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

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


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. 1,2Where positive independent E. coli counts have been demonstrated, such as those collected by public health researcher Edda Weimann 3 , 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.
][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 Asia 7 ; ethinylestradiol, one of the active ingredients in the contraceptive pill, has been associated with endocrine disruption and feminisation in fish 8 ; 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. 9In South Africa, Ncube et al. 10 suggested a protocol for the selection and prioritisation of contaminants in drinking water.Patterton 11 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.
These authors stated 13 : The priority list cannot be seen as an exhaustive list as each reclaimed potable water reuse project should interrogate the relevance according to the specific 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 challenging the City's use of the Blue Flag ensign to promote its beaches. 3Her 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 (10 5 -10 6 ).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. 14th 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. 15,16redictive modelling is consistent with South Africa's policy for the disposal of land-derived wastewater in the sea, published in 2006. 17cause seawater is constantly in a state of movement we also investigated 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.
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. 18ter 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-d 4 ) 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 UPLC TM (Waters, Milford, MA, USA).Simultaneous determination of all the compounds of interest was achieved using an Acquity UPLC BEH C18

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 (N 2 ) 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 ascertain 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 http://www.sajs.co.za  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-inflammatory drugs acetaminophen (also known as paracetamol) and diclofenac, the anti-seizure medication phenytoin, the antibiotic sulfamethoxazole and the antiretroviral lamivudine are made to be stable and effective at low doses.They are polar, lipophilic, soluble and nonvolatile compounds. 20For 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. 21Their 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][23][24] and bioaccumulate in wild-caught fish populations at concentrations of nanograms per gram. 25,26Huerta 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 study 11 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. 27e 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 iopromide 28 , other pharmaceuticals such as natural and synthetic sex hormones pose considerable risks to the aquatic environment 29 .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 tissues 30 , which in turn may be deleterious to human health.Moreover, the synergetic effects of pharmaceuticals and other compounds on living organisms are unknown. 31inking water supplies from the seawater desalination plants should be carefully tested for toxicity, which need not be costly. 13,32Apart 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][34][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 byproducts and trichloroamines should also be monitored and removed from the recovered water. 13diment A Sediment B Mussels

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's 11 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. 13,32en 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. 13The 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. 13With 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 regulators 13 , 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 ozonation 36 , ozone/hydrogen peroxide 37,38 , ozone/UV 39 , hydrogen peroxide/UV 40 , UV/chlorine [41][42][43] , UV/TiO 2 44 , ultrasonic irradiation 45 or sonolysis 46,47 , photocatalysis 48,49 , photo fentons 50 , dielectric barrier discharge 51,52 and electrochemical 53 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 participate 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 infrastructure to adequately manage human waste.The City of Cape Town has outgrown its current water supply and sanitation infrastructure. 54hile 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

Figure 1 :
Figure 1: Location of sampling and microbial load of seawater and beach water (Granger Bay, Cape Town).

Figure 5 :
Figure 5: Concentration of perfluorinated compounds in marine organisms and sediments from the shores near Granger Bay, Cape Town.

Figure 6 : 7 South
Figure 6: Concentration of pharmaceuticals in marine organisms and sediments from the shores near Granger Bay, Cape Town.
A; TS, triclosanNote: Sediment A is from wet beach sand and Sediment B from where the organisms were found.

Figure 7 :
Figure 7: Concentration of industrial and household chemicals in marine organisms and sediment from the shores near Granger Bay, Cape Town.

Figure 8 :
Figure 8: The difference in the level of selected compounds in marine organisms sampled in July 2015 and July 2017.
December 2017 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: Volume 113 | Number 11/12November/ PFUnDA PFOA PFHpAPFUnDA, 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.http://www.sajs.co.zaDSS, diclofenac; SUL, sulfamethoxazole; PHE, phenytoin; CAR, carbamazepine; LA, lamivudine; CA, caffeine; ACT, acetaminophenFigure 3: Concentration of pharmaceuticals in seawater samples collected off Granger Bay, Cape Town.Figure 4: Concentration of industrial and household chemicals in seawater samples collected off Granger Bay, Cape Town.http://www.sajs.co.za Volume 113 | Number 11/12 November/December 2017 , 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.

Commentary Desalination and seawater quality at Green Point, Cape Town http
December 2017 hydrological system, and therefore managed as a single ecology, not via the separation of environment, sanitation and water supply.