Case Study Detail

PX® Technolgy Reducing Energy and Overall Costs

The Industry Standard Solution
The efficiency and lifecycle costs of a plant’s energy recovery technology is critical to both winning SWRO projects and achieving maximum plant profitably through the lowest operating costs. Leading international OEM’s such as Acciona Agua, Aqua Engineering, Befesa, CH2MHill, Cobra Tedagua, Doosan Hydro Technology, Fisia Italimpianti, GE Water Process and Technologies, GEIDA, IASUR, INIMA, Metito, Siemens and Suez Degrémont have selected the ERI® PX modular technology for their recent projects because it consistently achieves real energy transfer efficiencies—up to 98%, making it the most efficient energy recovery device available today. At the core of the PX device is a single moving rotor made of tough engineered ceramic that is unaffected by chemicals, will not corrode, and requires no periodic maintenance. Over 80 OEMs are standardizing on PX technology with installations around the world, including plants such as Al Shuaibah III, Barcelona, Chennai, Hamma, Perth, Skikda, Torrevieja and Yuhuan.

Cyprus Project Facts

• CAPACITY: 40,000 m3/day [10.5 MGD]
• 8 trains - 4,300 m3/day [1 MGD]
• 8 PX-220 PRESSURE EXCHANGERS PER SWRO TRAIN
• 95% EFFICIENCY GUARANTY
• PLANT STARTUP – MAY 2007

“We have been working with ERI for over nine years now and relied on their PX technology to assist us in providing affordable water to Cyprus. ERI’s technical services manager provided excellent support during installation and beyond. Most importantly, we’ve reduced our energy costs by approximately 0.5 kWh per cubic meter. “

Olga Sallangos

Plant Manager, CARAMONDANI DESALINATION PLANTS LTD.

The Situation
Dhekelia, located on the southeast coast of Cyprus, is situated on the eastern Mediterranean Sea. In 1997, Caramondani Desalination Ltd., the plant’s builder, owner and operator, undertook a BOOT (Build, Own, Operate and Transfer) contract for the original desalination facility to produce 40,000 m3/day of fresh water. The plant used hollow-fiber membranes. It was the first large scale (10,000 m3/day per train) to employ ERI PX technology which was implemented as a retrofit for the original Francis turbines energy recovery solution.

Late last year, the Cyprus Desalination Plant initiated an upgrade of its desalination process to achieve a more scalable, more energy efficient operation. The new process which came on line in May 2007 still produces 40,000 m3/day of fresh water but consumes considerably less energy than it used to, supplying drinking water to approximately 200,000 Cyprus residents.

The Challenge
The plant had been operating with hollow fiber membranes at high pressure. Feed water conditions varied because of seasonal temperature changes ranging from 12 to 32 degrees Celsius. Although the Cyprus plant was able to provide consistent high-quality water throughout the year, Caramondani requested that changes be made to the plant design to reduce energy consumption. PX technology was introduced in 1998; however, energy costs could be further reduced. The plant design also needed to accommodate for future expansion capacity in a streamlined approach.

The Solution
Caramondani , having successfully operated ERI PX devices for the past nine years, upgraded the Cyprus plant to a more efficient overall process with a total of eight trains containing eight PX units each for a total of 64 PX devices. The new plant employs a pressure-center design consisting of a common high-pressure pump feed header fed with three pumps; two running and one on standby. Each SWRO membrane train has a dedicated PX device array and booster pump. This design accommodates larger, more efficient high-pressure pumps while providing operational flexibility and maximum uptime.

To allow for expansion and additional flexibility, the plant was built with two extra PX devices installed per array. A boron removal system was installed that utilizes a boron-selective ion exchange resin and a partial second pass. Permeate may be taken from both ends of racks to allow for segregation as conditions vary to reduce the load on the second pass.

ERI also provided technical support services including control system review and start up support service during the commissioning of the first set of arrays. Follow-up visits were also provided after the entire plant was in operation. ERI’s technical services manager evaluated the PX-120 devices that were removed during the upgrade after having run continuously for six years. These units were determined to be in suitable condition for redeployment in other plants. The total project was completed in approximately six months, with completion in April 2007.

The Result
Thanks to the PX devices and low energy membranes, the plant is operating at or better than designed. Energy consumption was reduced by an estimated 0.5 kWh per cubic meter of permeate produced. The use of PX technology allows for varying recovery rates to lower the energy cost during seasonal feed water temperature and salinity changes. Other plant design features, including spiral wound membranes provide operational flexibility and maximize process uptime. As a result, the plant is now a “state of the art” facility.

Energy Recovery, Inc. (ERI®) is a leading manufacturer of energy recovery devices, which help make desalination affordable. ERI’s PX Pressure Exchanger® technology (PX®) is a rotary positive displacement pump that recovers energy from the high-pressure waste stream of sea water reverse osmosis (SWRO) systems at up to 98% efficiency with no downtime or scheduled maintenance.

ERI has research, development and manufacturing facilities in the San Francisco technology corridor as well as direct sales offices and technical support centers in key desalination hubs such as Madrid, Dubai, Shanghai and Florida. ERI service representatives are based in Algeria, Australia, China, India, Korea, Mexico, Taiwan and the Caribbean.