New Energy and Industrial Technology Development Organization (NEDO) and Hitachi, Ltd. are engaged in a demonstration project for a seawater desalination and water reuse integrated system in the eThekwini Metropolitan Municipality, known as the City of Durban in the Republic of South Africa. The project has recently started demonstration operation of the system at the demonstration site of a wastewater treatment plant in the eThekwini Metropolitan Municipality.
This demonstration project uses a system developed during a demonstration project by NEDO in Japan, and construct demonstration facilities aiming for desalinating 6,250 tons of drinking water from seawater and treated and discharged waste water every day, while saving 30% more energy compared to conventional seawater desalination systems and reducing the impact on the nearby marine environment. In the future, Hitachi plans to introduce this technology in Republic of South Africa and to other regions with serious water shortages, thus contributing to the development of water infrastructure and industry.
Background
The Republic of South Africa not only suffers from a serious water shortage due to large-scale droughts and other factors, but also has a power shortage that forces them to frequently conduct load shedding.
Against this background, NEDO engaged in a seawater desalination and water reuse integrated system demonstration project to solve the country’s water shortage issue and to promote the introduction of energy-saving water production technology. To demonstrate the energy-saving seawater desalination and water reuse integrated system developed during NEDO’s demonstration project in Japan, a Memorandum of Understanding (MOU) was signed with the eThekwini Metropolitan Municipality, South Africa in 2016. Furthermore, the implementing agent Hitachi concluded an Implementation Document (ID) with eThekwini Metropolitan Municipality, the owner of the waste water treatment plant where the demonstration plant is located.
Recently, NEDO and Hitachi have completed construction, equipment installation, and commissioning of the demonstration facilities, and have commenced demonstration operation of the system.
In this demonstration project, the system “RemixWater”, which was developed in a demonstration project by NEDO in Japan, replaces the high-pressure pumps (6-7MPa(60-70 bar)) needed by conventional seawater desalination systems with medium-pressure pumps (3-4MPa(30-40 bar)) by using brine water (water separated in the process to treat waste water for reuse) to dilute the salinity of the seawater. The aim is to implement demonstration facilities capable of producing 6,250 tons of drinking water per day, and cut power consumption by at least 30%. Moreover, in regards to the desalinating seawater, it is considered to be an issue that the discharge of desalination process which has high salinity is discharged to the sea and has impact on the nearby marine environment, but with the system to be demonstrated in this project, the discharged water’s salinity becomes the same level as the seawater as raw water is diluted with the brine water of wastewater, which reduces the impact on the marine environment.
Energy saving
Conventional seawater desalination systems have had the issue of high energy consumption due to the use of high-pressure pumps (6-7MPa) in the desalination through RO (Reverse Osmosis) membranes. This system uses water drained during wastewater reuse to dilute the seawater and lower the salinity. This makes it possible to use medium-pressure pumps (3-4MPa) and cut power consumption by at least 30%.
During the demonstration operation, Hitachi aims to demonstrate that the power needed to desalinate one ton of water is at least 30% less compared to conventional methods.
Reducing the impact of the marine environment
Conventional seawater desalination systems have to discharge high salinity water into the nearby sea following seawater treatment, which raise concerns of impacting the marine environment. The system demonstrated in this project uses brine water from the waste water reuse to dilute the seawater before desalination, which makes the salinity of the discharged brine same as the seawater, thereby minimizing the impact on the marine environment.
During the demonstration operation, Hitachi aims to demonstrate that the salinity of the drainage water from the system is at the same level as compared to seawater.
Stable water production
During the demonstration operation, Hitachi aims to demonstrate that stable water production of the designed volume (6,250 tons per day) will be achieved, and that the quality of the water produced meets South African National Standards for drinking water.
Future Plans
Making this demonstration project the first foothold in Africa, NEDO is aiming to introduce Japanese technology broadly to South Africa and other regions with serious water shortages, and contributing to the development of water infrastructure and the industries in those regions.
