Patent ID: 6796741
Filing Date: 2004-09-28
Classification: B09C,F16K,Y10T

Abstract:
A method for in-situ remediation of an aquifer having a treatment zone through which passes water contaminated with at least one chemical contaminant which method comprises:a) delivering to the treatment zone a microbial culture capable of degrading at least one chemical contaminant present in said aquifer using an apparatus comprising: a pipe with a diameter of from about to about 0.6 to about 36 cm having (a) from one to ten exit ports in the peripheral wall, each port being from about 3 mm to about 5 cm in effective diameter, (b) an open upper end adapted to receive fluid to be injected, and (c) a closed bottom end; an axial plug coaxially disposed concentrically inside said pipe and adapted to slide up and down inside the pipe, wherein said plug is tapered at the upper end and having an upper surface adapted to be acted on by the pressure of the fluid fed into said pipe; a stationary seat, disposed inside the upper end of the pipe in abutment against the inner wall of said pipe, adapted to seat said slidable plug when the plug is disposed at a position blocking said port(s); and said seat is concave and adapted to seat the tapered plug at the tapered end, and the plug and seat have surfaces mating to each other with sufficient surface contact to prevent fluid flowing therethrough; a mechanical or pneumatic spring held in place between said slidable plug and said closed bottom end of said pipe, said spring is adapted to continuously urge said plug in an upward direction away from said closed bottom end, wherein said spring is designed to seat the axial plug against the seat thereby closing said exit port(s) when the actual differential pressure Pâ€² is equal or less than a design differential pressure value P, wherein P is a pressure ranging from about 2 to about 5,000 pounds per square inch; Wherein, at an Pâ€² greater than P, excess fluid pressure forcing the axial plug downward, thus separating the mating axial plug and stationary seat surfaces, continuously urging said axial plug downward within the pipe, the sliding plug progressively opening the exit ports in the pipe wall to a non-blocking position, allowing fluid flow from within the pipe to exit through the exit ports in the pipe; optionally at least one groove, located (a) at the tapered section of said plug or (b) in the seat, having an o-ring inserted therein adapted to improve sealing between the plug and the seat; and optionally a spring stop within the spring to prevent overstressing the spring or excessive plug travel; and b) injecting, by at least two conduits, an oxygen-containing gas at a pressure of at least 5 psig above the hydrostatic pressure at injection points with injection frequency and volume at each injection point having the relationship according to the following equation: e[(âˆ’VÃ—FÃ—NÃ—H)/(WÃ—BÃ—Q)]>0.50 Wherein:e=natural exponential V=volume of gas injected at each injection point (ft3) F=frequency of injections (number of injections per day) N=number of gas injection points W=width of the treatment zone perpendicular to groundwater flow path (ft) B=vertical thickness of treatment zone (ft) Q=specific discharge of treatment zone to the treatment zone (ft/day) H=Henry's Constant for contaminant of interest ((mg/L-water)/(mg/L-air)).