This is a component of a course entitled CE 571 Physical Principles in Environmental Engineering which has the following components

Mass balances, equation of motion for small particles, small particle interactions, particle collision/fast coagulation, partitioning, adsorption isotherms, fluid mechanics, diffusion, interphase mass transport and resistance models, elementary/non-elementary reactions, residence time distributions.

This is a first year graduate course in environmental engineering. However, any graduate class that is educating students about mass balances in engineered systems will benefit from performing this exercise. Prior to doing this experiment, the instructor should remind graduate students about the concept of mass balances. Slides are provided as a suggested starting point as one of the documents in this card.

1) a blue or other type of visually distinctive chemical tracer that the students can see its motion clearly

2) a hand held blender to mix the contents in a 8 ounce cup

3) 4 cups, three 64 oz cups, one 8 oz clear cup

4) a chemical bleaching agent (household Clorox)

5) two Mini submersible small aquarium pump

6) Medium size Binder clips

7) Sodium Thiosulfate 

Tracking pollution in natural and engineered systems requires knowledge about the fate and transport of these pollutants. It is important that engineers know how these contaminants/pollutants are transported through these systems and what happens within these systems. This card will provide a concrete example of a pollutant transport and understand the effects of dispersion and a reaction term that causes its disappearance. Note that the instructions here do not necessarily provide detailed values for concentrations or flow rates. It is only a guide. Part of the skillsets being demonstrated is the ability to develop specifics in the experimental plan to observe the effects of dispersion and reaction on pollutant transport.

The activity should be performed in groups. Groups should initially meet outside of class to discuss the experimental plan and setup. They should submit the plan to the instructor for approval as the first deliverable for this activity. They should provide any citations that they used to help them develop the detailed experimental plan. Curiosity and connections should be demonstrated in this first deliverable.

The example here involves the use of a common household oxidant to react with water that contains a food-coloring agent. The goal is to produce flow from an influent container containing a diluted concentration of the oxidant and flow from a second influent container that has a diluted concentration of food coloring into third mixing container. Both of these flows will go into this third container to explore the impact of dilution and reaction between these two influent solutions. Students will adjust the flow rate contributions from each of the two influent containers to change both the hydraulic residence time in the third receiving container as well as the amount of mixing in the receiving container using the handheld mixer.

Students will be asked to explore the influence of three different variables: 1) Hydraulic Residence Time (HRT), 2) dilution of the food-coloring stream, 3) oxidant flow rate, and 4) with and without mixing in the receiving container. They will visually observe the color of the outflow from the receiving cup relative to the inflow.

The first set of experiments will involve no oxidant. The goal here is to understand the influence of dilution, mixing, and residence time on the effluent concentration from the receiving container. In this first set of experiments, one of the influent containers will contain the food coloring solution, the second influent container will only contain water. Students should test with three different HRTs, and a couple of different flow rates from each of the influent containers. Once they have determined a testing plan, each test should be performed with and without mixing in the receiving container.

The second set of experiments will explore both dilution and contributions of a chemical reaction. In these experiments, students will not only assess dilution, mixing, and residence time, but also the impact of the reaction rate since this process is considered a pseudo first order reaction where the reaction rate constant is a function of the oxidant concentration in the second influent container. Students should also test with three different hydraulic residence times, and a couple of different flow rates from each of the influent containers. Once they have determined a testing plan, each test should be performed with and without mixing in the receiving container. To test the impact of the rate constant, the student should conduct this set of experiments with two different concentrations of oxidant in the second influent tank.

Samples should be collected from the effluent of the receiving container. Each sample collected should then be mixed with sodium thiosulfate solution created by the student to neutralize the reaction bleaching process. A paper is provided in the attachment to allow the students to determine the concentration needed to neutralize the reaction process.

Students should develop graphs and or tables to describe the results. Graphs and tables may spell out the effluent food coloring level as a function of influent bleach concentration, effluent food coloring level as a function of HRT, and both of these plots with and without using the mixing device just to name a few examples. They should explain how mixing in the receiving container influenced the effluent food coloring. They should also note the speed of the bleaching reaction when different concentrations of bleach was used.

EM concepts that students should demonstrate include the following:

Resourcefulness: Makes the most of limited resources and thinks creatively about how to solve problems with those resources.

Strategic Thinking: Identifies key milestones, develops strategies to achieve them, and sees the long-term implications of choices.

Curiosity: Cultivates a natural curiosity, is always on the lookout for new opportunities and ideas, and is open to exploring these new ideas and perspectives.

Connections: Integrates information from many sources, thinks outside of the box, and finds new ideas at the intersection of disparate concepts.

Communication: Communicates complex ideas clearly and concisely, ensuring understanding between audiences.