Event Debrief: Talk on Microbial populations in groundwater: The good and the bad (GWD Northern Branch)

Event Debrief: Talk on Microbial populations in groundwater: The good and the bad (GWD Northern Branch)

08 Jul 2021
Elanda
In South Africa and several developing and developed countries studies were concerned with microbiological quality of ground water. This talk will explore some of the results from these studies and a focus on the quality of groundwater from the North West Province.
Home News Event Debrief: Talk on Microbial populations in groundwater: The good and the bad (GWD Northern Branch)
Prof Carlos Talkhead

 

"Prof Carlos, a sincere thank you for taking time from your busy schedule to share this valued presentation with us at the GWD!"  Dr Rainier Dennis (on behalf of the Northern Branch)

 

ABOUT THE TALK 

Groundwater have for a long time been seen as free from nasty microbes due to the percolating processes that drives the replenishment of these underground reservoirs that harbour this water. Many South African communities are dependent on such water sources. The perception of the safety of this water has resulted in it being used for household purposes, including drinking, without any treatment. However, due to unavailability of surface water because of drought, the dependence on this source has increased with more boreholes being drilled in drought affected regions such as the Karoo and the Eastern Cape. It may thus be an appropriate time to consider the microbiology of groundwater. In South Africa and several developing and developed countries studies were concerned with microbiological quality of ground water. This talk will explore some of the results from these studies and a focus on the quality of groundwater from the North West Province.

ABOUT THE SPEAKER

Carlos Bezuidenhout is employed at the North-West University as a Professor in Microbiology and is currently the Research Director in the Unit for Environmental Sciences and Management. His post PhD career has focused on various aspects of aquatic microbiology, including surface and groundwater quality, as well as aspects of water treatment. He has over 22 years of experience, has supervised a large number of postgraduate students that are active in the water sector and has published numerous peer-reviewed publications in this field. Carlos is also a member of the Ground Water Division and a Fellow of WISA.

TALK RESOURCES

Opening slide

Q&A SESSION

(Please note that it's live transcriptions of the feedback on the questions, we apologise for any errors which we will correct once confirmed)

Q Ligavha-Mbelengwa Lufuno: When traced in the groundwater, can the bacteria species be used as indicators of specific source of contamination? example, is there a bacteria that can be used as an indicator of agricultural/landfill contamination? similar to how E.coli can be used as an indicator of faecal contamination?

Answer: Some of the studies that I’ve seen actually used bacterial viruses called phages that are the type of technology that is generally used for tracing as well as free DNA. Bacterial species might be a bit challenging, depending on the characteristics of it. In Examples I’ve shown look at bacterial composition and specific bacterial groups that were present in the two aquifers that they investigated to look at levels of the these bacterial species that were present. Tracers, I’m uncertain about the specific bacterial species but as I’ve indicated phages have been used.

Q Michael Maluleke : If not treatment taking in the aquifer, can these microbes survives continuously naturally or it depends on the conditions in the water ( groundwater)? and secondly, if there is continuously pumping of groundwater where no treatment is taking place. Can this minimize the growth of these bacteria?

Answer: So the first Q: The bacteria group we used – the heterotrophic plate count bacteria and lipotropic media – the media contains limited nutrients and in the water environment nutrients available is even more limited but there are species that can survive in the limited nutrient environment. Lipotropic bacteria can survive and utilize chemicals present and could provide some organic material for the survival of other bacteria. (2) It might have an impact on the survivability of the bacteria and the population. But where there is an influx of elsewhere and that is typically what the Japan study have shown through that earthquake event – there was an influx of bacteria from elsewhere – and particularly the denitrifying bacteria that came into that system – so it depends on the environment, the aquifer and the geochemistry of that aquifer.

Q Fanus Fourie : Is there bacteria species that may be used to combat iron bacteria (preventing clogging)?

Answer: There has been some work that has been done by one of the Companies * that worked with microbial reduced corrosion especially utilizing bacteria to prevent iron oxidising bacteria but don’t know how far that study is. Refer to the listed studies in my presentation that look at microbial influence corrosion so perhaps you might find some answers there.

Q Eunice Ubomba-Jaswa : Managed Aquifer Recharge - will the microbial dynamics be significantly different especially from a risk perspective?

Answer: It depends on what you put into the system and that needs to be measured and from a risk perspective one should determine what lands up in the aquifer and I think like a reduction in COD  and that sort of thing might have potential of introducing the risk into it.

Q Ockie Scholtz : Thank you Prof. A typical drinking water analyses will include TC, EC and TVC. IF TC, EC is negative and TVC is say high for example, would you recommend treatment? Your studies do show that it may well be? But also, what percentage could be secondary contamination?

Answer: Yes, if it high one should look at it as I’ve shown as some of these bacteria may have harmful features so it’s important to look what is there and do screening and have reduction in heterotrophic bacterial  levels. The plant I mentioned using the rapid sand filtration, but T another plant – also getting water from an eye- everything is extremely low and they just immediately chlorinate the water after abstracting it and then distribute it.

Q Christo Louw : Great talk Prof Carlos. I believe ID'ing bacteria in areas where coal mining is active and the upcoming Gas Fracking as a contaminant could work and give guidance to water quality protocols knowing that these bacterias such cyanobacteria and archeo...bacteria are IDd to determine the type of gas/oil resources during exploration.

Answer: Absolutely Christo. You are right.

Q Donovan Samuels : What does it mean when your Standard Plate Count (SPC) results are way above the standard limit, but E coli and Total Coliforms are zero? Are these SPC then indicators of the 'harmless' bacteria?

Answer: Yes, Donovan, they definitely are indicators of these “harmless bacteria” so if they have features that cause diarrhea etc. Then it might not be as harmless as thought. I have given the example of Klebsiella which  is part of the Total Coliforms – and sometimes you pick them up and sometimes you don’t when doing total Coliforms counts.

 

Please, if unclear, feel free to send Prof Carlos an email where he is willing to respond to the questions further.

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