Apparatus and method for phosphate-accelerated bioremediation

• US 5,753,109 A
• Filed: 12/28/1995
• Issued: 05/19/1998
• Est. Priority Date: 01/25/1994
• Status: Expired due to Term

• Current Assignee: United States Of America As Represented By The Department Of Energy
• Original Assignee: United States Department of Energy
• Inventors: Hazen, Terry C., Lombard, Kenneth H., Borthen, James W., Pfiffner, Susan M., Looney, Brian B., Phelps, Tommy J.
• Primary Examiner(s): Wyse, Thomas G.
• Application Number:
  US08/579,910
• Time in Patent Office: 873 Days
• Field of Search: 210/610, 210/612, 210/614, 210/747, 210/170, 210/149, 210/251, 166/68, 166/246, 405/128, 405/129
• US Class Current: 210/149
• CPC Class Codes: B09C 1/10 microbiologically, biologically or by using enzymes
• CPC Class Codes: B09C 2101/00 In situ

Abstract

An apparatus and method for supplying a vapor-phase nutrient to contaminated soil for in situ bioremediation. The apparatus includes a housing adapted for containing a quantity of the liquid nutrient, a conduit in communication with the interior of the housing, means for causing a gas to flow through the conduit, and means for contacting the gas with the liquid so that a portion thereof evaporates and mixes with the gas. The mixture of gas and nutrient vapor is delivered to the contaminated site via a system of injection and extraction wells configured to the site and provides for the use of a passive delivery system. The mixture has a partial pressure of vaporized nutrient that is no greater than the vapor pressure of the liquid. If desired, the nutrient and/or the gas may be heated to increase the vapor pressure and the nutrient concentration of the mixture. Preferably, the nutrient is a volatile, substantially nontoxic and nonflammable organic phosphate that is a liquid at environmental temperatures, such as triethyl phosphate or tributyl phosphate.

Claims

1. An apparatus for supplying a nutrient to a subsurface region, said region containing microorganisms that are capable of degrading contaminants present in said region, said nutrient having a vapor form and a liquid form with a vapor pressure, said apparatus comprising:

a housing having an interior, said housing adapted for containing a quantity of said liquid nutrient;

a temperature regulator for controlling a temperature of said liquid nutrient;

a conduit in fluid communication with said interior of said housing;

means for causing a gas to flow through said conduit;

means for contacting said gas with said liquid nutrient so that a portion of said liquid nutrient vaporizes and mixes with said gas, a mixture of said gas and said vaporized nutrient having a partial pressure of nutrient vapor no greater than said vapor pressure; and

means for delivering said mixture into said subsurface region to promote growth and reproduction of said microorganisms.

2. The apparatus as recited in claim 1, wherein said vapor pressure is dependent on said temperature so that said vapor pressure is changed thereby.

3. The apparatus as recited in claim 1, wherein said gas-contacting means further comprises a pump, said pump injecting said liquid nutrient into said flowing gas so that said injected nutrient vaporizes and mixes with said gas.

4. The apparatus as recited in claim 1, wherein said housing has an inlet and an outlet, and wherein said gas-contacting means further comprises a gas-liquid contactor contained in said housing, said contactor receiving said gas at said inlet, said contactor releasing a mixture of said gas and said vaporized nutrient at said outlet.

5. The apparatus as recited in claim 1, wherein said gas has a flow rate, wherein said liquid nutrient has a molecular weight and a density, and wherein said gas-contacting means further comprises means for adding a quantity of said liquid nutrient into said gas at a flow rate no greater than approximately Q=4.1×

10^-5 (w/d)β

₁ Q_gas, where Q_gas is said flow rate of said gas in L/min, β

₁ is said vapor pressure in atm, w is said molecular weight in g/mole and d is said density in g/cm³.

6. The apparatus as recited in claim 1, wherein said housing has an inlet and an outlet, and wherein said causing means further comprises:

a first pump for pumping said gas into said inlet; and

a second pump for pumping said gas from said outlet.

7. The apparatus as recited in claim 1, wherein said delivering means further comprises:

at least one injection well adjacent said region;

at least one extraction well adjacent an opposing side of said region; and

means for causing said mixture to flow from said injection well towards said extraction well so that said mixture is dispersed through said region.

8. An apparatus for supplying a nutrient to a subsurface region, said region containing microorganisms that are capable of degrading contaminants present in said region, said nutrient having a vapor form and a liquid form with a vapor pressure, said apparatus comprising:

a housing having an interior, said housing adapted for containing a quantity of said liquid nutrient;

a conduit in communication with a head space defined by said interior of a housing;

a barometric pump for causing a gas to flow through said conduit so that a vaporized portion of said liquid nutrient mixes with said gas, a mixture of said gas and said vaporized nutrient having a partial pressure of nutrient vapor no greater than said vapor pressure; and

means for delivering said mixture into said subsurface region to promote growth and reproduction of said microorganisms.

9. The apparatus according to claim 8 wherein said barometric pump further comprises a housing, said housing defining an upper conduit and a lower conduit, said first conduit in communication with the well and said second conduit being open to an atmosphere pressure;

a chamber defined within said housing, said chamber further defining a valve seat; and

a ball disposed in said valve seat, said ball being sized such that a pressure differential between said well and said atmosphere lifts said ball from said valve seat.

10. An apparatus for supplying a nutrient to a subsurface region, said nutrient having a vapor form and a liquid form, said apparatus comprising:

a valve in communication with a lower inlet and an upper outlet, said inlet in communication with an above ground atmospheric pressure and said outlet in communication with a subsurface region of a well, said valve further defining a ball seated within said valve, said ball opening said valve when said above ground atmospheric pressure exceeds by a cracking value the pressure of said subsurface region;

a chamber defining a reservoir for a liquid nutrient and a headspace for the accumulation of a vapor phase of said nutrient, said chamber further defining an inlet and an outlet, said inlet and said outlet in communication with said headspace, said chamber inlet in further communication with said valve outlet and said chamber outlet in further communication with said subsurface region;

wherein, when said ball of said valve is in an open position, air flows through said valve and enters said headspace through said chamber inlet, said air mixing with said nutrient vapor phase within said headspace to form a gaseous mixture, said mixture leaving said head space through said chamber outlet and entering said subsurface region.