In the spotlight: Nikolay Voutchkov
Water Technology Magazine – By Amy Lasek, Associate Editor
Huntington Beach recently backed a plan by Poseidon Resources Corp. to build a desalination facility that would produce 50 million gallons of fresh drinking water per day. Poseidon Senior Vice President of Technical Services Nikolay Voutchkov talked about the plant and large-scale desalination.
Summary: Seawater desalination has been a topic of discussion as water resources diminish and the nation’s thirst continues to grow. Huntington Beach, CA, recently moved one step closer to building the nation’s largest desalination plant, when the city backed a plan by Poseidon Resources Corp. to build a facility that would produce 50 million gallons of fresh drinking water per day. What would plants like this mean for their communities and the water supply industry? Poseidon Senior Vice President of Technical Services Nikolay Voutchkov talked about the plant and large-scale desalination.
Water Technology®: What types of technology will the Huntington Beach desalination plant use?
Nikolay Voutchkov: The plant will use a reverse osmosis (RO) membrane-based seawater desalination system to separate the salts. The membranes are capable of rejecting over 99.75 percent of salts and producing fresh potable water with a salt content lower than 400 milligrams per liter (mg/L).
The salt content of ocean water is 33,500 mg/L, and the federal Safe Drinking Water Act standard is 500 mg/L. Approximately 18,000 membrane elements are needed to produce 50 million gallons per day (mgd) of fresh water.
WT: Poseidon specializes in seawater desalination — have you seen an increase in the number of proposals for desalination plants in US coastal cities?
NV: With dwindling resources and longer drought cycles, it is likely that desalinated seawater will become a measurable portion of the water supply portfolio of coastal communities in the US.
Over 75 percent of the population is located within 50 miles of an ocean coast and could be supplied with desalinated seawater. Currently less than 1 percent of this population uses desalinated seawater.
There are over 20 seawater desalination projects in various stages of planning and implementation along the California coast. The Texas coastal communities of Freeport, Corpus Christi and Brownsville are embarking on large seawater desalination projects as well. The Tampa seawater desalination plant is anticipated to begin continuous production of 20 to 25 mgd of desalinated seawater in 2006.
WT: The Huntington Beach desalination plant has seen its share of opponents. Do you believe there are environmental risks when building these plants?
NV: Detailed environmental studies completed in the US, Israel, Spain and Cyprus indicate that the environmental risks associated with the operation of well-planned, -designed and -maintained seawater desalination plants are comparable to those associated with the operation of conventional water treatment plants.
Seawater desalination plants, because of their interaction with the ocean, potentially alter the local marine environment by withdrawing the water and returning the concentrated seawater back to the ocean. By siting a plant away from sensitive habitats and fixed habitats, such as reefs and kelp beds, and controlling the velocity and the volume of the water withdrawn, you can significantly minimize the entrainment and impingement of marine life and you can significantly reduce the concentration of salt in the discharged water below levels that will affect the local marine life.
WT: What about the byproducts of desalination such as mineral salts and brine? How can these be safely disposed of or used?
NV: Byproducts can be safely returned to the ocean as long as the plant discharge outfall is designed with adequate provisions for rapid mixing of the byproduct and the ambient ocean water.
Since the membrane separation process is mechanical rather than chemical in nature, the concentrate does not contain “unnatural” or added substances that have not come from the same ocean they are returning to.
Discharge can be achieved in one of two ways: either co-discharge the byproduct with the discharge of a power plant or wastewater treatment plant, or build diffusers at the end of the desalination plant discharge in order to accelerate byproduct mixing with the ocean water.
Under the co-location configuration, the power plant discharge serves both as an intake and discharge to the desalination plant. Four key benefits stem from this arrangement: first, the construction of a separate desalination plant outfall is avoided, thereby decreasing the overall costs and alleviating the environmental impact; second, the salinity of the desalination plant discharge is reduced as a result of the mixing and dilution of the membrane concentrate with the power plant discharge; third, because a portion of the discharge water is converted to potable water, the total amount of the power plant thermal discharge is reduced; and fourth, the blending of the desalination plant and the power plant discharges results in accelerated dissipation of both the salinity and thermal discharges.
WT: Have overseas markets been more accepting of desalination development?
NV: The overseas market has always led the development of seawater desalination in terms of installations. The Middle East has seen the largest area of historic growth, but now Spain and other Mediterranean countries are seeing a significant increase in seawater desalination.
According to a desalination plant inventory report prepared by the International Desalination Association, by the end of 2003 there were over 17,000 desalination units worldwide with total installed treatment capacity of 37.8 million cubic meters per day.
WT: Is desalination technology cost-effective or economically competitive for its users? Would it be cost-effective in small-scale treatment applications?
NV: The cost of production of fresh drinking water [by other methods] is still higher than that of seawater [desalination]. However, the gap is closing due to rapid advances of membrane technology.
Similar to computers, the reverse osmosis membranes of today are many times smaller, more productive and cheaper than the first working prototypes. Over the last 10 years, the cost of desalinated water has dropped more than twofold.
With an increase in regulations and the steady increase in water treatment costs, people are expected to increase their reliance on the ocean as an environmentally friendly and competitive water source.
Producing desalinated water in a small scale is several times less efficient than building large seawater desalination plants. Despite that, there are many small desalination plants worldwide serving coastal communities, resorts, hotels and individual coastal developments. For example, most of the small Caribbean islands are supplied by desalinated water produced by simple, pre-packaged and pre-assembled desalination systems.
Small desalination plants are also widely used to provide emergency water supply in areas of natural disasters. All modern cruise ships, navy ships and submarines use reverse osmosis systems for drinking water supply.
WT: In the future, do you foresee every coastal residence having its own individual desalination device? Will desalination play a larger role in smaller-scale commercial or residential POU/POE water treatment applications?
NV: For the US, the future is likely to be very limited. With the exception of some isolated hotels, homes or communities, it does not make sense economically [because] most coastal communities are served by local water systems . . .
However, most of the large cities in the US are over 100 years old and their distribution systems are reaching the edge of their useful lives. The aging water infrastructure of old metropolitan areas is likely to pose increasing challenges to the water quality at the tap — taste, color, odor and pathogen contamination. POU/POE water treatment systems have proven to be a good final barrier of protection against these water quality challenges.
It is expected that the use of POU/POE devices will increase in the coming years, especially in old metropolitan areas. The use of such devices provides an additional barrier of protection against acts of vandalism and terrorism involving the water distribution system.