The distribution of Th on the molecular fraction, the fine particle (colloid) fraction and the coarse particle fraction in three different groundwaters after equilibration with the corresponding sediments taken at the same places, and the sorption ratios R s of Th in these three groundwater/sediment systems are determined as function of the following parameters : time of equilibration, way of equilibration (smoothly or by shaking), volume to mass ratio V/m, way of separation of groundwater and sediment, variation of pH, and initial concentration of Th.A broad spectrum of R s values is obtained, depending on the chemical properties of the system and on the parameters mentioned. Of particular interest is the strong dependence on V/ m and on the way of separation (filtration, ultrafiltration); often a linear or nearly linear dependence of R s on V/m is observed. The variations are explained by the chemical properties of the systems, especially those of macrocomponents in the system (e.g. silicic acid) and by the presence of colloids carrying Th. The problems of choosing suitable standard conditions for batch experiments and of selecting appropriate R s values for assessment or modeling of the migration behaviour of Th are emphasized.

The different behaviour of Th and U in aqueous solutions is discussed. Hydrolysis, colloid formation and retention of Th are sludied by paper chromatography and by filtration and ultrafiltration as function of pH and time. The behaviour of Th in ihree natural groundwaters is investigated as function of time by filtration and ultrafiltration and by means of a scanning electron microscope with microprobe. Autoradiography is also applied. -Evidence for the formation of colloids of Th is presented. In groundwaters silicic acid serves as carrier. After filtration and ultrafiltration new fine (colloid) and coarse particles are formed carrying Th. The percentage of Th in the coarse particle fractions increases with the concentration of Th and with the salinity of the groundwater.

No abstract

Hydrogen sulfide, H 2 S, causes major odor problems at wastewater treatment facilities. A primary method of removing hydrogen sulfide from air is to use a wet scrubber. In a wet scrubber the air stream comes in contact with a liquid scrubbing solution. In order for hydrogen sulfide to enter into solution, the pH of the scrubbing solution must be raised. Sodium hydroxide (NaOH) also known as caustic soda, is typically used in odor control systems to raise the pH of the scrubbing liquid. Neglecting carbonate effects leads to incorrectly low dosages for the amount of sodium hydroxide needed to raise the pH.The design of a system to add sodium hydroxide requires the correct calculation of dosage to determine feed pump requirements and storage requirements. This is also important in determining systems operating costs. For these reasons the correct calculation of sodium hydroxide dosage is important. This purpose of this paper is to:• Define chemistry terms that are used in this paper.• Show why the pH must be raised in order for hydrogen sulfide to go into solution.• Show why carbon dioxide in the atmosphere effects carbonate level in solution. • Show how the carbonate level effects sodium hydroxide dosage.• Give sample calculations for sodium hydroxide dosage and cost estimation.