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Desalination and seawater quality at Green Point, Cape Town: A study on the effects of marine sewage outfalls

Authors:
1
South African Journal of Science
http://www.sajs.co.za
Volume 113 | Number 11/12
November/December 2017
© 2017. The Author(s).
Published under a Creative
Commons Attribution Licence.
Desalination and seawater quality at Green Point,
Cape Town: A study on the effects of marine
sewage outfalls
AUTHORS:
Leslie Petrik1
Lesley Green2
Adeola P. Abegunde1
Melissa Zackon2
Cecilia Y. Sanusi1
Jo Barnes3
AFFILIATIONS:
1Environmental and Nano
Science Group, Department
of Chemistry, University of the
Western Cape, Cape Town,
South Africa
2Environmental Humanities
South and Department of
Anthropology, School of
African and Gender Studies,
Anthropology and Linguistics,
University of Cape Town,
Cape Town, South Africa
3Senior Lecturer Emeritus,
Division of Community Health,
Stellenbosch University,
Stellenbosch, South Africa
CORRESPONDENCE TO:
Lesley Green
EMAIL:
lesley.green@uct.ac.za
KEYWORDS:
microbial pollution;
pharmaceuticals; perfluorinated
compounds; common household
chemicals; marine organisms
HOW TO CITE:
Petrik L, Green L, Abegunde AP,
Zackon M, Sanusi CY,
Barnes J. Desalination and
seawater quality at Green
Point, Cape Town: A study
on the effects of marine
sewage outfalls. S Afr J Sci.
2017;113(11/12), Art. #a0244,
10 pages. http://dx.doi.
org/10.17159/sajs.2017/a0244
This paper presents our collection methods, laboratory protocols and findings in respect of sewage pollution
affecting seawater and marine organisms in Table Bay, Cape Town, South Africa, then moves to consider their
implications for the governance of urban water as well as sewage treatment and desalination. A series of seawater
samples, collected from approximately 500 m to 1500 m offshore, in rock pools at low tide near Granger Bay,
and at a depth under beach sand of 300–400 mm, were investigated for the presence of bacteriological load
indicator organisms including Escherichia coli and Enterococcus bacteria. A second series of samples comprised
limpets (Patella vulgata), mussels (Mytilus galloprovincialis), sea urchins (Tripneustes ventricosus), starfish
(Fromia monilis), sea snails (Tegula funebralis) and seaweed (Ulva lactuca), collected in rock pools at low tide
near Granger Bay, and sediment from wet beach sand and where the organisms were found, close to the sites
of a proposed desalination plant and a number of recreational beaches. Intermittently high levels of microbial
pollution were noted, and 15 pharmaceutical and common household chemicals were identified and quantified in
the background seawater and bioaccumulated in marine organisms. These indicator microbes and chemicals point
to the probable presence of pathogens, and literally thousands of chemicals of emerging concern in the seawater.
Their bioaccumulation potential is demonstrated.
In respect of proposed desalination, the findings indicate that desalinated seawater must be subjected to
treatment protocols capable of removing both bacterial loads and organic chemical compounds. The terms of
reference for desalination plants must specify adequate testing and monitoring of chemical compounds as well as
microorganisms in the intake and recovered water. Drinking water supplied by the proposed seawater desalination
plants should be carefully tested for its toxicity.
In respect of water management, our findings suggest the need for the City of Cape Town to move to an integrated
water and sewage management plan that treats urban water, including seawater, as a circulating system that is
integral to the health of the City, and which excludes marine outfalls.
Background to the study
The ongoing drought in the Western Cape has led to the proposal to produce drinking water via seawater desalination
plants for the City of Cape Town. The terms of reference provided in the tender documents make the assumption
that the tens of millions of litres a day of untreated sewage effluent discharged into the ocean via the marine outfalls
located around the Peninsula are dispersed out to sea and that intake seawater to the desalination plants will
contain only inorganic salts, and not organic chemical pollutants or microorganisms.
However, kayakers, long-distance swimmers, and citizen groups like the Camps Bay Ratepayers, have claimed
that untreated effluent from the marine outfalls washes back to shore in specific conditions.1,2 Where positive
independent E. coli counts have been demonstrated, such as those collected by public health researcher
Edda Weimann3, the City has argued that the E. coli results are a result of stormwater run-off.
Resolving the matter requires evidence of factors that can only have been sourced from human sewage, such as
specific bacteriology and pharmacological compounds that can only have entered seawater via faecal contamination
from the marine outfalls and not from surface run-off. If those compounds are present, the findings have relevance
to the City’s desalination plants, beach management and sewage management system.
Persistent organic pollutants include pharmaceutical and personal healthcare products such as over-the-counter
and prescription drugs (antibiotics, analgesics, blood lipid regulators, natural and synthetic hormones, β-blockers,
antidiabetics, antihypertensives, etc.) and household products such as soaps, detergents, disinfectants, per fumes,
dental care products, skin and hair products, and surfactants, as well as these compounds’ degradation products.4-6
There is growing evidence that certain emerging contaminants could affect human and environmental health. For
example, the veterinary use of diclofenac, which is also a human pharmaceutical used as an anti-inflammatory
treatment, was found to be responsible for the massive decline in populations of vulture species in certain areas
of Asia7; ethinylestradiol, one of the active ingredients in the contraceptive pill, has been associated with endocrine
disruption and feminisation in fish8; and there is concern that long-term exposure to antibiotic pharmaceuticals and
disinfectant products may be contributing to the selection of resistant bacteria with significant impacts upon human
health.9 In South Africa, Ncube et al.10 suggested a protocol for the selection and prioritisation of contaminants
in drinking water. Patterton11 surveyed seven cities in South Africa and showed the presence of 32 compounds
in drinking water, predominantly pharmaceuticals and pesticides, including carbamazepine (anticonvulsant),
phenytoin (antiepileptic) and diclofenac. Osunmakinde et al.12 compiled a priority list including the antiretroviral
lamivudine, based on data collected from the health sector in South Africa. These compounds could cause far more
harm than the sewage itself, such as feminisation or sterility of fish populations, cancer, growth deformities, foetal
abnormalities and hormonal disturbances. These compounds may bioaccumulate in marine organisms, and thus
move up the food chain to humans who eat seafood, ultimately causing the same effects. Also in South Africa,
Swartz et al.13 identified carbamazepine, sulfamethoxazole (antibiotic), triclosan (biocide), bisphenol A (plasticiser)
and caffeine (stimulant) amongst others as priority pollutants for water quality assessment in water reuse.
Commentary
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Commentary Desalination and seawater quality at Green Point, Cape Town
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These authors stated13:
The priority list cannot be seen as an exhaustive
list as each reclaimed potable water reuse project
should interrogate the relevance according to the
specic area to consider whether extra chemicals
might need to be added to the priority list.
These authors also reported that many of the compounds tested for,
escaped through the conventional wastewater treatment plants in trace
quantities into the environment. For instance, α-ethinylestradiol, which
has a recommended reference dose of 0.0015 µg/L, was present in
some effluents at levels of 2–6 µg/L.
This study presents the laboratory findings from seawater, sediments as
well as samples of marine organisms collected near the marine sewage
outfalls in Green Point, close to the site of the proposed Granger Bay
desalination plant.
Water samples: Collection methods and laboratory protocols
Seawater samples for microbiological and chemical testing were
collected at 22 different points (Figure 1) near Granger Bay in the
months of June, July and August 2017, together with kayakers on days
on which winds and swell conditions allowed for kayak trips. In addition,
seven samples were taken of water in beach sands of the intertidal
swash zone at depths of approximately 300 mm. All water samples
for microbiological testing were collected in bottles provided by the
South African Bureau of Standards (SABS) in a sealed packet 24 h prior
to collection, and samples were delivered to the SABS laboratories in
Rosebank, Cape Town, within 1 h of collection and stored on ice en route.
Tests were requested for E. coli as the indicator organism of choice for
checking sewage contamination in fresh water while Enterococcus is
more stable in seawater. At the SABS laboratories, which are accredited,
samples were tested in terms of the SANS 5221 protocol for E. coli and
SANS 7899 for Enterococcus. Figure 1 shows the location of sampling
points in the ocean and on the shoreline and flags the hot spots of
contamination above the Blue Flag limits of 250 colony-forming units
per 100 millilitres (CFU/100 mL).
Microbial findings
The results of microbial tests for seawater and beach water samples are
consistent with kayakers’ claims that on occasion the water is a health
risk. While the majority of markers were clear, there was significant
variability. One sample – taken 1.7 km from shore – contained an E. coli
count of 12 650 CFU/100 mL. This sample was collected on the edge
of what kayakers identified as the sewage plume that had led to several
complaints, and although the plume was visibly more dense further on,
the kayakers were not willing to risk paddling into it to collect additional
water samples. On the same day, a sample taken 1 km from the shore
contained an E. coli count of 4700 CFU/100 mL.
Water collected in sand evidenced similar variability. One sample
contained an Enterococcus count of 1460 CFU/100 mL and that on
another day had a count of 7200 CFU/100 mL. The majority of microbial
results were within specification, as shown on the map.
Discussion
In 2014, Edda Weimann, an endocrinologist, published a paper challen-
ging the City’s use of the Blue Flag ensign to promote its beaches.3 Her
samples, taken six times at Clifton Beach over a 4-week period in early
2013, showed that only on one day was the E. coli level within the Blue
Flag acceptable range of below 250 CFU/100 mL and Enterococcus
below 100 CFU/100 mL. On two separate days she found the values for
E. coli had been in the tens of thousands, and on a further two days the
values ranged in the hundreds of thousands and closer to one million
(105–106). Nonetheless, on every day that she had sampled Clifton’s
waters, the Blue Flag had been hoisted. Weimann’s findings contradict
Blue Flag’s criteria pertaining to water quality.14
Both Weimann’s findings and ours suggest that predictive modelling
will be more effective in managing potentially hazardous beach sewage
levels than the form of water quality monitoring currently used in the City
via the Blue Flag protocols, which are used to assert the health of the
seawater on the basis of one or two samples taken per month.15,16
Figure 1: Location of sampling and microbial load of seawater and beach water (Granger Bay, Cape Town).
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Predictive modelling is consistent with South Africa’s policy for the
disposal of land-derived wastewater in the sea, published in 2006.17
Because seawater is constantly in a state of movement we also investi-
gated the presence in marine organisms of compounds that could only
come from long-term exposure to sewage-contaminated seawater.
A variety of species was collected from rock pools at low tide near
Granger Bay (Figure 1).
Bioaccumulation of persistent organic pollutants
in marine organisms
The selection of compounds for this study was based on their known
persistence in the environment as well the availability of testing protocols
and standards. The compounds tested for included perfluorinated
compounds and a variety of pharmaceuticals, a cleaning agent, caffeine
and bisphenol A.
Caffeine (Ca) was chosen as a broad indicator of faecal contamination.
Caffeine passes from the human digestive system via faeces into the
environment in unmodified form. Perfluorinated compounds are a
large family of synthetic chemicals, broadly used in industrial and
consumer products. They are used as industrial surfactants and surface
protectors for food containers, paper, leather, carpet, fabric coating
and firefighting foams because of their water and oil repelling ability.
Perfluorinated compounds selected here include perfluorooctanoic
acid (PFOA), perfluoroheptanoic acid (PFHpA), perfluorononanoic acid
(PFNA), perfluorodecanoic acid (PFDA) and perfluoroundecanoic acid
(PFUnDA). Pharmaceuticals tested for were acetaminophen (ACT),
diclofenac (DSS), lamivudine (LA), phenytoin (PHE), carbamazepine
(CAR) and sulfamethoxazole (SUL). The household product tested for
was triclosan. Triclosan (TS) is an antibacterial and antifungal agent
commonly found in household and personal cleaning products including
some toothpastes. The industrial chemical tested for was bisphenol A
(BPA), which is an organic synthetic compound that mimics oestrogen
and is used in plastics, the lining of some food and beverage cans and
thermal paper used in point-of-payment slips.
Sample collection and handling
Limpet (Patella vulgata), mussel (Mytilus galloprovincialis), sea urchin
(Tripneustes ventricosus), starfish (Fromia monilis), sea snail (Tegula
funebralis) and seaweed (Ulva lactuca) samples were collected from
rock pools along the shoreline near Granger Bay in 2017. In 2015,
samples were collected at a depth of ~30 m in the ocean close to the
marine outfall diffusers. Samples were wrapped in foil and stored on
ice for transportation to the laboratory. All marine organism samples
were delivered to the laboratory within 1 h of collection, and stored at
-20 °C at the laboratory. The samples were analysed according to the
protocols below.
Analytical protocols
All sample bottles, extraction and volumetric flasks used were washed
in methanol, rinsed with tap water and deionised water, then air dried.
Reagents
Methanol, acetonitrile and acetone were HPLC grade. The standards,
purchased from Sigma Aldrich (Johannesburg, South Africa), were:
perfluorooctanoic acid (PFOA 96%), perfluoroheptanoic acid (PFHpA
99%), perfluorononanoic acid (PFNA 97%), perfluorodecanoic acid
(PFDA 98%), perfluoroundecanoic acid (PFUnDA 95%), bisphenol
A (≥99%), acetaminophen (≥99%), caffeine, ibuprofen sodium
salt (≥98%), diclofenac sodium salt, lamivudine (≥98%), triclosan
(≥97%), phenytoin, sulfamethoxazole (≥97%), sulfisoxazole (≥99%)
and acetaminophen-d4 (≥97%). Ultrapure water was purified using a
Milli-Q system (Millipore, Bedford, MA, USA).
Primary stock solutions of individual analytes were prepared in methanol
at a concentration of 1000 µg/mL and appropriately diluted in methanol.
Sample preparation: Extraction and clean-up
In this study, Oasis HLB was selected over Strata X cartridge for
sample extraction.18
Water samples
Seawater samples of 500 mL were extracted based on the method used
by Valdés et al. 19, with some modifications. The extract was concentrated
to 2 mL under a gentle nitrogen stream and then transferred to amber
vials and centrifuged for 25 min prior to analysis.
Tissue samples
Tissue from marine organisms was freeze dried and ground into a fine
powder. Approximately 10 g was weighed and placed into an extraction
thimble. Surrogates (sulfisoxazole, acetaminophen-d4) were added
to each sample. The mixture was extracted with 100 mL methanol/
acetone 3:1 (v/v). The extract was concentrated to 10 mL using a rotary
evaporator at reduced pressure, and the sample pH was adjusted to 6
by adding 1 M NaOH or HCl so as to allow the precipitation of lipids. The
extract was centrifuged at 3000 rpm for 20 min. The supernatant was
transferred to glass bottles and Millipore water was added to make up
to a volume of 100 mL. These aqueous extracts were further extracted
and cleaned using the procedure of Valdés et al.19 for seawater samples.
The final eluate was concentrated under nitrogen and then reconstituted
to 2 mL with methanol. Recovery standards were added to each sample
prior to analysis.
Chromatographic conditions
The chromatographic separations were performed with the Acquity
UPLCTM (Waters, Milford, MA, USA). Simultaneous determination of all
the compounds of interest was achieved using an Acquity UPLC BEH
C18 1.7-µm column (2.1 mm × 1000 mm) with an Acquity BEH C18
1.7-µm VanGuardTM precolumn (2.1 mm × 5 mm), supplied by Waters.
The column temperature was set to 50 °C. The mobile phase consisted
of a mixture of 0.02 M formic acid (solvent A) in water and acetonitrile
(solvent B). Linear gradient elution of 0.35 mL/min was used starting
with a mixture of 80% solvent A and 20% solvent B for 9 min. At 10 min,
the acetonitrile percentage was increased linearly from 90% to 100% and
was later maintained at 80% of solvent A and 20% of solvent B. A volume
of 5 µL of each sample was injected into the LC/MS system. Standards
and the test samples were subjected to a 12-min chromatographic run.
Mass spectrometry
The UPLC was coupled to a triple quadrupole mass spectrometer (Xevo
TQ-MS), with an electrospray ionisation source. During optimisation, a
multiple reaction monitoring scan mode was generated for all analytes.
In addition, for maximum sensitivity, other conditions such as source
temperature, capillary voltage, cone voltage, cone gas flows and
desolution temperatures were standardised. This standardisation was
achieved by direct injection of stock solutions with a concentration of
10 µg/mL. A capillary voltage of 3.5 kV, desolvation gas (N2) flow of
800 L/h, source temperature of 140 °C and desolvation temperature
of 400 °C were finally used. The analytical operation control and data
processing were performed with Masslynx software.
Method modification, validation, quality control and calibration
The volume of each water sample used for the extraction technique
was increased from 250 mL to 500 mL. To ascer tain the concentration
and consistency in the extraction technique for all the analytes, each
extraction round was triplicated. The analytical method was validated
using EU Commission Decision 2002/657/EC as a guideline. To show
the applicability of the analytical method, a validation study was carried
out. The validation procedure included the assessment of method
linearity, specificity/selectivity, precision, recovery and calculation of
the limits of detection and quantification. Six-point calibration curves
were constructed (four replicates). The multi-matrix capacity of the
analytical technique was checked with an identical validation study using
ultrapure water and seawater. To monitor for potential contamination,
blank samples of ultrapure water were extracted and analysed along with
Commentary Desalination and seawater quality at Green Point, Cape Town
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the seawater samples and laboratory spikes. Methanol blanks were also
run between samples in order to monitor for instrumental contamination
and carry-over. None of the compounds of interest was detected in
the ultrapure water and reagents used. Chromatographic peak area,
signal noise and height were used to define and quantify the analytes
of interest. Calibration standards were analysed prior to each analysis
batch. The final analyte concentration was calculated as follows:
Final analyte concentration =
initial concentration x sample volume injected
sample volume extracted
Findings: Organic pollutants in marine organisms and seawater
All 15 indicator chemical compounds were present in the seawater samples
in trace concentrations (Figures 2 to 4) and considerably higher levels were
present in limpets (Patella vulgata), mussels (Mytilus galloprovincialis),
sea urchins (Tripneustes ventricosus), starfish (Fromia monilis), sea
snails (Tegula funebralis), seaweed (Ulva lactuca) and sediment samples
(Figures 5 to 7). The high levels of all the chemical compounds in marine
organisms are evidence of bioaccumulation over time as the organisms
have no way of escaping the pervasive presence of these chemicals in
the seawater. The significant increase in their levels in 2017 against our
findings of 2015 (Figure 8) is noteworthy. None of these compounds
would normally be found in seawater and should definitely not be
present in these marine organisms. With the exception of caffeine, all
are manufactured substances. The finding that all 15 tested compounds
were present in every organism and in the background sediments and
seaweed tested, is a clear indication of faecal pollution of the shoreline,
and that additional chemical substances are likely present in the seawater
and thus in the marine organisms.
Discussion
Pharmacological compounds such as the analgesic and anti-inflam-
matory drugs acetaminophen (also known as paracetamol) and
diclofenac, the anti-seizure medication phenytoin, the antibiotic sulfame-
thoxazole and the antiretroviral lamivudine are made to be stable and
effective at low doses. They are polar, lipophilic, soluble and nonvolatile
compounds.20 For these reasons, many pharmaceutical compounds or
secondary metabolites do not decompose, but survive in the environment
to become persistent organic pollutants. Unknown quantities of partially
metabolised drugs which may be toxic are also released in faeces and
urine.21 Their molecular sizes in the nanometre (10-9) and Angstrom
range (10-10) make it impossible for marine organisms to exclude them.
It has been widely reported that these compounds are continuously
released into the environment,22-24 and bioaccumulate in wild-caught
fish populations at concentrations of nanograms per gram.25,26 Huerta
et al.25 showed that diclofenac and carbamazepine were the most
highly bioaccumulated at 18.8 ng/g in fish liver. Current regulations
do not specify that they should be monitored in our water supplies or
in sewage effluents (South African National Drinking Water Standard
(SANS) 241: 2015), even though Patterton’s study11 demonstrated
their presence in South African tap water. Moreover, it is known that
disinfectants and antibiotics cause selection for resistance in the gene
pool of microorganisms, ultimately making them impervious to the
antibiotic or antimicrobial agents.27
The full impact of constant, low-grade, chronic exposure to a plethora
of pharmaceuticals, antibiotics and cleaning products on marine
organisms, the marine food chain, and human health is not yet fully
known, but their ubiquitous presence in trace levels in the desalination
intake water poses a potential risk to human health.
Although some pharmaceuticals are unlikely to constitute a risk to
humans as they are found in low concentrations and have a low toxicity,
such as iopromide28, other pharmaceuticals such as natural and synthetic
sex hormones pose considerable risks to the aquatic environment29.
1.4
1.2
1
0.8
0.6
0.4
0.2
0
PFUnDA PFDA
Location 1 Location 2 Location 3 Location 4
Location 5 Location 6 Location 7 Location 8
PFNA
Perfluorinated compounds
Concentration in ng/L
PFOA PFHpA
PFUnDA, perfluoroundecanoic acid; PFDA, perfluorodecanoic acid; PFNA, perfluorononanoic acid; PFOA, perfluorooctanoic acid; PFHpA, perfluoroheptanoic acid
Figure 2: Concentration of perfluorinated compounds in seawater samples collected off Granger Bay, Cape Town.
Commentary Desalination and seawater quality at Green Point, Cape Town
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0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
DSS SUL PHE CAR LA CA ACT
Pharmaceuticals
Concentration in ng/L
Location 1 Location 2 Location 3 Location 4
Location 5 Location 6 Location 7 Location 8
DSS, diclofenac; SUL, sulfamethoxazole; PHE, phenytoin; CAR, carbamazepine; LA, lamivudine; CA, caffeine; ACT, acetaminophen
Figure 3: Concentration of pharmaceuticals in seawater samples collected off Granger Bay, Cape Town.
Location 1 Location 2 Location 3 Location 4
Location 5
BPA
Concentration in ng/L
Industrial chemicals and personal care products
TS
Location 6 Location 7 Location 8
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
BPA, bisphenol A; TS, triclosan
Figure 4: Concentration of industrial and household chemicals in seawater samples collected off Granger Bay, Cape Town.
Commentary Desalination and seawater quality at Green Point, Cape Town
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Sediment A Sediment B Mussels
Seaweed
Limpets
Sea snailsStarfishUrchins
PFUnDA PFDA PFNA PFOA PFHpA
Perfluorinated compounds
Concentration in ng/L
14
12
10
8
6
4
2
0
PFUnDA, perfluoroundecanoic acid; PFDA, perfluorodecanoic acid; PFNA, perfluorononanoic acid; PFOA, perfluorooctanoic acid; PFHpA, perfluoroheptanoic acid
Note: Sediment A is from wet beach sand and Sediment B from where the organisms were found.
Figure 5: Concentration of perfluorinated compounds in marine organisms and sediments from the shores near Granger Bay, Cape Town.
Sediment A Sediment B Mussels
Seaweed
Limpets
Sea snailsStarfishUrchins
Pharmaceuticals
Concentration in ng/L
10
9
8
7
6
5
4
3
2
1
0
DSS SUL PHE CAR LA CA ACT
DSS, diclofenac; SUL, sulfamethoxazole; PHE, phenytoin; CAR, carbamazepine; LA, lamivudine; CA, caffeine; ACT, acetaminophen
Note: Sediment A is from wet beach sand and Sediment B from where the organisms were found.
Figure 6: Concentration of pharmaceuticals in marine organisms and sediments from the shores near Granger Bay, Cape Town.
Commentary Desalination and seawater quality at Green Point, Cape Town
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Even where seafood accounts for only about 10% of the diet, it has been
shown to be one of the main routes by which chemical contaminants
find their way into human tissues30, which in turn may be deleterious to
human health. Moreover, the synergetic effects of pharmaceuticals and
other compounds on living organisms are unknown.31
Drinking water supplies from the seawater desalination plants should
be carefully tested for toxicity, which need not be costly.13,32 Apart from
the many compounds present in seawater, industrial effluents as well
as hydrocarbon pollution as a result of shipping, pleasure craft and
harbour effluents also impact intake water. Natural incidences such
as red tide or harmful algal blooms have also been linked to marine
sewage outfalls,33-35 which could also impact the quality of intake water.
As their combined effects and concentrations are mostly unknown,
the precautionary principle should be followed with regard to sewage
disposal into the environment. Formation of chlorine disinfection
byproducts such as inorganic chloramines, organohaloginated bypro-
ducts and trichloroamines should also be monitored and removed from
the recovered water.13
Sediment A Sediment B Mussels
Seaweed
Limpets
Sea snailsStarfish
BPA
Concentration ng/g
Industrial chemicals and personal care products
TS
Urchins
12
10
8
6
4
2
0
BPA, bisphenol A; TS, triclosan
Note: Sediment A is from wet beach sand and Sediment B from where the organisms were found.
Figure 7: Concentration of industrial and household chemicals in marine organisms and sediment from the shores near Granger Bay, Cape Town.
2015
Sea Sediment A Sea Sediment B Urchins
(Tripneustes ventricosus)
Starfish
(Fromia monilis)
Sea snails
(Tegula funebralis)
2015 2015 2015 20152017 2017 2017 2017 2017
Acetaminophen Bisphenol A Caffeine PFOA PFNA PFDA PFHpA PFUnDA
Concentration ng/g
9
8
7
6
5
4
3
2
1
0
PFOA, perfluorooctanoic acid; PFNA, perfluorononanoic acid; PFDA, perfluorodecanoic acid; PFHpA, perfluoroheptanoic acid; PFUnDA, perfluoroundecanoic acid
Figure 8: The difference in the level of selected compounds in marine organisms sampled in July 2015 and July 2017.
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Conclusions
Implications of findings for desalination
Apart from the high microbial load being discharged into the ocean
daily, the complexity and toxicity of chemicals that are being disposed
into the City’s sewage are imposing a growing chemical pollution risk
to the nearshore coastal environment, and thus to the desalination
plant’s intake water. Given the diversity of contaminants shown to be
ubiquitously present in the intake water in such close proximity to the
marine outfall in Green Point, it is probable that the water recovered from
desalination may still be contaminated with traces of complex pollutants
after the reverse osmosis process, as Patterton’s11 study also showed.
This probability represents a public health issue. Drinking water supplied
by the seawater desalination plants should be regularly screened for its
toxicity. Adequate disinfection and monitoring of the efficacy of tertiary
treatment to ensure complete decomposition of harmful pharmaceuticals
and other chemicals is essential to ensure that the water supplied to the
City is not toxic. Screening for specific compounds is very costly but
toxicity tests give rapid results.13,32
Even if most of the compounds were removed by the reverse osmosis
step, they are not destroyed and remain in the brine retentate; returning
these compounds in the brine retentate to the sea as is planned, only to
be filtered indefinitely while toxic compounds build up in marine life, is
a futile exercise.
In the long term, it would be technically more efficient and cost-effective
to prevent the sewage from entering the ocean in the first place.
Moreover, desalination intake water treatment and sewage treatment
should include a tertiary stage of combined advanced oxidation, capable
of fully decomposing pharmaceutical compounds. In the best performing
wastewater treatment plant for potable reuse of sewage that has been
studied in the Western Cape region, the treatment train was composed of
a modern dual-membrane treatment process.13 The membrane system
received secondary treated wastewater from a treatment train comprised
of a conventional activated sludge treatment process with an optional
chemical phosphate removal after chlorination. The secondary treated
wastewater entered the water recovery plant where it was treated using
a sand filter, ultrafiltration membrane, reverse osmosis membranes
and, finally, with advanced oxidation including ultraviolet (UV) light and
hydrogen peroxide before being blended with conventionally treated
water and distributed. This system currently allows direct potable
reuse of sewage and is already operational in the region. This type of
system may be able to provide potable water of reasonable quality from
wastewater but the water from this well-operated plant was still not
passing Ames mutagenicity and oestrogen mimicry tests for toxicity in
our previous study.13 With a rise in the use of chemical compounds on a
daily basis, and many thousands of regulated and unregulated emerging
contaminants being discharged and detected in the aquatic environment,
many of which exceed the recommended reference dose (mg/kg/day) of
various regulators13, great caution is needed. Implementation of barriers,
monitoring programmes and assessment programmes to eliminate or
minimise these risks is essential.
Compact, new treatment systems that can treat the sewage to high
standards and recover the water before discharge to the ocean can
eliminate the need for desalination. Advanced oxidation systems include
ozonation36, ozone/hydrogen peroxide37,38, ozone/UV39, hydrogen
peroxide/UV40, UV/chlorine41-43, UV/TiO2
44, ultrasonic irradiation45 or
sonolysis46,47, photocatalysis48,49, photo fentons50, dielectric barrier
discharge51,52 and electrochemical53 reactions, which all work by
producing short-lived but highly reactive free radicals and have been
used most effectively in combined systems for the degradation or
destruction of complex organic compounds in water. A thorough
investigation is needed in the Western Cape on viable advanced oxidation
technologies to add to the conventional treatment train of coagulation,
flocculation, adsorption, precipitation, reverse osmosis, membrane
bioreactors, nanofiltration and electrodialysis, recognising that the
treatment of sewage and wastes is just as important to public health as
the supply of fresh water is.
Implications for the City of Cape Town
The idea of sending a sewer pipeline out to sea was approved when
the volumes of effluent being discharged to the ocean were relatively
small, based on the incorrect assumption that ‘the solution to pollution
is dilution’, and at a time when the variety and volume of manufactured
chemicals and pharmacological compounds impacting the sewage was
far lower than is the current situation.
Pipeline extension
These findings demonstrate that the assumptions behind marine sewage
outfalls are incorrect and outdated. Extending the pipeline out to sea
will not solve the problem, as it is clear that, under certain conditions,
sewage flows back to shore in quantities that are harmful, and toxic
chemicals will be released, albeit further from the shore, impacting
marine life.
Predictive modelling
Until the sewer outfall is replaced, predictive modelling based on daily
weather and sea conditions offers a better tool for seawater quality
and beach management than sample-based monitoring. Much of the
information that is required for predictive modelling is already being
collected daily by ocean users who have set up WindGuru stations or
similar, and who would actively par ticipate in a citizen science project.
A study consolidating such data with daily water samples is needed.
The precautionary principle
The measurable presence of indicator organisms and indicator chemicals
points to the presence of pathogens and many other persistent chemicals
in our ocean. The potential for their bioaccummulation is demonstrated.
Because of the hazards of these compounds, the precautionary principle
is highly relevant in terms of human health. Should desalination of
seawater be the main option for augmenting potable water supplies, the
health risks of pharmacological and chemical compound accumulation
need to be quantified by daily monitoring and mitigated prior to the
release of the water into the potable water reticulation system. An
example of such a monitoring system is the Windhoek reclamation
system. Testing the provided water to South African National Drinking
Water Standard (SANS) 241: 2015 is not adequate as these compounds
are not yet regulated.
The ‘polluter pays principle’
In terms of the ‘polluter pays principle’, the costs of the chemical and
pharmaceutical compound clean-up ought to be borne by the companies
producing the substances. Pharmaceutical and chemical companies
are among the wealthiest multinational corporations globally. While
air polluters are required to ensure emissions are cleaned from the
commons that is the air breathed by all, pharmaceutical companies
and the chemical industry have not been contributing to the clean-up of
pollutants in water systems.
Purchasing power
Retailers and consumers of pharmaceuticals and common household
chemicals need to review their contribution to the growing pollution of
ocean ecologies. Our individual decisions have a huge collective impact.
Politics of water, environment and sanitation
Historically, cities were made possible by the development of infra-
structure to adequately manage human waste. The City of Cape Town
has outgrown its current water supply and sanitation infrastructure.54
While the City has vigorously opposed the politics of the ‘poo flingers’
such as Andile Lili who have dumped human waste to force the argument
about improved sanitation in Khayelitsha and elsewhere, the City itself is
daily depositing a volume of many Olympic-size swimming pools into
the ocean. One might indeed quip that in terms of the current sewage
management infrastructure, ‘Je suis Andile Lili’. The convergence of
sanitation activism in seaside suburbs and shack settlements in a time
of drought suggests that the City’s water should be understood as one
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hydrological system, and therefore managed as a single ecology, not via
the separation of environment, sanitation and water supply.
Acknowledgements
We gratefully acknowledge funding from the National Research
Foun dation (South Africa) for the Human Social Dynamics Grant
(HSD141104109103 Grant 96035 titled Race and the Making of
an Environmental Public) to Environmental Humanities South at
the University of Cape Town. We are indebted to Tracy Fincham and
Billy Fisher at Kaskazi Kayaks for guiding the sampling team and for
the use of kayaks; to the SABS Rosebank for E. coli and Enterococcus
results; to the laboratories at Stellenbosch University and the University
of the Western Cape for the CAF results; and to Nicholas Lindenberg for
assistance with the map.
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... Compared to other countries worldwide, most African and Asian countries lack reports on the occurrence of pharmaceuticals in the environment with a considerable number of reports documented in Africa, particularly South Africa [149,162]. However, literature demonstrates that various types of pharmaceuticals detected depend on some factors including agricultural, social, technological and cultural factors which are common for various geographical regions and water bodies [127]. ...
... However, some are pseudo-persistent; they are not persistent but their constant release into the environment makes them ubiquitous [184]. African countries have always been behind about monitoring, occurrence and removal of pharmaceuticals, with dominating articles reported in Africa (South Africa particularly) [162]. This concludes that South Africa among other African countries, is more developed and has enough resources to monitor pollutants in the environment [118]. ...
... An example should be noticed when flumequine and oxytetracycline were detected in marine invertebrates at levels ranging from 2500-2900 and 60-380 μg kg −1 , respectively. Some of the studies are available reporting the direct occurrences of pharmaceuticals on the aquatic organisms [97,162,168]. For example, acetaminophen, clarithromycin and azithromycin were detected at concentrations between 0.9-1.5 ng g −1 [136] in hake, red mullet and mussels, respectively in Bay of Biscay, Southern France while levonorgestrel and progesterone were detected at concentrations up to 15 ng g −1 in mussels [14]. ...
Article
Full-text available
Environmental ubiquity of pharmaceuticals has stimulated a lot of societal and global concerns. The occurrence of pharmaceuticals in the environment differs from country to country depending on the extent of consumption and monitoring. Most studies reporting the occurrence of pharmaceuticals are conducted in coastal regions with numerous articles and reviews reported in developed countries. The current review reports the occurrence of pharmaceuticals in inland waters with major focus devoted to developing countries in Africa and Asia. The focus was further dedicated to sources and distribution mechanisms, which contribute greatly to their ubiquity in the environment. Antibiotics and non-steroidal anti-inflammatory drugs (NSAIDs) are the most reported pharmaceuticals in African waters. For example, an antibiotic (sulfamethoxazole) was detected in more than four African countries with highest concentrations reaching 53.8–56.6 μg L⁻¹ detected in Kenya and Mozambique. Furthermore, highest concentrations of amoxicillin ranging from 0.087–272.2 μg L⁻¹ were detected in Nigeria. Ibuprofen, which is NSAID was detected at highest concentrations reaching 67.9 and 58.7 μg L⁻¹ in Durban city and Msunduzi River (KwaZulu-Natal, South Africa), respectively. However, highest concentration of antiretroviral drug (lamivudine) up to 167 μg L⁻¹ was found in surface water samples collected from Nairobi and Kisumu city, Kenya. In Asian countries, antibiotics were detected at highest concentration reaching 365.05 μg L⁻¹ in surface water samples. However, concentrations of other pharmaceuticals were comparably below the concentrations detected in African environmental waters. Health risks associated with their fate in the environment are critically reviewed. Sample preparation techniques and analytical instruments necessary for the occurrence studies were also reviewed. The concluding remarks were based on deliberating the possible future prospects within the research expertise.
... These authors also report many persistent organic pollutants from sewage being present in the near shore environment and found bioaccumulated in benthic organisms as well as in fish caught in the environs of the Cape Peninsula, South Africa Petrik et al, 2017). ...
... There is a growing concern about perfluorinated compounds owing to their persistence, potential for accumulation in organisms and their toxic properties, which include developmental toxicity and possibly carcinogenicity (Skutlarek et al., 2006;McLachlan et al., 2007). Detection of perfluorinated compounds have been reported in surface waters across Europe (Ahrens et al., 2009;Loos et al., 2010;Kwadijk et al., 2010) and are widespread in the near shore marine environment of Cape Town (Petrik et al., 2017). They pose a serious problem for groundwater and seawater, where they are capable of remaining for a very long time due to their persistence, even when the source of contamination is removed. ...
... Patterton, (2013) presented a scoping study and research strategy development on currently known and emerging contaminants influencing drinking water quality showing many different pharmaceuticals being simultaneously present in drinking water sampled in South Africa. Our own recent studies have shown significant contamination of seawater, fish and marine organisms with pharmaceuticals (Ojemaye & Petrik, 2021;Oyemaje & Petrik, 2019 a&b;Petrik et al, 2017), not all drinking water and source waters may contain emerging contaminants. In cases where contaminants are present, they vary significantly in concentration, type and number relative to location and circumstances (Bull et al., 2011;Focazio et al., 2008;Ternes, 2001;Mons et al., 2003). ...
... All marine organisms were processed (rinsed, deshelled, and dissected) and preserved at -20°C in a refrigerator for analysis. The choice of compounds analyzed in the present study was based on previous work for consistency (Petrik et al. 2017;Ojemaye and Petrik 2019b) and according to a list compiled on the most prescribed drugs in the public health sector of South Africa by Osunmakinde et al. (2013). The choice of compounds was also based on a study of 5 WWTPs in the Western Cape (Swartz et al. 2018a(Swartz et al. , 2018b, which showed that these compounds escaped into WWTP effluents being discharged into the marine environment. ...
... Water samples. For seawater sample extraction, the method was based on Valdés et al. (2014) and Petrik et al. (2017). From each seawater sample 500 mL was used for analysis. ...
... LC-MS analysis. The instrumental analysis methods were optimized based on previous studies (Petrik et al. 2017;Ojemaye and Petrik 2019b). Extracted samples were analyzed by the Waters ACQUITY UPLC TM system with ACQUITY UPLC binary solvent manager and ACQUITY UPLC sample manager. ...
Article
Pollution of the marine environment has been increasing as a result of anthropogenic activities. The preservation of marine ecosystems as well as the safety of harvested seafood are nowadays a global concern. In the present study, levels of pharmaceuticals and personal care products were assessed in different environmental compartments in the near‐shore marine environment of False Bay, Cape Town, South Africa. The study revealed the presence of these persistent chemical compounds in different environmental samples from this location. Diclofenac was the most dominant compound detected, with higher concentration than the other pharmaceutical compounds, as well as being present in almost all the samples from the different sites (seawater, 3.70–4.18 ng/L; sediment, 92.08–171.89 ng/g dry wt; marine invertebrates, 67.67–780.26 ng/g dry wt; seaweed, 101.50–309.11 ng/g dry wt). The accumulation of pharmaceuticals and personal care products in the different species of organisms reflects the increasing anthropogenic pressure taking place at the sampling sites along the bay, as a result of population growth, resident lifestyle as well as poorly treated sewage effluent discharge from several associated wastewater‐treatment plants. The concentration of these contaminants is in the order marine biota > sediments > seawater. The contaminants pose a low acute and chronic risk to the selected trophic levels. A public awareness campaign is needed to reduce the pollution at the source, as well as wastewater discharge limits need to be more stringent
... These plastics may enter CTH by means of urban and stormwater run-off from Cape Town during the rainy season in winter (Weideman et al. 2020) and in summer, offshore winds blow urban litter from land to the sea (Ryan 2020). Other potential sources of microplastic pollution in CTH may include municipal sewage discharged and stormwater systems into Table Bay (Petrik et al. 2017) as well as maritime and shing activity. Plastic pollution reduces the aesthetic value of tourist hotspots such as the V&A Waterfront and has the potential to damage vessels where discarded ropes, nets and packing bands may become entangled in propellers (Andrady 2011). ...
... At site 1, H was category IV (very high risk) and PRI at category V (very dangerous). The high risks recorded for site 1 requires further investigation as the site was at the furthermost site of all sampled in CTH and is downstream from a sewage outfall pipe (Petrik et al. 2017), which are known to be sources of MPs (Mahon et al. 2017). Based on source, all risk indices analyzed were highest in water samples when compared to mussels (Fig. 6e-f), suggesting that organisms (such as mussels) have the potential to reject and eject MPs (Graham et al. 2019), thereby reducing the potential effects of ingested MPs. ...
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Knowledge about the abundances and characteristics of microplastics (MPs) is becoming important to assess the potential effects MPs have on organisms and ecosystems. The aim of this study was to provide a baseline of MPs in Cape Town Harbour (CTH) and the Two Oceans Aquarium (TOA) in Cape Town, South Africa from 2018 to 2020. Water and mussel samples were analyzed for MPs at 3 sites in CTH and TOA, respectively. Microplastics were mainly filamentous, black/grey and 1000–2000 µm in size. A total of 1778 MPs, with an average of 7.50 (± 0.6 SEM) MPs/unit was recorded for the study period. MP concentrations were higher in water (10.3 ± 1.1 MPs/L) than mussel samples (6.27 ± 0.59 MPs/individual and 3.05 ± 1.09 MPs/g soft tissue wet weight). Mean MP concentrations in water samples collected in CTH (12.08 ± 1.3 SEM MPs/L) were significantly higher (4.61 ± 1.1 MPs/L) than inside the TOA, (U = 536, p = 0.04). A risk assessment (Pollution Load Index, Polymer Risk Index and Pollution Risk Index) of MPs sampled indicated that MPs in water poses a greater ecological risk when compared to mussels. Our results indicate that there is a need to monitor MPs in coastal waters and aquaria facilities in South Africa.
... For instance, in some regions like Asia, the populations of vulture species have dropped significantly. This decline has been attributed to the veterinary use of diclofenac, which is a human pharmaceutical used to treat anti-inflammations (Petrik et al. 2017). It has also been associated with one of the active ingredients in the contraceptive pill associated with endocrine disruption and feminization in fish, called the ethynylestradiol (Petrik et al. 2017). ...
... This decline has been attributed to the veterinary use of diclofenac, which is a human pharmaceutical used to treat anti-inflammations (Petrik et al. 2017). It has also been associated with one of the active ingredients in the contraceptive pill associated with endocrine disruption and feminization in fish, called the ethynylestradiol (Petrik et al. 2017). ...
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... Acetaminophen, in the same study, was not identified in either the field or the laboratory. On the contrary, in M. galloprovincialis from Granger Bay, Cape Town, Petrik et al. (2017) verified a degree of bioaccumulation of acetaminophen with concentrations approaching 9 ng l −1 , in contrast to diclofenac which was identified in concentrations that were <2.5 ng l −1 . However, after a 12-month monitoring of individuals of the species M. galloprovincialis and M. edulis (Linnaeus, 1758) on the coasts of Ireland, no bioaccumulation was recorded for diclofenac despite the presence of this drug in effluents (<3000 ng l −1 ) and sea water (<600 ng l −1 ) (McEneff et al., 2014). ...
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The occurrence of emerging contaminants (ECs) such as pharmaceuticals, personal care products (PPCPs) and pesticides in the aquatic environment has raised serious concerns about their adverse effects on aquatic species and humans. Because of their toxicity and bioactive nature, PPCPs and pesticides have more potential to impair water systems than any other contaminants, causing several adverse effects, including antibiotic resistance, reproductive impairment, biomagnification, bioaccumulation, etc. Over 35 publications from Africa have reported on the occurrence and fate of PPCPs and pesticides in African water systems with little or no data on remediation and control. As a result, adequate intervention strategies are needed for regulating the persistence of PPCPs and pesticides in African water systems.
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Abstract This study investigated the degradation of 2-nitrophenol (2-NP) in aqueous solution by dielectric barrier discharge (DBD) system alone and its combination with supported TiO2 photocatalysts. The TiO2 photocatalyst supported on a stainless steel mesh was synthesised using sol–gel solution of 8% polyacrylonitrile (PAN)/dimethylformamide/ TiCl4 followed by pyrolysis in the furnace under N2 atmosphere at temperatures of 300, 350, or 400 �C for 3 h holding time. The supported catalysts were characterized for their morphologies, functional groups, crystallinity, surface areas and elemental chemical states by high resolution scanning electron microscope (HRSEM), Fourier transform infrared, X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area, and X-ray photoelectron spectroscopy. The influence of solution pH on the degradation of 2-NP was investigated. The residual concentration of 2-NP and the intermediate compounds were quantified and identified using high-performance liquid chromatography coupled with mass spectrometry (HPLC–MS). The concentration of the dissolved ozone, hydrogen peroxide and hydroxyl radicals generated by the DBD in the presence or absence of a catalyst was monitored using ultraviolet–visible spectroscopy and photoluminescence spectroscopy. The HRSEM, HRTEM, XRD and BET analysis revealed that the optimal thermal conditions to obtain well supported uniformly grown, highly active crystalline TiO2 catalysts with high specific surface area was 350 �C at a 3 h holding time in N2 atmosphere with a flow rate of 20 mL/min. The supporting procedure simultaneously carbon doped the photocatalyst. The DBD system alone without catalysts successfully mineralised 58.6% of 2-NP within 60 min while combined DBD/supported TiO2 nanocrystals achieved 77.5% mineralisation within the same treatment time. The increase in mineralisation rate was attributed to the existence of a synergistic effect between theDBD system and the supported catalysts. 2-NP degradation proceeded via hydroxylation, nitration and denitration using DBD alone and combined DBD/Supported TiO2 photocatalyst. Catechol, hydroquinone, hydroxyl-1,4-benzoquinone, 2-nitrohydroquinone, and 2,4-dinitrophenol were identified as major intermediate products. The order of production of free reactive species by DBD alone and combined DBD with supported photocatalyst was OH�[H2O2[O3.The results showed that the combined system was more than effective than DBD alone for the degradation of the 2-NP in aqueous solution.
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Effective treatment of textile effluent prior to discharge is necessary in order to avert the associated adverse health impacts on human and aquatic life. In the present investigation, coagulation/flocculation processes were evaluated for the effectiveness of the individual treatment. Effectiveness of the treatment was evaluated based on the physicochemical characteristics. The quality of the pre-treated and post-flocculation treated effluent was further evaluated by determination of cytotoxicity and inflammatory activity using RAW264.7 cell cultures. Cytotoxicity was determined using WST-1 assay. Nitric oxide (NO) and interleukin 6 (IL-6) were used as biomarkers of inflammation. NO was determined in cell culture supernatant using the Griess reaction assay. The IL-6 secretion was determined using double antibody sandwich enzyme linked immunoassay (DAS ELISA). Cytotoxicity results show that raw effluent reduced the cell viability significantly (P < 0.001) compared to the negative control. All effluent samples treated by coagulation/flocculation processes at 1 in 100 dilutions had no cytotoxic effects on RAW264.7 cells. The results on inflammatory activities show that the raw effluent and effluent treated with 1.6 g/L of Fe-Mn oxide induced significantly (P < 0.001) higher NO production than the negative control. The inflammatory results further show that the raw effluent induced significantly (P < 0.001) higher production of IL-6 than the negative control. Among the coagulants/flocculants evaluated Al2(SO4)3.14H2O at a dosage of 1.6 g/L was the most effective to remove both toxic and inflammatory pollutants. In conclusion, the inflammatory responses in RAW264.7 cells can be used as sensitive biomarkers for monitoring the effectiveness of coagulation/flocculation processes used for textile effluent treatment.
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The hydroxyl radical (OH •) is a powerful oxidant produced as a consequence of cavitation in water. It can react nonspecifically in breaking down persistent organic pollutants in water into their mineral form. It can also recombine to form hydrogen peroxide which is very useful in water treatment. In this study, terephthalic acid (TA) and potassium iodide dosimetry were used to quantify and investigate the behaviour of the generated OH radical in a laboratory scale sonicator. The 2-hydroxyl terephthalic acid (HTA) formed during terephthalic acid dosimetry was determined by optical fibre spectrometer. The production rate of HTA served as a means of evaluating and characterizing the OH • generated over given time in a sonicator. The influence of sonicator power intensity, solution pH and irradiation time upon OH • generation were investigated. Approximately 2.2  10-9 M s-1 of OH radical was generated during the sonication process. The rate of generation of the OH radicals was established to be independent of the concentration of the initial reactant. Thus, the rate of generation of OH • can be predicted by zero order kinetics in a sonicator.
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Visible light (VIS) photocatalysis has large potential as a sustainable water treatment process, however the reaction pathways and degradation processes of organic pollutants are not yet clearly defined. The presence of cyanobacteria cause water quality problems since several genera can produce potent cyanotoxins, harmful to human health. In addition, cyanobacteria produce taste and odor compounds, which pose serious aesthetic problems in drinking water. Although photocatalytic degradation of cyanotoxins and taste and odor compounds have been reported under UV-A light in the presence of TiO2, limited studies have been reported on their degradation pathways by VIS photocatalysis of these problematic compounds. The main objectives of this work were to study the VIS photocatalytic degradation process, define the reactive oxygen species (ROS) involved and elucidate the reaction mechanisms. We report carbon doped TiO2 (C-TiO2) under VIS leads to the slow degradation of cyanotoxins, microcystin-LR (MC-LR) and cylindrospermopsin (CYN), while taste and odor compounds, geosmin and 2-methylisoborneol, were not appreciably degraded. Further studies were carried-out employing several specific radical scavengers (potassium bromide, isopropyl alcohol, sodium azide, superoxide dismutase and catalase) and probes (coumarin) to assess the role of different ROS (hydroxyl radical OH, singlet oxygen (1)O2, superoxide radical anion [Formula: see text] ) in the degradation processes. Reaction pathways of MC-LR and CYN were defined through identification and monitoring of intermediates using liquid chromatography tandem mass spectrometry (LC-MS/MS) for VIS in comparison with UV-A photocatalytic treatment. The effects of scavengers and probes on the degradation process under VIS, as well as the differences in product distributions under VIS and UV-A, suggested that the main species in VIS photocatalysis is [Formula: see text] , with OH and (1)O2 playing minor roles in the degradation.