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Advantages <br />Disadvantages <br />Virtually any material can be used for <br />construction. <br />Sampling is labor intensive and time <br />consuming. <br />Device is inexpensive. <br />Aeration, degasing, and turbulence occur <br />during sampling. <br />No external power source is required. <br />Sampling technician is susceptible to <br />exposure to any contaminants in the <br />sample. <br />Mechanism can be constructed in any size <br />and shape. <br />Device does not provide a continuous <br />supply of sample. <br />Device is easy to use and easily cleaned; <br />requires little training for operation and <br />little maintenance. <br />Aeration and turbulence occur with <br />centrifugal pump. <br />Table 5. Grab -Type Mechanism Advantages and Disadvantages <br />B.6.7. Suction -Lift Mechanisms <br />Suction -lift mechanisms consist of peristaltic -type pumps and centrifugal pumps that apply a <br />vacuum which causes the liquid to be drawn upward through a suction line. Their use is <br />generally limited to purging wells of stagnant water and sampling for inorganic analytes. Table <br />6 presents the advantages and disadvantages of a suction -lift mechanism and Table 7 presents <br />the advantages and disadvantages of an inertia pump mechanism. Suction -Lift Mechanisms are <br />not currently used by NS. <br />Advantages <br />Disadvantages <br />Flow rates are easily adjustable <br />Use is limited to situation where the liquid <br />level is less than 25 ft below the surface. <br />Device has no contact with the sample. <br />Drop in pressure of suction -lift mechanism <br />causes degasing of the sample and Toss of <br />volatiles. <br />Device can be used in wells of any <br />diameter. <br />Choice of construction material is limited. <br />High flow rates are obtainable for well <br />purging. <br />Centrifugal pumps need to be primed <br />resulting in possible sample contamination. <br />Only the tubing requires cleaning <br />(peristaltic pumps only). <br />Aeration and turbulence occur with <br />centrifugal pump. <br />Table 6. Suction -Lift Mechanism Advantages and Disadvantages <br />Daub & Associates, Inc. <br />Page B-15 <br />Natural Soda LLC 2015 S A P <br />