Questions For Thinking And Discussing

1. Go to the proper U.S. environmental legislation and obtain the MCLs for the chemicals listed in Table 9.

2. Complete the following reactions that take place with hydrogen cation-exchange resins:

3. Complete the following reactions that take place for anion exchange reactions (weakly basis and strongly basis):

R3N + H2S04 = R3N + 2HC1 = R3N-H2S04 + Na2C03 = R4NOH + H2Si03 = (R,N)2S04 + 2NaOH =

The symbol R3N represents the complex weakly basic anion-exchanger radical. The symbol R,N represents the complex strongly basic anion-exchanger radical.

4. The company Rhom and Hass has done a cost comparison between several design cases of RO versus ion exchange. Go to www.rohmhaas.com and review the three design cases presented. Then develop criteria and an analysis which shows a point where the two technologies are equivalent in terms of cost. Be specific in identifying the conditions under which the two technologies become nearly identical in cost in achieving the same degree of water treatment.

5. Although we did not discuss this, you should be able to readily identify commercial adsorbents that can compete with activated carbon in water treatment applications. What are they, what are their properties, and how do unit costs compare? In performing the cost analysis, take into consideration the volumes of adsorbents needed to achieve comparable degrees of water treatment. To do this, you should develop a base case scenario.

6. For a period of ten years, a company was regularly dumping about 50 gallons per month of spent TCE from their degreaser operation on the back lot. It is estimated that about 2 % of this solvent, as free phase, reached the groundwater table. Assuming an average groundwater contamination level of 100 ppb, what volume of groundwater may have been impacted by the illegal dumping?

7. Soil samples have been found to contain 500 ppm of TCE and 750 ppm of benzene. Two technologies are being considered to remediate the soil. One is based on vapor extraction combined with carbon adsorption. The other technique is simply to inject steam into the ground, vaporize the solvents and then withdraw them as a vapor extraction technique, discharging the vapors directly to the air. It is estimated that the area and soil depth contaminated are 500 m2 and 10 m, respectively. Address the following: (a) what MCLs will need to be achieved in soil?; (b) instead of steam injection, what other thermal techniques could be applied to treat the soil in-situ?; (c) Of the two solvents, which one is likely to be more effectively removed by carbon adsorption and why?; (d) What possible biotransformations could occur for either of these si vents, and how would you go about removing these daughter compounds?

8. Develop a detailed process scheme for decolorizing recycle water used in a fabric dyeing operation. Assume the operation to be continuous.

9. Develop a detailed list of all parameters that impact on the operation of a carbon filter.

10. The following data were obtained from a pilot adsorption test for refinery wastewater, where the concern is for COD removal. Develop the _breakthrough curves for this process._

Time,

COD Remaining, %

Hours

Column 1

Column 2

Column 3

Column 4

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