Groundwater equipment for professionals

Passive samplers & bailers

Equilibrator diffusion sampler Sample VOC's without bailing or purging Diffusion sampling is a proven and accepted technique for determining concentrations of Volatile Organic Compounds (VOCs) in groundwater monitoring wells. A semi-permeable sample chamber is filled with deionized or distilled water, then lowered into the well screen and left in place. VOCs in the groundwater diffuse into the sampler until the concentration gradient equilibrates between the water in the formation and the sampler. The sampler is retrieved and the contents emptied into VOA vials for laboratory analysis.		PR28
Waterra supply a comprehensive range of accessories including weights and filling kit, to make sampling with the Equilibrator simple and straightforward.

Equilibrator samplers are widely in use at sites where volatile organic compounds require on-going periodic monitoring. The elimination of well purging, and ease of use, result in substantially lower sampling costs. This simple technology combined with excellent correlation of analytical results to other methods has propelled diffusion sampling into acceptance and use by industry, consultants, and regulators alike. How it works Diffusion sampling is based on the underlying principle that water in the screened interval is in constant dynamic equilibrium with the aquifer so that there is constant flow from the aquifer through the screen. In addition to natural groundwater flow, molecular diffusion causes soluable compounds to remain evenly dispersed and in equilibrium from the aquifer through the screened portion of the well. The same dynamics hold true within the water-producing fracture zones of rock wells. Comparative Data Numerous installations exist from which correlative data compare the results of diffusion sampling with other techniques such as bailing and low-flow sampling. One such comparison, conducted by Bunnell-Lammons Engineering, Inc. (BLE) and shown graphically below, is based on a 28-well comparative study. For analytical data and case histories see the USGS Guidance Document "User's Guide for Polyethylene-Based Passive Diffusion Bag Samplers...", Report 01-4061.

Equilibrator field method

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