1. Technical Field
This invention relates to a fluid pumping apparatus and, more particularly, to a system for pumping an underground floating liquid layer.
2. Discussion
Recent expanded concern for the environment has resulted in various government-imposed environmental regulations. Among such regulations are requirements relating to the monitoring and improvement of groundwater quality. In response to these requirements, water quality analytic capabilities have been improved and water sampling and pumping equipment has been developed. Once it has been determined that groundwater is contaminated, it is often desirable to decontaminate the groundwater by pumping the contaminant from the well. This is feasible where, for example, the contaminant is a floating, or sinking layer lying above, or below, the groundwater. By selectively pumping the contaminant from the groundwater the site may be thereby decontaminated. An added benefit and incentive to pumping groundwater contaminants such as hydrocarbons, is that the pumped hydrocarbons may be recycled for reuse. Much of the previously-developed floating layer equipment has not been effective, however, in permitting the efficient pumping of the floating layer to the exclusion of the groundwater.
For example, in some systems, in order to create adequate depth of the floating layer within a well, it is required that the pumping of groundwater in the vicinity of the well separately to create a "cone of depression". This, thereby, creates a deeper floating layer for pumping. Such systems however present the added expense of the extra pumping apparatus required to remove the groundwater. In addition, relatively large volumes of groundwater must be pumped to create the cone of depression, which creates problems with disposal of the pumped water. Further, this method can contaminate additional soil layers, thereby raising cleanup costs. In other systems, hydrophobic semipermeable membranes are used to pump hydrocarbons to the exclusion of water. However, such membranes are easily clogged and are thus unacceptable in many applications.
An additional problem with prior systems is that such systems frequently pump near the water where they are prone to clogging. This is because of bacterial growth near the floating layer/water interface which tends to clog the system. Also, when prior systems approach the water layer they sometimes and begin to pump a combination of water and the floating layer. In such cases, the water must later be separated from the floating layer before recycling is possible. Thus, it would be desirable to provide a system which will pump a floating layer well above the water interface when the floating layer is thick enough.
In addition, undesirable pumping of water can occur when the buoyancy of the float is effected by the weight of the discharge line carrying the floating layer. In some prior systems, when the discharge line becomes full, the weight of the full discharge line will pull the float down below desired levels, and when the discharge line is empty the float will raise again. Thus, it would be desirable to provide a system which is unaffected by the weight of filled discharge lines.
An additional problem with discharge lines in prior floating layer pumping systems is due to the fact that the float in the floating layer must necessarily move up and down, and the discharge line must contain extra length to permit this motion to be unimpeded. It is known that sometimes this loop of discharge line gets caught or rubs on the sides of the well and thus interferes with the free movement of the float. This may prevent the float from rising to the proper level and may cause the inlet to take in water instead of the floating layer. Thus it would be desirable to have a floating layer pumping apparatus wherein the discharge line does not interfere with free vertical motion of the float.