Sampling Equipment

Drums should be opened using a spark-proof brass bung wrench. Drums with bulged heads are particularly dangerous. The bulge indicates that the contents are under extreme pressure. To sample a bulged drum, a remotely operated drum opening device should be used, enabling the sampler to open the drum from a safe distance. Such operations should be carried out only by fully trained technicians in full personnel protective gear.

Liquid waste in tanks must be sampled in a manner that represents the contents of the tank. The EPA specifies that the colawassa sampler is used for such sampling. The colawassa is a long tube with a stopper at the bottom that opens or closes using the handle at the top. This device enables the sampler to retrieve representative material at any depth within the tank. The colawassa has many shortcomings, including the need for completely cleaning it and removal of all residues between each sampling. This is difficult, and it also creates another batch of hazardous waste to be managed.

A glass colawassa, which eliminates sample contamination by metals and stopper materials, is available through technical and scientific supply houses. In most situations, ordinary glass tubing can be used to obtain a representative sample, and can be discarded after use.

Bomb samplers that are lowered into a liquid waste container, then opened at the selected depth, are also useful in special situations.

Long-handled dippers can be used to sample ponds, impoundments, large open tanks, or sumps: however these devices cannot cope with stratified materials. Makeshift devices using tape or other porous or organic materials introduce the likelihood of sample contamination.

Dry solid samples may be obtained using a thief or trier, or an augur or dipper. Sampling of process units, liquid discharges, and atmospheric emissions all require specialized equipment training.

The EPA has published several guidance documents detailing hazardous waste, soil, surface water and ground-water and waste stream sampling (EPA 1985a, 1985b; De Vera et al. 1980; Evans and Schweitzer 1984).

Procedures used or materials contacting the sample should not cause gain or loss of pollutants. Sampling equipment and sample containers must be fabricated from inert materials and must be thoroughly cleaned before use. Equipment that comes into contact with samples to be analyzed for organic compounds should be fabricated of (in order of preference):

• Glass (amber glass for organics; clear glass for metals, oil, cyanide, BOD, TOC, COD, sludges, soil, and solids, and others)

• Teflon (Teflon lid liners should be inserted in caps to prevent contamination normally supplied with bottles)

• Stainless steel

• High-grade carbon steel

• Polypropylene

• Polyethylene (for common ions, such as fluoride, chloride, and sulfate)

Classic commercial analytic schedules require a sample of more than 1,500 ml. Commercial field samplers collect samples of 500 to 1,000 ml. If such volumes are insufficient, multibottle samples can be collected. Special containers may be designed to prolong sample duration.

0 0

Post a comment