Making a case for direct potable wastewater reuse in South Africa
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SOUTH Africa is a water stressed country with sparse annual rainfall of about 500mm and a high evaporation rate of about 85% of mean annual rainfall.
In addition to these problems is the pollution to surface water from domestic and industrial sources.
Water stress results in the deterioration of freshwater through rapid exhaustion of surface and groundwater sources and a deterioration of water quality.
Freshwater is a finite resource, and the unpredictability of the effects of climate change is a worry to the sustainability of freshwater.
The pressure on freshwater can be decreased significantly by the reuse of treated municipal wastewater for direct potable applications.
However, the question of what a sustainable water reuse scheme is, and how its implementation can be assessed, need to be answered.
Based on population growth trends, economic growth projections and current efficiency levels, the Department of Water and Sanitation estimates daily demand for water to rise to 17.7 billion m³ in 2030 while water supply is projected to amount to 15 billion m³, representing a 17% gap between water supply and demand.
According to the last publicly available Green Drop Report, South Africa has 824 wastewater treatment systems across 152 municipalities which have a collective design capacity to receive about 6.5 billion litres of wastewater a day.
The report from 2013 states these systems received about 5.12 billion litres nationwide.
Assuming 50% of the 5 billion litres of wastewater received nationally, is treated to the standard for direct potable reuse, then 2.5 billion litres of water is available to be returned to society for consumption.
This closes the gap between supply and demand that is envisioned to impact South Africa within a decade.
International best practice in wastewater management is the reuse of wastewater. The reuse of domestic wastewater has several benefits for the municipalities. The reuse of wastewater for direct potable consumption can abate the water stress and provide a sustainable source of potable water.
The direct reuse of wastewater is a means of ensuring longevity of available water supplies by conserving and extending its lifespan.
Other benefits include the reduction in removal of freshwater from water vulnerable ecosystems, the reduction in pollutants in surface water as effluent from wastewater treatment works become reused, and cost saving from removal of need to expand water supply infrastructure.
For effective implementation and success of a direct potable wastewater reuse option, there must be development of an integrated water and sanitation planning scheme using a decision support tool.
This must be done at all levels of government. The decision support tool would enable a balance between the institutional, social, economic, technical and environmental attributes involved in the sustainability of water reuse for potable applications.
This will ensure the addition of potable wastewater reuse in water and sewerage planning.A decision support system will integrate the work streams and identify potential hazards and opportunities that will arise from the implementation of a wastewater reuse intervention. This will ensure potential public stakeholder perceptions are identified and addressed.
The system will also ensure benefits from reuse interventions such as cost savings and green credits are maximised.
All in line in ensuring every drop counts and safeguarding the future of South Africa’s water.
Emeka Umeche is a senior consultant at NIC where he manages projects in the infrastructure planning and development space.
The views expressed herein are not necessarily those of Independent Media.