Science: Treatment versus transport: smart use of local and distant water sources in coastal areas

Published on
April 19, 2021

Within the framework of ETE’s Water Nexus program, PhD scientists Alessio Belmondo Bianchi studied smart ways to match the increasing water demands by the chemical industry DowDuPont in Terneuzen. By combining previously developed simulation models, he concluded that a combination of treating local brackish water and transporting fresh water from distant sources was the most cost-effective and sustainable way to balance the companies water demands.

Due to climate change and increased water demand by the industry, agriculture and households, water scarcity will be an increasing problem in the future. Especially in coastal areas of The Netherlands, where a lot of industry is located, saltwater intrusion affects groundwater quality up to several kilometers inland, which may increase the scarcity of fresh water. This water stress can be diminished though by promoting freshwater use only when absolutely necessary, while using local brackish water resources as much as possible. ‘Different users have different requirements for their water’, Belmondo Bianchi explains. ‘Cooling water in powerplants and the chemical industry could as well use brackish instead of fresh water. Besides, brackish water can be treated to meet the quality requirements of the user.’ Not without reasons Water Nexus’ slogan is ‘Use fresh water where needed, salt water when possible’.

Best Trade-off

However, treating brackish water on-site is not necessarily a better option than transporting fresh water to the user. There is a trade-off in environmental consequences and expenses between treatment and transport, depending on the water quality needed and the amount of water available. For the industry, the big question is whether to transport fresh water from tens of kilometers away, or treat brackish water on site. ‘Each trade-off is case-specific and can’t be generalized’, Belmondo Bianchi says. ‘In our case study, we modelled the best trade-off for DowDuPont in Terneuzen: should they use treatment or transport, or maybe a combination of the two to operate cost-effectively and as sustainably as possible?’

Existing digital models

To decide the best balance between treatment and transport of available water for DowDuPont, the scientists combined two existing digital models. The first model, developed by ETE scientists Jessica Wreyford, calculated costs and impacts of the treatment (desalination) process, while the second model, made by Joeri Willett, did the same for water transport through a pipeline.

The model on desalination took various crucial factorsinto account during operation, like the design of the treatment technology, the achievable water quality, energy consumption and the overall environmental impact, based on complete life-cycle analysis. For this analysis, information on materials used as well as associated CO2 emissions were included. The model’s output included the total expenses and environmental costs, expressed as CO2 units.

The transport optimization model relied on a detailed information system (GIS), where geographical information regarding fresh and brackish groundwater sources and surface waters were stored. Water extraction limits linked to land use, like agricultural use and nature conservation, were also included. This resulted in an information map containing all possible water sources and possible pipeline routes. The subsequently built model was able to find the shortest and most efficient network to connect water sources to the end user. In a second decision-making stage, the expenses and environmental costs were calculated and compared to the outcome of the treatment model. Belmondo Bianchi: ‘My study included the integration of these two models into a decision-making framework to be able to identify the optimal trade-off between water treatment on-site and water transport.’

Graphical abstract of the treatment vs transport research
Graphical abstract of the treatment vs transport research

Practical limits

For DowDuPont the water sources locally available included wastewater from the cooling towers, brackish ground water and brackish water from the deltas. The decision-making framework considers three main criteria to decide between treating these sources or transport fresh water from longer distances: the cost for supplying a cubic meter of useable water, total energy consumption, and finally the environmental impact based on the equipment’s life cycle. ‘Our model showed that treatment and transport can be complementary in finding the optimum tradeoff’, Belmondo Bianchi says. ‘In our case, treatment reduces energy consumption and emissions, while transport is more cost-effective.’ For DowDuPont, the best configuration was a combination of 20-30% treatment and 70-80% transport.

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Although, treatment on-site is usually more expensive than transport, there are practical limitations to utilize the more cost-effective transport. DowDuPont extracts water from De Biesbos, a nearby nature area, but there are limits to the amount. Belmondo Bianchi: ‘Increasing the amount of water taken from De Biesbos is difficult, since this may damage the ecosystem. It’s therefore important to use treatment as an additional option, to prevent this area from drying out.’

Selected publication:
Belmondo Bianchi, A., Wreyford, J.M., Willet, J., Gerdessen, J.C., Dykstra, J.E., and Rijnaarts H.H.M. 2021. Treatment vs. transport: A framework for assessing the trade-offs between on-site desalination and off-site water sourcing for an industrial case study. J. of Cleaner Prod. 285 (2021) 124901.