Postdoctoral Research Associate
From an environmental engineer’s point of view, uranium contaminations of greatest concerns are into the groundwater from uranium mines and subsequent migration into the drinking water systems. In general, soluble uranium can be immobilized and retained through adsorption, complexation, and reductive precipitation. Among these strategies, promoting microbial reduction has been recognized as more economic, efficient, and sustainable for practical applications. In situ bioremediation of uranium contaminated sites has been widely studied and realized during the past decades. However, microbial uranium removal has very limited application in ex situ drinking water treatment.
The hydrogen (H2)-based Membrane Biofilm Reactor (MBfR) is one of the renowned trademarks of Dr. Rittmann and SCEB. This novel technology allows selected microorganisms to gain energy for growth from utilization of bubbleless H2 and reduction of oxidized contaminants. So far, many bench- and pilot-scale studies have documented that H2-based MBfRs were successfully used to remove a broad spectrum of contaminants, including reductive immobilization of chromate, selenate, arsenate, etc. Under this scenario, why not just give uranium a shot? That was where we started at the end of 2012 – ‘the daydream before Christmas’.
The uranium-MBfR team includes Dr. Ontiveros-Valencia, myself, and several colleagues under the supervision of Dr. Rittmann and Dr. Krajmalnik-Brown. This special team is composed of all volunteers – no one has been paid for the project: we were either working on it for fun or to kill time. The greatest fun is that our first two MBfRs steadily achieved 95% uranium removal from synthetic groundwater while 13 months time was killed. Now we are operating the third reactor fed by a synthetic medium simulating to the greater extent the real condition in uranium contaminated groundwater.
Looking at the larger picture, we expect to further explore the versatility of MBfR in uranium treatment in a few different directions. One is to upgrade the system scale towards the practical demand. It is more challenging, yet more promising, since California Department of Public Health permitted the commercial MBfR process for public use in 2013. In addition, the scientific and technical focus will be shifted from removal of uranium as a contaminant towards recovery of uranium as a renewable resource. Both can build upon the foundation laid by our current achievements and are expected to lead to practical benefits.