For example, the amount of radiation being given off, or emitted, by a radioactive material is measured using the conventional unit curie Ci , named for the famed scientist Marie Curie, or the SI unit becquerel Bq. The radiation dose absorbed by a person that is, the amount of energy deposited in human tissue by radiation is measured using the conventional unit rad or the SI unit gray Gy.
The biological risk of exposure to radiation is measured using the conventional unit rem or the SI unit sievert Sv. When the amount of radiation being emitted or given off is discussed, the unit of measure used is the conventional unit Ci or the SI unit Bq. A radioactive atom gives off or emits radioactivity because the nucleus has too many particles, too much energy, or too much mass to be stable.
The nucleus breaks down, or disintegrates, in an attempt to reach a nonradioactive stable state. As the nucleus disintegrates, energy is released in the form of radiation. The Ci or Bq is used to express the number of disintegrations of radioactive atoms in a radioactive material over a period of time. For example, one Ci is equal to 37 billion 37 X 10 9 disintegrations per second.
The Ci is being replaced by the Bq. Since one Bq is equal to one disintegration per second, one Ci is equal to 37 billion 37 X 10 9 Bq. Ci or Bq may be used to refer to the amount of radioactive materials released into the environment. For example, during the Chernobyl power plant accident that took place in the former Soviet Union, an estimated total of 81 million Ci of radioactive cesium a type of radioactive material was released.
When a person is exposed to radiation, energy is deposited in the tissues of the body. The amount of energy deposited per unit of weight of human tissue is called the absorbed dose. Absorbed dose is measured using the conventional rad or the SI Gy. The rad, which stands for radiation absorbed dose, was the conventional unit of measurement, but it has been replaced by the Gy.
One Gy is equal to rad. This consortium reduced This consortium could reduce ppm and ppm nitrate load within 7 and 5 h, respectively. The above data show the aerobic consortium BN7 to perform the fastest nitrate removal by a microbial system to the best of our knowledge. On further analysis, this consortium was found to accumulate both nitrate and phosphate simultaneously 2. Cd, Sr, and Ce inhibited the bacterial growth even at a concentration of 0.
For Cu, Fe, and Zn salts, lower concentrations had minimal impact on the nitrate reduction, and the reduction efficiency in the presence of Pb salts was at par with the control set.
After 4 h of growth, 0. The two-sample one-tailed paired t -test for means was Therefore, the nitrate reduction enhancement in the presence of Cu was significant. However, the extent of this reduction decreased with increasing time due to the toxic effect of the metal on the microbes.
For metals such as Fe, 0. The negative impact of metals on the reduction efficiency was significant for Co and Cr salts. Hence, the difference in accumulation upon varied metal treatment was significant for BN7. A consortium capable of growing and accumulating such metals can be used for the bioremediation of nitrate and metal co-contaminants. The lyophilized form was less efficient relative to the other three storage methods. Thus, using a glycerol stock could be an efficient strategy for the long-term maintenance of the microbial consortium.
At the molecular level, the BN7 harbored members which closely resembled Pseudomonas sp. The low Shannon diversity index value 0. An equitability index value 0. The genus Pseudomonas and Bacillus could be involved in the phosphate accumulation and nitrate reduction. Hence, a microbial consortium was developed which was acclimatized to low-level radioactive waste and could remove nitrate from it within 4 h of incubation at room temperature while generating little dead mass. Phylogenetic tree depicting the position of one of the clones from BN7 constructed using the neighbor joining method.
Nitrate removal by denitrification and assimilation is well documented for bacterial species. Nitrate accumulation by bacterial genus Beggiatoa , Thioploca, and Thiomargarita [ 9 , 10 ] is relatively a rare phenomenon. Moreover, all reports of such accumulation are in a mixed form or from environmental mixed samples [ 9 , 10 ]. Before this study, no pure culture of a nitrate accumulator was reported. Serial dilution and streaking on nitrate agar plates were used to isolate the only pure culture of Bacillus sp.
MCC [ 11 ]. MCC shows terminal endospore formation like Bacillus subtilis and unlike Bacillus cereus which shows central endospore. Paraspore is absent, while the size is 1. It has a generation time of This indicates the possibility that the isolate is a nitrate accumulator.
The nitrate accumulation study following sonication-based lysis of the harvested pellet and measurement of released nitrate from the intracellular cell free supernatant as per the method of Cataldo et al. It is less than the extent of accumulation reported for Beggiatoa but is the first pure isolate of a nitrate accumulator and also the first Bacillus reported to perform such function.
The isolate accumulated The extent of phosphate accumulation was higher than that reported by type strain of Acinetobacter baumanii. The strain showed polysaccharide formation starting from the fourth hour that continued till the eighth hour. This property might provide the benefit of attachment to suitable surfaces to the strain. Active log-phase culture was used to determine whether the isolate could form biofilm according to the method of Martin et al. The performance in terms of nitrate and phosphate removal was checked for repeated recharges with sterile nitrate broth.
The biofilm formation showed saturation by eleventh hour. This optimization was further utilized for immobilization of the isolate in the reactor. Since the isolate grows as biofilm, it could be used for setting up of a biofilm-based bioreactor for continuous waste water treatment in terms of nitrate removal. However, a prerequisite for it was to design the minimal growth condition for the same. This would ensure that enrichment culture components would not be needed to run the process and in turn the influent would not add to the COD load of the effluent.
Dextrose, glycerol, and citric acid were chosen to check the growth of MCC in minimal condition. The isolate showed the best growth in glycerol, and hence, it was further utilized as the carbon source to determine the optimum percentage of carbon source for growth as well as performance. One percentage of glycerol showed the optimum growth as well as nitrate and phosphate removal under minimal condition. Oxygen depletion in anaerobic state resulted in a decrease in activity.
Highest amount of nitrate reduction and subsequent conversion to ammonia was also in aerobic state due to the assimilatory pathway. Substantial accumulation also occurred in aerobic state so that the accumulated nitrate could be used as terminal electron acceptor in oxygen-depleted state. Percent reduction in nitrate and phosphate concentration with time using MCC in 5 L suspended bioreactor. Fixed packed bed configuration has high surface area to volume ratio, thereby increasing the microbial density and improving the conditions necessary for nutrient removal.
Biofilm-based reactors also have the advantage over other types of bioreactors with respect to ease of operation, high-density accumulation of microbe, resistance of the system to environmental stress [ 13 ] and do not require any additional measure to retain biomass in culture [ 14 ].
Rotating biological contractors RBC , trickling filters and biofilm membrane bioreactor are some of the widely used biofilm-based bioreactor. Thus, in order to make the system more cost-effective along with better nutrient sequestration rate, the abilities of the isolate were further exploited.
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In order to exploit these biofilm forming, nitrate, and phosphate sequestration abilities, a reactor packed with suitable matrix with a fixed bed was developed. The isolate could bind equally well to steel and plastic. The total capacity of the bioreactor was 9 L with a working volume of 5 L post-filling up with steel matrix up to sixty percent capacity.
The steel mesh acted as the matrix for the formation of MCC biofilm. The graphical representation shows the initial acclimatization period for proper biofilm development. The initial rise and fall in the performance correlate well with the biofilm character of slough off and growth to achieve stability.
It required about 30 loadings to attain stability. This was done in order to acclimatize the reactor to minimal conditions before exposure to waste water.
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Environmental scanning electron micrograph taken using Zeiss EVO-MA 10 of the biofilm on the inert matrix of a packed bed bioreactor. Post-acclimatization of the biofilm to minimal media, non-radioactive wastewater was charged. Since the isolate is from a consortium acclimatized to radioactive waste water, it is expected to show similar performance with low-level radioactive waste. Kinetics of nitrate removal from waste water in batch mode.
Complete nitrate removal from wastewater took place in 11 h. The longer retention time for waste water treatment as compared to that in minimal media in terms of nitrate removal may be due to the presence of other contaminants to which the biofilm is sensitive. The figure shows the response of nitrate concentration and flow rate on nitrate reduction in the bioreactor.
The packed bed bioreactor system could treat waste water optimally removing Singh et al. For them the isolates positively affected all characteristics except HCN production [ 15 ]. Since the isolate MCC could accumulate both nitrate and phosphate simultaneously and also produce phosphatase, its effect on plant growth promotion was checked in case of mung bean Vigna radiate var Samrat. It was expected since the isolate produces plant growth hormones. The table shows the germination parameters in case of mung bean upon application of MCC Soil application gave better result, and so further experiments were conducted by sowing soaked seeds, followed by soil application of the isolate.
The germination in the presence of antifungal agent Saaf was better upon application of the isolate to soil. Chance in elemental content of seed grown without fertilizer control , with chemical fertilizer and with biofertilizer. The control was taken as reference and that for biofertilizer and chemical fertilizer was calculated accordingly. Pot trial and field trial were carried out. For field trial, randomized block design with four replicates was carried out.
The sowing was done in the north—south orientation. The inoculum for the germination trial was 4. The yield per hectare of land was calculated for the consortium when compared with control without fertilizer and chemical fertilizer application. The yield per hectare for control, MCC application, and chemical fertilizer application was This shows that not only the yield improves as compared to chemical fertilizer but also the elemental content was better as compared to control as well as chemical treatment in MCCtreated seeds.
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Starting at the top of the head, cover the entire body, monitoring carefully the forehead, nose, mouth, neckline, torso, knees, and ankles. Have the person turn around; repeat the survey on the back of the body. Monitor the soles of the feet. All compounds. All insoluble compounds and SrTiO 3. Uranium 2. All compounds, except. Health Phys. Risk of death among children of atomic bomb survivors after 62 years of follow-up: a cohort study.
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