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UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington D.C. 20549 Form 10 - K ( Mark One ) ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31 , 2020 or 0 TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Delaware ( State or Other Jurisdiction of Incorporation ) Commission File Number : 001-34112 Title of each class Common Stock , $ 0.001 par value energy recoveryⓇ Energy Recovery , Inc. ( Exact Name of Registrant as Specified in its Charter ) 1717 Doolittle Drive San Leandro , California 94577 ( Address of Principal Executive Offices ) ( Zip Code ) ( 510 ) 483-7370 ( Registrant's telephone number , including area code ) 01-0616867 Securities registered pursuant to Section 12 ( b ) of the Securities Exchange Act of 1934 : Trading Symbol ERII ( I.R.S. Employer Identification No. ) Name of each exchange on which registered The Nasdaq Stock Market LLC Securities registered pursuant to Section 12 ( g ) of the Act : None Indicate by check mark whether the registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . Yes No Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15 ( d ) of the Act . Yes No Indicate by check mark whether the registrant ( 1 ) has filed all reports required to be filed by Section 13 or 15 ( d ) of the Securities Exchange Act of 1934 during the preceding 12 months ( or for such shorter period that the registrant was required to file such reports ) , and ( 2 ) has been subject to such filing requirements for the past 90 days . Yes No Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S - T ( § 232.405 of this chapter ) during the preceding 12 months ( or for such shorter period that the registrant was required to submit such files ) . Yes No Indicate by check mark whether the registrant is a large accelerated filer , an accelerated filer , a non - accelerated filer , or a smaller reporting company . See the definitions of “ large accelerated filer , " " accelerated filer , ” “ smaller reporting company , ” and “ emerging growth company " in Rule 12b - 2 of the Exchange Act :