Case Study Detail

With 37 million residents, diminishing water resources due to droughts and agricultural misuse of water, as well as a tough economy and tight budget, California is a state of constrained resources. Yet with an extended coastline and abundance of inland water resources, desalination has emerged as a solution to purify these resources and address the demand for fresh water.

 

The cost and energy required for desalination has historically raised economic and environmental concerns. Advancements in membrane technology, improvements in pump efficiency and, most importantly, the introduction of energy recovery devices has helped make reverse osmosis an economically feasible, environmentally friendly desalination process available today.

 

 

The Eastern Municipal Water District in Perris, California had been pursuing efficient desalination with Energy Recovery Inc (ERI) TurboCharger centrifugal energy recovery devices since 2002 and 2005, respectively. In an effort to increase production of potable water while avoiding spikes in energy costs, in 2010, the water district expanded the installation of ERI’s devices in their purification facilities—a strong testament to the municipalities’ satisfaction with the quality and performance of ERI’s products.

 

Approximately 75 percent of the Eastern Municipal Water District’s (EMWD) potable water is supplied by imported water from the Colorado River Aqueduct. The remaining 25 percent is supplied by groundwater wells gathered from the water throughout the local pores and cracks in soil and rock. This type of water resource is considered brackish water, which has lower salinity levels than seawater, but can similarly be converted to drinking water using brackish water reverse osmosis (BWRO).

 

Although BRWO doesn’t require the same high pressures as SWRO, it still consumes significant amounts of energy. EMWD had been working with Pump Engineering Inc (PEI), an ERI company, since 2005. In 2010, EMWD started an expansion to efficiently produce 10 million gallons per day using ERI’s Low Pressure TurboCharger 1000 (LPT-1000) for its BWRO desalination system.

 

ERI’s Low Pressure TurboCharger (LPT) energy recovery device handles flows from 30 to 4,000 gallons per minute (6.8 to 908 m3/hr) and pressures up to 650 psi (45 bar), which is optimal for the brackish water desalination needs of EMWD.

 

The LPT device consists of a pump section and a turbine section. Both pump and turbine sections contain a single stage impeller or rotor. In the reverse osmosis process, hydraulic energy is extracted from the high pressure concentrate (brine) stream by the turbine side of the TurboCharger and converts it to mechanical energy. In turn, the turbine drives the pump impeller on a common shaft, reducing the energy required by the high-pressure pump to push water through the semi-permeable membrane.

 

With its unique design, the LPT is also able to be entirely energized by the concentrate stream, thus requiring no electricity, nor pneumatic requirements, which minimizes maintenance and lengthens the product lifecycle.

 

Serving a combined population of over one million residents, the LPT energy recovery device provides up to 70% savings in low-pressure BWRO water treatment to bring affordable, fresh water to California regions in need.