Pseudomonas cepacia is known as a rock phosphate (RP) solubilizer in bioreactors and in soils. The objectives of this study were to determine the production rates of gluconic acid (GA, pKd 3.41) and 2‐ketogluconic acid (KGA, pKd 2.66) by the bacteria in the presence of clay minerals which prevail in soils, and the resulting rate and extent of orthophosphate (OP) release into the suspension solutions. Suspensions (1:40) of RP, RP + Ca–kaolinite (CaKL), RP + Ca–montmorillonite (CaMT), and RP + K–montmorillonite (KMT) were inoculated with P. cepacia E37. The electrical conductivity (EC) and pH, and the OP, glucose, GA, KGA, Ca, and Al concentrations were determined in the suspension solutions as functions of time. In a given clay system, the rate‐limiting step in RP dissolution was the rate of GA release by the E37. This acid lowered the pH of all the clay suspensions to 2.7 to 2.8, which resulted in a pronounced increase in the OP concentration in solution, Cp. As glucose was depleted from the system, the KGA concentration increased with a concomitant lowering in pH to ≈2.5. At this pH, a sharp decline in Cp occurred, which was attributed to Al release by the alumosilicates, and formation of a new, stable Al–P or Fe–P solid phase. The E37 glucose oxidation efficiency (GOE) was considerably inhibited in CaKL as compared with CaMT or KMT. The GA and KGA adsorption by the clays or their Ca complexation did not play a role in the E37‐mediated RP solubilization.

No abstract

DISCLAIMERNUREGKR-5229 is not a substitute for NRC regulations and compliance is not required. The approaches andor methods described in this NUREGKR are provided for information only. Publication of this report does not necessarily constitute NRC approval or agreement with the information contained herein.

Because of its apparent structural integrity, cement has been widely used in the United States as a binder to solidify Class B and C low-level radioactive waste (LLW). However, the resulting cement preparations are susceptible to failure due to the actions of stress and environment.This paper contains information on three groups of microorganisms that are associated with the degradation of cement materials:sulfur-oxidizing bacteria (Thiobacillus), nitrifying bacteria (Nitrosomonas and Nitrobacter), and heterotrophic bacteria, which produce organic acids.Preliminary work using laboratory-and vendor-manufactured, simulated waste forms exposed to thiobacilli has shown that microbiologically influenced degradation has the potential to severely compromise the structural integrity of ion-exchange resin and evaporator-bottoms waste that is solidified with cement.In addition, it was found that a significant percentage of calcium was leached from the treated waste forms. Also, the surface pH of the treated specimens was decreased to below 2. These conditions apparently contributed to the physical deterioration of simulated waste forms after 30 to 60 days of exposure.

Corrosion of massive concrete structures is a costly and environmentally dangerous problem. Many low level waste disposal vaults, both above and below ground, are constructed of concrete. When the integrity of these structures is compromised, potential for soil and water contamination is significantly increased. There are literally thousands of massive concrete structures within the U.S. infrastructure that are in a serious state of disrepair due to corrosion. One potential contributing agent to the destruction of concrete structures is microbially-influenced degradation (MID). MID occurs when microorganisms in the environment produce mineral or organic acids that dissolve or disintegrate the cement matrix. Three groups of bacteria are known to create conditions that are conducive to destroying concrete integrity. They are sulfur oxidizing bacteria, nitrifying bacteria, and heterotrophic bacteria.Research is being conducted at the Idaho National Engineering Laboratory to assess the extent of naturally occurring microbially influenced degradation (MID) and its contribution to the deterioration of massive concrete structures. The preliminary steps to understanding the extent of MID, require assessing the microbial communities present on degrading concrete surfaces. Ultimately such information can be used to develop guidelines for preventive or corrective treatments for MID and aid in formulation of new materials to resist corrosion. An environmental study was conducted to determine the presence and activity of potential MID bacteria on degrading concrete surfaces of massive concrete structures. Scanning electron microscopy detected bacteria on the surfaces of concrete structures such as bridges and dams, where corrosion was evident. Enumeration of sulfur oxidizing thiobacilli and nitrogen oxidizingNitrosomonas sp.andNitrobacter sp.from surface samples was conducted. Bacterial community composition varied between sampling locations, and generally the presence of either sulfur oxidizers or nitrifiers dominated, although instances of both types of bacteria occurring together were encountered. No clear correlation between bacterial numbers and degree of degradation was exhibited.