Sludge chlorination solutions

Table 8 indicates the common process shortcomings and their respective solutions. Table 9 is a sludge chlorination trouble shooting guide. 

Common Design Shortcomings of Sludge Chlorination and Solutions... 

Chlorinating the aqueous waste sludge suspension (to oxidize the chromium) at temperatures of 20 to 80°C and pH values between 4 and 13. The chlorinated sludge is then acidified with sulfuric acid to a pH of 1.0 to 3.0. The insoluble components are then separated, followed by the separation of the chromium(VI) from the solution using a fixed-bed anion exchanger (at pH values of <3). 

Table 1 can be used as a guide to define hazardous wastes from textile plants. Besides the direct toxicity of substances like chlorinated hydrocarbons, organo-Hg compounds, or concentrated alkaline solutions, other parameters have been defined with regard to problems during biodegradation or accumulation in the sludge from CWWT. A particular situation is found with colored effluents, where limits for spectral absorption have been defined. While the toxicity of textile dyes is comparably low, these limits were derived from the visual aspect of the water released from a textile plant because they look unhealthy. ... 

The treatment of polonium(lV) with nitric acid/potassium permanganate under reflux yields a sludge of manganese dioxide which contains all the polonium originally present the valency state is uncertain. Polonium (IV) in weighable amounts is not oxidized by persulfate, ceric salts or chlorine in alkaline solution (12), although trace scale work indicates that both ceric salts and dichromate do oxidize polonium to polonium(VI) (94). 

Mark G, Schuchmann H-P, Sonntag C VON (1994) Application of Excimer Inco-herent-UV Sources as a New Tool in Photochemistry Photodegradation of Chlorinated Dibenzodioxins in Solution and Adsorbed on Aqueous Pulp Sludge, J. Photochem. Photobiol. A Chem. 79 141—... 

If we were to conduct an experiment in which a ferrous iron solution was dosed with increasing amounts of chlorine, we would obtain a plot of dosed chlorine versus residual chlorine like that in Fig, 7-23. No residual chlorine appears until all the Fe " has been oxidized to Fe . When this has taken place, chlorine residuals appear and the further dosing of chlorine results in the appearance of chlorine equal to the additional dose. Reactions of chlorine with S(—II), Mn II), and N02 all follow this pattern except that the reaction with Mn(Il) only occurs at pH > 8.5. When present at high pH values, chlorine oxidation of sulfide tends to form polysulfides. It is a common complaint of operators of activated sludge plants that encounter partial nitrification that "It is impossible for me to maintain a chlorine residual." Almost without fail this is because of the presence of nitrite, NOa , in the effluent that chlorine will oxidize to nitrate, NOa". 

With brine at or near its full process temperature, the operating pressure is reduced to about a third or a half of an atmosphere. Nearly all the chlorine in the depleted brine is recovered and can be returned to the process. The resulting brine is not suitable for return to a membrane-cell process. There is need for further dechlorination, which is the topic of Section 7.S.9.3. In a mercury-cell process, on the other hand, there actually are advantages to incomplete dechlorination. The presence of free chlorine in the brine returned to the salt dissolver, given suitable materials of construction, helps to keep mercury in solution and prevents its deposition on the brine sludge that will be removed from the process. Typical concentrations are 10-50 ppm CI2. Especially given the inherently lower solubility of chlorine, conditions used to dechlorinate mercury-cell brines therefore can and should be less rigorous. 

The first route used for harvesting the polymer from the bacterial cells involved the use of large quantities of solvent, about 20 times the amount of polymer recovered. This large excess was needed because of the high viscosity of the solution, even when very dilute. The most effective solvents were chlorinated alkanes. Such heavy use of these environmentally problematic solvents was undesirable, and eventually an aqueous system was developed to wash the polymer free from cell debris. The result is production of a white powder, which is subsequently melted, extruded, and pelletized. The aqueous effluent from harvesting is suitable for conventional activated sludge treatment before discharge. 

Tin recovery from sludge [28]. In the electrodeposition of tin from a fluoroborate electrolyte, a sludge containing approximately 50% tin is formed. The tin can be recovered by electrodeposition of a leachate of the sludge obtained by reacting with concentrated hydrochloric acid. After dilution of the leachate to give a Sn(IV) ion concentration of 50 g dm , the tin can be electrodeposited onto steel plate in tank elec-trolysers. The anode reaction in this process is chlorine gas evolution which is absorbed in sodium hydroxide solution to form sodium hypochlorite which is used in another part of the plant. Tin is recovered as a 3 mm thick compact deposit with a current efficiency >90%. 

Zirconium-containing raw is a promising scandium source [19-23]. It was established that Sc is accumulated in carbon-containing residue after chlorination [21] and in manifold after separation of base zirconium sulfate [22-23], The extraction technology used for Sc recovery is based on leach neutralization, sludge separation, sludge leaching by nitric or hydrochloric acid, and scandium extraction by TBP solution in kerosene. The treated solution free of Sc is a valuable source of Zr and Hf. 

Phenylacetaldehyde. An alkaline solution of sodium hypochlorite is prepared by passing 55 g. of chlorine into a mixture of 600 g. of cracked ice and a cold solution of 100 g. of sodium hydroxide (95%) in 150 cc. of water. Water is then added until the total volume of the solution is 11. (The solution is best kept in the dark until used.) To a solution of 14.7 g. (0.1 mole) of cinnamic amide (m.p. 147°) in 125 cc. of methanol is added 130 cc. of the stock solution of sodium hypochlorite. The mixture is warmed on the water bath. A thick sludge of crystals soon forms. The mixture is cooled rapidly and filtered, and the crystals are washed with dilute ethanol and with water. The yield of methyl styrylcarbamate so obtained is 13 g. (70%), m.p. 117-118°. 

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