Managed aquifer recharge in South Africa (MARSA)

Project summary

Existing freshwater resources are threatened by overexploitation due to population growth, urbanisation, and climate change and many regions experience water shortage. South Africa is a water-scarce country and during the 2017-19 Southern African drought, water suppliers experienced severe difficulties supplying enough water to the population. Water scarcity is expected to become even more critical in the future due to climate change and improved utilization of available water resource is therefore urgent. Managed aquifer recharge (MAR), the purposeful recharge of water to aquifers for subsequent recovery, is used globally to replenish over-exploited groundwater resources. Due to increased water shortage worldwide, there is growing interest to use unconventional water resources for MAR such as reclaimed water. This, however, raises major concerns related to pollution of the drinking water resources. The primary aim of MARSA is to develop MAR technologies that allow for a broader span of water qualities to be used for MAR. It is hypothesised that improved removal of organic pollutants, nitrogen species, and pathogens from e.g. reclaimed water can be achieved by establishment of reactive barriers or injection of oxidizing agents to anaerobic aquifers during recharge as different redox environments are thus created. First, we will investigate the capacity of South African aquifer sediments to remove organic pollutants, nitrogen species, pathogens, and antimicrobial resistance genes and how this can be improved. Then specific MAR technologies will be tested at field conditions in South Africa using real Berg River water or reclaimed water. Finally, the potential of implementation of MAR for the groundwater resource in South Africa will be assessed considering the use of broader spans of water qualities for recharge. The outcome of MARSA will be new MAR water recycling tools to be used by water managers to combat water scarcity in South Africa and globally.

Outputs

Midterm report
Managed aquifer recharge (MAR), the purposeful recharge of water to aquifers for subsequent recovery, is used globally to replenish over-exploited groundwater resources. MARSA aims to develop technologies that allow for a wider range of water qualities to be used for MAR. In Denmark, joint laboratory columns were set up and operated for > 4 months to evaluate the impact of reactive barriers with 1% biochar or hydrochar on the leaching of organic micropollutants (pesticides and pharmaceuticals) and pathogens (S. Senftenberg bacteria and two model bacteriophages, 28B and T4). The findings indicate that biochar has a higher sorption capacity for most organic micropollutants compared to hydrochar and pure sand. Therefore, the amended columns with biochar experienced delayed leaching of micropollutants, followed by hydrochar and then pure sand. Degradation seemed slightly increased when hydrochar was used as a barrier compared to pure sand, while biochar did not affect the degradation efficiency. Pathogen adhesion revealed strong adhesion of S. Senftenberg to all three materials, while the bacteriophages adhered most to biochar and limited adhesion was observed to hydrochar and sand. The results have been presented at international conferences, and an article is being prepared. Currently similar columns are in operation in South Africa to investigate the capacity for contaminant removal at selected field sites. Additionally, MARSA will support the education of two PhD candidates.