THE MILWAUKEE COLUMN: A SIMPLE, AFFORDABLE, AND EFFECTIVE APPARATUS FOR TEACHING AND RESEARCH OF ONE-DIMENSIONAL FLOW AND TRANSPORT IN POROUS MEDIA

One-dimensional soil column apparatus are widely used for teaching and research of flow and transport in porous media at the bench scale. However, the design, construction, and operation of a simple, affordable, and effective apparatus has yet to be firmly established in the scientific literature. This study aims to firmly establish such an apparatus and at a cost of less than 100 United States dollars (USD). The materials for the column were largely purchased from local plumbing, automotive, and pet supply stores. The porous media (coarse sand) was purchased from a local landscaping store. A Mariotte bottle was used to provide steady-state flow through the column. Food coloring (red dye) was used as a visual tracer and chloride was used as a chemical tracer. Both tracers were pulse-injected at the influent and periodically monitored at the effluent. The concentration of the red dye at the effluent was analyzed visually using a simple rank-based colorimetric method to generate a breakthrough curve; chloride was analyzed using an ion-specific electrode (ISE) to verify the flow and transport of the red dye. The column was operated at low, medium, and high flow conditions; a pressure transducer was used at the effluent reservoir to verify steady-state flow. Quantitative analysis of the red dye breakthrough curve, e.g., mean retention time and percent mass recovery, was comparable to chloride when considering the error-propagated uncertainty in the data. Steady-state laminar flow was also confirmed by the pressure transducer data. The apparatus was relatively simple to design, construct, and operate and costs less than 100 USD; not including the ISE and pressure transducer which were used to verify the red dye and Mariotte bottle. Further development of the Milwaukee Column is needed to scale down the current version in volume and mass and to verify its effectiveness with various types of porous media (gravels and silts).