International Master of Science in Environmental Technology and Engineering Impact of aeration ...

76 Pages·2015·6.56 MB·English

Master’s dissertation submitted in partial fulfilment of the requirements for the joint degree of

International Master of Science
in Environmental Technology and Engineering

an Erasmus+: Erasmus Mundus Master Course jointly organized by
Ghent University, Belgium
University of Chemistry and Technology, Prague, Czech Republic
UNESCO-IHE Institute for Water Education, Delft, the Netherlands

Academic year 2014-2015

Impact of aeration on the performance of wastewater
treatment wetlands – a pilot scale study

Ghent University, Belgium

Iva Havran

Promotor: Prof. dr. ir. Gijs Du Laing
Co-promotor: Prof. dr. ir. Diederik Rousseau

This thesis was elaborated at Ghent University, Belgium and defended at Ghent University, Belgium within
the framework of the European Erasmus Mundus Programme “Erasmus Mundus International Master of
Science in Environmental Technology and Engineering " (Course N° 2011-0172)

© [2015] [Ghent], [Iva Havran], Ghent University, all rights reserved.

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Abstract
In this study, a horizontal subsurface flow constructed wetland (HSSF CW) was used to examine the
effects of artificial aeration and hydraulic retention time on the removal of traditional contaminants and
pharmaceutical compounds from domestic wastewater. The HSSF CW was placed at an Aquafin
wastewater treatment plant and it had a surface area of 1.09 . The HSSF CW was installed at the site
in March 2015 and monitored weekly for 8 weeks before the sampling campaign started. Within the
campaign, the following three treatment designs were applied: continuous aeration at HRT=1d (AER-
HRT1), continuous aeration at HRT=0.5d (AER-HRT0.5) and no aeration at HRT=1d (N-AER). Generally, the
experiment showed that removal rates were always higher for the aerated treatment designs when
compared to non-aerated phase of the study. The statistically significant differences concerning aeration
were found for all targeted pollutants, except for several recalcitrant pharmaceutical compounds
(carbamazepine, diclofenac, sotalol and tramadol). HRT influence seemed to be negligible since statistical
analysis of data did not show any positive correlation between effluents in regard to HRT. Enhanced
oxygen transfer rate within the wetland and internal mixing of the influent promoted aerobic processes
which proportionally increased removal efficiency of conventional quality parameters such as COD, TSS,
-N, -P. However, high dissolved oxygen (DO) rates suppressed anaerobic mechanisms which

halted the removal of -N by means of denitrification. N-AER had lower treatment efficiency than

commonly reported for HSSF CWs. This is probably due to the fact that HRT of 1 day was too short for
the anaerobic removal pathways to be completely carried out or that anaerobic microbial community did
not have time to fully develop during the N-AER treatment phase ( 3 weeks). Targeted pharmaceutical
compounds could be divided into two groups according to the results: readily degradable compounds
(valsartan and metformin) that were almost fully eliminated during the applied aeration and recalcitrant
compounds that were not significantly affected. First group was presumably removed by biodegradation
under aerobic conditions prevailing in the pilot during aeration, while the other group was either
affected by several removal mechanisms (diclofenac and solatol) or mainly removed by sorption
(carbamazepine and tramadol). Findings of this study suggest that artificially aerated HSSF CW for
treating domestic wastewater is able to provide not only better effluent quality when compared to
conventional HSSF CW but also to save operational and building costs due to higher treatment efficiency.

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Acknowledgements
First of all, I would like to sincerely thank my Promotor Professor Gijs Du Laing for giving me the
opportunity to work on this thesis topic and whose guidance helped me in writing of this thesis.
Furthermore, I would like to express my gratitude to my Co-promotor Professor Diederik Rousseau
for hosting me in his lab and whose guidance led me through the thesis research and writing of this
document. Moreover, my special thanks goes to Hannele Auvinen for going above and beyond her
call of duty as being my tutor during this study and for all the help I received from her from the
beginning of the research until the final revision of this thesis.
I would also like to thank Ghent University for providing me with the equipment for the part of
analytical analyses during my thesis work and Joachim Neri who helped me with this process.
Moreover, I would express my appreciation to the Aquafin Company for their cooperation and for
providing us with the possibility for conducting our research at their site. Furthermore, I would
express my gratitude to the Institut für Siedlungswasserwirtschaft in Aachen, Germany for facilitating
the analysis of pharmaceutical compounds and in that manner helped me to complete my research
results. In addition, I would like to thank Dion Van Oirschot for his help with the design of the pilot
wetland and for sharing his expert opinion.
The last, but not the least I would like to acknowledge my family and my best friend for all their love,
patience and support they unselfishly shared with me not only while writing this thesis but throughout
my life. Special words I would dedicate to my boyfriend Dušan who loved me and supported me during
these 2 years of long-distance relationship and whose love, trust and care helped me to endure through
all the difficult times.

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List of Tables
Table 2.1 Treatment efficiency of HSSF CWs for removal of organics , total suspended solids
(TSS), total nitrogen (TN) and total phosphorus (TP) based on the annual average values ....................... 15
Table 3.1 Operation of the pilot system and sampling strategy ................................................................. 26
Table 3.2 Monitored pharmaceutical compounds ...................................................................................... 30
Table 4.1 Physico-chemical characteristics (maximum, minimum and mean ± SD) of the samples gathered
during the different phases of the experiment ........................................................................................... 32
Table 4.2 COD in influent and effluent samples from the sampling campaign .......................................... 34
Table 4.3 TSS in influent and effluent samples collected during the 3-phase sampling campaign ............ 36
Table 4.4 -N in influent and effluent samples collected during the 3-phase sampling campaign ...... 38
Table 4.5 -N in influent and effluent samples collected during the 3-phase sampling campaign ...... 40
Table 4.6 -P concentrations in influent and effluent samples collected during the 3-phase campaign
..................................................................................................................................................................... 42
Table 4.7 Pharmaceutical compounds found in treated municipal wastewater ........................................ 46
Table 4.8 Pharmaceutical compounds in influents and effluents collected during the 3-phase sampling
campaign ..................................................................................................................................................... 46
Table 5.1 Influent and effluent concentrations (mean ± SD) and removal efficiency of Aquafin treatment
system and pilot wetland ............................................................................................................................ 54

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List of Figures
Figure 3.1: Picture of the pilot wetland under construction ....................................................................... 24
Figure 3.2 Schematic representation of the experimental setup ............................................................... 25
Figure 3.3 Picture of a fully operational pilot wetland installed in-situ ...................................................... 27
Figure 3.4 (a) Effluent and influent sample (aerated wetland); (b) Influent and effluent sample (non-
aerated, wetland) ........................................................................................................................................ 31
Figure 4.1 Boxplot representing the distribution of COD in the samples of three phases of the campaign
..................................................................................................................................................................... 34
Figure 4.2 Boxplot representing the distribution of TSS in samples of all three phases of the sampling
campaigns .................................................................................................................................................... 36
Figure 4.3 Boxplot representing the distribution of -N concentrations in the samples of 3-phase
sampling campaign ...................................................................................................................................... 38
Figure 4.4 Boxplot representing the distribution of -N concentrations in the samples of 3-phase
sampling campaign ...................................................................................................................................... 40
Figure 4.5 Boxplot representing the distribution of -P concentrations in the samples of 3-phase
sampling campaign ...................................................................................................................................... 42
Figure 4.6 Boxplots representing the distribution of pharmaceutical concentrations in the samples of 3-
phase sampling campaign. .......................................................................................................................... 47

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List of Abbreviation
Anammox Anaerobic Ammonium Oxidation
APIs Active Pharmaceutical Ingredients
BOD Biological Oxygen Demand
Canon Completely autotrophic nitrogen removal over nitrite
COD Chemical Oxygen Demand
CWs Constructed Wetlands
Deammox Denitrifying Ammonium Oxidation
DO Dissolved Oxygen
FWS CWs Free Water Surface Constructed Wetlands
HC Hydraulic Conductivity
HLR Hydraulic Loading Rate
HRT Hydraulic Retention Time
HSSF CWs Horizontal Subsurface Flow Constructed Wetlands
LECA Light Expanded Clay Aggregate
O&M Operation and Maintenance
PhCs Pharmaceutical Compounds
PVC Polyvinyl Chloride
SS Suspended Solids
SSFCWs Subsurface Flow Constructed Wetlands
TN Total Nitrogen
TP Total Phosphorus
TSS Total Suspended Solids
VF Vertical Flow
WWTP Waste Water Treatment Plant

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