WateReuse Association develops ERD comparison tool

A spreadsheet tool to evaluate commercially available energy-recovery devices (ERDs) used in desalination or treatment of brackish water, seawater and wastewater effluent has been developed under a WateReuse Association (WRA) project just reported.

The WRA says that a major impediment to additional implementation of desalination technologies is the lack of an independent tool to evaluate energy consumption and minimization of energy use.

The objectives of the project, Evaluation and Optimization of Emerging and Existing Energy Recovery Devices for Desalination and Wastewater Membrane Treatment Plants (WRA 08-14- 1), were to create a thoroughly researched guidance manual that assesses currently available and emerging ERDs for desalination systems, and to create a computer tool to evaluate them.

The project, led by CH2M Hill’s Robert Huehmer, developed an Excel-based computer tool with the following functionality:

· Reverse osmosis (RO) mass balance
· RO projections
· Incorporation of ERDs
· Calculation of power consumption
· Estimation of capital costs
· Estimation of electrical operating costs.

The tool allows the user to develop an optimum RO system design (such as number of stages, recovery and flux, and flow and pressure of various streams) based on feed water quality and desired product water quality. The membrane type (low-pressure or high-rejection), number of passes, percentage of bypass, and ERD are examples of the options available to the user to customize the model run to a project.

The tool, based upon common process configurations utilized in desalination plants, will output the energy consumption when no ERD is used, display comparative performance (based on energy consumption, operating costs and life-cycle costs) of these devices, and indicate the overall energy consumption, operating costs and capital costs associated with the system.

The tool provides a valuable new resource for municipal planners, operators and consulting engineers in evaluating energy-recovery options in desalination of brackish water, treated wastewater and seawater using RO technology.

The download for this project includes both the guidance manual and the tool.