Exhibit 10.1

AGREEMENT OF AMENDMENT

Dated as of March 30, 2018

Reference is made to that certain Loan and Pledge Agreement dated as of
January 27, 2017 (as amended, supplemented, waived or otherwise modified from
time to time prior to the date hereof, the “Loan and Pledge Agreement”) between
Energy Recovery, Inc., as borrower (the “Borrower”), and Citibank, N.A., as
lender (the “Lender”). Capitalized terms used herein but not defined shall have
the meaning assigned to such terms in the Loan and Pledge Agreement.

The parties hereto agree that, effective as of the Amendment Effective Date, the
definition of the term “Termination Date” set forth in Section 1.1 of the Loan
and Pledge Agreement is hereby amended by replacing the date “March 31, 2018”
set forth therein with the date “March 31, 2020”.

The Borrower agrees to pay to the Lender a closing fee (the “Closing Fee”) in an
amount equal to $16,000.00. The Borrower shall pay the Closing Fee to the Lender
by deposit to the account as the Lender shall designate to the Borrower on or
prior to the Amendment Effective Date. For the avoidance of doubt, the failure
of the Borrower to pay the Closing Fee in accordance with this paragraph shall
constitute an Event of Default for all purposes of the Loan and Pledge Agreement
and the other Loan Documents, and the Lender may rely upon all rights and
remedies in the Loan and Pledge Agreement.

The Borrower agrees to pay to the Lender an annual fee (the “Annual Fee”) in an
amount equal to $16,000.00. The Borrower shall pay the Annual Fee to the Lender
by deposit to the account as the Lender shall designate to the Borrower on or
prior to March 29, 2019. For the avoidance of doubt, the failure of the Borrower
to pay the Annual Fee in accordance with this paragraph shall constitute an
Event of Default for all purposes of the Loan and Pledge Agreement and the other
Loan Documents, and the Lender may rely upon all rights and remedies in the Loan
and Pledge Agreement.

As used herein, the term “Amendment Effective Date” shall mean the first date
upon which (i) the Lender shall have executed and delivered one or more
counterparts of this agreement of amendment (the “Agreement of Amendment”) and
shall have received one or more counterparts of this Agreement of Amendment
executed by the other parties hereto, and (ii) the Lender shall have received
payment of the Closing Fee.

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The Borrower represents and warrants to the Lender that (i) immediately after
giving effect to this Agreement of Amendment and the transactions contemplated
hereby, its representations and warranties set forth in the Loan and Pledge
Agreement and the other Loan Documents are true and correct in all material
respects (unless such representations and warranties relate to an earlier date,
in which case such representations and warranties shall be true and correct as
of such earlier date), (ii) no Default or Event of Default has occurred and is
continuing or will result from the transactions contemplated by this Agreement
of Amendment, and (iii) this Agreement of Amendment has been duly and validly
executed and delivered by it and constitutes its legal, valid and binding
obligation, enforceable against it in accordance with its terms, except as
enforceability may be limited by applicable insolvency, bankruptcy, or other
laws affecting creditor’s rights generally, or general principals of equity,
whether such enforceability is considered in a proceeding in equity or at law.

All references in any Loan Document to the Loan and Pledge Agreement on and
after the Amendment Effective Date, shall be deemed to refer to the Loan and
Pledge Agreement, as amended hereby, and the parties hereto agree that on and
after the Amendment Effective Date, the Loan and Pledge Agreement, as amended
hereby, is in full force and effect.

This Agreement of Amendment may be executed in any number of counterparts, each
of which when so executed shall be deemed to be an original and all of which
when taken together shall constitute one and the same agreement.

THIS AGREEMENT OF AMENDMENT SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE
WITH THE LAWS OF THE STATE OF NEW YORK.

[Signature Pages Follow]

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IN WITNESS WHEREOF, the parties hereto have caused this Agreement of Amendment
to be executed and delivered by their duly authorized officers as of the date
first above written.

ENERGY RECOVERY, INC.,
as Borrower

By:    /s/ Sharon Smith-Lenox    
Name:    Sharon Smith-Lenox
Title:     Acting CFO

CITIBANK, N.A.,
as Lender

By:    /s/ Nanci Dias    
Name:    Nanci Dias
Title:     SVP and Sr. Relationship Manager

[Signature Page to Agreement of Amendment]