Award Date

8-2010

Degree Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering

Department

Civil and Environmental Engineering

First Committee Member

Jacimaria R. Batista, Chair

Second Committee Member

Sajjad Ahmad

Third Committee Member

David E. James

Fourth Committee Member

Richard F. Unz

Graduate Faculty Representative

Charalambos Papelis

Number of Pages

255

Abstract

Ion-exchange (IX) is possibly the most feasible technology for perchlorate removal and perchlorate-selective and non-selective IX resins are commercially available for this purpose. The use of both resins has shortcomings. Selective resins are incinerated after one time use, and non-selective resins produce a regenerant waste stream that contains high concentration of perchlorate. A process involving directly contacting of spent IX resin containing perchlorate with perchlorate-reducing bacteria (PRB) to bioregenerate the resin has been developed and proven recently. In this process PRB biodegrade perchlorate ions which are attached to the functional groups of the resin.

Although its feasibility has been proven, there are two issues related to resin bioregeneration technology that deserve attention and were addressed in this research. The first issue relates to the investigation of the mechanisms responsible for resin bioregeneration. It was envisioned that the bioregeneration process involves four steps. First, resin-attached perchlorate (RAP) ions are desorbed from their original functional groups by chloride ion. Second, perchlorate ions are diffused through the pores of the resin. It was expected that this diffusion is affected by both resin bead size and structure. Third, perchlorate ions are transferred through the liquid film surrounding the resin to the bulk liquid. Forth, perchlorate ions are utilized by the PRB present in the bulk liquid. The results of the bioregeneration experiments suggested that chloride, the waste product of perchlorate biodegradation, is more likely the desorbing agent of RAP, and increasing the concentration of chloride enhances the bioregeneration process. For commercially available resins, both film and pore diffusion were found to affect the rate of mass transfer. In addition, macroporous resins were found to be more effective than gel-type resins in the bioregeneration process. Bioregeneration rates were faster for resins of smaller bead diameter. The outcome of this study implies that in resin bioregeneration, the use of macroporous resin with relatively smaller bead size in presence of chloride would be preferred. Chloride concentration, however, should be kept below the inhibitory level for PRB microbial activities.

The second issue of bioregeneration process is the possibility of multi-cycle bioregeneration of IX resin. The results of the experiments revealed that capacity loss, which is the main concern in multi-cycle bioregeneration process, stabilized after a few cycles of bioregeneration indicating that the number of loading and bioregeneration cycles that can be performed is likely greater than the five cycles tested. The results further indicated that as bioregeneration progresses, clogging of the resin pores results in the decrease in mass transfer flux from the inner portion of the resin to the bulk microbial culture contributing to stronger mass transfer limitation in the bioregeneration process. Perchlorate buildup, resulting from un-degraded perchlorate accumulation in the inner portion of the resin, after each bioregeneration cycle is a major drawback that limits the number of bioregeneration cycles that can be performed.

Keywords

Bioregeneration; Gums and resins – Recycling; Ion exchange; Perchlorate; Regeneration; Water — Purification — Ion exchange process; Water — Purification — Perchlorate removal; Water treatment

Disciplines

Civil Engineering | Environmental Engineering | Water Resource Management

Language

English


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