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                                                                 Exhibit 10.7(b)
                              AMENDMENT NO. 1 TO
                             EMPLOYMENT AGREEMENT

     THIS AMENDMENT NO. 1 TO EMPLOYMENT AGREEMENT is made as of this 3rd day
of November, 1998 between Envirogen, Inc., a Delaware corporation ("Envirogen"),
and Richard W. Schowengerdt (the "Executive").

     WHEREAS, Envirogen and Executive entered into an Employment Agreement dated
as of April 10, 1997 (the "Agreement").

     WHEREAS, Envirogen and Executive now desire to amend the Agreement as
provided herein.

     NOW, THEREFORE, for good and valuable consideration, the receipt and legal
sufficiency of which are hereby acknowledged, and intending to be legally bound
hereby, the parties hereto agree as follows.

     1.   The letter from Envirogen to Executive dated September 28, 1998
notifying Executive of Envirogen's determination not to renew the Agreement is
hereby rescinded.

     2.   Section 1.B of the Agreement is hereby amended to read in its entirety
as follows:

     "B.  Expiration Date.  The employment of the Executive by Envirogen shall
          ---------------
be for the period commencing on the date hereof and expiring on December 31,
1999 (the "Expiration Date"), unless such employment shall have been sooner
terminated as hereinafter set forth. As used herein, the term "Contract Year"
means the twelve-month period beginning April 10 of each year this Agreement is
in effect."

     3.   The first paragraph of Section 2 of the Agreement is hereby amended to
read in its entirety as follows:

"2.  POSITION AND DUTIES.  The Executive shall serve the Fluid Management
Operations Group of Envirogen and/or Envirogen in an executive capacity or
capacities, and shall report to, be accountable to and subject to the
supervision of, and shall also have such powers, duties and responsibilities as
may from time to time be prescribed by, the Chief Executive Officer of
Envirogen, provided that such powers, duties and responsibilities are not
inconsistent with the bylaws of Envirogen."

     4.   Section 5.D of the Agreement is hereby amended by adding the following
clause at the end of the second sentence thereof:

"or (E) any requirement or written demand by Envirogen to relocate the
Executive's principal place of employment outside of the Milwaukee, Wisconsin
area without the written consent of the Executive."

     5.   Section 6 of the Agreement is hereby amended to read in its entirety
as follows:

"6.  COMPENSATION UPON TERMINATION

     A.   Death or Incapacity.  Notwithstanding any other provision of this
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Agreement, if the Executive's employment shall be terminated by reason of his
death or incapacity, Envirogen shall pay or cause to be paid all sums accrued
and unpaid to the Date of Termination under Sections 3.A, 3.C, 3.D and 3.E
hereof (in respect of accrued and unused vacation).  In the event of the
Executive's death, unexpired stock options held

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at his death shall remain exercisable for such period or periods as are set
forth in the plan or plans under which they were granted. In the event of
termination by reason of incapacity, Envirogen shall continue to pay the
Executive the Base Salary as then in effect through December 31, 1999 and shall
continue in effect through December 31, 1999 all medical and life insurance
which was maintained by Envirogen for the benefit of the Executive on the Date
of Termination.

     B.   Cause or Executive's Termination other than for Good Reason.
          -----------------------------------------------------------
Notwithstanding any other provision of this Agreement, if Envirogen shall
terminate the Executive's employment for Cause, or if the Executive shall
terminate his employment other than for Good Reason, then (i) Envirogen shall
pay to the Executive all sums accrued and unpaid to the Date of Termination
under Sections 3.A, 3.C, 3.D and 3.E hereof (in respect of accrued and unused
vacation); (ii) Envirogen shall permit the Executive to exercise any stock
options vested to the Date of Termination to the extent permitted by the terms
of such options; (iii) the covenants of Executive set forth in Sections 5.16(a)
and (c) of the Agreement and Plan of Merger dated as of January 17, 1997 between
Envirogen, FMI and all of the stockholders of FMI, including Executive (the
"Merger Agreement"), shall apply only until the second anniversary of the Date
of Termination; and (iv) Envirogen shall have no further obligations to the
Executive under this Agreement after the Date of Termination.

     C.   Good Reason or Other Termination.  If Envirogen shall terminate the
          --------------------------------
Executive's employment other than pursuant to Sections 5.A, 5.B or 5.C hereof
(it being agreed that the expiration of Executive's employment term on the
Expiration Date shall not constitute termination by Envirogen), or if the
Executive shall terminate his employment for Good Reason, then (i) Envirogen
shall pay to the Executive all sums accrued and unpaid to the Date of
Termination under Sections 3.A, 3.C, 3.D and 3.E hereof (in respect of accrued
and unused vacation); (ii) Envirogen shall pay severance pay to Executive, bi-
weekly through December 31, 1999, at a rate equal to Executive's Base Salary as
in effect on the Date of Termination; (iii) Envirogen shall continue through
December 31, 1999 all medical and life insurance benefits maintained by it for
the benefit of the Executive on the Date of Termination; (iv) all options held
by the Executive which would vest on or before December 31, 1999 shall become
exercisable on the Date of Termination; and (v) the covenants of Executive set
forth in Section 4.A of this Agreement and in Sections 5.16(a) and (c) of the
Merger Agreement shall terminate on the Date of Termination.  The payments
provided for in this paragraph under the circumstances set forth in this
paragraph shall constitute the sole obligation of Envirogen to the Executive for
any termination of Employment referred to in this paragraph."

     6.   Except as amended hereby, all other provisions of the Agreement shall
remain in full force and effect.  Terms used but not otherwise defined herein
shall have the same meanings as set forth in the Agreement.

     IN WITNESS WHEREOF, the parties hereto have hereunto set their hands as of
the date first above written.

                                       ENVIROGEN, INC.

                                  By:  /s/ Robert S. Hillas
                                       -------------------------------------
                                           Robert S. Hillas
                                       President and Chief Executive Officer

                                       /s/ Richard W. Schowengerdt
                                       -------------------------------------
                                           Richard W. Schowengerdt

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