Exhibit
      10.6





FOURTH
      AMENDMENT TO CREDIT AGREEMENT





FOURTH
      AMENDMENT TO CREDIT AGREEMENT dated as of September 15, 2008 (this “ Fourth
      Amendment ”),
      among
      CALGON CARBON CORPORATION, a corporation organized under the laws of the State
      of Delaware (the “ Company ”),
      CALGON CARBON INVESTMENTS INC., a corporation organized under the laws of the
      State of Delaware (“ Calgon
      Investments ”),
      CHEMVIRON CARBON LIMITED, a private company limited by shares organized under
      the laws of England and Wales with company number 02208285 (“ Chemviron ”),
      WATERLINK (UK) HOLDINGS LIMITED, a private company limited by shares organized
      under the laws of England and Wales with company number 03181974 (“ Waterlink ”),
      SUTCLIFFE SPEAKMAN LIMITED, a private company limited by shares organized under
      the laws of England and Wales with company number 029081113 (“ Sutcliffe ”),
      LAKELAND PROCESSING LIMITED, a private company limited by shares organized
      under
      the laws of England and Wales with company number 02926645 (“ Lakeland ”),
      CHARCOAL CLOTH (INTERNATIONAL) LIMITED, a private company limited by shares
      organized under the laws of England and Wales with company number 02743909
      (“ Charcoal
      International ”),
      BSC
      COLUMBUS, LLC, a limited liability company organized under the laws of the
      State
      of Delaware (“ BSC ”),
      and
      CCC COLUMBUS LLC, a limited liability company organized under the laws of the
      State of Delaware (“ Columbus ”),
      the
      Lenders party hereto, J.P. MORGAN EUROPE LIMITED, as the European Administrative
      Agent, JPMORGAN CHASE BANK, N.A., as the US Administrative Agent, and J.P.
      MORGAN SECURITIES, INC., as Sole Bookrunner and Sole Lead Arranger.




WHEREAS,
      the Loan Parties are party to a Credit Agreement dated as of August 18, 2006,
      as
      amended (the “ Existing
      Credit Agreement ”),
      with
      the Lenders party thereto (the “ Lenders ”)
      and
      the Administrative Agents party thereto (as further amended and modified by
      this
      Fourth Amendment and as the same may be further amended, modified, supplemented
      or restated from time to time, the “ Credit
      Agreement ”);
      and




WHEREAS,
      the Loan Parties, the Administrative Agents and the Lenders have agreed to
      amend
      Section 5.10(a) of the Credit Agreement as more fully set forth
      below.




NOW,
      THEREFORE, in consideration of the foregoing and the agreements contained
      herein, the parties hereby agree as follows:




1.  Capitalized
      Terms .




Capitalized
      terms used herein which are defined in the Credit Agreement have the same
      meanings herein as therein, except to the extent that such meanings are amended
      hereby.




2.  Amendment
      to Credit Agreement.




Subject
      to the terms and conditions set forth herein and in reliance on the
      representations set forth in Section 3 hereof, the Loan Parties, the Lenders
      and
      the Administrative Agents agree that Section 5.10(a) of the Credit Agreement
      be,
      and it hereby is, amended, by deleting Section 5.10(a) of the Credit Agreement
      and replacing it with the following new Section 5.10(a):




“(a)  Each
      Loan
      Party will, and will cause each Subsidiary to, (i) maintain with financially
      sound and reputable carriers having a financial strength rating of at least
      A-
      by A.M. Best Company (a) insurance in such amounts (with no greater risk
      retention) and against such risks (including loss or damage by fire and loss
      in
      transit; theft, burglary, pilferage, larceny, embezzlement, and other criminal
      activities; business interruption; and general liability) and such other
      hazards, as is customarily maintained by companies of established repute engaged
      in the same or similar businesses operating in the same or similar locations
      and
      (b) all insurance required pursuant to the Collateral Documents; (ii) maintain
      such other insurance as may be required by law; and (iii) upon request by an
      Administrative Agent, which request need not be made in writing, furnish the
      Administrative Agents with certificates evidencing the insurance required by
      this paragraph. In the event of Loan Parties’ failure to obtain or maintain the
      insurance required by this paragraph, the Administrative Agents shall have
      the
      right to obtain the required coverage and bill the applicable Borrowers for
      the
      premium payments therefor.”







3.  No
      Default; Representations and Warranties, etc .




Each
      of
      the Loan Parties represents and warrants to the Lenders and the Administrative
      Agents that as of the date hereof and after giving effect to the amendments
      set
      forth herein (a) the representations of the Loan Parties contained in Article
      III of the Credit Agreement are true and correct in all material respects as
      of
      the date hereof as if made on such date (except to extent that such
      representations and warranties expressly relate to an earlier date, in which
      case they shall be true and correct in all material respects as of such date);
      (b) the Loan Parties are in compliance in all material respects with all of
      the
      terms and provisions set forth in the Credit Agreement and the other Loan
      Documents to be observed or performed by them thereunder; (c) no Default shall
      have occurred and be continuing; and (d) the execution, delivery and performance
      by the Loan Parties of this Fourth Amendment (i) have been duly authorized
      by
      all necessary corporate and, if required, shareholder action on the part of
      the
      Loan Parties, (ii) will not violate any applicable material law or regulation
      or
      the organizational documents of any Loan Party, (iii) will not violate or result
      in a default under any material indenture, agreement or other instrument binding
      on any Loan Party or any of its assets and (iv) do not require any consent,
      waiver or approval of or by any Person (other than the Administrative Agents
      and
      the Lenders) which has not been obtained.




4.  Effective
      Date .




Upon
      receipt by the Administrative
      Agents from each party hereto of either (i) a counterpart of this Fourth
      Amendment signed on behalf of such party or (ii) written evidence reasonably
      satisfactory to the Administrative Agents (which may include telecopy
      transmission of a signed signature page to this Fourth Amendment) that such
      party has signed a counterpart of this Fourth Amendment, the amendments set
      forth in this Fourth Amendment shall be deemed to be effective as of the date
      of
      this Fourth Amendment.




5.  Confirmation
      of Guarantee and Collateral Documents .




Each
      Loan
      Guarantor hereby confirms that all Obligations of the Borrowers under the Credit
      Agreement are and shall continue to be entitled to the benefits of the guarantee
      set forth in Article X of the Credit Agreement, and each Loan Party hereby
      confirms that the Obligations under the Credit Agreement, and in respect of
      its
      guarantee under Article X of the Credit Agreement (in the case of the Loan
      Guarantors), are and shall continue to be entitled to the benefits of the
      collateral security provided by the Collateral Documents. Each
      Affiliate or Subsidiary of any Loan Party that is a party to any Other
      Collateral Documents hereby confirms that the Obligations under the Credit
      Agreement are and shall continue to be entitled to the benefits of the
      collateral security provided by the Other Collateral Documents.


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6.  Miscellaneous .




(a)  The
      Loan
      Parties, the Lenders and the Administrative Agents hereby ratify and confirm
      the
      terms and provisions of the Credit Agreement and the other Loan Documents and
      agree that, except to the extent specifically amended hereby, the Credit
      Agreement, the other Loan Documents and all related documents shall remain
      in
      full force and effect. Nothing contained herein shall constitute an amendment
      or
      waiver of any provision of the Loan Documents, except such amendments as are
      expressly set forth herein.




(b)  The
      Loan
      Parties jointly and severally agree to pay all reasonable out-of-pocket costs
      and expenses incurred by JPMorgan Chase Bank, N.A. and its respective Affiliates
      (including the reasonable fees, charges and disbursements of counsel for the
      Agent), in connection with the preparation of this Fourth
      Amendment.




(c)  This
      Fourth Amendment may be executed in any number of counterparts (including by
      way
      of facsimile transmission), each of which, when executed and delivered, shall
      be
      an original, but all counterparts shall together constitute one
      instrument.




(d)  This
      Fourth Amendment shall be governed by the laws of the State of New York and
      shall be binding upon and inure to the benefit of the parties hereto and their
      respective successors and assigns.




[ *Signature
      Pages Follow* ]


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




**BORROWERS:**CALGON
                CARBON CORPORATIONBy:
            /s/
                Leroy M. BallName:
                Leroy M. BallTitle:
                DirectorCALGON
                CARBON INVESTMENTS, INC.By:
            /s/
                Leroy M. BallName:
                Leroy M. BallTitle:
                DirectorBSC
                COLUMBUS, LLCBy:
            /s/
                Leroy M. BallName:
                Leroy M. BallTitle:
                DirectorCCC
                COLUMBUS, LLCBy:
            /s/
                Leroy M. BallName:
                Leroy M. BallTitle:
                Director


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EXECUTED
                AND DELIVERED as a Deed by
              CHEMVIRON
                CARBON LIMITED acting by:Director:
            /s/
                C.H.S.(Kees)MajoorDirector/secretary: 
                C.H.S. (Kees) MajoorEXECUTED
                AND DELIVERED as a Deed by
              WATERLINK
                (UK) HOLDINGS LIMITED acting by:Director:
            /s/
                C.H.S.(Kees)MajoorDirector/secretary: 
                C.H.S. (Kees) MajoorEXECUTED
                AND DELIVERED as a Deed by
              SUTCLIFFE
                SPEAKMAN LIMITED acting by:Director:
            /s/
                C.H.S.(Kees)MajoorDirector/secretary: 
                C.H.S. (Kees) MajoorEXECUTED
                AND DELIVERED as a Deed by
              LAKELAND
                PROCESSING LIMITED acting by:Director:
            /s/
                C.H.S.(Kees)MajoorDirector/secretary:
                C.H.S. (Kees) MajoorEXECUTED
                AND DELIVERED as a Deed by
              CHARCOAL
                CLOTH (INTERNATIONAL)LIMITED
                acting by:Director:
            /s/
                C.H.S.(Kees)MajoorDirector/secretary: 
                C.H.S. (Kees) Majoor




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**ADMINISTRATIVE
                AGENTS AND LENDERS:**JPMORGAN
                CHASE BANK, N.A., as
              US Administrative
                Agent and as a LenderBy:
            /s/
                Donna DiForioName:
                 Donna DiForioTitle:   
                Vice PresidentJ.P.
                MORGAN EUROPE LIMITED, as
              European Administrative
                AgentBy:
            /s/
                Tim JacobName:  
                Tim JacobTitle:
                Senior Vice PresidentCITIZENS
                BANK OF PENNSYLVANIA,as a LenderBy:
            /s/
                Paul RebholzName: 
                Paul RebholzTitle:   
                Vice President


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