Abstract: Pumping apparatus for recovering a first liquid, such as a pollutant, floating on a second liquid, such as ground water. A pump immersed in the second liquid, or ground water, operates to produce a cone of depression and discharge the second liquid into a pressure vessel. A variable volume chamber inside the pressure vessel contracts and displaces any contents through an outlet conduit to a product discharge point. When the pump turns off, the variable volume chamber expands and draws product into the chamber to be driven from the chamber during successive pumping operations. Over time periodic pumping operations cause the variable volume chamber to recover the first liquid and move it to a discharge point.

Abstract: Apparatus for measuring the total mass of the fluid in a container, having pressure responsive, density determination means adapted to determine the localized density of the fluid as a function of pressure differential between two closely spaced, vertically separated measuring points in the fluid, means enabling the density determination means to determine the localized density values throughout the depth of the fluid, storage means for storing predetermined horizontal cross-sectional area values of the container as a function of depth, and computational circuitry responsive to the density determination means and the storage means for providing a total mass signal corresponding to the integral, over the depth of the fluid, of the product of localized density values times the corresponding area values.