biological nitrogen removal from dairy farm wastewater using coupled anoxic upflow and aerobic ...

254 Pages·2013·4.57 MB·English

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BIOLOGICAL NITROGEN REMOVAL FROM
DAIRY FARM WASTEWATER USING COUPLED
ANOXIC UPFLOW AND AEROBIC BIOREACTORS

Dilawar Farhan Shams

A thesis submitted in fulfilment of the requirements for the degree of
Doctor of Philosophy in Engineering, The University of Auckland, 2013

ABSTRACT

Elevated nitrogen concentrations in dairy farm wastewater (DFW) demand alternative
treatment technologies to meet increasingly stringent regulations. Treatment of DFW with
an upflow bioreactor in combination with an aerobic unit and a secondary clarifier (UBR-
A process) offers advantages of increased biomass retention and faster conversion rates.
However, research is needed firstly to establish the effect of different operational
conditions and varying wastewater characteristics on system behaviour, and secondly to
achieve complete nitrogen removal via post-denitrification without increasing the
footprint. In this study, two lab-scale UBR-A systems, one fed with real DFW and the
other with synthetic wastewater (SWW), were studied for the effect of wastewater
characteristics and key operational variables of hydraulic retention time (HRT, 2-4 days),
internal recycle ratio (R, 2-4) and solids retention time (SRT, >100 to 30 days).
Additionally, enhancement in stability using attached media was investigated at R of 3
and 4, and at doubled carbon loading (with SWW). Finally, post-denitrification in both
systems was investigated with a novel technique of retrofitting the clarifiers with alginate
beads containing immobilised biomass and carbon source. In this connection, a batch
study was first performed to identify suitable carbon sources for co-immobilisation
among acetate, glucose, calcium tartrate, starch and canola oil on the basis of
denitrification kinetics, stoichiometry and bead stability. The findings showed that in
suspended growth, shorter HRT of 2 days significantly lowered (P<0.05) nitrification
whereas higher R>3 proved unfavourable for denitrification in both systems especially
with SWW (~60% drop in efficiency). Lowering the SRT produced similar performance
however, kinetic rates were significantly increased in both systems. The HRT of 4 days,
R=3 and SRT>100 days was established as the optimum operational regime in suspended
mode. The attached growth media and COD/NO -N ratio >8 (with SWW) enhanced the
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denitrification at R=4, raised the nitrification rate by ~55% and total nitrogen removal by
~12%. For both wastewaters, system behaviour was comparable in terms of performance
and vertical solids profile in UBR. However, DFW exhibited significantly lower kinetic
rates and yield coefficients, a smaller VSS/TSS ratio, and higher inert COD fraction.
These outcomes indicated that DFW is not truly represented by SWW to depict system
behaviour. From the batch study, the co-immobilised canola oil and starch exhibited
significantly higher denitrification rates (1.05 mg/L/h and 0.72 mg/L/h respectively) and
bead stability with low nitrite accumulation. Post-denitrification in the clarifier with
starch and canola oil beads demonstrated denitrification efficiency of >90%. Duration of
the denitrification phase increased with the raise in carbon fraction, alginate concentration
and use of BaCl as hardening solution. However, due to prevalence of alginate lyase
2
activity and phosphates, degradation of beads was faster than complete carbon
consumption, and therefore necessitates the use of more stable gels.
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TO
MY PARENTS

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ACKNOWLEDGEMENTS

All praise and deep thanks are due to Allah Almighty, the most Beneficent, the most
Compassionate, Who bestowed upon me the ability and skills to complete this work.

My sincere gratitude goes to the Higher Education Commission of Pakistan for providing
me with the opportunity and funding to undertake my PhD studies at the University of
Auckland.

I would like to thank my supervisor A/Prof. Naresh Singhal for his guidance and helpful
feedback in the research, and critical input to the work presented here. I am thankful to
my co-supervisor, Dr. Takis Elefsiniotis for his valuable advice and encouragement
during the study and reviews on the written work. I am very appreciative of both the
supervisors’ comments and critical insights concerning the study that helped me a great
deal in streamlining and polishing my work.

Completion of this work couldn’t have been possible without the technical help and
support of Anthea Johnson, Dr. Sandra Uy and Abel Francis. I would like to pay my
sincere gratitude to Anthea for her help in the arduous job of collecting wastewater from
the farm for three years; her inputs in proofreading of this manuscript and wholehearted
support during this research. Dr. Sandra has been very supportive and helpful during the
various laboratory activities. I am grateful for her time and prompt help especially with
organic fractionation and analytical procedures. Without the help of Abel Francis, hardly
could I think I would be able to smoothly operate the bioreactors and collect the data. His
expertise and assistance was really helpful in continuously and successfully operating the
reactors for more than three years.

A number of people deserve appreciation for contributing to this research. For my work
on immobilized beads, Alexandre Rubio made important contribution in the experimental
work for the batch tests with immobilized beads. I enjoyed working with him and
appreciate his enthusiasm and dedication towards research. I would also like to gratefully
acknowledge the contributions by Alizeé Jenck in the organic fractionation, Kevin Ng in
the beads abrasion tests, Emma Zhang in the batch studies with attached media, and Heba
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Akasha, Sophie Bannister and Melissa Douglas in the batch experiments with alginate
beads.

Operation of the bioreactors was a challenging task and a number of colleagues extended
their help to ensure successful running of the systems. I am thankful to Naeem Ejaz and
Felix Meier for their help in setting up the reactors, maintenance and cleanup at times of
overspills, intensive analysis and collection of dairy farm wastewater during the first year.
Alexandre Rubio and Thomas Beaumont also deserve praise for their help in operation of
the reactors and collection of wastewater from the farm. I would also like to thank Cody
Mankelow, Octavio Perez, Emad, Nicole, Amir Jamal and Emma Zhang for wastewater
collection and looking after the reactors during my overseas visits.

I will surely miss the joyful time I spent with fellow students in the post-grad office and
environmental lab who have become very good friends. I am thankful to Buddhika,
Claudia, Anthea, Marya, Apra, Somi, Yantao, Cody, Octavio, Katherine, Emily, Emad,
Mahshid, Yousuf, Marija, Karine, Anushka, Lucy, Reza and all the other colleagues in
the Environmental group whom I may have missed to mention, for the pleasant working
environment and the wonderful time we shared.

My time in New Zealand was made memorable by the many good friends and flatmates. I
feel myself lucky to have Arif, Shafiq, Gul, Saeed, Tariq, Asad, Khalid, Attaullah, Aziz
Khattak, Javed, Ajmal, Aziz and a long list of other friends who provided a great
company and support that made me feel less away from home. Special thanks to Aziz
Khattak for his inputs in proofreading of the written material. I would also like to thank
all the HEC colleagues and Pakistan Student Association for their support and for the
wonderful gatherings and social events.

Thanks to the University of Auckland for funding the research through the PRESS
account. Thanks also to the New Zealand Foundation for Research, IIOF and Korea
Ministry of Environment, Republic of Korea for co-funding this research work.

Last and the utmost, my parents, sisters, brothers and my wife for their constant prayers,
patience, motivation and support throughout this study.
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TABLE OF CONTENTS

Abstract ................................................................................................................... iii
Acknowledgments ............................................................................................................... v
List of Tables ................................................................................................................... xi
List of Figures ................................................................................................................. xiii
List of Symbols and Abbreviations ................................................................................. xvi
Co-Authorship Forms ....................................................................................................... xx

CHAPTER 1 INTRODUCTION ......................................................................................... 1
CHAPTER 2 LITERATURE REVIEW .............................................................................. 5
2.1 Nitrogen removal from wastewater .......................................................... 5
2.2 Biological nitrogen removal ..................................................................... 5
2.2.1 Nitrification .................................................................................... 7
2.2.2 Denitrification ................................................................................ 9
2.3 Biological nitrogen removal process configurations .............................. 11
2.4 Problems relating to dairy farm wastewater ........................................... 13
2.4.1 Common treatment practices ........................................................ 14
2.5 Biological nitrogen removal systems for dairy farm wastewater ........... 15
2.5.1 Upflow anoxic reactors ................................................................ 16
2.5.2 The Upflow Bioreactor ................................................................ 17
2.6 The coupled UBR-Aerobic process for dairy farm wastewater .............. 20
2.6.1 Influence of hydraulic retention time and internal recycle rate ... 22
2.6.2 Solids retention time .................................................................... 25
2.7 Influence of DFW composition and variability ...................................... 25
2.8 Attached growth media in UBR-aerobic system .................................... 26
2.9 Biodegradability and transformation of organic matter .......................... 29
2.10 Pre- and post-denitrification ................................................................... 30
2.10.1 Use of clarifier for post-denitrification ........................................ 32
2.10.2 Immobilisation technology for post-denitrification in the
clarifier ......................................................................................... 33
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2.10.3 Co-immobilisation of sludge and carbon source .......................... 36
2.11 Research objectives................................................................................. 38
2.12 Approach ................................................................................................. 40
CHAPTER 3 MATERIAL AND METHODS ................................................................... 43
3.1 Lab-scale system design ......................................................................... 43
3.1.1 Configuration and schematic........................................................ 44
3.2 Operation of the systems......................................................................... 45
3.2.1 Wastewater characteristics ........................................................... 46
3.2.2 Operational phases ....................................................................... 49
3.2.3 Attached growth media ................................................................ 51
3.2.4 Clarifier design modification for post-denitrification .................. 52
3.2.5 Operation and maintenance of the system ................................... 53
3.3 Immobilisation of activated sludge and carbon source ........................... 53
3.3.1 Gel preparation for immobilisation of biomass and mixing of
carbon source ............................................................................... 53
3.3.2 Addition of inoculum and carbon substrate ................................. 54
3.3.3 Production of beads ...................................................................... 54
3.3.4 Experimental conditions for denitrification with beads in
batch studies ................................................................................. 55
3.4 Sampling and analytical procedures ....................................................... 56
3.4.1 Sampling ...................................................................................... 56
3.4.2 Analytical methods....................................................................... 58
3.4.3 Attached biomass measurement ................................................... 60
3.4.4 Organic fractionation ................................................................... 60
3.4.5 Scanning electron microscopy of beads ....................................... 61
3.4.6 Alginate lyase activity test ........................................................... 63
3.5 Computations for operational variables and performance ...................... 63
3.6 Statistical analysis ................................................................................... 65
3.7 Quality control ........................................................................................ 66
CHAPTER 4 EFFECT OF OPERATIONAL CONDITIONS .......................................... 67
4.1 Background ............................................................................................. 67
4.2 Operation of the systems......................................................................... 68
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