Measuring and testing – Sampler – sample handling – etc. – Automatic control
Patent
1990-12-05
1993-07-06
Williams, Hezron E.
Measuring and testing
Sampler, sample handling, etc.
Automatic control
7386434, 166250, 166264, 166 68, 166 72, 417 44, G01N 114
Patent
active
052243893
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a national phase application of PCT/DE 90/00260 filed 2 Apr. 1990 and based, in turn, upon German application P 39 11 366.3 filed 7 Apr. 1989.
1. Field of the Invention
This invention relates to a method for taking samples from a groundwater monitoring site, using a pump adapted to be lowered into the well of the groundwater monitoring site, and an apparatus for implementing this method.
2. Background of the Invention
It is particularly useful in areas of water procurement plants where a plurality of groundwater monitoring sites, also referred to as groundwater observation wells, are provided. They serve the function of observing the groundwater level and taking water samples which are subsequently analyzed to provide information on the quality and purity of the groundwater. As a rule, the groundwater monitoring sites comprise a well which is sunk into the water bearing stratum to be observed and includes a piping with a length of filter for the inflow of groundwater. The water samples are conveyed through the piping by means of a pump which has to be lowered in the piping at groundwater levels below the maximum suction head. In view of the conventionally small diameters of the piping of the monitoring sites, the volumetric output of the pumps for the withdrawal of samples is selected as large as possible in order to be able to purge the monitoring site prior to the taking of samples within the shortest possible time, purging involving an exchange of the groundwater that has collected at the monitoring site. To obtain the water sample, the required amount of the sample is diverted from the fluid displaced by the pump through a bypass. However, this results in the disadvantage that the sample may be contaminated as a result of the high delivery. If pumps with a lower volumetric output are used, the purging cycle of the monitoring site which precedes the sampling cycle is too time-consuming.
OBJECT OF THE INVENTION
It is an object of the present invention to provide a method of the type initially referred to which permits withdrawing of groundwater samples as free from contamination as possible with little expenditure of time and material.
Another object of the present invention is to provide an apparatus implementing the method according to the invention.
SUMMARY OF THE INVENTION
To accomplish this object, the method of the present invention provides for operation of the pump initially at high RPM or at a high frequency to obtain a high volumetric output adapted to the rate of inflow of the groundwater monitoring site and, following purging of the groundwater monitoring site, at lower RPM or at a lower frequency for the delivery of a substantially noncontaminated groundwater sample.
In a first step, the method of the invention makes possible for the groundwater monitoring site be purged in a short time in order to provide the prerequisites for the obtainment of an unadulterated water sample. A second step then involves the pumping up of the water sample without involving a change of the equipment installed, at a delivery rate reduced to such an extent as to avoid that the water pumped up is altered, for example, by degassing or the entrainment of deposits.
In one embodiment, the method of the invention involves the further steps of sensing and monitoring, during the purging cycle, a measured value characteristic of the groundwater quality and of initiating the sampling cycle after a predetermined minimum variation of this measured value is determined over a predetermined period of time. In this manner, the purging cycle is reliably prevented from being terminated prematurely or lasting unnecessarily long. According to the invention, the conductivity of the groundwater may serve as the characteristic value measured.
The apparatus includes according to the invention an electrically driven pump means suitable for installation in the piping of the groundwater monitoring site and adapted to have its RPM controlled by a controllable frequency conv
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Christensen Jorgen
Gries Konrad
Jensen Niels D.
Jordan Hans-Joachim
Brock Michael
Dubno Herbert
Grundfos International A/S
Preussag Aktiengesellschaft
Williams Hezron E.
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