At its time of opening, the Hadera SWRO facility is one of the largest membrane plants in operation, with a capacity of 456,000 m3/day |
While large unit size is typically an advantage for thermal desalination, the modularity of the SWRO technology makes it practically insensitive from the cost standpoint if the plant capacity is greater than 100,000 m3/day. This feature allows two advantages. The first benefit is that the plant can be designed for installation in more decentralized locations closer to the utility point, therefore decreasing the associated transmission and distribution costs and the energy footprint.
A second advantage is that the risk profile of a medium- to large-sized project is clearly more moderate than the risk profile of a mega ton project. This becomes an important factor in addressing the difficulty in securing the necessary level of investment associated with such developments in the current and near-term financial climate.
The particular advantage of SWRO is that it allows modularity of installation, whereby an infrastructure designed for long-term expansion could be enlarged gradually and according to the demand for
additional capacity. In this scenario, limited recourse or non recourse loans could be easily made available for small- to mid-size plants. This type of investment presents a much more moderate risk profile and could be revisited for expansion or reduction in size in accordance with demand development. However, producing this large amount of water imposes again, and with a much higher emphasis, the necessity to meet the dual objectives of a sustainable management of water resources and high competitiveness
Putting this into context, if we think about the large numbers, the operation of a mega SWRO desalination plant (for example, capacity of 1,000,000 m3/day) would involve a quantity equivalent to three to four million m3/day of seawater abstracted from the sea, and two to three million m3/day of brine disposal discharging back to the sea. With today's state-of-the-art technologies, the energy required to power this plant would be equivalent to 200 MW.
Things change dramatically if we think about a similar size plant driven by thermal technology. This would involve a quantity equivalent to eight to 10 million m3/day of seawater abstracted from the sea and seven to nine million m3/day of brine disposal with a thermal discharge. In this case, the energy required to drive this plant would be equivalent to 1,500 MW.
However, the majority of this energy – 1,000 to 1300 MW – would be discharged as low grade heat into the sea.
Both scenarios pose dramatic questions on the environmental load related to mega ton water projects and energy conservation.
If addressing the environmental aspect is a clear goal, today's technology would not enable the installation of such facilities for less than US$1 to 2 billion per mega project, with estimated annual running costs of not less US$200,000,000 per plant. This is not an easy deal for today's market.
Our generation needs to be aware that building plants to simply satisfy our water needs for tomorrow is not enough. Now is the time now that we must contribute to solving global water problems by establishing novel desalination and water treatment technology that would enable us to achieve the ultimate goal of solving the global water-energy-food problem.
However, we are still far from this situation. Mega projects are a solution for today and perhaps tomorrow, but we need to act to ensure that the day after tomorrow we have a solution at hand that is revolutionary if we compare it to the traditional approach.
Desalination is a fast-moving and dynamic industry as far as research and development is concerned. There are countless papers on the advantages of: Forward osmosis; Carbon nanotubes; Membrane distillation; Biomimetics and Renewable water generation associated to LT distillation or renewable power.