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Orano: worth its salt

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EDP was the first, and remains one of the very few, desalination facilities to be built in southern Africa. Image credit: Leon Louw for WhyAfrica

Orano: worth its salt

 Through an innovative energy recovery system and a PPA solar energy deal, Orano Mining Namibia has been able to reduce energy consumption at its Erongo Desalination Plant (EDP) close to Swakopmund in Namibia by more than 40%.   

 By Leon Louw founder and editor of WhyAfrica

The west coast of Namibia is a harsh environment. It is hot, cold, dry, wet, and windy; all in one day. The mist belt that gathers precipitation from the icy Benguela Current sustains the isolated patches of biological life that survives in this moon landscape of the Namib.

The mist drops its sustenance in the morning, for almost 300 days of the year. Its reach is limited though, and the moist bank of misty clouds stretches for only 20km inland before it dissipates in the dry Namibian sun.

Towns like Swakopmund, Walvis Bay, and the fishing village of Henties Bay (all in the Erongo region), have sprung up within this mist belt. Half-hearted green Salt Bushes, Dollar Bushes, and a range of orange, red and off-green lichens dot the flat earth close to the ocean.

Beyond this vegetation belt, which is maintained by the mist, lies the drylands. It is here where most of Namibia’s uranium is found, in abundance. Several world-class uranium mines have been developed in the region, including Paladin Energy’s Langer Heinrich,  Rössing uranium, and Swakop Uranium’s Husab Mine. Before the 2011 nuclear disaster at Fukushima in Japan, nuclear energy was part of most countries’ energy plans, the uranium price was sky-high, and the mines of Namibia were feasting on their large resources.

Although uranium is back in demand, for more than 10 years the mills in Erongo slowed down and most uranium operations avoided care and maintenance by the skin of their teeth. Mines, towns, and people need water, a natural resource not as abundant in the desert as uranium. In fact, Swakopmund and Henties Bay suffered from severe water shortages in the past when Omdel aquifer, which provided the surrounding areas with groundwater, started running dry.

The Erongo Desalination Plant (EDP) was inaugurated in 2010. In 2021, the EDP set a new record by producing 12.7 million cubic meters (Mm3) of fresh water. The cumulative production since 2013 has now reached over 83Mm3.

EDP was the first, and remains one of the very few, desalination facilities to be built in Southern Africa and is located in the village of Wlotzkasbaken, about 30km north of Swakopmund. State entity NamWater taps into the treatment facility’s water production and distributes it to Swakopmund and surrounds. Ironically, the desalination plant was initially constructed by a mining company; it was never intended to provide the Erongo region with drinking water.

The water pipeline between Swakopmund and Henties Bay in Erongo, Namibia. Image credit: Leon Louw for WhyAfrica

From mining company to water provider

French company Orano Mining Namibia, previously Areva Resources Namibia (the company changed its name in January 2018), acquired a mining license to develop the Trekkopje uranium mine in 2008. The mine was poised to become the tenth-largest uranium mine in the world. The estimated life of mine was 12 years.

Construction got under way and the mine was nearing completion, on target to start production in 2011, when disaster struck at the Fukushima nuclear power station in Japan (the mine and plant actually completed a test run in 2011). Production was planned for that same year. Fukushima pulled the rug from the uranium market’s feet, and Trekkopje postponed production until the jitters settled. The uranium price, however, tanked and continued its slide to rock bottom. Since then, it has recovered somewhat, but not enough to ensure Trekkopje’s profitability. More than 14 years later, this project is still on care and maintenance.

Trekkopje was going to use a heap leach method to extract uranium, which requires a lot of water that is not readily available in the desert. The desalination plant was built for one specific reason: to ensure a continuous supply of good quality water to the mine. The water produced by the plant would be carried across the desert to Trekkopje by a 48km pipeline measuring 800mm in diameter and equipped with three pumping stations. A 132kV power line was also built along the pipeline to supply electricity to the plant.

At peak activity, the mine was expected to use about 12Mm3 of water, so there was always going to be approximately eight million cubic metres surplus, which would have been available to industrial and domestic users in the Erongo region. So, when Trekkopje never actually started producing uranium, the town of Swakopmund, various mega uranium mining operations, and, most of all NamWater, were presented with a very welcome present. Mines like Husab and Rössing are major beneficiaries. In fact, Husab’s fortunes are totally dependent on the water provided by the desalination plant.

The Erongo plant was built in two years. It is a simple and straightforward processing plant. Although, understandably, the process requires a lot of electricity and the initial capital costs were high, the long-term benefits far outweigh the costs.

The EDP is not only a case study for mining companies operating in desert or semi-desert areas, it is proof that salt water can provide coastal populations with potable water. More than that, it shows that if government and the private sector work together, it is much easier to find solutions to what is not always such complicated problems. EDP uses ultra-filtration (UF) and reverse osmosis (RO).

Desalination process

The first step in the desalination process is the collection of seawater through an intake unit anchored one kilometre off the coast at a depth of 10m. The seawater passes through a screen that catches anything larger than 40mm in diameter, thus removing large debris, aquatic plants, fish, and animals.

Two pipelines transfer the seawater from the intake structure to a pump station located on the seashore. The seawater is pumped to the plant through a single pipeline which is 1.2m in diameter. The incoming seawater passes through a rotary screen fitted with panels that remove particles larger than 60mm in diameter. From the screening building, the water is collected in a tank that feeds the UF trains. There are five installed rotary screens, with provision for a further three if required.

The filtering in the UF process takes place in what can best be described as horizontal pressure vessels, each one six metres long and 200mm in diameter. Inside each pressure vessel, there are four UF membranes. Each membrane consists of hundreds of straws each about 0.5mm in diameter. The walls of the straws are the filter medium. The water enters the inside of the straw and passes through the pores in the wall.

The solids in the water collect in the straws as they are too big to pass through the pores. The effective cut point of the UF membranes is 0.01mm. The clean water that has filtered through the UF membranes is collected in the RO feed tank.

The UF membranes are backwashed regularly to remove the solid particles that build up in the straws. About once a month, the trains are cleaned with a detergent to remove the solids not cleaned out by the backwashing.

The plant was designed to have 14 UF trains at full capacity. There are currently 11 trains installed and nine in operation. Each train has 308 membranes installed, giving a total of 2 772 UF membranes on the site. The typical membrane lifespan is five years.

The next step in the desalination process is the RO unit. The clean seawater is pumped up to 70 bar pressure and into the RO vessels. These resemble the UF vessels, but they are eight metres long and have six membranes per vessel. The RO membranes consist of alternating layers of semi-permeable membrane. The membranes are wrapped in a spiral around the central collection pipe.

Approximately 47% of the water entering the RO vessels passes through membranes and out as pure water. The remaining 53% (and all the dissolved solids) leaves the membrane as brine. The brine is still at high pressure and is used to pressurise a portion of the feed to the unit before flowing back to the sea.

The plant was designed to have nine RO trains at full capacity. Of the nine trains, eight are in operation at present. There are 512 membranes per train — 4 096 installed on the plant and again, the expected life expectancy of a membrane is five years.

The permeate from the RO units is too pure and needs to be re-mineralised before it can leave the plant. This is achieved by passing the water through a bed of limestone where calcium carbonate dissolves into the water. Chlorine is dosed in the water to sterilise it and the pH is adjusted to the product specification before the water is pumped into the NamWater supply line.

The brine stream from the plant is a mixture of the brine from the RO units, the backwash water from the UF units, and flush water from the screens. Roughly 70% of the seawater pumped to the plant is returned to the sea as brine.

Costs of desalination

The major costs in operating the desalination plant are the cost of membranes, maintenance, and electricity. It is an extreme environment and therefore the maintenance costs are high. Another challenge is dealing with the algal blooms, red tides, and sulphur events that happen frequently along the Namibian coast. The region often experiences sulphur outbreaks in the ocean and when this enters the plant, it creates major problems in the UF and RO sections. Sulphur is very hard to remove from the membranes — you have to be careful not to damage the membranes. As soon as high sulphur levels are detected, the plant is shut to protect the membranes. It is a seasonal phenomenon, but it is more prevalent in summer.

Efficient energy recovery system

Orano Mining Namibia recently entered into a 10-year Power Purchase Agreement (PPA) with French company InnoSun Energy Holdings to provide 5MW solar electricity to EDP.

Orano’s desalination plant is a landmark along the C34 from Swakopmund to Wlotzkasbaken. One can follow the large water distribution pipes all the way driving out of Swakopmund to Henties Bay on the west coast.

Desalination plants are by nature energy intensive and expensive to operate. Therefore, Orano has implemented an energy recovery system, and in addition signed an agreement with InnoSun to provide solar electricity to further reduce reliance on the national grid.

These energy reduction measures will enable Orano to make the provision of water to the Erongo Region from a green electricity source more affordable in the long term and contribute greatly to efforts to reduce the carbon footprint of the EDP. This project is part of the Orano group policy aiming to lower its carbon footprint and increase the share of low-carbon electricity at its operating sites worldwide

The EDP has contributed to the overall supply of potable water in the Erongo Region for more than 12 years of continuous operation without a single lost time injury (LTI) and its environmental management system adheres to the highest standards, as confirmed by ongoing impact testing around the operating site by independent third parties.

The EDP is a good example of what mines can achieve and what contribution they can make to the wider society.

Leon Louw is the founder and editor of WhyAfrica. He specialises in the extraction and responsible utilisation of natural resources, the primary sector of African economies and Africa’s political economy. 

WhyAfrica reports about, and publishes newsletters, magazines and research reports about natural resources and the primary sectors of African economies, and the infrastructure, equipment and engineering methods needed to extract and utilise these resources in an efficient, responsible, sustainable, ethic and environmentally friendly way, so that it will benefit the people of Africa.

Furthermore, WhyAfrica promotes Africa as an investment and travel destination, analyses the continent’s business environment and investment opportunities, and reports on how the political economy of African countries affects its development.         

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