Nutrient Limitation and Microbially Mediated Chemistry:Studies Using Tuff Inoculum Obtained from the Exploratory Studies
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because the greatest impact of concrete on aqueous chemistry, especially before the thermal pulse, could be the production of an alkaline pH (as much as 12 or higher, depending on the formulation), we have included medium formulations that are quite alkaline. EXPERIMENTAL STUDIES Each flow-through bioreactor consists of a medium reservoir, a reaction chamber, and an effluent sampling port. These are contained by sterile methods and connected by sterile tubing. Polyethersulfone filters (0.2 .tm) are located at the exit port of the reaction chambers and retain all cell mass in the bioreactor. Thus, these flow-through bioreactors contrast with the chemostats of Matin [2] in which cell mass is required to escape. Flow to and from the reaction chamber is governed by a peristaltic pump having a set rate of 100 ml/day. In reality, because of progressive accumulation of debris, the nominal rate varies between 50 and 100 ml/day with a volume in the reactor remaining at roughly 400 ml. Two 0 bioreactors are fed with each medium formulation in controlled temperature environments: one at 21 C and the other one at 50TC. Medium is supplied to each reservoir periodically to ensure a continual supply to the reactors. Each reaction chamber contains an inoculum of 100 g crushed tuff. Tubing and filters are changed periodically as the flow rate is impeded. The change ill flow rate varies depending on the formulation. Effluent is sampled periodically for analysis. Topopah Spring tuff was collected from the Exploratory Studies Facility (ESF) at Yucca Mountain, Nevada, by sterile methods and crushed and sieved aseptically to a mesh of 1.68 mm < x
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