Model-based analysis of aeration in lab and full-scale activated sludge systems

78 Pages·2014·3.9 MB·English

Faculty of Bioscience Engineering
Academic year 2013 – 2014

Model-based analysis of aeration in lab and full-scale
activated sludge systems

Giacomo Bellandi
Promoter: Prof. dr. ir. Ingmar Nopens
Tutor: Ing. Youri Amerlinck

Master’s dissertation submitted in partial fulfillment of the requirements for
the degree of
Master in Environmental Sanitation

Faculty of Bioscience Engineering
Academic year 2013 – 2014

Model-based analysis of aeration in lab and full-scale
activated sludge systems

Giacomo Bellandi
Promoter: Prof. dr. ir. Ingmar Nopens
Tutor: Ing. Youri Amerlinck

Master’s dissertation submitted in partial fulfillment of the requirements for
the degree of
Master in Environmental Sanitation
ad Ivaldo
04-06-2014

De auteur en de promotor geven de toelating dit afstudeerwerk voor consultatie beschikbaar te
stellen en delen ervan te kopiëren voor persoonlijk gebruik. Elk ander gebruik valt onder de
beperkingen van het auteursrecht, in het bijzonder met betrekking tot de verplichting uitdrukkelijk
de bron te vermelden bij het aanhalen van resultaten uit dit afstudeerwerk.

The author and the promoter give the permission to use this thesis for consultation and to copy
parts of it for personal use. Every other use is subject to the copyright laws, more specifically the
source must be extensively specified when using results from this thesis.

The promoter, The tutor, The author,

Prof. dr. Ir. Ingmar Nopens Youri Amerlinck Giacomo Bellandi

Contents
Contents ................................................................................................................................................ i
Acknowledgments............................................................................................................................... iii
Abstract ............................................................................................................................................... iv
Summary .............................................................................................................................................. v
1. Introduction and literature review ................................................................................................ 1
1.1. Brief history of wastewater treatment.............................................................................................................. 1
1.2. Wastewater treatment plants ................................................................................................................................ 3
1.2.1. The UCT (University of Cape Town) configuration .......................................................................... 4
1.2.2. Submerged aeration systems ....................................................................................................................... 6
1.3. Modelling of wastewater treatment plants..................................................................................................... 6
1.3.1. Mathematical models ....................................................................................................................................... 6
1.3.2. Activated sludge model ................................................................................................................................... 7
1.3.3. Modelling Oxygen transfer ............................................................................................................................ 7
1.3.4. Predictions of oxygen transfer in presence of surfactants ......................................................... 10
1.3.5. Bubble column tests ....................................................................................................................................... 12
2. Materials and methods ................................................................................................................ 16
2.1. The Eindhoven WWTP............................................................................................................................................. 16
2.2. The Eindhoven wastewater treatment plant model in WEST® .......................................................... 17
2.3. Experimental data collection................................................................................................................................ 19
2.3.1. Off-gas measurements ................................................................................................................................... 19
2.3.2. Bubble column ................................................................................................................................................... 21
2.3.3. Imaging and bubble size measurements .............................................................................................. 23
3. Results ........................................................................................................................................ 27
3.1. Bubble column ............................................................................................................................................................. 27
3.1.1. Rheological measurements ......................................................................................................................... 27
3.1.2. Bubble size measurements ......................................................................................................................... 28
3.1.2.1 Clean water bubble size measurements ............................................................................................... 28
3.1.2.2 Effects of salt addition (50 mg/l) ............................................................................................................. 30
3.1.2.3 Effects of salt addition (100 mg/l) .......................................................................................................... 33
i
3.1.2.4 Effects of viscosity variation (0.2 g/l Xanthan TER) ...................................................................... 36
3.1.2.5 Effects of viscosity variation (0.8 g/l Xanthan TER) ...................................................................... 39
3.1.3. Lab scale oxygen transfer measurements ........................................................................................... 42
3.2. Full-scale aeration efficiency ................................................................................................................................ 45
3.2.1. Off-gas measurements ................................................................................................................................... 45
3.2.2. The Eindhoven aeration model performances on αSOTE prediction ................................... 50
3.2.2.1 Predictions of DO and NH using full scale αSOTE measurements ........................................ 53
4
4. Discussion ................................................................................................................................... 59
4.1. Bubble column tests .................................................................................................................................................. 59
4.2. Off-gas measurements ............................................................................................................................................. 60
4.3. Aeration model of Eindhoven WWTP .............................................................................................................. 60
5. Conclusions and perspectives ..................................................................................................... 62
References .......................................................................................................................................... 64

ii
Acknowledgments
First and foremost, I would like to thank my academic promoter Ingmar Nopens for his always kind
availability, contagious positive energy and strength which always characterize his person and
motivate who is in contact with him. I have a secret question to ask myself in the hard times, “What
would Ingmar do?!”, and that’s the answer too.
In the same warm way I would like to thank very much my tutor Youri who sustained me through
the long forest of the bad results, through which every student has to pass sooner or later (in my
case quite some time later), with stimulating ideas, precious organization and motivation.
There are so many people that have been important in this period and I would like to thank all and
each one of them. First of all Tinne (before I forgot like the last time!) for the precious help and
source of noise in the lab, Thomas who’s my very good friend and excellent colleague, Stijn who has
always been keeping my back, Andreia who came directly from Portugal to help me, Daan for all the
loughs and the motivational playlist, Sophie for her kind attitude and surprising skills with the
ADCP, Michael for the excellent learning curve on Italian statements to catch girls, Robin for the
memorable time in the BIOMATH weekend, and last but not least Chaim and Stijn for all the
respirometer parties in the lab. Nonetheless, all the BIOMATH family to which I’ll always owe a lot
of gratitude. Thanks Elena, Ivo, Ashish, Usman, Wouter, Séverine, Timothy, Stijn, Wim, Andres,
Katrijn and everyone that passed through the BIOMATH walls.
Ora, dopo tutti i discorsi di rito, vorrei però arrivare al dunque. Voglio ringraziare la mia famiglia, la
forza che mi ha sostenuto e mi sostiene tutti i giorni. Babbo e mamma, vi voglio un bene che scoppio
e vi voglio ringraziare per tutto il sostegno e la fiducia che mi avete dato, spero siate fieri di me
almeno un millesimo di quanto lo sono io di voi. Gianluca e Elena, che sono tutto il mondo per me, li
voglio ringraziare per essere cosi bellini che li mangerei, ma soprattutto per essere sempre nei miei
pensieri vicini vicini. Ci sono stati e ci saranno sempre momenti duri, e questa tesi non è uno di
quelli, e se c’è qualcosa che mi da la forza per tirare avanti anche un carro armato in quei momenti,
quella cosa e il pensiero di Gianluca, Elena e Annalisa. Grazie Na’, che ci sei sempre come un pilastro
in ogni cosa che faccio, e ci portiamo sempre insieme.
Linda, semplicemente la persona piu bella del mondo. La persona che mi fa ridere e innamorare,
arrabbiare e scompisciare. Mi regali ogni giorno quella scintilla che rende le giornate piene di vita.
Grazie, senza di te questa tesi non l’avrei mai fatta.
Sicuramente prima di finire voglio ringraziare la mia altra parte della famiglia, Massimo, la Tiziana,
Simone (Toxy) e Simone (Gloxy), che per me sono importanti come parti del corpo, e che per me
son tutti fratelli (Tiziana compresa), vi voglio bene. E grazie a tutti i letterati che allietano le serate
al barre con poemi e sonetti, ma soprattutto grazie a Grazia, Graziella e Grazialcazzo (che tanto i
ringraziamenti non li legge mai nessuno ☺).
iii
Abstract
Aeration in activated sludge treatment is used to supply the amount of oxygen needed in order to
accomplish the oxidation of part of the nutrients and pollutants unwanted in our river systems. As
the most energy intensive step in wastewater treatment, oxygen supply needs to be performed
efficiently, facilitating the transport of oxygen from the gas to the liquid phase. To do so, the
available surface for exchange needs to be maximized and the coalescence process hindered.
Moreover, the chemical and physical properties of the liquid play an important role affecting the
surface tension and ultimately the diffusion coefficient of oxygen. In the framework of the
development of a sound aeration model, this work studied the (i) effects of salt addition and
viscosity variation on oxygen transfer in a lab scale bubble column, along with (ii) aeration
efficiency measurements performed at a full scale wastewater treatment plant and (iii) the
evaluation and analysis of the prediction performances of one available aeration model. The bubble
column tests provided precious informations on the role singularly played by typical wastewater
characteristics (i.e. low electrolyte concentrations help the oxygen transfer process while
increasing viscosity not necessarily hinders it) and were a valuable tool for the interpretation of the
off-gas measurements performed at the full scale municipal facility of Eindhoven. However, further
experiments should be carried out to rigorously answer some unsolved questions. The model
results confirm the need of a better understating and finer representation of those dynamics
important in the oxygen transfer process, and of the definition of new dependencies for the
accomplishment of robust predictions.

iv