Behaviour of estrogenic endocrine-disrupting chemicals in permeable carbonate

Environ Sci Pollut Res
DOI 10.1007/s11356-015-4238-8
RESEARCH ARTICLE
Behaviour of estrogenic endocrine-disrupting chemicals
in permeable carbonate sands
Benjamin O. Shepherd & Dirk V. Erler & Douglas R. Tait &
Lukas van Zwieten & Stephen Kimber & Bradley D. Eyre
Received: 16 September 2014 / Accepted: 13 February 2015
# Springer-Verlag Berlin Heidelberg 2015
Abstract The remediation of four estrogenic endocrinedisrupting compounds (EDCs), estrone (E1), estradiol
(E2), ethinylestradiol (EE2) and estriol (E3), was measured in saturated and unsaturated carbonate sand-filled
columns dosed with wastewater from a sewage treatment
plant. The estrogen equivalency (EEQ) of inlet wastewater was 1.2 ng L−1 and was remediated to an EEQ of
0.5 ng L−1 through the unsaturated carbonate sand-filled
columns. The high surface area of carbonate sand and
associated high microbial activity may have assisted the
degradation of these estrogens. The fully saturated sand
columns showed an increase in total estrogenic potency
with an EEQ of 2.4 ng L−1, which was double that of the
inlet wastewater. There was a significant difference
(P < 0.05) in total estrogenic potency between aerobic
and anaerobic columns. The breakdown of conjugated estrogens to estrogenic EDCs formed under long residence
time and reducing conditions may have been responsible
for the increase in the fully saturated columns. This may
also be explained by the desorption of previously sorbed
estrogenic EDCs. The effect of additional filter materials,
such as basalt sediment and coconut fibre, on estrogenic
EDC reduction was also tested. None of these amendments provided improvements in estrogen remediation
relative to the unamended unsaturated carbonate sand columns. Aerobic carbonate sand filters have good potential
to be used as on-site wastewater treatment systems for the
reduction of estrogenic EDCs. However, the use of fully
saturated sand filters, which are used to promote denitrification, and the loss of nitrogen as N2 were shown to
cause an increase in EEQ. The potential for the accumulation of estrogenic EDCs under anaerobic conditions
needs to be considered when designing on-site sand filtration systems required to reduce nitrogen. Furthermore,
the accumulation of estrogens under anaerobic conditions
such as under soil absorption systems or leachate fields
has the potential to contaminate groundwater especially
when the water table levels fluctuate.
Keywords Estrogenic EDCs . Saturation state . Carbonate
sand . Remediation . Wastewater treatment systems .
Groundwater
Responsible editor: Hongwen Sun
B. O. Shepherd (*) : D. V. Erler : D. R. Tait : B. D. Eyre
Centre for Coastal Biogeochemistry, School of Environment, Science
and Engineering, Southern Cross University, Lismore, NSW 2480,
Australia
e-mail: [email protected]
L. van Zwieten : S. Kimber
Department of Primary Industries, Bruxner Highway,
Wollongbar, NSW 2477, Australia
L. van Zwieten
Southern Cross Plant Science, School of Environment, Science and
Engineering, Southern Cross University, Lismore, NSW 2480,
Australia
Introduction
A growing area of environmental and human health concern is
contamination of groundwater with endocrine-disrupting
chemicals (EDCs) (Jenssen 2006; Kookana et al. 2007). The
United States Environmental Protection Agency (USEPA) defines an EDC as Ban exogenous agent that interferes with the
synthesis, secretion, transport, binding, action or elimination
of natural hormones in the body that are responsible for the
maintenance of homeostasis, reproduction, development and/
Environ Sci Pollut Res
or behaviour^. Chronic, low-level exposure to EDCs in both
humans and animals has been linked to a number of reproductive disorders (Kookana et al. 2007).
EDCs encompass a wide variety of chemical classes, including natural and synthetic hormones, plant constituents,
pesticides, certain compounds in plastics, personal care products, pharmaceuticals, pollutants and by-products of industry
(Damstra et al. 2002). EDCs are widely dispersed in the environment and have been found in rivers, estuaries, coastal samples and even in the arctic (Braga et al. 2005a; Jenssen 2006).
Some of the most potent EDCs include steroid estrogens such
as estrone (E1), 17β-estradiol (E2), estriol (E3) and 17αethinylestradiol (EE2). These estrogenic EDCs have been
shown to have adverse affects on the reproductive systems
of marine and freshwater animals at less than 5 ng L−1 (Jobling
et al. 1998, 2002a, b, 2006; van Aerle et al. 2001; Pelley
2003). Estrone is a metabolite of estradiol and is an important
pregnancy estrogen. Estradiol is a reproductive hormone naturally excreted by female animals including humans and in
much smaller quantities by males. Ethinylestradiol is the main
ingredient in the female contraceptive pill and hormone replacement medication (Trussell 2001; Song et al. 2009).
A major source of estrogenic EDCs to natural waterways is
wastewater treatment plant effluent and leachate of sewage
sludge either buried in landfill or applied as fertilizer (Jobling
et al. 2006; Koyama et al. 2006; Thorpe et al. 2009;
Karnjanapiboonwong et al. 2011; Marti and Batista 2014).
Concentrations of estrogenic EDCs in wastewater can range
from nanograms per litre (ng L−1) to micrograms per litre (μg
L−1) (Ying and Kookana 2005). Other potential sources of
estrogenic EDCs in developed and agricultural catchments
include on-site wastewater management systems, effluent
run-off following manure application or run-off of livestock
wastes (Reneau and Degen 1989; Hanselman et al. 2003;
Zhang et al. 2011).
Water contamination by sewage is common in all island
countries of the Pacific region with many streams and groundwater supplies currently considered unsafe for human consumption without treatment (UNESCAP 2000). In the porous
carbonate sands of many Pacific islands, groundwater is particularly susceptible to contamination from poorly performing
sanitation systems. Indeed ground and surface water pollution
associated with septic tank and absorption trench disposal
systems is common in many Pacific countries (Dakers and
Evans 2007). Some soil absorption systems which are used
as on-site treatment systems in these countries can operate
successfully for years, whilst others can fail within weeks of
installation (Beal et al. 2005). Studies by
Karnjanapiboonwong (2011) showed that EDCs that were
present in the effluent from a wastewater treatment plant were
able to reach the groundwater after land application of the
effluent. Given the porous nature of the soil in most Pacific
islands, the steadily increasing human population and greater
use of synthetic compounds, such as the contraceptive pill, it
is quite likely that groundwater may contain elevated concentrations of estrogenic EDCs. However, it is also possible that
carbonate sands may act to physically, chemically and/or biologically remove estrogenic EDCs from effluent water.
There is some evidence that EDCs can be effectively degraded during transport through porous media (Nakada et al.
2007). Biodegradation of EDCs has been shown to be the
most cost-effective way of removing EDCs relative to advanced removal mechanisms such as activated carbon, membrane filtration, chemical advanced oxidation and ozonation
(Liu et al. 2009). Using quartz sand filtration systems, Nakada
et al. (2007) showed a 50 % removal rate of estrogenic EDCs.
Carbonate sands may be particularly effective for the treatment of EDCs (Rasheed et al. 2003). They may be an ideal
candidate for incorporation into wastewater treatment systems
in developing Pacific nations due to their ready availability.
However, the behaviour of EDCs in carbonate sands has not
been studied previously. In particular, it is not understood how
the biodegradation of estrogens will be affected by the degree
of saturation within carbonate sands. Other studies have
shown that unsaturated aerobic soils are more likely to degrade EDCs relative to saturated anaerobic soils. Permeable
carbonate sands however are unique in that they have extremely high surface areas capable of sustaining a large microbial biomass and contain greater adsorption capabilities
and pH buffering relative to quartz sands (Rasheed et al.
2003; Schöttner et al. 2011). The behaviour and degradation
of EDCs in permeable carbonate sands therefore may be enhanced relative to other sands and soils. To date, there have
been no studies that have looked at the removal of EDCs in
carbonate sands under saturated or unsaturated conditions.
The aim of this study was to investigate the behaviour of
estrogenic compounds in permeable carbonate sands under
saturated and unsaturated conditions. A broader goal of this
research was to assist in the development of low-cost on-site
wastewater treatment technologies for EDC removal in developing Pacific countries.
Materials and methods
Equipment and experimental design
In this study, the main objective was to test the reduction of
EDCs within large columns containing permeable carbonate
sands. A secondary objective was to test whether estrogenic
EDC removal would be affected by the addition of other soils/
materials (e.g. basalt soil, coconut fibre) to some of the sand
columns. Basalt sediment and coconut fibre were used as
amendments as these are readily available and commonly
used with carbonate sand in wastewater treatment systems
throughout the Pacific.
Environ Sci Pollut Res
The columns were operated under a range of saturation
states, and some were amended with alluvial basalt soil and
coconut husk fibre. Different saturation states and media types
were used to increase retention times, adsorption capacity and
degree of aeration and/or availability of microbial habitat.
Basalt and carbonate sand sediments were shipped from
Rarotonga in the Cook Islands (21°14′05″ S, 159°46′30″ W)
and sterilized (Australian customs requirement) with gamma
irradiation (Steritech Pty Ltd). Sediments were loosely packed
into vertical flow PVC columns (diameter 150 mm, length
1.8 m). Columns were kept in a dark temperature-controlled
room at the South Lismore sewage treatment plant (STP),
Lismore, NSW, Australia. In all, there were seven carbonate
sand treatments, with each treatment containing two columns.
All columns contained 100 mm of 20-mm blue metal gravel above the carbonate sand to distribute the effluent evenly to
the underlying media. Treatment 1 (T1) was a fully unsaturated carbonate sand column, treatment 2 (T2) was similar to T1
except that it received a double dosing of influent and treatment 3 (T3) was fully unsaturated sand with a 100-mm layer
of coconut fibre at the top of the column. Treatment 4 (T4)
contained an unsaturated homogenous mixture of sand and
basalt sediment. Treatment 5 (T5) contained unsaturated carbonate sand with a 100-mm basalt sediment layer 900 mm
from the top of the column. Treatment 6 (T6) contained carbonate sand with a saturated zone of 800 mm, created by
lifting the outlet tubing to the desired height, and treatment 7
(T7) contained carbonate sand with a 1500-mm saturated
zone. Grain size for the carbonate sand was ~81 % greater
than 0.5 mm. Basalt soil was with ~49 % of grains less than
50 μm. Chemical composition of the sediments showed that
trace metals were higher in the basalt soils. The carbonate
sands contained 12 % carbon, and the basalt had 3 % carbon;
both sediments had <0.5 % nitrogen. Grain size and soil analysis results were taken from unpublished studies by Tait et al.
(manuscript submitted for publication).
Columns were dosed regularly with effluent from the
STP’s primary sedimentation tank. Primary treated effluent
was transferred via a 25-mm pipe from the sedimentation tank
to a control valve attached to a 200-μm filter (Arkal). The
filter was intended to mimic septic tank discharge effluent
and remove larger particulate matter that had potential to clog
dosing lines. The primary treated influent was connected to a
240-L PVC barrel with a 15-mm ball float valve to maintain a
constant volume. Primary treated influent was pumped from
the barrel via a 12-V submersible pump (Amazon) to a capped
450×90 mm PVC header tank above the columns. The header
tank allowed for even distribution of effluent to columns. The
cap on the bottom of the header tank had 5 mm evenly distributed outlets inserted. The outlets were connected to 1.5 m
of 6-mm PVC tubing. The header tank would fill and feed
effluent through the tubes to distribution bars in the top
50 mm of the columns. The distribution bar consisted of a
modified 50-mL plastic syringe with a series of 10-mm holes
drilled along the bottom side. The distribution bar allowed for
less restriction on outlet tube flow and created an even dispersal of influent over the media. The submersible pump was
connected to a 12 V timer that was set to dose six times daily
(7:00 am, 9:00 am, 11:00 am, 3:00 pm, 6:00 pm and 9:00 pm).
The pump was set to deliver approximately 140 mL per column, which is equivalent to a hydraulic loading rate of
48 mm day−1. The double-dose treatment (T2) had two inlet
tubes and was given 280 mL per dose equivalent to a hydraulic loading rate of 96 mm day−1. Figure 1 shows a picture of
the experimental design. Flow rates were monitored regularly
to maintain a consistent effluent flow to columns. Dosing rates
were based on the maximum daily loading rates used for carbonate sand sediments in the Lagoon Protection Zone for the
Cook Islands (CIMH 2009).
Initially there was an equilibration period where columns
were dosed with 2 L of primary treated effluent weekly for
6.5 weeks (20 April to 6 June 2011). The equilibration period
allowed sediments to settle within columns and a biofilm to
develop on amendments and previously sterilized sediments.
Following this period, the columns were dosed daily, as described above, from 6 June 2011 to the end of the experiment.
The experimental assay ran for 7 weeks (1 July 2011 and
ended 21 August 2011).
Sampling and analysis
In the first 2 weeks of the experiment, a relative measure of
column residence time was obtained using a pulsed addition
Fig. 1 Experimental column design for T1 (unsaturated), T2
(unsaturated, double dosed), T3 (unsaturated, coconut), T4 (unsaturated
basalt mix), T5 (unsaturated basalt layer), T6 (partially saturated), T7
(fully saturated)
Environ Sci Pollut Res
of a conservative tracer (NaBr) added to the inlet barrel
(1680 μg L−1). The barrel was then disconnected from the
incoming STP effluent to prevent the dilution of the NaBr.
Samples of Br− were collected daily from the inlet barrel and
every second day from the outlet of the columns.
Following the tracer addition, the collection and analysis of
influent and column outlet water for the determination of EDC
concentrations commenced. Influent samples were collected
three times a week, whilst column outlet sampling occurred
once a week. The sampling was performed for four consecutive weeks, and samples were collected in 500-mm plastic
PVC bottles. After collection, samples were stored on ice
and processed within 3 h.
Processing of water samples for EDC concentrations involved extraction using 4 mL (200 mg) C18 solid-phase extraction (SPE) cartridges (Grace Scientific). These cartridges
were pre-conditioned by running 10 mL of acetonitrile
through the cartridge under vacuum, followed by 10 mL of
50 % v/v methanol/milli Q water, 10 mL of methanol and then
20 mL of dilute phosphoric acid (pH<3). Extraction of EDCs
from the wastewater involved filtering 200 mL of each effluent sample through a 47-mm glass microfiber filter (GF/F
nominal pore size 0.7 μm). The filtered sample was then
passed through a conditioned SPE cartridge under vacuum.
The cartridge was then rinsed with 10 mL of the phosphoric
acid under vacuum. Cartridges were oven-dried for 2 days at
50 °C. To extract the EDCs from the dry SPE cartridges,
10 mL of 50 % acetonitrile/ethanol was passed under vacuum.
The eluate was collected in 15-mL centrifuge tubes, capped
and refrigerated.
The eluted samples were placed in a dry block heater
(Ratek) at 60 °C, evaporated down to 0.5–1 mL under a
stream of dry N2 gas and then transferred to 20-mL auto-sampler vials with a glass pipette. Centrifuge tubes were washed
with 0.5–1 mL of hexane to remove any residue, and contents
were put into the sampler vials. The vials were then dried at
70 °C whilst under a stream of dry N2 gas and derivatised with
100 μL of N,O-bis(trimethyl-silyl) trifluoroacetamide with
1 % trimethylchlorosilane (BSTFA +1 % TMCS) solution+
100 μL of pyridine (see method by Li et al. (2007)). Vials
were recapped with a lid containing a teflon insert and placed
in the dry block heater for 30 min at 70 °C. Vial caps were then
removed, and excess reagents were evaporated with a stream
of dry N2. Hexane (0.5 mL) was then added to vials, caps were
replaced and vials were shaken ready for analysis via gas
chromatography/mass spectrometry (GCMS). An automated
Agilent 7890 GCMS in EI (SIM) mode controlled by
Chemstation software measured the EDC analyte concentrations. The 5975C Mass Spectrometer had a triple axis detector
installed with a 30 M J&W DB5-MS column. The carrier gas
was helium set at a constant flow rate of 1 mL min−1. The
temperature program starts at 80 °C, is ramped up to 180 °C at
20 °C min−1, is held for 1 min, then ramped up to 280 °C at
20 °C min−1 and then held for 18 min. Samples were analysed
for estrone, estriol, estradiol and ethinylestradiol. Standards,
blanks and control samples were prepared similarly. An eightpoint calibration curve was plotted from standards, which
were injected in a descending order of 10, 8, 6, 4, 2, 1, 0.5
to 0.2 μg L−1. Linearity was obtained across the calibration
range for all compounds. For the E1 and EE2, the RSD of the
peak areas from 10, 8, 6, 4, 2 to 0.5 μg L−1 were in the range of
3–15 and 3–17 %, respectively; those for E2 and E3 calibrations were in the range of 3–15 % when the calibration were
from 10 to 1 μg L−1.
Chemical analyses were undertaken within an
ISO9001:8000 certified facility. Standards, spikes and recoveries were run with each batch of samples. Recoveries ranged
from 60 to 90 %, and results were adjusted for recoveries.
Analytical method was as described by Li et al. (2007).
Auxiliary measurements
Measurements were taken using handheld probes (Hach
HQ40D) in situ for pH, temperature and dissolved O2 (DO).
Influent samples were collected three times a week, and outlet
samples were tested once a week using the same equipment.
Data analysis
One-way analysis of variance tests were performed on treatment flow rate, pH and EEQ (estrogen equivalency) concentrations in all treatment outlets and the inlet barrel. Post hochonest significant difference tests were performed when
P<0.05 or Fcalc > Fcrit to determine significant differences.
Percentage reduction of EDCs was calculated by dividing outlet average by inlet average. All results are presented with the
standard deviation of the measurement. Estrogen equivalency
(equivalent to 17B estradiol) was defined by the sum of concentrations of individual estrogens (C) multiplied by their relative toxicity TEF, (EEQ = ∑ (Ci) × (TEFi). The TEF potency
values used were taken from Metcalfe et al. (2001). These
potency values were obtained by using yeast estrogenicity
screening assays on estrogens in sewage treatment plants to
determine TEF potency values relative to 17β-estradiol (E2).
The TEFs used were 17β-estradiol (E2) = 1, 17α
ethinylestradiol (EE2) = 0.38, estrone = 0.14 and estriol =
0.037.
Results
Flow and geochemistry
The average flow rate from the inlet barrel to the columns was
143±19 mL dose−1. No significant difference (P>0.05) was
found between the flow rates to the columns. The conservative
Environ Sci Pollut Res
tracer breakthrough curves for the seven treatments are shown
in Fig. 2. The saturated treatments had the longest residence
times followed by the mixed sand basalt columns (Fig. 2).
The pH and DO of the column outlets and the inlet barrel
are shown in Fig. 3b, c. Average inlet pH and DO concentrations were 7.93±0.33 and 1.27 mg L−1, respectively. The pH
generally increased, and the DO generally decreased with increasing residence time (Fig. 3a–c). Treatment 2 (doubledosed unsaturated carbonate sand) had the highest DO with
an average of 5.5 mg L−1. Treatment 7 had the lowest DO with
an average of 2.0 mg L−1.
Estrogens
The average EEQ of the influent barrel over the 4-week experimental period was 1.2 ng L−1 (EEQ equivalent to 17β
estradiol). Estrone was the dominant component of the inlet
EDCs and constituted 58 % of the total EDC concentration
(Fig. 4). Estradiol was the least abundant EDC in the inlet
(6 %). Ethinylestradiol and estriol both contributed 18 % to
the total estrogenicity of the inlet sample.
The EEQs from the outlets of treatments 1–6 were lower
than EEQ for inlet water (Fig. 5). T1 had the best reduction of
EEQ with an EEQ of 0.5 ng L−1, followed by T5 which had an
EEQ of 0.6 ng L−1. Both treatments T1 and T5 were significantly different (P<0.05) than treatment 7. In the fully saturated columns (T7), there was a 6 % increase of measured
EDCs (ethinylestradiol and estradiol) to the outlet water.
Treatment (T7) had the highest EEQ of 2.4 ng L−1, which
was double that of the inlet wastewater which had an EEQ
of 1.2 ng L−1.
Discussion
Surface and groundwater contamination from EDCs has the
potential to significantly affect human and environmental
health in developing countries that are increasingly using
and disposing of EDCs. The behaviour of EDCs in carbonate
sands under saturated and unsaturated conditions is poorly
understood but is essential for developing low-tech on-site
wastewater treatment systems for the removal of EDC-laden
effluent in developing countries. The main objective of this
study was to quantify the removal of EDCs within carbonate
sand columns operated under different degrees of saturation.
A secondary objective was to test whether estrogenic EDC
removal would be affected by the addition of other soils/
materials (e.g. basalt soil, coconut fibre) to the sand columns.
Retention time was an important factor on all of the measured parameters (pH, DO and EDC concentration). In the
fully saturated columns, the DO concentration was the lowest,
and pH was similar to the inlet water. However, in the unsaturated carbonate sand treatments with the shortest retention
time, the pH was significantly lower, and the DO was significantly higher than the saturated columns. The decrease in pH
is likely caused by nitrification in the unsaturated sediments
through the release of H+ ions (Sharma and Ahlert 1977). The
8
Br-1 Concentrations (mg L-1) in column outlets
Fig. 2 Concentration of Br
(mg L−1) at the outlet of all seven
treatments following addition to a
common inlet wastewater tank.
T1 (unsaturated), T2 (unsaturated,
double dosed), T3 (unsaturated,
coconut), T4 (unsaturated basalt
mix), T5 (unsaturated basalt
layer), T6 (partially saturated), T7
(fully saturated)
All treatments reduced estrone below average influent
levels. All treatments with the exception of T7 reduced estriol.
Treatments 1 (unsaturated sand) and T6 (saturated sand
800 mm) reduced all estrogens (E1, E2, EE2, E3) below average inlet influent levels. Positive fluxes of estradiol were
observed in all treatments except T1 and T6 (Fig. 4).
T1 - Unsaturated
T2 - Unsaturated double dose
T3 - Unsaturated coconut
T4 - Unsaturated basalt mixed
T5 - Unsaturated basalt layer
T6 - Partially saturated
T7 - Fully saturated
6
4
2
0
0
5
10
15
Days after addition
20
25
Environ Sci Pollut Res
Fig. 3 a Hydraulic residence time in days for each of the seven
treatments, b mean pH for each treatment and the inlet wastewater tank
and c mean dissolved oxygen concentration (DO mg L−1) for each
treatment including the wastewater inlet tank. Error bars are standard
deviations of multiple measurements (n=8)
reduction in DO in the saturated columns is most likely due to
the oxidation of wastewater organic carbon.
Estrogen equivalency concentration in the inlet barrel was
variable over the experimental period. EDC concentrations are
known to be variable in STP inlet waters (Roda et al. 2006).
Estrone was the dominant component of the measured EDCs
in the inlet barrel, and estradiol was the least abundant. The
influent used for this study came from the primary settling
tank at the STP, and it has been shown by Dytczak et al.
(2006) that estrone levels were higher leaving primary treatment than inlet levels largely due to the conversion of estradiol
to estrone. The same study demonstrated that estrone was one
of the least degraded in primary treatment and is added to by
the cleavage of conjugated forms of estrone by microbial
transformations in the activated sludge.
The only treatments able to reduce all four measured estrogens and have an EEQ below the level of the inlet barrel were
the fully unsaturated sand treatments T1 and T6. There is a
considerable amount of literature on the increased removal of
EDCs under aerobic conditions as opposed to anaerobic conditions (Kowalchuk and Stephen 2001; Braga et al. 2005b;
Ying and Kookana 2005; Czajka and Londry 2006; Nakada
et al. 2007; Ren et al. 2007; Koh et al. 2008; Cajthaml et al.
2009; Zhang et al. 2011). Studies have shown that
chemolitho-autotrophic ammonia-oxidizing bacteria are responsible for the rate-limiting step of nitrification and use
the conversion of ammonia to nitrate as their sole energy
source (Kowalchuk and Stephen 2001). Ren et al. (2007) stated that estrogens are removed either by the direct use as electron donors for heterotrophs or by the co-metabolic degradation of ammonia-oxidizing bacterium. Shi et al. (2004)
showed that Nitrosomonas europaea, an autotrophic nitrifying
bacterium, was able to oxidize estrone, estriol, estradiol and
ethinylestradiol in the presence of ammonia. Redox conditions play an important role in the removal efficiency of estrone and ethinylestradiol, with the highest removal occurring
under aerobic conditions where estroneis reduced to estradiol
(Joss et al. 2004). Bioreactor tests have shown a linear relationship between nitrification and ethinylestradiol (EE2) removal by enriched cultures of autotrophic ammonia oxidizers.
These results suggested a cometabolic transformation of
ethinylestradiol (EE2) by the aerobic organisms (Cajthaml
et al. 2009). Therefore, there is a clear link between the activity of nitrifying bacteria and the degradation of EDCs.
The treatment receiving double the loading rate of other
treatments (T2) was able to reduce the EEQ of inlet water.
Ren et al. 2007 stated that higher organic loading rates create
higher rates of organic matter transformation, which causes
less ammonia oxidation and less degradation of estrone, estradiol and ethinylestradiol. However, in this study, the removal
of estrogenic EDCs in unsaturated carbonate sand filters was
not affected by dosing rate. This may be due to the ability of
carbonate sands to provide a much higher surface area for
bacterial growth and therefore greater capacity to degrade
EDCs. Most sand filters used for wastewater use either secondary treated effluent, are anaerobic or have other forms of
treatment involved.
There was a clear link between the degree of saturation and
the removal of total EDCs. The variability in the inlet EDC
concentrations could have been responsible for this result.
Despite sampling the inlet EDCs 12 times over the study
period, it is possible that large spikes in EDC concentration
in the inlet water may have been missed. This would reduce
the average inlet EDC concentration and would make
treatment 7 appear as if it were a source of EDCs. The
positive flux of total EDCs from treatment 7 could also be
due to conjugated estrogens not detected as EDCs in the
inlet. Studies by Koh et al. (2008) showed that conjugated
Environ Sci Pollut Res
6
Fig. 4 Individual concentrations
of estrone, estradiol,
ethinylestradiol and estriol for
each treatment (T1 to T7) and the
common inlet wastewater. All
concentrations given in ng L−1;
error bars are the standard
deviations of multiple
measurements (n=8)
3.0
Estradiol
5
2.5
4
2.0
Estradiol
Estrone (ng L-1)
Estrone
3
2
1
0.0
In
3.0
2.0
Ethinylestradiol
2.5
2.0
1.5
1.0
Treatment
estrogens make up to 50 % of estrogens found in wastewater.
These conjugated estrogens can be partially degraded to their
former compound within the treatment and therefore show up
as an EDC flux. There is also the possibility that estrogens
sorbed onto carbonate sand becoming desorbed and released
in outlet water. There were occasional large spikes recorded in
the outlets of the semi-saturated and saturated treatments.
Studies by Lai et al. (2000) showed that both anoxic and
anaerobic conditions favour the sorption process of EDCs
when compared to aerobic.
The majority of estrogens excreted from humans are conjugated (mainly glucuronides) and are broken down to their
original compounds in the treatment works (Kumar et al.
3.5
3
EEQ ngL-1
2.5
2
1.5
1
0.5
0
T5
T6
Estriol
1.5
1.0
0.5
0.0
T1 T2 T3 T4 T5 T6 T7
T4
In
0.5
0.0
T3
T1 T2 T3 T4 T5 T6 T7
Estriol (ng L-1)
Ethinylestradiol (ng L -1)
T1 T2 T3 T4 T5 T6 T7
T2
1.0
0.5
0
T1
1.5
T7
Inlet
Fig. 5 Estrogen equivalencies (EEQ) relative to 17β estradiol for each
treatment (T1–T7) and common inlet wastewater. All concentrations given in ng L−1; error bars are the standard deviations of multiple measurements (n=8)
In
T1 T2 T3 T4 T5 T6 T7
In
Treatment
2012; Griffith et al. 2014). This can lead to higher concentrations found during treatment than those recorded for inlet
levels (Andersen et al. 2003). The estradiol fluxes observed
within the treatments may be explained by the reversible interconversion of estradiol (E2) and estrone (E1) as observed by
Andersen et al. (2003) and Czajka and Londry (2006).
Ethinylestradiol (EE2) is the most resistant to degradation of
all the estrogens.
Our results confirm the work of Nakada et al. (2007) and
show that there is limited removal of EDCs under anaerobic
saturated conditions. There were also positive fluxes of EDCs
reported by Nakada (2007); however, in the study, effluent
was secondary treated with EDC concentrations measuring
in the tens to hundreds of nanograms per litre. Furthermore,
in the Nakada et al. (2007) study, the secondary treated effluent was introduced at the bottom of a sand column (2.5 m in
outer diameter and 7.0 m in height) and flowed upwards
through the sand bed. The flow rate and retention time through
the sand were 110 m day−1 and 1 h, respectively. The differences in effluent levels and dilution, retention times, flow
rates, filter size, compound levels and EDC analysis techniques make comparisons between this and the Nakada
(2007) study difficult, although one main point seems consistent in that limited degradation of EDCs occurs under anaerobic conditions.
The additional amendments of basalt sediments and coconut fibre (both readily available and commonly incorporated
into sewage treatment systems in South Pacific islands) were
put in to encourage microbial activity or increase retention
Environ Sci Pollut Res
time. Although the results vary, the amended treatments were
not as efficient at estrogenic EDC reduction as carbonate sand
treatments (T1).
In the context of on-site wastewater treatment in the Pacific, the transformation of EDCs is an important consideration.
Aerobic sand filters are known to nitrify ammonium to nitrate,
which is then reduced to N2 gas via anaerobic denitrification.
However, this study has shown that the anaerobic conditions
that favour N removal can lead to EDC accumulation. Designing sand filtration systems specific to the constraints of South
Pacific countries that contain both unsaturated aerobic environment and saturated anaerobic environment is essential (Tait
et al. 2013). The environmental concern is that in groundwater
where DO concentrations are low, e.g. under septic tanks and
waste disposal fields, there is the potential for EDC accumulation. The results from this study show a clear pattern between aerobic treatments and estrogenic EDC reduction and
anaerobic treatments and accumulation of estrogenic EDCs.
Conclusion
This study aimed to investigate the behaviour of estrogenic
EDCs in permeable carbonate sands under saturated and unsaturated conditions. The broader goal of this research was to
develop low-cost on-site wastewater treatment technologies
for estrogenic EDC removal in developing countries. One of
the main findings in this study was that aerobic conditions
within carbonate sand treatments encouraged EDC reduction
even at high dosing rates. Fully saturated conditions led to
incomplete degradation of conjugated forms of estrogens or
accumulation or transformation of inlet estrogens measured.
Fully saturated systems had low EDC reduction with the tendency to accumulate EDCs. Semi-saturated systems that had
an aerated section before a saturated section had high EDC
reduction. All the amended aerobic treatments performed better than fully saturated treatments. The accumulation of EDCs
in anaerobic treatments suggests that additional aerobic treatment, post-denitrificiation, would help to reduce accumulated
EDCs. The results from this study show that aerobic environments greatly increase the reduction of estrogenic EDCs as
opposed to anaerobic environments. Therefore, in order for
estrogenic EDCs to be removed efficiently from wastewater,
an aerobic stage or two is needed in the treatment process. The
efficiency will depend on size, flow rate, and placement; these
are parameters that need further investigation.
Acknowledgments This project was supported by the School of Environmental Science and Management, Centre for Coastal Biogeochemistry
and ARC Linkage project LP100200732. We would like to thank the
technical staff at the Wollongbar Department of Primary Industries. We
also thank the technical staff at the School of Environment, Science and
Engineering at Southern Cross University.
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