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                                                                     EXHIBIT 3.4
                                                                     -----------

                             CERTIFICATE OF MERGER

                                      OF

                            FLUID MANAGEMENT, INC.

                                     INTO

                                ENVIROGEN, INC.

                                    *******


     ENVIROGEN, INC. hereby certifies that:

     (1)  The name and state of incorporation of each of the constituent
corporations of the merger are:

          (a) Fluid Management, Inc., a Wisconsin corporation ("FMI"); and

          (b) Envirogen, Inc., a Delaware corporation ("Envirogen").

     (2)  An Agreement and Plan of Merger dated January 14, 1997 among FMI,
Envirogen and William C. Smith, Douglas W. Jacobson, Gary W. Hawk and Richard W.
Schowengerdt (the "Merger Agreement") has been approved, adopted, certified,
executed and acknowledged by Envirogen and by FMI in accordance with the
provisions of Section 252(c) of the General Corporation Law of the State of
Delaware.

     (3)  The name of the surviving corporation of the merger is Envirogen, Inc.
(the "Surviving Corporation")

     (4)  The Certificate of Incorporation of Envirogen shall be amended so that
the Article Fourth shall be amended and restated in its entirety as follows:

          "FOURTH:  The aggregate number of shares of stock which the
          Corporation shall have authority to issue is 52,000,000 shares,
          divided into two classes, one class consisting of 50,000,000 shares of
          common stock, par value $.01 per share, and the other class consisting
          of 2,000,000 shares of preferred stock, par value $.01 per share.

          The Board of Directors of the Corporation is hereby expressly
          authorized, at any time and from time to time, to divide the preferred
          stock into one or more
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          series, to issue from time to time in whole or in part the stock of
          any such series, and in the resolution or resolutions providing for
          the issue of stock of a series to fix and determine the dividend
          rates, voting rights, designations, preferences, qualifications,
          privileges, limitations, options, conversion rights, redemption
          rights, restrictions and special or relative rights of the series that
          may be desired.

          Except for and subject to the rights expressly granted to the holders
          of preferred stock or any series thereof, pursuant to the authority
          hereby vested in the Board of Directors, and except as may be provided
          by the laws of the State of Delaware, the holders of common stock
          shall have exclusively the rights of stockholders."

The Certificate of Incorporation of Envirogen, as so amended, as in effect
immediately prior to the date hereof shall thereafter continue in full force and
effect as the Certificate of Incorporation of the Surviving Corporation until
altered or amended as provided therein or by law.

     (5)  The executed Merger Agreement is on file at an office of the Surviving
Corporation located at 4100 Quakerbridge Road, Lawrenceville, New Jersey 08648.

     (6)  A copy of the Merger Agreement will be furnished by the Surviving
Corporation, on request and without cost, to any stockholder of FMI or
Envirogen.

     (7)  The authorized capital stock of FMI is 560,000 shares of common stock,
par value $.10 per share.


     IN WITNESS WHEREOF, Envirogen, Inc. has caused this Certificate of Merger
to be signed by Harch S. Gill, its President, on ____________________, 1997.


                                    ENVIROGEN, INC.

                                    By:________________________________
                                      Harch S. Gill
                                      President