Water-softening systems

Similarly, installed costs of water-softening systems can be correlated in United States dollars (M S = 1000) as follows ... 

Ion exchange is similar to adsorption in that both involve affinity between a species i in solution and functional groups on a substrate surface ion exchange may even be considered as a particular case of adsorption, where coulombic affinity is prevalent in a completely reversible process. This reversibility is promoted by competition between two ions for the same adsorption sites. In common water-softening systems, calcium ions replace sodium ions in the ion exchange resin, according to the following reaction ... 

Automation, both in the laboratory ( ) and in industry (29), became noticeable around 1900. Most, but not all of the early devices were entirely mechanical. Mention may be made of a water-softening system, patented in 1906, that claimed to electrophotometrically analyze the feed water and to automatically adjust the dosages of lime and soda ( ). Nowadays computerization can control a single instrument, a fully-automated laboratory, or an entire factory. 

To avoid high resin chloride content associated with the use of high concentrations of aluminum trichloride, a ttialhylalurninum—water cocatalyst system in a 1.0 0.5 to 1.0 mole ratio has been used in conjunction with an organic chloride for the polymerization of P-pinene (95). Softening points up to 120°C were achieved with 1—3 Gardner unit improvement in color over AlCl produced resins. 

Ton-exchange systems vary from simple one-column units, as used in water softening, to numerous arrays of cation and anion exchangers which are dependent upon the appHcation, quaHty of effluent required, and design parameters. An Hlustration of some of these systems, as used in the production of deionized (demineralized) water, is presented in Figure 7. 

Sodium alumiaate is used ia the treatment of iadustrial and municipal water suppHes and the use of sodium alumiaate is approved ia the clarification of drinking water. The FDA approves the use of sodium alumiaate ia steam generation systems where the steam contacts food. One early use of sodium alumiaate was ia lime softening processes, where it iacreases the precipitation of ions contributing to hardness and improves suspended soHds removal from the treated water (17). Sodium alumiaate reacts with siHca to leave very low residual concentrations of siHca ia hot process water softeners. Sodium alumiaate is often used with other chemicals such as alum, ferric salts, clays, and polyelectrolytes, as a coagulant aid (18,19). 

Home desalinators are possible only for industrialized countries with a central service organization. They will eventually become available on a rental/service contract basis, as is standard practice for water softeners in many communities. Although rental of water softeners is common in the United States, home membrane-system rental is not estabUshed. 

Because of their compact size, packaged vertical boilers can be custom-designed as a complete boiler plant system and simply shipped to the customer on a steel skid or platform. This type of system may comprise a dual boiler arrangement, with a pretreatment unit (water-softening and chemical-feed system), boiler blowdown and condensate return facilities, and also possibly a dual stack containing an economizer. This type of packaged system may reach 85% GCV efficiency. 

Where water softening is provided and there is no reduction in system water TDS, treatments are primarily based on inorganic corrosion inhibitor blends (nitrite, molybdate, etc.). Under these circumstances, there is no benefit in using an expensive organic oxygen scavenger to keep the TDS level low, and a common chemical such as catalyzed sodium sulfite may be used. 

In practice, however, it is often the case that for small LP steam heating boiler systems with a very high percentage of CR, and in those regions of countries where soft water is supplied, no water softener is provided or deemed necessary. Instead there is merely a reliance on internal chemical treatments (or sometimes magnetic devices or other types of gadget ). A good rule of thumb is ... 

AVT Barg BD BDHR BF BOF BOOM BOP BS W BSI BTA Btu/lb BW BWR BX CA CANDUR CDI CFH CFR CHA CHF CHZ Cl CIP CMC CMC CMC COC All-Volatile treatment bar (pressure), gravity blowdown blowdown and heat recovery system blast furnace basic oxygen furnace boiler build, own, operate, maintain balance of plant basic sediment and water British Standards Institution benzotriazole British thermal unit(s) per pound boiler water boiling water reactor base-exchange water softener cellulose acetate Canadian deuterium reactor continuous deionization critical heat flux Code of Federal Regulations cyclohexylamine critical heat-flux carbohydrazide cast iron boiler clean-in-place carboxymethylcellulose (sodium) carboxy-methylcellulose critical miscelle concentration cycle of concentration... 

Condensate drainage devices, 70 148 Condensate polishing ion exchange in, 74 417 in steam-generating systems, 23 227 water softening method for, 26 122-123 Condensate return, in heat pipes, 73 226 Condensate return systems, 70 147-148 Condensate systems, in industrial water treatment, 26 136-137 Condensation, 9 281-282. See also Polycondensation control of VOCs by, 26 679-680 ketone, 74 570... 

Use water softeners in cooling water systems to extend the useful life of the water. 

Pave runoff areas to rednce transfer of solids to waste systems. Use water softeners in cooling-water systems to extend the nsefnl cycling time of the water. 

Figure 15.20. Fixed bed ion exchange vessels and arrangements, (a) Typical design of a water softener, showing bed support, distributor, and effluent collector, (b) Vessel with radial-type distributors and collectors (Illinois Water Treatment Co.), (c) A double-dish underdrain system (Permutit Co.), (d) Some arrangements of vessels for cation and anion exchange.

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