When is desalination the right choice?

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Sydney Water
2010 February

Jonathan Andrews spoke to a select panel to break down some of the more common controversies surrounding desalination, and asks if water scarcity can make desalination plants environmentally, financially and politically feasible

When–if ever–will desalination become economically and politically competitive with other water supply options for thirsty cities?

Michel Canet, Business Development Advisor, Veolia Water Technologies

Take Saudi Arabia as an example where thermal multi-stage flash [MSF] plants have been installed for more than 30 years. It is clear that the only economical and political water supply option is to continue to use desalination but the authorities should take into account the availability of new technologies such as multiple- effect distillation [MED] and reverse osmosis [RO], which can be combined. A 15-year-old MSF plant can be replaced by a hybrid plant of MED and RO technology to produce more than double the quantity of water with less electricity and steam consumption.

Heather Cooley, Co-Director, Water Programme, Pacific Institute

Desalination is among the most expensive options, and water managers may reduce the output of a desalination plant when demand drops or when less expensive options are available. Because of the fixed costs of the plant, reducing the output can increase the unit cost of the water produced which can further reduce demand or make other supply options even more economically attractive. In response, water managers may temporarily or permanently shut down the desalination plant. This can reduce the variable operating costs associated with the plant but ultimately leave ratepayers to pay off a plant while receiving little to no benefit from it. This would be a disservice to the community and the industry.

Emilio Gabbrielli, Director, Overseas Business Development, Toray and President of the International Desalination Association (IDA)

It already is. If fact, when you consider both desalination per se and advanced reuse, these should be considered as complements or alternatives to mainstream water supply in most situations where water resources planning is done. The technology involved is mature and reliable, and costs are often competitive with traditional treatment processes. In many cases, they are actually already cheaper, not only safer in terms of quality. The value of desalination and advanced water reuse is being recognised more and more, and political interest and support to explore these alternatives is growing fast.

Denys Neymon, Chief Executive Officer, Treatment Infrastructure and Executive Vice-President, Suez

For coastal cities, desalination is a complementary solution to other water supply systems. It is the best and only solution when no other options are available, and due to its cost of under US$1 per cubic metre, it is always economically and politically competitive, especially for coastal cities in developed countries.

Shannon McCarthy, Co-Founder and Partner of United4Water and 1st Vice-President, International Desalination Association (IDA)

Desalination is not in competition with dependable conventional water sources. Desalination competes economically and politically with the costs of no freshwater at all or inadequate quantities of freshwater. Desalination can provide a sustainable source of freshwater for coastal cities that have either limited or no dependable freshwater sources. More than 300 million people around the world rely on desalinated water for some or all of their daily needs. Increased efficiency has already achieved substantial reductions, and there is every indication it will continue to do so.

Adam Scow, California Director, Food & Water Watch

Smart water agencies are making great strides in adopting efficient water management practices such as conservation, groundwater cleanup, reuse, and recycling. Desalination is an expensive and speculative option that could drain resources away from these and other more practical solutions. It should only be the option of last resort after all other and better supply options have been fully developed. Desalination will not fix or make up for the many water abuses and blunders that exist in the world today.

David Zetland, Assistant Professor, Leiden University College

Constantly improving technology means lower costs for desalination, but also lower costs for similar technology like wastewater recycling. Cities interested in saving money should therefore always consider recycling before desalinating water. From a political perspective, this can also be easier, as wastewater is easier to access than salty or brackish water that may be part of fragile ecosystems. Both of these technologies are less efficient than using rain water and cheaper surface and ground sources, of course, so we’re talking about ‘always more competitive, never the most competitive’.

How might desalination cause as many problems as it solves, or indeed solve more problems than it creates?

Canet, Veolia

It is difficult to weigh the social developments of a remote and thirsty region created by the viability of desalinated water versus the environmental problems created by brine rejection, global warming pollution, and water pricing for a low-income community. The only recommendation is that desalination projects should be done after a detailed feasibility study where comparisons between alternative solutions such as wastewater reuse, ground water, or recharged water tables are available for a final decision.

Cooley, Pacific Institute

Poorly planned, sited, or executed desalination projects would create as many or more problems than they solve. Indeed, the siting, building, and operation of desalination facilities are likely to be delayed or halted if local conditions, sentiments and the public interest are not adequately acknowledged and addressed. To help address these issues, the process of designing, permitting, and developing desalination facilities must be transparent and open. Moreover, affected community members should be invited to participate in desalination project planning, implementation, and management during the early stages of the process.

Gabbrielli, Toray and IDA

Desalination solves problems; it does not create them. It is an essential part of the water supply in many parts of the world, providing vital freshwater resources to growing populations and economies. It is unique in its ability to provide our thirsty planet with the only new and reliable source of freshwater. As our world deals with increasing water scarcity and the effects of climate change, seawater desalination becomes an ever more important strategy to ensure an adequate and essentially drought-proof supply of freshwater.

Neymon, Suez

Where there is a shortage of resources, desalination is the only solution able to supply water and thus, allow human development. Its outcomes are more positive than the effects resulting from its higher energy consumption compared to conventional solutions, or the discharge of concentrated water (brine) in the sea. In the last 20 years, energy use has significantly fallen. For example, daily energy consumption to supply desalinated water to a family of four is the equivalent to ironing clothes for one hour or using a laptop for a day.

McCarthy, United4Water and IDA

It is difficult to visualise a situation where desalination causes more problems than it solves or fails to solve more problems than it creates. Desalination requires energy, however there is great progress in the use of clean, renewable energy for desalination. The first utility size desalination plant using concentrated solar power (CSP) is under construction in Saudi Arabia. Seawater desalination plants must have dilution methods and outtakes that are carefully and correctly designed to discharge the treated brine at distances and depths that avoid harming the marine environment and marine life. For inland facilities that are desalinating brackish ground water, there is promising ongoing research in chemical and electrical methods of extracting the salt from the resulting brine. These could also be used to reduce brine from seawater desalination.

Scow, Food & Water Watch

Desalination creates many problems. It can be greater than ten times more energy intensive than other supply sources, thus potentially spurring their emission of global warming pollution. Producing water through ocean desalination costs three or more times what it costs to produce water from traditional supplies. It often requires multiple subsidies of both water and electricity to break even, and it entails pricey upfront construction and long-term operation and maintenance costs. Many proposed ocean desalination plants are now planning to rely on ‘once-through’ intake structures that kill fish and other organisms. Further, the disposal of the brine also has the potential to upset our delicate coastal ecosystems.

Zetland, Leiden University College

Desalination adds to supply, thereby reducing water scarcity. If demand is not capped (growth continues; lawns get bigger, and so on), then scarcity will return. The water authority in San Diego is bringing in desalinated water supplies of about 7 percent of total use but spreading US$1 billion of new costs among all customers. The small change in price is unlikely to dampen demand from existing customers or people moving to the area, which means that San Diego will again face water scarcity problems in the future.

Carlsbad desalination plant in San Diego is the US’s largest, most technologically advanced and energy-efficient’ seawater desalination plant
Carlsbad desalination plant in San Diego is the US’s largest, most technologically advanced and energy-efficient’ seawater desalination plant

Which beneficiaries should directly underwrite or finance investments in desalination plants, and why?

Canet, Veolia

With energy being the key element in producing desalinated water, it seems normal to consider that large energy producing companies like EDF, ENGIE, ACWA Power, and others should be investors. However, very often the costs of desalinated water is greatly affected by financing constraints and guarantees required by banks, so it could be cheaper to require governments or international financial institutions to give soft loans and/or guarantees to such projects.

Cooley, Pacific Institute

The financing of a desalination plant will depend on the unique circumstances of a given project. As a general rule, all beneficiaries of the desalination plant should pay for a portion of the project. The water users are the major beneficiaries of a project and would therefore likely bear much of the cost. Companies that profit from the project are other possible beneficiaries. Public subsidies are only appropriate in cases where the facilities come with an explicit guarantee of public benefits, such as restoration of ecosystem flows.

Gabbrielli, Toray and IDA

As desalination and reuse have become a mainstream freshwater supply alternative, their underwriting or financing will follow the same pattern as with other freshwater resources. This is clearly the case with municipal water utilities, whether this is done on a direct investment basis or through a form of public-private partnership. What seems to be happening more is that industries are deciding to invest in desalination and reuse within their fences to become independent from the services of the local utility. This is also done to secure its water supplies in case the utility has to cut the supply in a situation of drought, when supply for human consumption takes priority.

Neymon, Suez

Most desalination plants are used for drinking water supply. Therefore the public sector has to underwrite such projects to guarantee delivery and attract contractors. In some projects, the private sector could become involved through a dedicated investment vehicle that will need to be endowed with guarantees to deliver the project, securing its financing. Such guarantees come from the public sector such as land agreements, water purchase agreements, electrical connection agreements, and others.

McCarthy, United4Water and IDA

Financing should be shared between government agencies originating the projects and private sources of finance investing in the construction and operation of the plants. Governments should finance the infrastructure for water distribution and wastewater recovery. Private capital should finance the plants and their supporting facilities. Government contracting and regulatory policies should facilitate this combination.

Scow, Food & Water Watch

Ocean desalination provides a new opportunity for private corporations to own and sell water, creating the possibility that private corporations would rate-gauge thirsty populations. Food & Water Watch values water as a public resource that must be managed by public institutions and not be privatised. A recent Food & Water Watch analysis compared average water rates charged by publicly and privately owned utilities in four US states–California, Illinois, Wisconsin, and New York–and found that privately owned water utilities charge customers significantly higher water rates than their publicly owned counterparts: anywhere from 13 percent to almost 50 percent more.

Zetland, Leiden University College

The users of the water, and in particular the new users of the water should be the underwriters. Economists tend to say that everyone should face the marginal cost of their use, that is the cost of getting another unit, to help them see the real cost of scarcity. Most water utilities charge average costs, which means that people use too much water. Say, for example, you get half your supply from groundwater that costs US$1/m3 and half from desalinated water that costs US$2/m3. Most utilities would sell that water at US$1.50/m3, which does mean that costs match revenues, but also means they are selling US$2 water for US$1.50. It’s much better– from the perspective of efficiency and fiscal security–to charge US$2/m3 on all water. The utility can then send back the ‘profits’ (on groundwater) by reducing fixed charges to customers. This works for all water supply systems, but it’s especially useful for desalination because it’s so expensive.

According to Suez, the daily energy consumption of a plant supplying desalinated water to a family of four is the same as using a laptop for a day
According to Suez, the daily energy consumption of a plant supplying desalinated water to a family of four is the same as using a laptop for a day

When is small, distributed or large- scale centralised desalination preferable?

Canet, Veolia

A key factor for desalination plants is energy. The drive behind installing a small or a large centralised desalination plant is the availability of energy at a given location. This means that when there is no issue to build a large power plant then a large desalination plant is obvious. However, when you use the grid or use small solar or wind power, then a small plant is better.

Cooley, Pacific Institute

The unit cost of water from small systems is typically more expensive than large systems due to economies of scale. As a result, project developers may build large plants in an effort to capture economies of scale and reduce the unit cost of water; however, this can lead to oversized projects that ultimately threaten its long-term viability. As a general rule, the size of the facility should be determined by the demonstrated need for the water produced. Additional capacity to desalinate water can be added as needed.

Gabbrielli, Toray and IDA

Careful estimates of the costs of distribution associated with the alternative number of plants and sizes have to be looked at in their entirety, and the most economical solution should be chosen. In areas with several small centres within a reasonable number of kilometres, the alternative to provide a centralised desalination plant and then distribute the product by pipe or tank trucks can produce a result similar to that of providing individual small-scale plants. In many cases, the apparent safety of a centralised operation can be offset by the increased reliability of an operation ‘bought’ by the same community, which takes direct responsibility.

Neymon, Suez

From an economic and lower water rates perspective, a large-scale centralised desalination plant is preferable, except if the distance to feed the population is too far, and huge networks and pumping stations are required. Only in isolated villages or regions, is building small plants an acceptable solution, combining them with the use of renewable energies.

McCarthy, United4Water and IDA

Transporting water is expensive. Small, distributed desalination facilities are best suited for the desalination of brackish groundwater. Smaller seawater desalination plants are also appropriate for coastal towns. Large- scale desalination is best suited for seawater desalination for large coastal urban areas or industrial complexes.

Scow, Food & Water Watch

Small is preferable, but only if absolutely necessary and all other options have been exhausted.

Zetland, Leiden University College

Scale should reflect political realities. A smaller plant may serve a single community better than a larger one that drives conflict among several communities sharing it.

Reverse osmosis, as seen here, can now be combined with older multi-stage flash technology to increase efficiencies
Reverse osmosis, as seen here, can now be combined with older multi-stage flash technology to increase efficiencies

How can desalination best mitigate and address the high energy, cost, and toxic effluent from membrane problems? And what is the best way to reduce the environmental impact of polluted membranes after use?

Canet, Veolia

Firstly developments of new membranes, energy recovery systems and new processes for pretreatment have already addressed the cost and the high-energy consumption for desalinated water. New developments such as forward osmosis and hybrid desalination are going to further reduce costs and energy consumption. What to do with used membranes is indeed an issue but we should consider that membrane life has been considerably increased and it is now standard to change membranes after only eight to nine years. Often those used membranes can be used a second time for a few more years. In addition, recycling companies have not looked at membrane products yet, as the quantities are quite small, but in a few years there may well be a solution and a recycling process found.

Cooley, Pacific Institute

Desalination increases the water supplier’s exposure to energy price variability and greenhouse gas emissions. Some of the most promising research on reducing energy use is focused on alternative desalination technologies, like forward osmosis and membrane distillation; hybrid membrane-thermal desalination; and improved energy recovery devices. While reducing energy use will reduce greenhouse gas emissions, other mitigation strategies include using renewable energy and purchasing carbon offsets. Even renewables have a social, economic, and environmental cost, albeit much less than conventional fossil fuels. Marine impacts of desalination must be understood and mitigated. More research is needed, especially on the long-term impacts. We do, however, know that there are several operational, design, and technological measures available to reduce the marine impacts of open water intakes and brine disposal.

Gabbrielli, Toray and IDA

The high-energy costs of desalination are partly a myth, as by now desalination and reuse often uses less energy than traditional treatment methods or transferring water from farther away. With known technologies like reverse osmosis, there is not much scope for further reduction in energy consumption. Where there is great potential is the increasing use of renewable energy in its several forms for desalination. Luckily desalination normally does not produce problematic wastes, and the concentrate, in the case of seawater desalination, is nothing more than concentrated seawater that can be discharged with practically no environmental effect if the discharge is located and designed correctly.

Neymon, Suez

Energy use is relative, and in the last 20 years, it has significantly fallen. The desalination market is so competitive that the cost of desalination plants has diminished over the years. While it remains a costly process among drinking water treatments, it should be pointed out that the water produced is of exceptional quality. When membrane production capacity is reduced, and they have reached the end of their lifecycle, the best way to discard them is to recycle their components, and incinerate them jointly with domestic waste making them a source of energy generation.

McCarthy, United4Water and IDA

In the last decade, advances in desalination technology have reduced the cost of membrane desalination by 50 percent. Energy is the largest single cost of desalination (44 percent of the total). The reduction means significantly less energy is required. An alternative to fossil fuels is the use of renewable energy, solar or wind, which has no emissions and, after the initial investment, much lower costs. Many regions where desalination is needed have ample sunshine. The newly formed Global Clean Water Desalination Alliance, H2O minus CO2, is promoting the use of renewable energy for desalination. The alliance was launched at the Paris Climate negotiations and aims for 80 percent to 100 percent of new desalination plants and at least 10 percent of old plants to be powered by clean energy by 2035.

Scow, Food & Water Watch

Because there are no ways to truly mitigate these major impacts, and better options exist, desalination should not be pursued in general.

Zetland, Leiden University College

I’d encourage the use of ‘best technology’ by making polluters pay for whatever impacts they are generating.