Raphaël Mergui
Humanity is on the verge of breaking the water poverty line – 1,000 m3 of water per year per capita – below which its food security would be seriously compromised. Science is challenged to make up for the planet’s water deficit without harming ecosystems, marine ecosystems in particular. Despite major advances, it seems to be slowing down.
The FAO believes that humanity faces a huge challenge: the demand for water from agriculture is expected to increase by 20 to 30% by 2050, otherwise our food security would suffer. Indeed, if the world’s population were to continue to grow at the same rate as in the last 30-50 years, we would need, mechanically, some 20 to 30% more water by 2050. However, one should always be cautious with predictions over such a long period of time.
Water needs change from country to country, from continent to continent. They even change within the same country, the same region, the same village. This forecast, which is not very precise, also indicates a possible margin of error of 10%. In addition, climate change contributes to making any prediction exercise somewhat uncertain.
We theoretically have the means to meet the water challenge. We have the technological and scientific means to do so. The real problem is that of cost. If the climate continues to change, we will have to resort to unconventional resources, i.e. water desalination and wastewater reuse. Obviously, countries with the necessary financial and technological means will be able to cope much more easily than poor countries. If, by some miracle, climate change were to be temporary, we would only need to mobilize conventional resources: surface water, rainwater and groundwater.
Today, we only talk about non-conventional resources (desalination and water reuse). But many other promising unconventional research is underway, even if it is still embryonic.
Distinguishing between water threshold and water poverty
For the time being, we can only note that the quantity of conventional water, which can be used on a global scale, is limited. The amount of water available per capita has fallen sharply over the past century, when it was abundant. We are currently in a situation, not of scarcity but of water poverty. It obviously varies from one region of the world to another. And this poverty is getting worse over the years. The poverty line is between 1000 and 1300 m3 per year and per inhabitant. The stress threshold is generally estimated at 1700 m3 per year and per inhabitant. Water stress refers to the problem of physical water availability. Water poverty, on the other hand, refers to problems of access to water and the management of water resources. We should sound the alarm because we are not far from the poverty line. If the world’s population continues to grow at the current rate, we risk, all other conditions being equal, rapidly sinking the 1,000 m3 floor.
The cost of the investments needed to escape this fate will deepen the global divide between rich and poor countries and endanger food security in continents such as Africa and Asia. This divide can cause geopolitical destabilization (including mass migration) that an organization like the United Nations has a duty to address. In the era of globalization, the solution can only be global. The reflection must begin by focusing on improving the management of conventional resources (groundwater and rainfall).
As for unconventional resources, we can only note that rich countries have reduced their infrastructure investments in poor countries even though soils are degrading in continents such as Africa. Does Europe, whose financial resources have declined, have the means to offer water desalination plants to Africa? We can doubt it. But this situation does not exempt all countries, rich or poor, from engaging in a global reflection on water poverty.
However, many developed countries have a great deal of know-how. France – via its two major groups, Veolia and Lyonnaise – has a 30% share of the global water market. However, this country does not have a single desalination plant. This is also the case in Great Britain, which is building a number of water desalination plants and wastewater recycling plants around the world. And let’s not forget the United States, which has built a few desalination plants at home.
These countries should support the countries of the South facing a drought in the face of which they are powerless. They must support them in mastering water management policies and looking for alternative solutions. United Nations agencies – including the World Bank – and other international organizations and NGOs can also play an important role in financing water infrastructure.
The water value chain
The cost of investments to eradicate water poverty is measured in hundreds of billions of dollars. It is estimated, for example, that achieving the water-related Sustainable Development Goals would require an investment of $100 billion to $300 billion per year. The cost of a municipal water desalination plant ranges from $100 million to $1 billion depending on its size and the technology used.
Public opinion and States are now aware of the urgency of combating water stress. To take the example of Morocco, King Hassan II anticipated this problem by a bold policy of dams when the quantity of water available per capita was 3,000 m3. Since then, the climate crisis has done its work and the kingdom has also been severely impacted. The country has continued to be proactive: it has adopted a national drinking water supply and irrigation plan 2020-2030 that uses non-conventional resources, desalination and wastewater reuse. Unfortunately, African countries do not have the financial means to pursue a similar policy.
In any case, water must be the subject of real monitoring. There is a real water value chain. We must scrupulously watch over each link in this chain. Every drop of water counts. It must be tracked from its source to its use, taking care to avoid waste and pollution. The first link is therefore the source of water, the second its use, the third the avoidance of waste or pollution and the fourth its recycling.
This monitoring must be particularly attentive to the catastrophic consequences on human health that uncontrolled water pollution could have. There is a case of mercury being released into water before its use that has caused many bouts of madness in the exposed population.
Choices in terms of investment in the fight against water stress must be made without any polemical spirit. Thus, some venture to advise against the installation of desalination plants on the pretext that they would be a waste if the rains were to become abundant… Against this kind of speculation, the precautionary principle must prevail. Desalination plants, even if underused, are an essential form of insurance because climate change is unpredictable.
Research on desalination plants is stalling
Very complex, this research on water is not the prerogative of any science. They concern all the sciences, whether it is sociology, law, economics or the hard sciences. The field of water is an ultra-sensitive subject. Don’t geopoliticians proclaim that this century is the century of water wars? Technological, strategic, political and economic monitoring is an important tool in any water policy. We need to develop the most pessimistic scenarios to protect us from catastrophic events.
Research should walk on its own two feet, the academic foot and the foot of applied and technological development. In academic terms, research is interested in evaluation, forecasting, particularly in terms of climate change, and value chain analysis. In terms of technology, it is interested in wastewater treatment and recycling and pollution by industrial effluents. In terms of technology, water desalination plants are a vast subject in themselves. They encompass materials science, automated processes, chemistry and biology.
Research on desalination techniques is geared towards reducing their environmental impact on marine ecosystems (brine discharges, for example) and saving energy. Initially, desalination by distillation of seawater dominated. This process involves heating salt water to turn it into steam and then condensing that steam to recover fresh water. One can imagine how expensive this technique is in terms of energy). This process was used by 80 to 90% of the factories. Today, it is largely supplanted by the reverse osmosis technique (it uses membranes to separate water and salt) which is much less energy-intensive. Especially since these factories are increasingly powered by renewable energy. 65 to 70% of the desalination plants under construction in the world are reverse osmosis.
In recent decades, more sophisticated techniques such as electrodialysis and nanofiltration have been developed. Desalination by absorption or freezing is still in the experimental phase. Above all, research is making great progress in the use of renewable energies to power desalination plants. However, it must be recognized that research is slowing down. She has been on a set for about twenty years. Laboratories are mainly trying to improve water quality and reduce production constraints and costs.
Adverse environmental impact of desalination
The problem is the same for wastewater treatment. Recycling techniques are not the prerogative of a single science, even biology because of the presence of bacteria in the water. Wastewater recycling is just as much a matter for civil engineers, automation engineers and equipment manufacturers. Progress in recycling is faster than in desalination. The techniques are complex. Recycling differs according to the final destination of the water: agriculture, industry, consumption, etc.
The amount of water recycled is lower than that from desalination. Priority should be given to recycling because it is less expensive and reduces pollution. The treatment of polluted water is much less advanced. Morocco, for example, produces one billion cubic meters of wastewater, while in some Middle Eastern countries such as Jordan or Israel have reached a stage of zero wastewater discharge.
However, in view of climate change and drought, the most urgent need to be addressed is to produce the billions of cubic metres missing in desalination plants in the Atlantic or the Mediterranean. But then the problem of pollution of the sea by the discharge of brine from contemporary mega stations arises.
This was certainly not a problem when desalination was practiced by American military ships for their consumption purposes only. Similarly, the first desalination plants – which produced only a few thousand cubic meters – had an insignificant impact on the environment. The Saumur was discharged by diffusers at a speed that limited its impact on the quality of the seawater.
The problem became different when drought set in and the growing water needs of agriculture had to be met. The latter consumes, on a global scale, between 65 and 85% of the quantities of water available. Desalination plants capable of satisfying these needs are at the same time enormous sources of pollution. Is it worth the risk if to produce a billion cubic meters of fresh water, 300 to 500 m3 of brine must be discharged? This discharge increases the salinity of seawater locally, disrupts ecosystems and affects biodiversity. To reduce their environmental impact, desalination plants pump seawater a few kilometres from the coast. This helps protect coastal ecosystems and disperse brine over larger areas. In addition, moving away from the coast, you get better quality water.
Advanced research on brine and graphene upgrading
The other environmental damage of water desalination is the chemical pollution caused by the factories. It comes from the chemicals used to treat seawater such as coagulants, disinfectants or antiscalants, saline residues, heavy metals (lead, mercury, arsenic) released by chemical reactions. This chemical pollution can have an indirect impact on human health and a direct impact on biodiversity.
Research on the recovery of brines is still in its infancy, but it has made some progress, although it can only concern small quantities. They include the recovery of minerals (sodium, calcium, magnesium and potassium), energy production through systems such as reverse osmosis or electrodialysis, use in agriculture (for crops that tolerate a high degree of salinity), industrial applications (manufacture of chemicals or ice) and reforestation (creation of ecological systems such as mangroves).
Research concerns many sciences. Some could appear to have nothing to do with water. This is the case with graphene. It is an innovative material that could revolutionize seawater desalination methods. Graphene-based filtration membranes can be designed to filter seawater more efficiently. Graphene can be made with nano-sized pores that allow the rapid passage of water molecules while blocking salt ions. Graphene-based membranes can be more durable and biodegradable. Thanks to its high filtration efficiency, graphene is much less energy-intensive than traditional membranes.