttp://dx.doi.org/10.1016/j.biortech.2017.05.043 0960-8524/Ó 2017 Elsevier Ltd. All rights reserved.…”

“…The identification of the interrelationship between operational conditions and GHG emissions represents a key issue in view of reducing the GHG emissions by maintaining feasible operational costs and good effluent quality. However, there are only few studies that have explored the N 2 O emission from advanced technologies based on biofilm growth (Todt and Dörsch, 2016;Mannina et al, 2017a;Sabba et al, 2017).…”