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Advantages <br />Disadvantages <br />Pump is constructed of inert materials; <br />most pumps are designed specifically to <br />sample for low levels of contaminants. <br />Deep sampling requires large volumes of gas <br />and longer cycles, thus increasing operating <br />time and expense and reducing portability. <br />Driving gas does not contact the sample, <br />thus minimizing sample aeration and gas <br />stripping. <br />Check valves in some models are subject to <br />failure in water and high solids content. <br />Pump is portable, though accessory <br />equipment may be cumbersome. <br />Most available models are expensive. <br />Relatively high pumping rate allows well <br />evacuation and collection of large sample <br />volumes. <br />Minimum rate of sample discharge of some <br />models may be higher than ideal for sampling <br />of volatile compounds <br />Sample delivery rate can be controlled on <br />some models. <br />Most models are capable of pumping lifts <br />in excess of 200 ft. <br />Pump diameters are variable, depending <br />on the application. <br />Pump is easily disassembled for cleaning. <br />Table 9. Gas -Operated Bladder Pumps Advantages and Disadvantages <br />6.6.9. Submersible Pumps <br />Submersible pumps are generally not used for sample collection and are not currently used by <br />NS. They are useful in purging Targe -volume wells of stagnant water; however, severe aeration <br />and turbulence of the sample occur because of their method of sample delivery. Table 10 lists <br />the advantages and disadvantages of using a submersible pump. <br />Advantages <br />Disadvantages <br />High pumping rates are <br />possible for well purging. <br />Sampling technician has little control of flow rates; not <br />possible to adjust from a high rate for purging to a low rate <br />for sampling. <br />Pump can be used at depths <br />of more than 200 ft. <br />Severe aeration and degassing of sample occurs, thus <br />volatilizing organics and other sensitive compounds. <br />Pump has limited portability and requires a power source <br />for operation. <br />Daub & Associates, Inc. <br />Table 10. Submersible Pump Advantages and Disadvantages <br />Page B-17 Natural Soda LLC 2015 S A P <br />