It is common knowledge that South Africa is facing a sewage crisis. We see it playing out in different parts of the country in different ways.
Cape Town is increasingly in the news as the human health impact of direct exposure to sewage manifests as medical emergencies. Durban is shuddering under the domino effect of infrastructure failure.
However, in terms of national impact, Gauteng is the epicentre, with Rand Water increasingly being the last line of defence.
All water for Gauteng is sourced from the Vaal River. It is therefore instructive to expose the reader to the complexity associated with the management of water supply out of the Vaal.
While we typically think of the Vaal as the source of drinking water in Gauteng, it is also the aquatic ecosystem into which all the effluent from the sewage works is discharged, along with the stormwater runoff from the southern edge of the Witwatersrand continental watershed.
The numbers are staggering. There are 32 wastewater treatment works (WWTWs) located in the Vaal River catchment area draining Gauteng. Collectively they discharge 1,500 Megalitres (million litres) per day (ML/d) into the various tributaries of the Vaal.
The location and size of each WWTW is shown on the map below, which was provided by Rosemary Anderson in her capacity as the National Chairperson of Fedhasa using the latest Green Drop Report as source data.
The first thing that is apparent from this map is that many municipalities discharge effluent into the tributaries of the Vaal. In terms of the Cooperative Governance Clause of the South African Constitution, no national government department can interfere in the affairs of a municipal-level department.
This means that Rand Water, as a state-owned entity, is unable to intervene in the affairs of any of the six municipalities that control the WWTWs directly impacting on the water quality in the Vaal.
Of these six municipal entities, East Rand Water has 16 WWTWs discharging into various tributaries of the Vaal. This is followed by Johannesburg, Midvaal and Metsimaholo, which each manage four WWTWs. Emfuleni manages the least number of WWTWs (three). It is also the most financially distressed municipality in the network.
When one analyses the total sewage flow into each of the tributaries, we have the following situation in descending order of significance:
- The Klip River receives direct discharge from three WWTWs collectively generating 420 ML/d, making it the biggest receiver of sewage;
- The Harrington Spruit has two WWTWs generating 350 ML/d. This discharges into the Klip River, which means that it receives a combined total of 925 ML/d when the Natalspruit flow is added;
- In third position, the Blesbokspruit receives effluent from 12 WWTWs with a combined flow of 224 ML/d;
- In fourth position is Rietspruit, receiving effluent from four WWTWs with a combined flow of 194 ML/d;
- In fifth position is Natalspruit that services three WWTWs with a combined flow of 155 ML/d that adds to the Klip load;
- In sixth position is the Vaal River itself with four WWTWs discharging directly into the river with a combined flow of 83,75 ML/d. This is a distorted number because everything eventually ends up in the Vaal, so the reader must be aware of the analytical limitations;
- In seventh position is the Rietpruit/Swartspruit with one WWTW producing 63ML/d of effluent; and
- The rest – Suikerbosrand, Taaibos and Vaal Dam – are numerically insignificant even if they receive effluent from three WWTWs with a combined discharge of 10 ML/d.
Reworking these numbers to determine the institutional capacity to manage sewage adequately, we arrive at an encouraging conclusion. Ranked in order of total contribution to the pollution load of the Vaal, we have both East Rand Water and Johannesburg each contributing 40% of the total flow.
These two entities combined constitute 80% of the total daily flow of 1,500 ML/d. Consequently, the institutional capacity of those two entities plays a disproportionate role in terms of water quality in the river.
Emfuleni Local Municipality contributes 15% and has the least capacity to cope, with a long history of institutional failure requiring intervention from the SANDF and East Rand Water at a cost of R2-billion without any apparent improvement.
In third position we have Metsimaholo with a 4% contribution to the total flow. Midvaal and Dipaleseng are statistically irrelevant at 1% of the total contribution to the effluent loading of the Vaal system.
Seen against this background, we note some positive developments. On the technology side, Rand Water has successfully implemented a remote sensing monitoring system using satellite data to track changes in the levels of blue-green algae caused by flows of sewage effluent and agricultural runoff.
There has also been a suggestion presented to the Department of Water and Sanitation (DWS) that consideration should be given to the creation of a water credit system. That proposal involves the creation of a real-time sensor network capable of monitoring effluent from each of the 32 WWTWs in real time.
This would feed into an artificial intelligence platform capable of predicting changes in system stability. Significantly, this would also yield verifiable data for compliance purposes, enabling DWS to know the actual compliance status, informing decisions about process control at the treatment plants that convert the sewage-contaminated river water into SANS 241 compliant drinking water.
More importantly, however, that data can also generate water credits that can be traded on the market.
This would incentivise the improvement in process control at the 32 WWTWs by monetising the improvement in water quality measured against a known and reliable baseline. Any measurable improvement of the quality of effluent discharged would generate a commercial value which can be traded.
This is cutting-edge stuff and is also entirely doable within the context of the Anti-Pollution Forum that has been created by the Water and Sanitation Deputy Minister Sello Seitlholo. This platform can measure key parameters, such as E. coli counts and nutrient loads that fuel the growth of invasive aquatic plants such as water lettuce and hyacinth.
There is nothing like a crisis to incentivise the need to change. The sewage crisis in the country has the potential to trigger positive change capable of stimulating the economy by attracting capital and creating jobs.
The digital platform mentioned above is a logical next step in the restoration of confidence and the prevention of future deterioration of our vitally important rivers and dams. Every cloud has a silver lining. DM