Retrofits

Retrofitting existing SWRO plants with ERI’s PX energy recovery devices (ERDs) can reduce the power consumption of existing systems by as much as 60%. Alternatively, the capacity of existing systems can be increased with little or no additional power requirements, and with minimal additional equipment. PX devices and a circulation pump can be installed between membrane racks or even in a piping trench in any orientation. Many owners of SWRO plants are choosing to retrofit with ERI’s industry-leading PX devices.

Full Retrofit
In a full retrofit of an SWRO train that has a Pelton turbine (or a turbocharger), the turbine (or turbocharger) is removed. The original high-pressure pump typically remains and an array of PX energy recovery devices and circulation pump are added. The number of membrane elements are approximately doubled, resulting in nearly double the permeate flow for the same size high-pressure pump. Alternately, two existing trains can be combined and one of the high-pressure pumps removed.

Centrifugal ERD Retrofit Schematic Diagram
Note: The capacity of pretreatment, post-treatment, and product water conveyance systems must be increased in proportion to any increase in permeate production. In addition, because the turbine(s) are removed, the high pressure pump motor must be of sufficient capacity to turn the high-pressure pump. This requirement can be met in most existing Pelton installations where the high-pressure pump motors have been sized to operate without the turbine if necessary. (If the turbocharger is fed with a centrifugal high-pressure pump, this pump must typically be replaced with a pump that can achieve the full membrane pressure. If the turbocharger is fed with a positive displacement pump, this pump can typically be used, provided the motor has the capacity to drive it.)

Partial or Hybrid Retrofit
A partial or hybrid retrofit scheme can be applied to a process equipped with a Pelton turbine. Additional membranes, an array of PX devices, and a circulation pump are added to the existing system. No changes are made to the high-pressure pump or Pelton turbine. The amount of water diverted from the Pelton turbine to the PX devices depends upon the capacity of the high-pressure pump motor, which must operate with reduced assistance from the Pelton turbine. A partial Pelton retrofit is relatively inexpensive to implement and can increase production capacity by 20% while reducing specific energy consumption by 10%.

Partial Retrofit Schematic Diagram