Fluoridation feeding system

The simplest feeding system would involve a manually prepared fluoride solution and a flow-paced feed pump that introduces the fluoride solution into a water supply at a fixed rate. The requirements for auxiliary equipment are minimal. This system would include a platform scale, dissolving tank with a manual paddle or electric mixer for stirring, and a solution tank with a solution feed pump, this is all the equipment needed. Depending on the type of pumps (non-positive displacement) used to feed the fluoride solution, a vacuum breaker can be incorporated into the design of the pump feeding system to prevent pulling unmetered quantities of fluoride solution into the water system in the event of a low-pressure situation. 

Equation (9) determines the theoretical feed rate of various fluoride feed solutions to obtain a desired level of fluoride in a water supply system. It is important to note that accurate values for weights or volumes of materials used are necessary for accurate calculations. Additionally, the use of appropriate units (which can be cancelled arithmetically) will produce a calculated result in the desired units and verify the proper insertion of figures into the equation. Case in point, all flow rate (Rl and R2) units must be the same (gal/min) and all concentration levels (Cl and C2) must be the same (ppm or mg/L). Without consistency of units, calculation errors will result. Typical calculations are presented below. 

A small community in the Midwestern US wants to fluoridate their potable water system. The community has a population of approximately 1700 and serves a large rural school with an equivalent school population of 2667. The community has two wells that are located 2 miles apart and are automatically controlled with pressure switches. Each well has a well house that contains bleach, polyphosphate, and soda ash storage and feed systems. Average daily production from both weUs is 0.210 MGD. The water has natural fluoride level of 0.13 mg/L. The optimal fluoride level for this community system is 0.8 mg/L. Determine (a) the feed rate and annual amount of sodium fluoride and (b) the feed rate and annual amount of fluorosiUcic acid solution, (c) Provide the advantages and disadvantage of each chemical feed system. 

A bank of four horizontal stirred beds is used, one above another, of the screw conveyor type. The top one is for calcination in air to remove traces of nitric acid, water and carbonaceous products, the middle two for hydrofluorination and the lower one mainly for partial sintering and den-sification of the product in hydrogen fluoride. Each stirred bed reactor is 20 ft long and 16 in. internal diameter, the lower ones made of inconel and the upper one of stainless-steel. The powder flows from a hopper at the top, via a seal hopper between the calcination and hydrofluorination sections, to another hopper and feeding system at the bottom, as shown in Fig. 5.8. Air and anhydrous hydrogen fluoride pass in counter-current flow to the solids in the appropriate reactors, the efBuent gases being conducted to suitable filters and dust collectors. 

EOS models were derived for polymer blends that gave the first evidence of the severe pressure - dependence of the phase behaviour of such blends [41,42], First, experimental data under pressure were presented for the mixture of poly(ethyl acetate) and polyfvinylidene fluoride) [9], and later for in several other systems [27,43,44,45], However, the direction of the shift in cloud-point temperature with pressure proved to be system-dependent. In addition, the phase behaviour of mixtures containing random copolymers strongly depends on the exact chemical composition of both copolymers. In the production of reactor blends or copolymers a small variation of the reactor feed or process variables, such as temperature and pressure, may lead to demixing of the copolymer solution (or the blend) in the reactor. Fig. 9.7-1 shows some data collected in a laser-light-scattering autoclave on the blend PMMA/SAN [46],... 

In a typical fluorination, the solid feed assembly F is filled with resublimed antimony(III) fluoride. The apparatus is evacuated by a vacuum pump connected through the trap T, which is immersed in liquid nitrogen. After the system is evacuated, dry air is admitted through drying tube DT containing barium oxide. This procedure of evacuating and rinsing with dry air is repeated ten times, and then the system is finally retained in vacuo. The liquid... 

In chronic-duration feeding studies, no adverse effects on the respiratory system were reported in 1-year studies of dogs given oral doses of 31 mg U/kg/day as uranium tetrachloride, 3,790 mg U/kg/day as uranium hexachloride, 8 mg U/kg/day as uranyl fluoride, or 4,407 mg U/kg/day as uranium dioxide (Maynard and Hodge 1949 Maynard et al. 1953). In 2-year studies, the respiratory system was unaffected in dogs and rats given 2 mg U/kg/day as uranyl nitrate hexahydrate and in rats given 12,141 mg U/kg/day as uranium dioxide, 664 mg U/kg/day as uranyl nitrate hexahydrate,... 

Lambert SL, Kim DS (1994) Tank Waste Remediation System High-Level Waste Feed Processability Assessment Report. Westinghouse Hanford Company, C-SP-1143, UC-811 Lexa D (1997) Development of a substituted-fluorapatite waste form for the disposition of radioactive and toxic fluoride salt materials. Argoime National Laboratory Report ANL-NT-52, 21 p Lindberg ML, Ingram B (1964) Rare-earth silicate apatite from the Adirondack Mountains, New York. U S Geol Surv Prof Paper 501-B 64-65... 

In the feed preparation step, uranyl sulfate solution from the reactor core and thorium oxide from the blanket system, freed of D2O and suspended in ordinary water, are fed into the dissolver tank. The di.s.solvent is 13 N nitric acid to which has been added catalytic amounts (0.04 N) of sodium fluoride. When short-cooled thorium is being processed, potassium iodide is added continuously to the dissolver to provide for isotopic dilution of the large amount of fission-produced which is present. The dissolver solution is continuously sparged with air, and the volatilized iodine is removed from the off-gases in a caustic scrubber. 

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