FOURTH AMENDMENT TO CREDIT AGREEMENT

This Fourth Amendment to Credit Agreement, is dated the 13^th day of April, 2016 (this "Amendment"), by and among Calgon Carbon Corporation, a Delaware corporation ("Calgon Carbon"), each of the Guarantors (as defined herein), each of the Lenders (as defined herein) and PNC Bank, National Association ("PNC"), as administrative agent for the Lenders (PNC, in such capacity, the "Administrative Agent").

WHEREAS, Calgon Carbon, the other Borrowers from time to time party thereto (together with Calgon Carbon, collectively the "Borrowers" and each a "Borrower"), the Guarantors from time to time party thereto (the "Guarantors"), PNC and various other financial institutions party thereto (PNC and such other financial institutions are each, a "Lender" and collectively, the "Lenders") and the Administrative Agent entered into that certain Credit Agreement, dated as of November 6, 2013, as amended by that certain (i) Letter Agreement, dated as of February 10, 2014, (ii) Second Amendment and Consent to Credit Agreement, dated November 6, 2014, (iii) Third Amendment to Credit Agreement, dated August 7, 2015 and (iv) Consent Letter, dated November 6, 2015 (as amended and as may be further amended, modified, supplemented or restated from time to time, the "Credit Agreement"); and

WHEREAS, the Loan Parties desire to amend certain provisions of the Credit Agreement and the Administrative Agent and the Lenders desire to permit such amendments pursuant to the terms and conditions set forth herein.

NOW, THEREFORE, in consideration of the premises contained herein and other valuable consideration, the receipt and sufficiency of which are hereby acknowledged, and intending to be legally bound hereby, the parties hereto agree as follows:

(ii)      any Loan Party (provided, however, that if such Loan Party is a Borrower, such Borrower shall survive the Permitted Acquisition) or any Subsidiary of any Loan Party may consolidate with, merge into, or acquire assets or capital stock (or any combination of the foregoing transactions) of another Person who is principally engaged in a business permitted hereunder (a "Target") or enter into any agreement or arrangement with a third party that would otherwise commit a Loan Party to enter into any of the foregoing acquisition transactions or a combination of the foregoing acquisition transactions (each, a "Permitted Acquisition"), so long as:

(E)      after giving effect to such Permitted Acquisition: (w) the aggregate consideration paid for all Permitted Acquisitions in any fiscal year does not exceed One Hundred Million and 00/100 Dollars ($100,000,000.00); provided that such amount shall be increased from One Hundred Million and 00/100 Dollars ($100,000,000.00) to Two Hundred Million and 00/100 Dollars ($200,000,000.00) for the fiscal year ending December 31, 2016 if the Loan Parties enter into any Permitted Acquisition on or prior to April 30, 2016, (x) after giving effect to such Permitted Acquisition and the incurrence of any Loans, other Indebtedness or contingent obligations in connection therewith, a pro forma Leverage Ratio not greater than 2.75 to 1.0 for the period equal to the four (4) consecutive fiscal quarters most recently ended for which financial statements are available prior to the date of such Permitted Acquisition, (y) the sum of (1) United States currency of the Parent on a Consolidated Basis held in domestic deposit accounts and (2) Undrawn Availability is at least Fifty Million and 00/100 Dollars ($50,000,000.00), provided that such Undrawn Availability threshold shall be decreased from Fifty Million and 00/100 Dollars ($50,000,000.00) to Forty Million and 00/100 Dollars ($40,000,000.00) for the fiscal year ending December 31, 2016 if the Loan Parties enter into any Permitted Acquisition on or prior to April 30, 2016,  and (z) with respect to each such Permitted Acquisition for which the aggregate consideration exceeds Five Million and 00/100 Dollars ($5,000,000.00), the Loan Parties demonstrate compliance with subsections (w) through and including (y) by delivering at least five (5) Business Days prior to such Permitted Acquisition a Compliance Certificate evidencing such compliance;

(a)

this Amendment, duly executed by the Borrower, the Guarantors, the Lenders and the Administrative Agent;

(b)

a certificate of an Authorized Officer of each Loan Party in form and substance reasonably satisfactory to the Administrative Agent;

(c)

a certificate of an Authorized Officer of each Loan Party as to (i) resolutions authorizing each Loan Party to enter into this Amendment, (ii) incumbency of the officers of each Loan Party and (iii) no amendments to the organizational documents of each Loan Party, all in form and substance satisfactory to the Administrative Agent;

(d)

evidence reasonably satisfactory to the Administrative Agent that (1) on or prior to April 30, 2016 the Loan Parties have either entered into (A) an acquisition agreement (or similar agreement) or (B) any agreement or arrangement with a third party that would otherwise commit a Loan Party to enter into one or more related acquisition transactions at a later date, relating to a Permitted Acquisition which shall be consummated in fiscal year 2016, and (2) the aggregate consideration for such Permitted Acquisition, together with all other Permitted Acquisitions entered into in fiscal year 2016, exceeds One Hundred Million and 00/100 Dollars ($100,000,000.00).

(e)

payment of all fees and expenses owed to the Administrative Agent and its counsel in connection with this Amendment; and

(f)

such other documents as may be reasonably requested by the Administrative Agent.

PNC Bank, National Association,

as Administrative Agent

The Tower at PNC

300 Fifth Ave. – 13^th Floor

Pittsburgh, PA 15222

Ladies and Gentlemen:

I refer to the Credit Agreement, dated as of November 6, 2013, by and among Calgon Carbon Corporation, a Delaware corporation ("Calgon Carbon"), each other Person which joins thereunder as a Borrower (Calgon Carbon and such other Persons are each, a "Borrower" and collectively, the "Borrowers"), the Guarantors (as defined therein) party thereto, PNC Bank, National Association ("PNC Bank") and various other financial institutions from time to time (PNC Bank and such other financial institutions are each a "Lender" and collectively, the "Lenders"), and PNC Bank, as administrative agent for the Lenders (in such capacity, the "Administrative Agent") as amended by that certain (i) Letter Agreement, dated as of February 10, 2014, (ii) Second Amendment and Consent to Credit Agreement, dated November 6, 2014, (iii) Third Amendment to Credit Agreement, dated August 7, 2015; (iv) Consent Letter, dated November 6, 2015 and (v) Fourth Amendment to Credit Agreement, dated April 13, 2016 (as may be further amended, modified, supplemented or restated from time to time, the "Credit Agreement").  Unless otherwise defined herein, terms defined in the Credit Agreement are used herein with the same meanings.

I, the ____________________ [Chief Financial Officer/Treasurer] of the Parent, does hereby certify on behalf of the Parent as of the _________ [quarter/year] ended _______________ ___, 201__ (the "Report Date"), as follows:

______

The annual financial statements of the Parent on a Consolidated Basis, consisting of an audited consolidated balance sheet as of the end of such fiscal year, and related audited consolidated  statements of income, stockholders' equity and cash flows being delivered to the Administrative Agent and the Lenders with this Compliance Certificate (a) are all in reasonable detail and set forth in comparative form the financial statements as of the end of and for the preceding fiscal year, and (b) comply with the reporting requirements for such financial statements as set forth in Section 8.3.2 [Annual Financial Statements] of the Credit Agreement.

______

The quarterly financial statements of the Parent on a Consolidated Basis, consisting of an unaudited consolidated balance sheet as of the end of such fiscal quarter and related unaudited consolidated statements of income and cash flows being delivered to the Administrative Agent and the Lenders with this Compliance Certificate (a) are all in reasonable detail and have been prepared in accordance with GAAP, consistently applied (subject to normal year-end audit adjustments), and set forth in comparative form the respective financial statements for the corresponding date and period in the previous fiscal year, and (b) comply with the reporting requirements for such financial statements as set forth in Section 8.3.1 [Quarterly Financial Statements] of the Credit Agreement.

[NOTE:  If any Event of Default, Potential Default, Material Adverse Change or event which may reasonably be expected to result in a Material Adverse Change has occurred or is continuing, set forth on an attached sheet the nature thereof and the action which the Loan Parties have taken, are taking or propose to take with respect thereto.]

7.    Permitted Acquisition (Section 8.2.6). [If applicable and if the consideration for the Proposed Permitted Acquisition (as hereinafter defined) is greater than Five Million and 00/100 Dollars ($5,000,000.00).].  _______________ [insert name of applicable Loan Party] intends to enter into a Permitted Acquisition with _____________ [enter name of the target company] pursuant to which _______________ [insert name of applicable Loan Party] will ________________ [provide a brief description of the transactions contemplated by such Permitted Acquisition] (the "Proposed Permitted Acquisition").  The aggregate consideration for all Permitted Acquisitions (including the Proposed Permitted Acquisition) in the current fiscal year is ___________ which is not greater than the permitted basket of One Hundred Million and 00/100 Dollars ($100,000,000.00)¹ .  After giving effect to the Proposed Permitted Acquisition and the incurrence of any Loans, other Indebtedness or contingent obligations in connection therewith, the pro form Leverage Ratio for the period equal to the four (4) consecutive fiscal quarters most recently ended for which financial statements are available prior to the date of the Proposed Permitted Acquisition is ____ to 1.0, which is not greater than the permitted ratio of 2.75 to 1.0.  The sum of (1) United States currency of the Parent on a Consolidated Basis held in domestic deposit accounts and (2) Undrawn Availability is ______________ which is not less than the required Fifty Million and 00/100 Dollars ($50,000,000.00)².

8.    Calculations.  The calculations supporting Sections 5 through and including 7 hereof, as applicable, are set forth in the spreadsheet attached hereto as Exhibit B.

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