Principal Amount: $___________________


 


PROMISSORY NOTE


 


FOR VALUE RECEIVED, ThermoEnergy Corporation,
a Delaware corporation (the “Borrower”), hereby promise to pay to the order of ____________ (the “Holder”)
on demand at any time on or after December 31, 2012 (the “Maturity Date”) the sum of ______________ Dollars ($__________)
(or such lesser amount as may be then outstanding) together with all interest thereon accrued and unpaid.


 


This Note shall bear interest at the rate
of twelve and one-half percent (12.5%) per annum, accruing quarterly on the last day of each December, March, June and September
commencing on December 31, 2011.


 


This Note is one of several substantially
identical promissory notes issued by the Borrower pursuant to that certain Bridge Loan Agreement dated as of December 2, 2011 by
and among the Borrower, the Holder and certain other persons (the “Bridge Loan Agreement”) (which promissory notes
are referred to herein as the “Series Notes”). So long as this Note is outstanding the Holder shall be entitled to
the benefit of, and subject to the provisions of, the Bridge Loan Agreement.


 


Pursuant to the Bridge Loan Agreement, the
Holder shall surrender this Note (or such portion thereof as may be necessary to satisfy the Holder’s purchase obligations)
in payment of the purchase price for shares of a new series of the Borrower’s convertible preferred stock upon satisfaction
of the conditions precedent to the sale and issuance of such shares as set forth in the Bridge Loan Agreement.


 


This Note may not be prepaid, in whole or
in part, without the prior written consent of the Holder. Partial prepayments shall be credited first to accrued and unpaid interest,
and the balance, if any, shall reduce principal.


 


The entire unpaid principal amount of this
Note, together with interest thereon shall, on written notice from the Holder, forthwith become and be due and payable if any one
or more Events of Default shall have occurred (for any reason whatsoever and whether such happening shall be voluntary or involuntary
or be affected or come about by operation of law pursuant to or in compliance with any judgment, decree or order of any court or
any order, rule or regulation of any administrative or governmental body) and be continuing.


 


The occurrence of any one or more of the
following events or conditions shall constitute an “Event of Default” under this Note:


 


(i)          The
Borrower’s failure to make any payment of principal or interest or any other sums within fifteen (15) days of the date when
due under this Note; or


 


(ii)         Any
representation or warranty or other statement made by the Borrower in the Bridge Loan Agreement proves to have been false or misleading
in any material respect when made or furnished; or


 




    	 



    	 



    

 


(iii)        Breach
of or failure in the due observance or performance in any material respect of any covenant, condition or agreement on the part
of the Borrower to be observed or performed pursuant to this Note or the Bridge Loan Agreement, and the failure to cure (if curable)
any such breach or failure within fifteen (15) days after receipt of written notice thereof from the Holder; or


 


(iv)        If
the Borrower shall (a) apply for or consent to the appointment of a receiver, trustee or liquidator of all or a substantial part
of any of its assets; (b) be unable, or admit in writing its inability, to pay its debts as they mature; (c) file or permit the
filing of any petition, case arrangement, reorganization, or the like under any insolvency or bankruptcy law, or the adjudication
of it as a bankrupt, or the making of an assignment for the benefit of creditors or the consenting to any form or arrangement for
the satisfaction, settlement or delay of debt or the appointment of a receiver for all or any part of its properties; or (d) any
action shall be taken by the Borrower for the purpose of effecting any of the foregoing; or


 


(v)         If
an order, judgment or decree shall be entered, or a case shall be commenced, against the Borrower, without its application, approval
or consent by any court of competent jurisdiction, approving a petition or permitting the commencement of a case seeking reorganization
or liquidation of the Borrower or appointing a receiver, trustee or liquidator of the Borrower, or of all or a substantial part
of the assets of the Borrower, and the Borrower, by any act, indicate its approval thereof, consent thereto, or acquiescence therein,
or such order, judgment, decree or case shall continue unstayed and in effect for any period of ninety (90) consecutive days or
an order for relief in connection therewith shall be entered; or


 


(vi)        If
the Borrower shall dissolve or liquidate, or be dissolved or liquidated, or cease to legally exist, or merge or consolidate, or
be merged or consolidated, with or into any other corporation.


 


All payment obligations arising under this
Note are subject to the express condition that at no time shall the Borrower be obligated or required to pay interest at a rate
which could subject the Holder to either civil or criminal liability as a result of being in excess of the maximum rate which the
Borrower is permitted by law to contract or agree to pay. If, by the terms of this Note, the Borrower is at any time required or
obligated to pay interest at a rate in excess of such maximum rate, the applicable rate of interest shall be deemed to be immediately
reduced to such maximum rate, and interest thus payable shall be computed at such maximum rate, and the portion of all prior interest
payments in excess of such maximum rate shall be applied and shall be deemed to have been payments in reduction of principal.


 


No failure or delay on the part of the Holder
in the exercise of any power, right or privilege hereunder shall operate as a waiver thereof, nor shall any single or partial exercise
of any such power, right or privilege preclude other or further exercise thereof or of any other right, power or privilege. All
rights and remedies existing hereunder are cumulative to, and not exclusive of, any rights or remedies otherwise available.


 


All questions concerning the construction,
validity, enforcement and interpretation of this Agreement shall be governed by and construed and enforced in accordance with the
internal laws of the Commonwealth of Massachusetts, without regard to the principles of conflicts of law thereof. Each party agrees
that any action, claim, suit, investigation or proceeding (including, without limitation, an investigation or partial proceeding,
such as a deposition), whether commenced or threatened. (a “Proceeding”) concerning the interpretation, enforcement
and of the transactions contemplated by this Note shall be commenced exclusively in the state or federal courts sitting in, or
having jurisdiction over, Boston, Massachusetts (the “Massachusetts Courts” ). Each party hereto hereby irrevocably
submits to the exclusive jurisdiction of the Massachusetts Courts for the adjudication of any dispute hereunder or in connection
herewith or with any transaction contemplated hereby or discussed herein, and hereby irrevocably waives, and agrees not to assert
in any Proceeding, any claim that it is not personally subject to the jurisdiction of any such Delaware Court, or that such Proceeding
has been commenced in an improper or inconvenient forum. If either party shall commence a Proceeding to enforce any provisions
of this Note, then the prevailing party in such Proceeding shall be reimbursed by the other party for its reasonable attorneys’
fees and other costs and expenses incurred with the investigation, preparation and prosecution of such Proceeding.


 




    	 



    	 



    

 


THE BORROWER HEREBY KNOWINGLY, VOLUNTARILY
AND INTENTIONALLY WAIVES THE RIGHT TO A TRIAL BY JURY IN RESPECT OF ANY CLAIM BASED HEREON, ARISING OUT OF, UNDER OR IN CONNECTION
WITH THIS NOTE. THIS WAIVER CONSTITUTES A MATERIAL INDUCEMENT FOR THE HOLDER TO ACCEPT THIS NOTE.


 


This Note may be amended or supplemented,
or any provision hereof waived, only by the written agreement of the Holder and the Borrower.


 


This Note shall be binding upon the Borrower
and its successors and assigns, and shall inure to the benefit of the Holder and its successors and assigns. The Borrower may not
assign any of its obligations under this Note without the consent of the Holder.


 


If default is made in the payment of this
Note, the Borrower shall pay the Holder hereof reasonable costs of collection, including reasonable attorneys’ fees, regardless
of whether the Holder commenced litigation in order to enforce its rights under this Note.


 


IN WITNESS WHEREOF, the Borrower
has caused this Note to be executed and delivered by its duly authorized President and Chief Executive Officer as of the 2nd day
of December 2011.


 


	 	ThermoEnergy Corporation
	 	 	 
	 	By: 	 
	 	 	Cary G. Bullock
	 	 	President and Chief Executive Officer