Radioactivity in municipal wastewater and its behavior in biological treatment

Bioleaching and removal of radiocesium in anaerobic digestion of biomass crops: Effect of crop type on partitioning of cesium

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Anaerobic digestion (AD) of radiocesium (RCs)-contaminated crops was investigated.

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Anaerobic degradation of crops releases RCs into aqueous phase of digestate.

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RCs-solubilization efficiency rose with increase in degradability of feedstocks.

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Solid-liquid partition coefficient widely varied depending on the types of adsorbents.

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90 % of RCs removal was achieved at 30 g-zeolite/L or 1 g-Prussian blue beads/L.

Cultivation of biomass crops for energy production is a promising land-use for farmland abandoned owing to radionuclide fallout. However, radionuclides in soil are easily taken up in the crop. To understand phase partitioning of radiocesium Cs (RCs) during anaerobic digestion (AD) of crops, semi-continuous AD experiments were carried out using two types of RCs-contaminated crops. Analysis of fractionated digestate effluent revealed that AD of the crops released RCs into the water phase (up to 82 %), and the efficiency of RCs solubilization depended on crop biodegradability. Adsorption treatment for removal of RCs from the water phase of the digestate indicated a water–zeolite partition coefficient of 0.287 L/g. The efficiency of removal from the water phase was 90 % at an adsorbent dose of 30 g/L.

Behavior of natural radionuclides in wastewater treatment plants

56 samples, including influent, primary effluent, secondary effluent and final effluent wastewater from two Spanish municipal wastewater treatment plants (WWTPs), were analyzed to assess both the occurrence and behavior of natural radioactivity during 12 sampling campaigns carried out over the period 2007-2010. Influent and final effluent wastewaters were sampled by taking into account the hydraulic residence time within the WWTP. A wide range of gross alpha activities (15-129 mBq/L) and gross beta activities (477-983 mBq/L) in liquid samples were obtained. A correlation analysis between radioactivity in liquid samples and the performance characteristics of the WWTPs was performed. The results in liquid samples showed that gross beta activities were not influenced by treatment in the studied WWTPs. However, gross alpha activities behave differently and an increase was detected in the effluent values compared with influent wastewater. This behavior was due to the increase in the total dissolved uranium produced during secondary treatment. The results indicate that the radiological characteristics of the effluents do not present a significant radiological risk and make them suitable for future applications.

Uptake and depuration of 131I by the macroalgae Catenella nipae--potential use as an environmental monitor for radiopharmaceutical waste

A study was initiated to establish the suitability of the macroalgae, Catenella nipae as an environmental surveillance monitor for radiopharmaceutical waste discharges to aquatic environments. A series of experiments were conducted to establish the radioactive iodine ((131)I) concentration factor, and uptake and depuration characteristics of C. nipae. The steady state concentration factor was estimated to be 630+/-80 mL g(-1), with an uptake half-time of 160+/-20 min. Elimination of (131)I was found to follow a two phase model, the first having a rapid elimination rate with a half-time of <1 min, followed by the second phase with a half-time of 3.2 days. Application of the Michaelis-Menton model allowed calculation of an estimate for activity concentration of (131)I in environmental waters from C. nipae sampling devices in the Brisbane River estuary, Australia. The results suggest that C. nipae may be used as an environmental radioactive waste sentinel.

The possible contribution of 129I in the drinking water and food supply to the nodular formation of thyroid tissue

Nodular formation of the thyroid tissue can occur as a result of exposure to radiation. The nodular goiter is a common disease seen in the city of Elazig and its surroundings, in the eastern part of Turkey. A prospective study was conducted in an effort to identify the role of 129I in drinking water supply. Specimens obtained from nodular and normal thyroid tissue during surgery and also water specimens were counted by nuclear spectrometric system. 129I radioactivity in nodular tissue was noted to be higher compared to normal tissue and the difference was statistically significant (p <0.05). There was no statistically significant difference (p >0.05) between 129I radioactivity in the water supply and tissue obtained from the patients who have malignant or benign nodular lesions. These results support that the 129I radioactivity level in the water supply is one of the risk factors of the nodular formation of the thyroid tissue in the eastern part of Turkey.