Exhibit 10.9(i)

                       FIRST AMENDMENT TO CREDIT AGREEMENT


                           Dated as of March 15, 2004



                  This FIRST AMENDMENT TO CREDIT AGREEMENT (this "Agreement") is
among IONICS, INCORPORATED, a Massachusetts corporation (the "Borrower"), UBS
AG, STAMFORD BRANCH, in its capacity as administrative agent for the Lenders (in
such capacity, the "Administrative Agent") and as collateral agent for the
Secured Parties (in such capacity, the "Collateral Agent") and the Lenders
signatory hereto, and is made pursuant to that certain Credit Agreement dated as
February 13, 2004 (as amended, modified, restated or supplemented from time to
time, the "Credit Agreement"), among IONICS, INCORPORATED, a Massachusetts
corporation, the Subsidiary Guarantors, the Lenders, the Administrative Agent,
the Collateral Agent, UBS SECURITIES LLC, as lead arranger (in such capacity,
the "Arranger"), sole bookmanager and documentation agent (in such capacity, the
"Documentation Agent"), FLEET SECURITIES, INC. and BANK OF AMERICA, N.A., as
syndication agents (in such capacity, the "Syndication Agents"), WACHOVIA BANK,
N.A. and GENERAL ELECTRIC CAPITAL CORPORATION, as co-documentation agents (in
such capacity, the "Co-Documentation Agents"), UBS LOAN FINANCE LLC, as
swingline lender (in such capacity, "Swingline Lender"), and HSBC BANK USA, as
issuing bank (in such capacity, the "Issuing Bank").

                  Terms used but not otherwise defined in this Agreement shall
have the meaning ascribed to such terms in the Credit Agreement.

                             PRELIMINARY STATEMENTS:

1. The Borrower has requested that the Required Lenders agree to extend the time
period within which certain of the items set forth on Schedule 5.16 of the
Credit Agreement are required to be delivered pursuant to Section 5.16 to the
Credit Agreement; and

2. Subject to the terms and conditions set forth below, the Required Lenders,
the Administrative Agent, and the Collateral Agent are willing to so amend the
Credit Agreement.

                  NOW, THEREFORE, in consideration of the premises and for other
good and valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the parties hereto agree as follows:

1. Amendments to Credit Agreement. Upon the terms and subject to the conditions
set forth in this Agreement and in reliance on the representations and
warranties of the Loan Parties set forth in this Agreement, the Credit Agreement
is hereby amended such that Schedule 5.16 to the Credit Agreement shall be
deleted in its entirety and replaced with the replacement Schedule 5.16 attached
hereto as Exhibit A.
<PAGE>

2. Conditions to Effectiveness. The effectiveness of this Agreement is
conditioned upon satisfaction of the following conditions precedent on or before
March 19, 2004; provided that once such conditions precedent have been satisfied
this Agreement shall be deemed to be effective as of March 15, 2004 (such date,
the "Amendment Effective Date"):

     a. the  Administrative  Agent  shall  have  received  counterparts  of this
Agreement  signed by the  Borrower,  the  Subsidiary  Guarantors,  the  Required
Lenders, the Administrative Agent and the Collateral Agent;

     b. each of the  representations  and warranties in Section 3 below shall be
true and correct in all material respects as of the Amendment Effective Date;

     c. after giving effect to the  amendment set forth in Section 1 hereof,  no
Default or Event of Default  shall have  occurred  and be  continuing  under the
Credit Agreement or any other Loan Document;

     d. the  Administrative  Agent shall have  received  payment in  immediately
available funds of all expenses incurred by the Administrative Agent (including,
without  limitation,  legal fees) for which invoices have been presented,  on or
before the Amendment Effective Date; and

     e. the Administrative Agent shall have received  satisfactory evidence that
the  execution,  delivery  and  performance  of this  Agreement  have  been duly
approved by all necessary corporate action of each Loan Party.

3. Representations and Warranties. The Borrower and each of the other Loan
Parties represents and warrants to the Administrative Agent, the Collateral
Agent and each Lender as of the date hereof as follows:

     a.  Authority.  Each of the Loan Parties has the requisite  corporate power
and  authority  to  execute  and  deliver  this  Agreement  and to  perform  its
obligations  hereunder and under the Credit Agreement (as modified hereby).  The
execution, delivery and performance by the Borrower and each other Loan Party of
this Agreement,  the Credit  Agreement (as modified hereby) and the transactions
contemplated  hereby  and  thereby  have been  duly  approved  by all  necessary
corporate  action of such person and no other corporate  proceedings on the part
of each such person are necessary to  consummate  such  transactions  (except as
expressly contemplated hereby and thereby).

     b. Due Execution; Enforceability. This Agreement has been duly executed and
delivered  by the Borrower and the other Loan  Parties.  Each of this  Agreement
and, after giving effect to this Agreement,  the Credit  Agreement and the other
Loan  Documents is the legal,  valid and binding  obligation  of each Loan Party
hereto and thereto,  enforceable  against such Loan Party in accordance with its
terms,  and is in full force and  effect.  Neither  the  execution,  delivery or
performance of this Agreement or of the Credit  Agreement (as modified  hereby),
nor the performance of the  transactions  contemplated  hereby or thereby,  will
adversely affect the validity,  perfection or priority of the Collateral Agent's
Lien, for the benefit of the Secured Parties, on any of the Collateral.

     c.  Representations and Warranties.  After giving effect to this Agreement,
the  representations  and warranties  contained in the Credit  Agreement and the
other Loan Documents (other than any such  representations  and warranties that,
by their terms, are  specifically  made as of a date other than the date hereof)
are true and  correct on and as of the date  hereof as though  made on and as of
the date hereof.
<PAGE>

     d. No Conflicts.  Neither the execution and delivery of this Agreement, nor
the consummation of the transactions contemplated hereby, nor performance of and
compliance  with the terms and  provisions  hereof by the  Borrower  or any Loan
Party will,  at the time of such  performance,  (a) violate or conflict with any
provision of its articles or  certificate  of  incorporation  or bylaws or other
organizational or governing documents of such Person, (b) violate, contravene or
materially  conflict with any  Requirement  of Law or any other law,  regulation
(including,  without  limitation,  Regulation U or Regulation  X), order,  writ,
judgment,  injunction,  decree  or  permit  applicable  to it,  except  for  any
violation,  contravention  or conflict which could not reasonably be expected to
have a Material  Adverse  Effect,  (c)  violate,  contravene  or  conflict  with
contractual  provisions of, or cause an event of default  under,  any indenture,
loan  agreement,  mortgage,  deed of  trust,  contract  or  other  agreement  or
instrument to which it is a party or by which it may be bound,  or (d) result in
or require the creation of any Lien (other than those contemplated in or created
in connection with the Loan Documents) upon or with respect to its properties.

     e. No Default. After giving effect to the amendments set forth in Section 1
hereof,  no Default or Event of Default has occurred and is continuing under the
Credit Agreement or any other Loan Document.

4. Reference to and Effect on Credit Agreement.

     a. Upon and after the  effectiveness  of this Agreement,  each reference in
the Credit Agreement to "this Agreement", "hereunder", "hereof" or words of like
import referring to the Credit  Agreement,  and each reference in the other Loan
Documents to "the Credit  Agreement",  "thereunder",  "thereof" or words of like
import referring to the Credit  Agreement,  shall mean and be a reference to the
Credit Agreement as modified hereby.

     b. Except as  specifically  modified  above,  the Credit  Agreement and the
other Loan  Documents are and shall  continue to be in full force and effect and
are  hereby  in all  respects  ratified  and  confirmed.  Without  limiting  the
generality of the  foregoing,  the Security  Documents and all of the Collateral
described therein do and shall continue to secure the payment of all Obligations
under and as defined therein, in each case as modified hereby.

     c. The execution,  delivery and  effectiveness of this Agreement shall not,
except as expressly provided herein,  operate as a waiver of any right, power or
remedy of any Secured  Party  under any of the Loan  Documents,  nor,  except as
expressly provided herein,  constitute a waiver or amendment of any provision of
any of the Loan Documents.

5. Counterparts. This Agreement may be executed in any number of counterparts
and by different parties hereto in separate counterparts, each of which when so
executed and delivered shall be deemed to be an original and all of which taken
together shall constitute one and the same agreement. Delivery of an executed
counterpart of a signature page to this Agreement by facsimile shall be
effective as delivery of a manually executed counterpart of this Agreement.

6. Severability. Any provision of this Agreement that is prohibited or
unenforceable in any jurisdiction shall, as to such jurisdiction, be ineffective
to the extent of such prohibition or unenforceability without invalidating the
remaining provisions hereof, and any such prohibition or unenforceability in any
jurisdiction shall not invalidate or render unenforceable such provision in any
other jurisdiction.
<PAGE>

7. Governing Law. This Agreement shall be governed by, and construed in
accordance with, the laws of the State of New York.

                            [Signature Pages Follow]

<PAGE>





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


                              IONICS, INCORPORATED



                              By: /s/Daniel M. Kuzmak
                                  -----------------------
                                  Name:  Daniel M. Kuzmak
                                  Title: Chief Financial Officer

                              SUBSIDIARY GUARANTORS:

                              AQUA DESIGN, INC.
                              FIDELITY PUREWATER, INC.
                              FIDELITY WATER SYSTEMS, INC.
                              IONICS KOREA, INC.
                              IONICS LIFE SCIENCES, INC.
                              IONICS SECURITIES CORPORATION
                              IONICS ULTRAPURE WATER CORPORATION
                              RESOURCES CONSERVATION CO. INTERNATIONAL
                              SEPARATION TECHNOLOGY, INC.
                              SIEVERS INSTRUMENTS, INC.
                              ECOLOCHEM, INC.
                              ECOLOCHEM HOLDINGS, INC.
                              ECOLOCHEM INTERNATIONAL, INC.
                              ECOLOCHEM JV HOLDINGS, INC.


                              By: /s/Stephen Korn
                                  -------------------
                                  Name:  Stephen Korn
                                  Title: Secretary/Clerk


                               ECOLOCHEM SERVICES - MEXICO, LLC
                               MOSON HOLDINGS, LLC

                               By: Ionics, Incorporated as Managing Member


                               By: /s/Stephen Korn
                                   -------------------
                                   Name:  Stephen Korn
                                   Title: Secretary/Clerk



<PAGE>


                               UBS AG, STAMFORD BRANCH, as Administrative Agent
                               and Collateral Agent



                               By: /s/Barbara Ezell-McMichael
                                   ------------------------------
                                   Name:  Barbara Ezell-McMichael
                                   Title: Associate Director
                                          Banking Product Services, US


                               By: /s/Janice L. Randolph
                                   -------------------------
                                   Name:  Janice L. Randolph
                                   Title: Associate Director
                                          Banking Products Services, US


<PAGE>


                                LENDERS:



                                UBS LOAN FINANCE LLC, as a Lender



                                By: /s/Barbara Ezell-McMichael
                                   ------------------------------
                                   Name:  Barbara Ezell-McMichael
                                   Title: Associate Director
                                          Banking Product Services, US


                                By: /s/Janice L. Randolph
                                   -------------------------
                                   Name:  Janice L. Randolph
                                   Title: Associate Director
                                          Banking Products Services, US




<PAGE>


                                 BANK OF AMERICA, N.A., as a Lender



                                 By: /s/Jennifer L. Gerdes
                                     -------------------------
                                     Name:  Jennifer L. Gerdes
                                     Title: Vice President




<PAGE>


                                  WACHOVIA BANK, N.A., as a Lender



                                  By: /s/Dean Gorton
                                      ------------------
                                      Name:  Dean Gorton
                                      Title: Vice President



<PAGE>


                                   SOVEREIGN BANK, as a Lender



                                   By: /s/Daniel M. Grondin
                                       ------------------------
                                       Name:  Daniel M. Grondin
                                       Title: Senior Vice President



<PAGE>


                                    GENERAL ELECTRIC CAPITAL CORPORATION, as a
                                    Lender



                                    By: /s/Eric Herr
                                        ----------------
                                        Name:  Eric Herr
                                        Title: Duly Authorized Signatory



<PAGE>


                                    HSBC BANK USA, as a Lender



                                    By: /s/Patrick J. Doulin
                                        ------------------------
                                        Name:  Patrick J. Doulin
                                        Title: Senior Vice President



<PAGE>


                                     FLEET NATIONAL BANK, as a Lender



                                     By: /s/Luanne T. Smith
                                         ----------------------
                                         Name:  Luanne T. Smith
                                         Title: Vice President