Phosphorus Removal From Stormwater Using Electric Arc Furnace Steel Slag

313 Pages·2013·3.02 MB·English

PHOSPHORUS REMOVAL FROM STORMWATER USING
ELECTRIC ARC FURNACE STEEL SLAG
A Thesis
Submitted to the Faculty of Graduate Studies and Research
In Partial Fulfillment of the Requirements
For the Degree of
Doctor of Philosophy
in
Environmental Systems Engineering
University of Regina
by
Nnaemeka Chinonyerem Okochi
Regina, Saskatchewan
July, 2013
© Copyright 2013: N.C. Okochi
UNIVERSITY OF REGINA

FACULTY OF GRADUATE STUDIES AND RESEARCH

SUPERVISORY AND EXAMINING COMMITTEE

Nnaemeka Chinonyerem Okochi, candidate for the degree of Doctor of Philosophy in
Environmental Systems Engineering, has presented a thesis titled, Phosphorus Removal
From Stormwater Using Electric Arc Furnace Steel Slag, in an oral examination held on
July 24, 2013. The following committee members have found the thesis acceptable in form
and content, and that the candidate demonstrated satisfactory knowledge of the subject
material.

External Examiner: *Dr. Graham Gagnon, Dalhousie University

Supervisor: Dr. Dena McMartin, Environmental Systems Engineering

Committee Member: Dr. Hussameldin Ibrahim, Process Systems Engineering

Committee Member: Dr. Renata Raina-Fulton,
Department of Chemistry & Biochemistry

Committee Member: Dr. James Kells, Adjunct

Committee Member: Dr. Darryl Dormuth, Adjunct

Chair of Defense: Dr. Sean Tucker, Faculty of Business Administration

*via teleconference
AUTHOR’S DECLARATION
I hereby declare that I am the sole author of this thesis. This is a true copy of the
thesis, including any required final revisions, as accepted by my examiners.
I understand that my thesis may be made electronically available to the public.
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Abstract
The use of electric arc furnace steel slag (EAF) as a viable add-on technology to
existing stormwater systems for the removal of dissolved phosphorus was investigated.
Existing popular stormwater treatment measures such as grassed swales, detention ponds
and constructed wetlands, while effective in removing certain components such as
suspended solids, have not fared very well in dealing with dissolved nutrients and heavy
metals. This can create a host of health and economic challenges for the communities
that rely on these water supplies for their upkeep and well-being.
Synthetic stormwater solutions of different metal to phosphorus concentration
ratios observed in actual stormwater were used in the experiments. Parameters such as
stormwater composition, phosphorus concentration, metal concentration, initial pH,
temperature, slag mass and slag particle size were varied in batch and column
experiments to determine the effects of different environmental and treatment system
conditions on the phosphorus removal efficiency of the slag. EAF used in the
experiments was also examined to uncover its mineral composition and propose a theory
on the pathway for phosphorus removal. Observations from the sorption experiments and
EAF characterization studies were subsequently considered to propose a theory for
phosphorus removal.
Results demonstrated that physisorption contributed to phosphorus uptake.
However, it was not the key phosphorus removal mechanism. Instead, surface
complexation and precipitation occurring on Fe sorption sites via ligand exchange were
found to significantly influence the removal of phosphorus from solution.
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The presence of cadmium, lead and zinc had a minimal effect on the phosphorus
removal process, while copper was a significant inhibitor of phosphorus uptake by the
EAF medium. Reduced removal of phosphorus by slag was evident in the copper-
dominant stormwater solution. This was attributed to the formation of a stable complex
between the copper and the slag at Fe sorption sites via the ion-exchange surface model.
The selective occupation of these active Fe sorption sites, as well as the stability of the
complex formed, inhibited further phosphorus uptake by EAF.
Stormwater composition, phosphorus concentration, metal concentration, initial
pH, temperature, slag mass and slag particle size were also found to significantly impact
the effectiveness of EAF in removing phosphorus from a given stormwater system.
Interactions between these factors were also significant in producing varying effects on
the phosphorus removal response.
An empirical model with an 87% correlation was proposed to predict the removal
of phosphorus via EAF from stormwater with parameters in the following range:
phosphorus concentration of 2 to 5 mg/L, copper concentration of 0 to 2.2mg/L, lead
concentration of 0 to 8.3 mg/L, zinc concentration of 0 to 11.9 mg/L and a temperature
of7 to 22 °C.
This study concludes that EAF is an adsorbent with the potential to effectively
sequester dissolved phosphorus from stormwater. This means that EAF can act as a
viable end-of-pipe add-on technology to existing stormwater treatment systems for
improved effluent quality.
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Acknowledgements
Dr. Dena McMartin deserves my heartfelt thanks for her valuable supervision,
unflinching support and kind encouragement at every stage of my program. I also thank
the members of my supervisory committee: Dr. Renata Raina-Fulton, Dr. Darryl
Dormuth, Dr. Jim Kells and Dr. Hussameldin Ibrahim for their guidance throughout the
course of my study.
My deep gratitude equally goes to Dr. Rodney Kelln and the Faculty of Graduate
Studies and Research for the exceptional support, and for providing me with a number of
scholarships and awards in the pursue of mydegree.
Also, I remember and appreciate Communities of Tomorrow for being such an
amazing employer during my time with them, and supporting me with the flexibility,
finances and encouragement to undertake myresearch alongside myjob.
To Robert Schutzman of Evraz Inc. NA and Faron Comaniuk of Tube City IMS,
Regina, for the provision of the EAFslag, I say thank you.
I cannot fail to extend my sincere appreciation to Ann Gottinger and Don Wild of
Mainstream Water Solutions Inc., as well as Benjamin Mede of Technische Universität
Bergakademie Freiberg, Germany, for theirhelp in setting up the column experiments.
To my wonderful family – the Okochis and the Somolus, and to mymanyfriends
and colleagues who cheered me on, thank you for all your love and encouragement.
Finally, and by no means the least, I thank Olufunke, my wife, my inspiration,
and the rock of my life, without whom the conclusion of this journey would have been
impossible. I am forever indebted to you for your unending love and unwavering
strength.
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Post Defense Acknowledgement
Dr. Graham Gagnon, the Director of the Centre for Water Resources Studies at
Dalhousie Univeristy and NSERC/Halifax Water Industrial Research Chair, graciously
agreed to be my external examiner. His feedback in the final stages of my degree was
invaluable and for that I am very grateful.
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Table of Contents
AUTHOR’S DECLARATION........................................................................................ii
Abstract............................................................................................................................iii
Acknowledgements...........................................................................................................v
Post Defense Acknowledgement ....................................................................................vi
Table of Contents...........................................................................................................vii
List of Figures................................................................................................................xiii
List of Tables................................................................................................................xvii
Notations........................................................................................................................xix
1. Introduction...............................................................................................................1
1.1 Problem Definition...................................................................................................2
1.2 Scope of the Research..............................................................................................3
1.3 Research Hypotheses................................................................................................4
1.4 Research Objectives.................................................................................................5
1.5 Original Contributions..............................................................................................6
1.6 Layout of the Thesis.................................................................................................7
2. Literature Review ........................................................................................................8
2.1 Stormwater Quality Parameters................................................................................9
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2.1.1 Nutrients........................................................................................................12
2.1.2 Total Suspended Solids..................................................................................13
2.1.3 Micro-organisms............................................................................................14
2.1.4 Metals............................................................................................................15
2.1.5 Hydrocarbons.................................................................................................16
2.1.6 Organics.........................................................................................................17
2.1.7 Salt.................................................................................................................18
2.2 Stormwater Regulations.........................................................................................20
2.3 Review of Stormwater Treatment Solutions..........................................................26
2.4 Phosphorus.............................................................................................................35
2.5 Phosphorus Removal Mechanisms.........................................................................37
2.6 Factors Affecting Phosphorus Removal.................................................................40
2.6.1 Composition of Treatment Medium..............................................................41
2.6.2 Phosphorus Loading......................................................................................42
2.6.3 Temperature...................................................................................................43
2.6.4 pH..................................................................................................................45
2.6.5 Adsorbent Particle Size and Porosity............................................................48
2.6.6 Other Factors .................................................................................................48
2.7 Review of Substrates for Phosphorus Removal.....................................................49
2.7.1 Natural Materials...........................................................................................49
2.7.2 Synthetic products .........................................................................................53
2.7.3 Industrial by-products....................................................................................54
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2.8 EAF as a Choice Medium ......................................................................................58
2.8.1 Production of EAF.........................................................................................58
3. Materials and Methods..............................................................................................61
3.1 General Experimental Procedures..........................................................................61
3.2 Adsorbent Preparation............................................................................................64
3.3 Adsorbent Characterization....................................................................................66
3.3.1 Physical Characteristics.................................................................................68
3.3.1.1 Particle Density......................................................................................68
3.3.1.2 Bulk Density...........................................................................................69
3.3.1.3 Porosity...................................................................................................70
3.3.1.4 BET Surface Area..................................................................................70
3.3.2 Chemical Characteristics...............................................................................71
3.3.2.1 X-ray Fluorescence Spectroscopy..........................................................72
3.3.2.2 Powder X-ray Diffraction.......................................................................72
3.3.2.3 Scanning Electron Microscopy with X-ray microanalysis.....................72
3.3.2.4 Replicate Characterization Experiments................................................73
3.4 Batch adsorption experiment design......................................................................73
3.4.1 Phase I Batch Experiments............................................................................74
3.4.2 Phase II Batch Experiments...........................................................................79
3.4.3 Phase III Batch Experiments .........................................................................81
3.5 Development of Sorption Isotherms.......................................................................87
3.5.1 Langmuir Isotherm Analysis...........................................................................87
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