Pumps in the growing global desalination market
The topic of water—its use, shortage, value—is currently pervasive. Developing countries face the brunt of this water scarcity as not even a well-known hero like James Bond could prevent the villainous seizing of control of the drinking water supply system in these areas. This serves to highlight the current situation involving the global water supply and how 21st century popular and political theater can shape the discussion.
Demand for Fresh Water
A glass of chilled water is fast becoming a hot commodity. Worldwide, water usage is increasing while the availability of fresh water sources is shrinking. Much of the Earth's freshwater is either locked up as ground water or as glaciers, with only a small percentage of per capita water economically available. This is most apparent in the Middle East where the per capita water consumption is almost equal to the per capita water availability. Asia Pacific and Africa also suffer from water scarcity.
Figure 1. World water availability and consumption
This issue is compounded by the rapid industrialization and high population growth in these regions. While most European countries witnessed a negative population growth rate and a negative or low economic growth rate in 2010, all the countries in the Middle East witnessed around a 2 percent population growth rate and around a 5 to 15 percent economic growth rate. The increased standards of living and rapid industrialization require better access to clean drinking water and better wastewater and sewage collection and treatment facilities. In the next few decades, increasing population and global warming will put additional burdens on strained water sources.
Sensing the need for better water and wastewater infrastructure, various governments have been focusing on improving their water policy to ensure the availability of clean drinking water for their country, including desalination efforts.
China
The Outline of the National Planning for Development of Ocean Economy targets to achieve a desalination capacity of 20 million tons per year, with a seawater utilization of 50.00 billion m3 per year by 2010. The aims are to meet this target with several integrated seawater utilization demonstration bases in water deficient northern cities and build up several demonstrations in coastal cities for large-scale seawater utilization.
Saudi Arabia
Saudi Arabia produces almost 8 billion gallons of water per day from desalination, about half the world's total, and continues to invest in various desalination projects across the country.
India
The Indian government has allocated $12 billion for urban water supply under the eleventh five year plan that will support more desalination plants in India.
The water scarcity problem is not isolated to emerging economies. Parts of developed countries face acute water shortage. For example, the 2011 summer in Texas has seen one of the worst droughts in decades. The Canary Islands and the coast along the Mediterranean in Spain face heavy water shortages. As a result, across the world, there is a need for better, reliable and cost-effective water treatment technology.
Desalination
Among the water treatment technologies, desalination is one of the most technologically promising. As oceans cover more than 70 percent of the Earth's surface, regions' focusing on extracting fresh water from seawater is a logical step. Vaporization and distillation of seawater to obtain fresh water was one of the first desalination technologies. These technologies need huge energy inputs to heat the water. As the oil boom spread in the water starved Middle East region, this area embraced the vaporization and distillation technique and quickly became the leader in the desalination market. Because of the challenges of large quantities of heat and space required for vaporization and distillation, researchers developed the reverse osmosis (RO) process. RO forces water, at high pressure, to separate from salt using a semi-permeable membrane. This new technology required much less energy and space and was increasingly adopted across the world.
Figure 2. Summary of three popular types of desalination processes
RO currently accounts for around 60 percent of the entire installed desalination base. Though RO technology is more efficient than multi-effect distillation (MED) or multistage flash (MSF), separating salt from water is still a very energy intensive process. See Figure 2. To increase the efficiency, recovery systems were developed to use the high pressure of the waste brine left after the RO process, leading to reduced operating cost. An estimated 18 billion gallons of water per day are treated using desalination across the world, and this market is expected to grow around 7 percent every year for the next five years. About 80 percent of the water being treated is seawater and brackish water.
Figure 3. Desalination equipment market
Pumps, Piping and Valves in Desalination
The global desalination equipment market is expected to generate revenue of around $6.78 billion in 2011. Of this $6.78 billion, 17.8 percent is being spent on pumps, piping, valves and control systems, and a majority of this money is spent on pumps. Pumps play a key role in the desalination process and are a critical process component. See Figure 3.
However, the use of pumps varies according to the desalination process. RO systems use pumps as the key equipment to purify water while other techniques such as MED or MSD use pumps to transfer water and brine.
To achieve optimal system performance and efficiency, four key factors must be considered:
1. Pump efficiency—As energy is one of the major operating costs, cost of desalination per liter of water depends on the optimal use of energy. Pump efficiency is a key criterion in keeping energy costs down. Positive displacement (PD) pumps operate with 80 to 95 percent efficiency, while centrifugal pumps operate at 40 to 65 percent efficiency. PD pumps are preferred for small- and medium-sized desalination plants while centrifugal pumps are preferred in large desalination plants. Increasing pump efficiency brings down the cost of desalination and increases the return on investment (ROI).
2. Material of the pump—Global warming has resulted in an increase in the salinity and temperature of sea water, which is highly corrosive. This impacts the pump's performance and operating life. It also increases the maintenance cost. Therefore, optimal selection of material is a key factor to reduce operating cost and increase the pump's life cycle. Pump material selection directly influences the ROI.
3. Uninterrupted flow—The pump system has to be designed to ensure uninterrupted water circulation while keeping the energy consumption low. To ensure that there is always a positive flow of water, secondary systems may be used but these additional pumps increase the initial investment and the operating costs, and reduce the ROI. Designing the system for optimal water circulation is critical.
4. Pumping system accessories—Accessories used in pumping are as important as the main pump. The pressure monitoring system and pressure relief valve ensure that the RO system does not rupture the membrane due to sudden blockage of water circulation. Components such as pulsation dampeners ensure that the pulsation created by the high pressure water pump do not damage the delicate membranes. Failure of these accessories can result in pump damage.
Conclusion
Water is a vital resource for human health and well-being, industry production and agriculture, and its demand will increase in the coming decades. Emerging nations with rapid industrialization and population growth are the most vulnerable. Desalination of seawater and brackish water is one of the best available alternative sources to fulfill growing water demand.
As pumps and other accessories form an integral part of desalination systems, growth in the desalination market is expected to spur the growth for demand of these products. However, to achieve higher efficiency, desalination equipment manufactures and pump manufacturers need to consider key factors that affect the efficiency and performance of desalination equipment.
Pumps & Systems, October 2011