Plant operators around the world select Calder Energy Recovery Turbines (ERTs) for their ease of operation, high efficiency, excellent reliability, proven durability and low maintenance costs.


Calder™ ERTs are designed and manufactured specifically for reverse osmosis desalination. They can recover as much as 90% of the hydraulic energy remaining in the brine stream, converting it into rotary power for the high-pressure pumps. Highly efficient and reliable, Calder ERTs are installed in nearly 1000 seawater and brackish water reverse osmosis plants worldwide, with a total installed capacity in excess of 350 MW.


Calder ERTs are designed to operate with either centrifugal pumps or positive displacement pumps and may be direct coupled to motors or pumps at speeds up to 3600 rpm. A range of standard turbines are available with a power recovery potential up to 1.5 W. Larger units are available as engineered product built to suit seawater and brackish water applications.

The ERT Operating Principle

Calder ERTs capture the high-pressure energy that remains in the brine concentrate from the reverse osmosis process. The high-pressure concentrate drives the ERT rotor, converting the pressure of the brine into rotational energy which is used to drive the high-pressure membrane feed pump.

ERT Schematic

The Calder ERT rotor and nozzle are optimized to maximize the conversion of the kinetic energy into rotating mechanical energy. Consequently, smaller, less costly motors may be utilized to drive the high-pressure feed pump. It is possible to size the electric motor for as little as 60% of the total power required to drive the high-pressure pump.

Types of Flowserve Turbines

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