Water nitrate removal

In the case of clarified feeds and low current densities, membrane lifetime can be as long as seven or 10 years for brackish water desalination or drinking water nitrate removal, respectively. However, if the feed solution is fouling or scaling or the ED separation plant has not been well designed or is not properly conducted, membrane lifetime is no longer than a year. 

Pronusing areas for MBR applications include food-processing waste-water, nitrate removal in drinking water and landfill leachates (Yang et al., 2006). MBR systems can be also combined with post-treatment operations... 

Water Treatment. The two primary appHcations in water treatment are softening and deionization. Other important but less frequendy used appHcations include dealkalization, softening of produced water, desilicizing, and nitrate removal. 

Caustic soda by reaction of sodium amalgam and water Nitration of organic compounds with aqueous nitric acid Formation of soaps by action of aqueous alkahes on fats or fatty acids Sulfur removal from petroleum fractious by aqueous ethauolamiues Treating of petroleum products with sulfuric acid... 

R/0 unit Reverse Osmosis Unit for water purification in small aquariums and miniature yard-ponds, utilizes a membrane under pressure to filter dissolved solids and pollutants from the water. Two different filter membranes can be used the CTA (cellulose triacetate) membrane is less expensive, but only works with chlorinated water and removes 50-70% of nitrates, and the TFC membrane, which is more expensive, removes 95% of nitrates, but is ruined by chlorine. R/0 wastes water and a system that cleans 100 gallons a day will cost ft-om 400 to 600 with membrane replacement adding to the cost. A unit that handles 140 gallons a day will cost above 700,00. 

A slight excess of a 10% sodium hydroxide solution was added to a solution of 23 grams of silver nitrate in 300 cc of water. The precipitated silver oxide was washed free of silver ion with distilled water. To a suspension of the silver oxide in 200 cc of water, a solution of 25 grams of (3-hydroxyphenyl)ethyl dimethylammonium iodide in 300 cc of water was added. The precipitate of silver iodide was removed by filtration and the filtrate concentrated to a volume of about 100 cc In vacuo. The remainder of the water was removed by lyophilization. (3-hydroxyphenyl)ethyl dimethylammonium hydroxide was obtained as a hygroscopic, amorphous solid,... 

Procedure. Precipitation is therefore made by adding a very dilute solution, say 0.05M, of silver nitrate slowly and with constant stirring to a dilute ammoniacal solution of the iodide until precipitation is complete, and then adding excess of nitric acid (1 per cent by volume). The precipitate is collected in the usual manner, washed with 1 per cent nitric acid, and finally with a little water to remove nitric acid. Peptisation tends to occur with excess of water. Other details of the determination will be found in Section 11.57. 

R. Grinstead K.C. Jonos, Nitrate Removal from Waste Water by Ion Exchange , Rpt 17010 FSJ, US Environmental Protection Agency (1971) 11) D.H. Rosenblatt, G-E. 

NitRem [Nitrate Removal] A process for removing nitrate from water supplies by elec-trodyalysis through a selective membrane. Developed in the 1980s by OTTO Oeko-Tech Company, Germany. 

Prediction of the nitrate removal rate under anoxic conditions in a sewer can be done by a simple empirical approach. The following equation including transformations in the water phase and the biofilm of a sewer pipe may be applied under substrate nonlimited conditions ... 

Vw,max = nitrate removal rate at 20°C in the water phase under substrate nonlimited conditions (gN03-N m-3 h-1)... 

Nitrate Removal for Small Public Water Systems 600375030 Nitrogen in the Subsurface Environment... 

Nitrate in drinking water above the standard poses an immediate threat to children under three months of age. In some infants, excessive levels of nitrate have been known to react with the hemoglobin in the blood to produce an anemic condition commonly known as blue baby. If the drinking water contains an excessive amount of nitrate, it should not be given to infants under three months of age and should not to be used to prepare formula. The standard allows for 10.0 mg of nitrate (as N) per liter of water. Nitrate can be removed from water by ion exchange, RO, or distillation [48]. 

Desilva, F.J. Nitrate removal by ion exchange. Water Qual. Prod. 2003, 8 (4), 9-30. 

The order and timing of the addition of reagents in the KA-process is varied but in a typical procedure three reagents, namely, acetic anhydride, a solution of ammonium nitrate in nitric acid, and solid hexamine dinitrate, are added slowly, in small portions and in parallel, into the reaction vessel which is preheated to 60-80 °C. On completion the reaction mixture is often cooled to 50-60 °C and the RDX filtered and sometimes washed with acetic acid. This process produces a product which melts over a 2 °C range but the RDX still contains up to 10 % HMX as a by-product. Dilution of the reaction mixture with water before removing the RDX produces a very impure product containing numerous unstable linear nitramine-nitrates. Based on the assumption that one mole of hexamine dinitrate produces two mole of RDX the KA-process commonly yields 75-80 % of RDX. 

Practical considerations and implementation. Most investigations involve the use of distilled/deionised water with KNO3 as the nitrate ion source thereby avoiding any potential impact of water hardness and dissolved salts on the catalytic removal of nitrates. It has been pointed out that in the presence of anions such as S04 and bicarbonates, which may be present in tap-water at concentrations of above 90 ppm, reduced nitrate reduction rates are to be expected as a result of competitive anion adsorption. Pintar and co-workers have indicated that nitrate removal rates are reduced when using drinking water as opposed to distilled water. Chloride ion is known to reduce the rate of nitrate removal while the choice of cation as counter ion influences the rate in the order, < Na < Ca < Mg + <... 

The basic material used by this technology, vegetable oil, is inexpensive (D14820J, p. 2). Column data suggest that 1 ounce of oil would remove 10 parts per million (ppm) nitrate from approximately 195 gal of oxygenated water. Based on this efficiency of nitrate removal, a dollar s worth of oil (about 0.4 gal) should remove 10 ppm nitrate from about 10,600 gal of water. Theoretically, under anaerobic conditions, 1 ounce of oil should remove 10 ppm nitrate from about 650 gal of water (D179424, p. 82). 

TNT is the abbreviation of the aromatic nitrated aromatic compound 2,4,6-trinitrotoluene. It is a pale-yellow crystalline solid that was first synthesized in 1863 by the German chemist Joseph Wilbrand (1811—1894), but it was not immediately used as an explosive. TNT is made by nitrating toluene using nitric acid, sulfuric acid, and oleum (a mixture of sulfuric acid and S03). Nitration of toluene occurs in stages, with the nitro units added sequentially in a stepwise process as the reaction proceeds. The last nitro unit is accomplished by using oleum (SO, dissolved in sulfuric acid). After nitration, unused acids are recycled, and the product is washed with sodium sulfite and water to remove impurities. 

Heat Requirement of the Process. Heat is required for vaporization in the extractive distillation column, and for the reconcentration of magnesium nitrate solution. Overall thermal effects caused by the magnesium nitrate cancel out, and the heat demand for the complete process depends on the amount of water being removed, the reflux ratio employed, and the terminal (condenser) conditions in distillation and evaporation. The composition and temperature of the mixed feed to the still influence the relative heat demands of the evaporation and distillation sections. For the concentration of 60 wt% HNO3 to 99.5 wt% HNO3 using a still reflux ratio of 3 1, a still pressure of 760 mm Hg, and an evaporator pressure of 100 mm Hg, the theoretical overall heat requirement is 1,034 kcal/kg HNO3. 

One additional step (added late in the desorption scheme) consisted of rinsing the column with 0.1 N HC1 in water to remove lead compounds. This step was necessary because lead nitrate at 25 ppb would precipitate, and lead was removed by the resin acting as a filter. This step may not be necessary in real field concentration-isolation of trace organic compounds. 

The filtrate from the iodide on evaporation in a desiccator yields a colourless crystalline solid (1 3 grams). Extraction with small quantities of hot water gradually removes any remaining iodide, a white powder remaining as residue. This is an anhydride of methyl hydroocytellurium oxide (telluracetic acid), CH3.TeO.OH, which cannot be obtained pure. In aqueous solution it is neutral to litmus, gives no precipitate with silver nitrate, and is reduced by potassium bisulphite to dimethyl ditelluride. It has a persistent odour, and gradually blackens above 230° C. 

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