Event Debrief: Fate and transport of Microplastics in Groundwater (GWD Western Cape)

Event Debrief: Fate and transport of Microplastics in Groundwater (GWD Western Cape)

19 Jun 2020
Home News Event Debrief: Fate and transport of Microplastics in Groundwater (GWD Western Cape)
This CPD event was hosted by the GWD Western Cape Branch, moderated by the Western Cape Branch Chair, Dr Sumaya Israel and supported by UWC student Clinton William Andries.



Microplastics are tiny particles (smaller than 5mm) found in the environment. They are synthetic polymers and are either produced in its microform to be utilized in personal care products and detergents or disintegrated from larger plastics or synthetic materials (e.g. recycled polyethylene terephthalate items), respectively known as primary or secondary microplastics. Sources of microplastic pollutants contributing to the environment occur through discharge of treated effluent, stormwater runoff, irrigation of grey water produced during laundry, etc. To date, microplastics have been found in the ocean, lakes, estuaries, rivers and recently in groundwater. As a result, this study will focus primarily on the presence of microplastics in groundwater. More specifically, the physical and chemical impacts it has on the Cape Flats Aquifer Scheme and the Atlantis Aquifer Scheme. Both these groundwater schemes are designed to artificially recharge the aquifer with either treated effluent or storm water. As previously mentioned these sources are contributors of microplastics to the environment, if not properly treated. The following research questions will therefore form the basis of this study:

1) What is the spatial distribution of microplastic in the City of Cape Town (groundwater, surface water, source water, processed water?
2) What is the fate and mobility of microplastic in the Cape Flats aquifer and Atlantis Aquifer?
3) Does the presence of microplastic in the aquifer influence the hydraulic properties of the aquifers?
4) Does microplastics change the fate of toxins in the aquifers?
5) How does this impact the Atlantis and Cape Flats Managed Aquifer Recharge Schemes?

A number of laboratory experiments have been designed to address the aforementioned research questions. The spatial distribution of microplastics in the City of Cape Town will however require field sampling. Information obtained from both the fieldwork and lab experiments will be used to determine the possible impacts of microplastics on the City of Cape Town Aquifers and a sampling and monitoring protocol will be developed to assist the City with the management thereof.

Presenter Mrs. Candice Lasher-Scheepers during her presentation.








Candice is a PhD UWC candidate supervised by Dr Jaco Nel and Dr Sumaya Israel. Candice Lasher-Scheepers (Pr. Sci. Nat, MSc.), a Principal Professional Officer – Geohydrology: Bulk Water Branch; Water and Waste Directorate at the City of Cape Town, did her BSc EWS and BSc Honours (EWS) and Masters at UWC. She is currently registered as a PhD candidate at UWC. 


As this area of interest speaks to a very topical issue worldwide, this event was very well attended. A total number of 148 registrations were received, with 112 total stations in attendance and 74 attendees logging in on the Chat and thus qualifying for CPD attendance.


 The presentation was very informative and covered all the basic knowledge required to enhance ones understanding of plastics in the environment. Topics covered included types and sizes of plastics in the environment.


Figure 1: Plastic materials are classified and named according to their shapes and sizes.











Some of the main aspects of the presentation included these classifications and the implications of the variable sized particles in different parts of the environment. Interestingly, not too many studies on the topic have been found for the groundwater environment.

This talk and study is thus on the edge of scientific advancement and presents a new and interesting field of research.

Ms. Lasher Scheepers also discussed how these plastics are likely to move in rivers. Figure 2 below shows size comparison for plastic debris commonly found in nature.


Figure 2: Size comparison chart for plastic debris commonly found in nature

Ms Lasher-Scheepers kept the audience interested and intrigued with her talk. A great deal of discussion and questions followed on from the talk. Some interesting facts about movement of plastics in soils and water environments showed that ionic strength impacts on the mobility of colloids and hence sorption and movement of plastics.   The fact that plastics are able to react with toxins or other compounds to make them toxic was also very interesting.



(Candice's live responses to these questions are transcribed and might contain capture errors. We will continue with the quality check and update the post accordingly.)

From  53732952 : DEA is now known as Department of Environment, Forestry and Fisheries (DEFF)

From  Melissa Lintnaar-Strauss : Microbeads in Europe is already banned in cosmetics, maybe Candice you can find out from the Dutch how they went about that

Adolf October: Question: Are there any groundwater chemistry signature related/ associated with this contaminant?

CANDICE: You can look at your total suspended solids but remember there are other particles that will be floating around as well that will be picked up when you are measuring TDS, have an influence on the TDS and turbidity. We are currently looking at something and it is a work in progress and we will hopefully present in the near future with results. We are trying to determine if we can pick up a signature using specific parameters.  

John Weaver: Question/ comment: I’m very involved in bottled water industry as Chairman of SANBWA – and the story of microplastic in water has been very much on the forefront in the bottled water industry - the simple reason that the only substance that researchers in microplastics can really look at -  is water. Can’t really look at any other consumables (e.g. hamburgers and coke cola – because you can’t see <it>) So, they are always looking at water. One of the things to be careful of is not to <get too> take the world’s worries on your shoulders because everybody is looking at water – that is just because they can that they do. And of course with the bottled water industry it’s a target of a lot of “attacks”. But moving away from that …One of the positives that I picked up here and it only struck me now, thanks to your talk, is that if your micro plastics is start clogging up your aquifer, then they are going to absorb harmful organic chemicals and retard them and would let them flow through the aquifer much slower than which they would have normally done..Microplastics in groundwater might then not necessarily be such a bad idea? One more comment: The two biggest contributors to micro plastics…..<break up comms> unfortunately. John was invited to type comment & question.  

From  Alanna Rebelo : Question: (apologies if I missed this) will the city do any social research on willingness to change?

CANDICE: Unfortunately not within my study scope. I am sure these questions can be answered approaching a relevant Department/ Branch at the City of Cape Town/ The City. We are a small unit in Bulk Water Branch and looking at this because we are doing MAR (Managed Aquifer Recharge) in the Cape Flats & Atlantis area.  

From  Kes : Question: Have you come across anything about whether the PVC casing used in primary aquifer boreholes could be a concern w.r.t. sampling?
From  Mikyle Cloete : I second Kes Question as well as various equipment at WWTPs
From  Jeanne Gouws : Kes, your question is of particular relevance now, due to the groundwater development in "new" areas, such as at Steenbras in the WC

CANDICE: So, it would definitely be a concern but we are not targeting boreholes with PVC casings.
Re. WWTPs, yes that also – if you looked at equipment used even in your bulkwater you have your HTPE pipes used for your linear infrastructure so you have many contributors – the fact is the objective of this study is not to determine where this is coming from, it is more an issue of what the impact will be and if there is in impact.

From  MajolaK : Question: When do microplastics become a health risk relative to exposure period, after long-term exposure or even short-term exposure could be a problem?
From  Martine Jordaan : @MajolaK, I suspect it is not only the microplastics themselves that are the problem but the fact that many pharmaceuticals can adsorb to them and increase exposure to these.  Comments anyone?
From Henk Coetzee : @MajolaK, @Martine, I'd imagine it's like natural adsorbents. If you remove something from the water column, you end up concentrating them somewhere else.
From  obri : @Martine, agree. the toxicology should vary depending on the composition of the final micro-particle including adsorbed toxicants

CANDICE: Unfortunately not within my study scope. We are not looking at the human risk but only risk to aquifer properties. Apologies! On the pharmaceuticals: On one of the slides I indicated that antibiotics can absorb through the microplastics, whether the antibiotic already had the ability to move in groundwater – yes, if it didn’t and now absorbs through the microplastic, and the microplastic can move through your aquifer then it does have the potential to spread the  contaminant faster or slower.

From  jia haili : Thank you Candice, it's very informative talk. I have a question, since microplastic is a relatively new contamination source in groundwater, can they be simulated using the current available geochemical transport and reactive modelling methods?

CANDICE:  So it depends on how it responds in the aquifer – is there something that responds in a similar manner that has been modelled before and we can use that - we have looked at the colloid transport models and hopefully they respond in a similar manner to these microspheres and we can use that.

From  Angelo Johnson : Question: Is there a way to determine whether micro plastics found in groundwater, if found during sampling, is from PVC or the aquifer itself?

CANDICE: For now we don’t do detection – but there are processes to detect it but the source we don’t know - but suggest if you do detect microplastics in that specific area and it can be from your PVC casing maybe broaden your hydrocensus find another borehole in the area – perhaps an open borehole and do sampling  there as well. But for now detection and sources – are all new – and so we are just taking it a step at a time. And focusing on the impacts. With more research we will be able to answer more of the questions (refere Adolf question too) – using all the information we will need to put everything together. As seen in my presentation - I could only find two papers on micro plastics – and that is it.  There are many questions and this is a start of a new area in research for all of us. Lots of research topics and hopefully many collaborations.

From  Henk Coetzee : Question: Do we have a method for qualitative analysis? I'm interested in looking at microplastics as a tracer in mine water. There has been some work done in the past using microspheres, but the cost becomes prohibitive in large systems.

CANDICE: I can send you some of the methods they use to detect microplastics. I can send you a manual/ guidelines. Depending on water and type of micro-plastics. And there is a processing technique you use. There are limitations to the processes – so you need to select your analysis process carefully.

From  Mzati Kanyerere : Thokozani here: Great study. Keep it up. The choice of sampling sites would of interest to show the epidemiology of the microplastics and human health implications

From  Adolf October : The dye testing is performed in the lab is it quantitative or qualitative. If quantitative, what are you measuring?

From  Regan Rose : What is the role of the unsaturated zone to help precipitate  the microplastics out of solution before they enter the groundwater? Will this process not cause clogging in the unsaturated zone with time? Potential impacts on a MAR system.

CANDICE: So that is the point of the study and we don’t yet know. The experiment done with the irrigation of micro plastic solution on a loamy soil shows that there is a change in water holding capacity and a change in bulk density. For that specific study there was no change in hydraulic conductivity but again that was in a loamy soil and the study is in the Cape Flats and the Atlantis aquifer so different geology and will be using different plastic material and different sizes so the outcome of this study is to determine if it will clog or if it will move.  


The presentation was well attended and receive great reviews from all attendees. Using the zoom platform to do these sessions has opened every event up to be national events.

Ms Candice Lasher Scheepers’ research wishes to address the spatial distribution of microplastic in the City of Cape Town, considering groundwater, surface water, source water, and processed water. Her work will also address the fate and mobility of microplastic in the Cape Flats aquifer and Atlantis Aquifer. Some questions that will be considered for the research include the following: Does the presence of microplastics in the aquifer influence the hydraulic properties of the aquifers? Does microplastics change the fate of toxins in the aquifers? How does this impact the Atlantis and Cape Flats Managed Aquifer Recharge Schemes?

The presentation considered an array of interesting facts about plastics including the types, sizes and reactivity where known. Many interesting case study examples were presented. A very interactive discussion session ensued after the presentation. Questions and responses have been recorded above for your perusal.

There is no doubt that this topic will have follow up presentations as progress is made with research into microplastics in our natural environment, in particular its impact on the unsaturated and saturated zones and potential to form toxins and reduce the hydraulic conductivity in aquifers. The audience left many positive comments regarding the content of the presentation. We will definitely be seeing more of this presenter at the GWD seminars in future!

It’s not only the plastics that are the issue but also all the plasticizers that are detectable in the water too. It was an interesting topic. RM