Dynamic α-factor models for fine-bubble- and surface aeration – impact of settleability and implications on N2O emission

Yuge Qiu; Vince Bakos; Nyle  Stewart-Campbell; Benedek Plosz

doi:10.1016/j.cej.2024.150650

Dynamic α-factor models for fine-bubble- and surface aeration – impact of settleability and implications on N2O emission

Yuge Qiu, Vince Bakos, Nyle Stewart-Campbell, Benedek Plosz

Research output: Contribution to journal › Article › peer-review

2 Citations (SciVal)

Abstract

In water resource recovery facilities (WRRF), aeration efficiency and N2O greenhouse gas emission are affected by the variability of the α-factor. Dynamic calibration of α using sensor data represents a significant knowledge gap this contribution aims to address. To assess factors influencing oxygen and N2O gas mass-transfer, a continuous flow laboratory-scale reactor system was operated to encourage the proliferation of filamentous bacteria. Gas mass-transfer was assessed using fine-bubble and surface aeration. Significant impacts of solid settling velocity on the α-factor – relative to that by MLSS concentration – is obtained. The feasibility of using solid settling velocity and concentration, as α-factor predictors, is tested. The theoretical approach of using relative diffusivity to dissolved oxygen – as an effective predictor of N2O liquid–gas mass-transfer stripping – is experimentally validated, for the first time. Plant-wide WRRF simulations show that surface aeration is inferior to fine-bubble aeration in terms of greenhouse gas emission and treated water quality.

Original language	English
Article number	150650
Number of pages	9
Journal	Chemical Engineering Journal
Volume	488
Early online date	26 Mar 2024
DOIs	https://doi.org/10.1016/j.cej.2024.150650
Publication status	Published - 15 May 2024

Data Availability Statement

Data will be made available on request.

Funding

We express our special thanks to Thomas Hug for the long-term full-scale WRRF measurement data from the Kloten-Opfikon WRRF, Switzerland. This research was partially funded by the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 893130 (project acronym: IDYEA). We are grateful for Prof. Tim Mays for the internal funding recived from Department of Chemical Engineering, University of Bath. We would like to thank Paul Frith, the departmental technician specialist (University of Bath) for building the laboratory-scale surface and fine-bubble aerated oxidation ditch-type reactor and providing all the techinical support. The authors have no conflict of interest to declare. We acknowledge the generous support of Mr. Yichen Qiu and Mrs. Pingyun Ge, parents of Ms. Yuge Qiu (first author), and their financial support received.

Keywords

Alpha-factor modelling
Filamentous bulking
Gas mass transfer in activated sludge reactors
Laboratory-scale experiments
WRRF simulations

ASJC Scopus subject areas

General Chemical Engineering
General Chemistry
Industrial and Manufacturing Engineering
Environmental Chemistry

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10.1016/j.cej.2024.150650Licence: CC BY

Cite this

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title = "Dynamic α-factor models for fine-bubble- and surface aeration – impact of settleability and implications on N2O emission",

abstract = "In water resource recovery facilities (WRRF), aeration efficiency and N2O greenhouse gas emission are affected by the variability of the α-factor. Dynamic calibration of α using sensor data represents a significant knowledge gap this contribution aims to address. To assess factors influencing oxygen and N2O gas mass-transfer, a continuous flow laboratory-scale reactor system was operated to encourage the proliferation of filamentous bacteria. Gas mass-transfer was assessed using fine-bubble and surface aeration. Significant impacts of solid settling velocity on the α-factor – relative to that by MLSS concentration – is obtained. The feasibility of using solid settling velocity and concentration, as α-factor predictors, is tested. The theoretical approach of using relative diffusivity to dissolved oxygen – as an effective predictor of N2O liquid–gas mass-transfer stripping – is experimentally validated, for the first time. Plant-wide WRRF simulations show that surface aeration is inferior to fine-bubble aeration in terms of greenhouse gas emission and treated water quality.",

keywords = "Alpha-factor modelling, Filamentous bulking, Gas mass transfer in activated sludge reactors, Laboratory-scale experiments, WRRF simulations",

author = "Yuge Qiu and Vince Bakos and Nyle Stewart-Campbell and Benedek Plosz",

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AU - Qiu, Yuge

AU - Bakos, Vince

AU - Stewart-Campbell, Nyle

AU - Plosz, Benedek

PY - 2024/5/15

Y1 - 2024/5/15

N2 - In water resource recovery facilities (WRRF), aeration efficiency and N2O greenhouse gas emission are affected by the variability of the α-factor. Dynamic calibration of α using sensor data represents a significant knowledge gap this contribution aims to address. To assess factors influencing oxygen and N2O gas mass-transfer, a continuous flow laboratory-scale reactor system was operated to encourage the proliferation of filamentous bacteria. Gas mass-transfer was assessed using fine-bubble and surface aeration. Significant impacts of solid settling velocity on the α-factor – relative to that by MLSS concentration – is obtained. The feasibility of using solid settling velocity and concentration, as α-factor predictors, is tested. The theoretical approach of using relative diffusivity to dissolved oxygen – as an effective predictor of N2O liquid–gas mass-transfer stripping – is experimentally validated, for the first time. Plant-wide WRRF simulations show that surface aeration is inferior to fine-bubble aeration in terms of greenhouse gas emission and treated water quality.

AB - In water resource recovery facilities (WRRF), aeration efficiency and N2O greenhouse gas emission are affected by the variability of the α-factor. Dynamic calibration of α using sensor data represents a significant knowledge gap this contribution aims to address. To assess factors influencing oxygen and N2O gas mass-transfer, a continuous flow laboratory-scale reactor system was operated to encourage the proliferation of filamentous bacteria. Gas mass-transfer was assessed using fine-bubble and surface aeration. Significant impacts of solid settling velocity on the α-factor – relative to that by MLSS concentration – is obtained. The feasibility of using solid settling velocity and concentration, as α-factor predictors, is tested. The theoretical approach of using relative diffusivity to dissolved oxygen – as an effective predictor of N2O liquid–gas mass-transfer stripping – is experimentally validated, for the first time. Plant-wide WRRF simulations show that surface aeration is inferior to fine-bubble aeration in terms of greenhouse gas emission and treated water quality.

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Dynamic α-factor models for fine-bubble- and surface aeration – impact of settleability and implications on N2O emission

Abstract

Data Availability Statement

Funding

Keywords

ASJC Scopus subject areas

Access to Document

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