Wastewater use in desalination, a viable drought solution

26th November 2021 By: Claire O'Reilly

Water treatment supplier Quality Filtration Systems (QFS) has designed a solution-based technology – the Coastal Drought Buster – for coastal towns to augment their conventional water sources.

The Coastal Drought Buster combines sea water desalination with wastewater reuse as a more sustainable solution for water security, explains QFS MD Herman Smit.

The intention of the technology is to have desalination available during drought to provide water security, and cost-effective potable water outside drought conditions.

Using desalination as a decentralised water treatment solution will provide water security for the immediate area and ensure less dependence on pipe network maintenance.

Smit says it is not feasible to solely rely on wastewater reuse because the water used for that is not as accessible as sea water, as the latter is more accessible, owing to its abundance and the logistics of not having to transport water to the desalination plant.

“Sea water desalination will always be part of the total solution,” he claims.

Sea water desalination plants can be situated only next to the ocean and abstracted through wells, open sea intakes or surface structures. The potable water produced through sea water desalination must be close to the end-user to make it affordable, compared to surface water, which is pumped over long distances.

Domestic wastewater reuse in residential areas and small businesses is fairly simple, as the dissolved solids are low and require only low-pressure membranes for purification.

However, industrial water is mostly more complex to reuse, as it contains a mixture of biological and chemical contaminants specific to each waste steam.

Municipal and industrial wastewater should be reused and included in the list of sources available for the distribution of potable water through the municipal network. Unfortunately, reusing municipal wastewater is deemed risky because of micropollutants, such as pharmaceuticals, Smit adds. The treatment of waste water to potable quality is done with mature technology and through a multibarrier approach to remove any contamination risk.

In South Africa, the water industry needs the support of government to provide a similar financial structure that the energy sector was provided with in terms of financial guarantees on offtake agreements. In theory, decentralised desalination, and reuse solutions up to ten-million litres a day can be implemented in 12 to 18 months, providing a much faster turnaround solution than the megaprojects that aim to centralise water treatment.

“It would take a few years to alleviate the national water shortages, but the smaller decentralised plants will remove the pressure on the current bigger plants. Immediate benefits will be realised, consequently removing pressure on the distribution of water over long distances,” he concludes.