Exhibit 99.2
CONSENT OF PERSON ABOUT TO BECOME DIRECTOR
The undersigned hereby consents to the use of his name and any references to him as a person who
will become a director of Energy Recovery, Inc. (ERI) after the completion of its initial public
offering in ERIs Registration Statement on Form S-1, and any and all amendments thereto, to be
filed with the Securities and Exchange Commission pursuant to the Securities Act of 1933, as
amended.
Dated: May 9, 2008
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    By:   | 
    /s/ Paul M. Cook
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    Paul M. Cook  | 
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