RESEARCHING NEW WAYS TO REDUCE N2O EMISSION FROM A GRANULAR SLUDGE SEQUENCING BATCH REACTOR TREATING DOMESTIC WASTEWATER UNDER SUBTROPICAL CLIMATE CONDITIONS

Gilberto C Daudt,Lorena B Guimarães,Jéssica A Xavier,Rejane H R Da Costa,Bianca Meotti

doi:10.1590/0104-6632.20190361s20170566

Abstract

ABSTRACT N2O emissions from wastewater treatment plants have become an important issue, since this compound is a significant greenhouse gas that affects the sustainability of sewage treatment. This work aimed to investigate and to reduce N2O emission from a pilot-scale aerobic granular sludge sequencing batch reactor (AGS-SBR) operated for carbon and nitrogen removal from domestic wastewater under subtropical climate condition. Three operational strategies (S-I, S-II and S-III) with different anoxic phase durations were compared regarding treatment efficiency and N2O emission. For all the studied strategies, volatile suspended solids (VSS) was between 1.0 and 1.2 g/L. S-III, with the longest anoxic phase, obtained the highest biological oxygen demand (BOD) and NH4+-N removal efficiencies (86% and 84%, respectively), the lowest N2O emission factor (16.99 gN2O-N/person·year) and the lowest total nitrogen (TN) to N2O conversion ratio (0.47%). The results indicated that the extension of the anoxic phase was an effective way to significantly reduce N2O emission and to improve treatment efficiency.

Highlights

Production and emission of greenhouse gases (GHG) from wastewater treatment plants (WWTP) is a very important issue, which is becoming increasingly significant (Foley et al, 2010; Mannina and Cosenza, 2015)
Biomass characteristics and composition aerobic granular sludge (AGS) was successfully cultivated in the Sequencing batch reactors (SBR) fed with domestic wastewater containing low concentration of organic substrate, without adding an external carbon source and without biomass inoculation
Considering granules to be the particles with diameters between 0.2 and 5.0 mm (Liu et al, 2010), granulometric analyses indicated average granular biomass fractions of 66%, 32% and 59% during Strategy I (S-I), Strategy II (S-II) and Strategy III (S-III), respectively

Summary

Introduction

Production and emission of greenhouse gases (GHG) from wastewater treatment plants (WWTP) is a very important issue, which is becoming increasingly significant (Foley et al, 2010; Mannina and Cosenza, 2015). Sequencing batch reactors (SBR) with aerobic granular sludge (AGS) are presented as a promising option for the biological treatment of domestic and industrial effluents, due to the efficiency and robustness of this type of system (Di Bella and Torregrossa, 2013; Moreira et al, 2015; Pronk et al, 2015). With this technique, it is possible to obtain high removal rates of organic matter and nutrients in a single reactor, producing a final effluent with high quality (De Kreuk et al, 2005; Liu et al, 2015). The dynamics of nitrogen removal in this process, including nitrous oxide emission, are not completely understood; further research is required

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