Potable water system

Silicates. For many years, siUcates have been used to inhibit aqueous corrosion, particularly in potable water systems. Probably due to the complexity of siUcate chemistry, their mechanism of inhibition has not yet been firmly estabUshed. They are nonoxidizing and require oxygen to inhibit corrosion, so they are not passivators in the classical sense. Yet they do not form visible precipitates on the metal surface. They appear to inhibit by an adsorption mechanism. It is thought that siUca and iron corrosion products interact. However, recent work indicates that this interaction may not be necessary. SiUcates are slow-acting inhibitors in some cases, 2 or 3 weeks may be required to estabUsh protection fully. It is beheved that the polysiUcate ions or coUoidal siUca are the active species and these are formed slowly from monosilicic acid, which is the predorninant species in water at the pH levels maintained in cooling systems. 

Potable Water Systems Process Water General Service... 

Blake, Richard T. Water Treatment for HVAC and Potable Water Systems. McGraw-Hill, Inc., USA, 1980. 

A study of the trace organics profile of raw and potable water systems [145]... 

HI Dept Health. 1999b. Rules relating to potable water systems. Hawaii Department of Health, Environmental Health, Safe Drinking Water, http //www.hawaii.gov/health... 

Sterilizing the potable water system and connected equipment. 

Cini et al. [25] reviewed those aspects of activated carbon which are often forgotten when applied to potable water systems. Among the adsorbate/adsor-bent interactions they mentioned dispersion forces, polarization forces and electrostatic forces but did not provide examples of their relative importance. 

Water Quality Control Division, Design Criteria for Potable Water Systems, Report, Colorado Department of Public Health, State of Colorado, 1997. 

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. 

Chlorine has been used as a disinfectant in potable water systems for over 100 yr. Free chlorine and combined chlorine (chloramines) are the two forms of chlorine widely used for the disinfection. Free chlorine is added as chlorine gas or sodium/cal-cium hypochlorite to the water. The reaction of chlorine in water produces hypochlor-ous acid and hydrochloric acid ... 

Monochloramine is a more effective oxidizing agent than di- and trichtoramines. In potable water systems, monochloramine is often the predominant species present. Combined chiorine is iess aggressive, more persistent, and reacts more stowty with oxi-dizable materiats and bacteria (3). Some utilities prefer chloramines over free chlorine for disinfection because it has a lower potential to form THMs and has tess taste and odor probtems. Atso, it travets further in the typical distribution system. 

In dilute, potable water systems the acidity (Q) is usually defined as... 

A flow diversion valve or automatic shut-off valve shall be installed which will permit flow into the potable water system only when at least the minimum ultraviolet dosage is applied. When power is not being supplied to the unit, the valve should be in a closed (fail-safe) position which prevents the flow of water into the potable water system. 

Corroclean F. [Stewart Hall] Corrosion and deposit inhibitor for potable water systems. 

A unique type of corrosion referred to as copper by-product release, cuprosolvency, or blue water occurs in potable water systems constructed of copper tubing, and has been reported worldwide [92-95]. The problem is most often attributed to EPS induced metal concentration cells. The condition is characterized by the release of copper as fine particles in plumbing systems distributing soft water in the neutral or neutral-alkaline pH range. Water may contain between 5 to 300 ppm copper (as Cu +) as finely suspended precipitates. A bacterial biofilm and associated acidic EPS bind copper ions at the metal surface and alter the porosity of the oxide film [96]. Geesey and coworkers [97] characterized binding of an acidic polysaccharide to thin copper films and su ested a cupric ion interaction with carboxyl groups on EPS. These interactions promoted ionization of metallic... 

A uniform slime film formation on the piping of potable water systems and on the heat-transfer surfaces of low-temperature heat exchangers is inconsequential unless it obstructs the flow leading to a health hazard by growth of the organisms or localized corrosion (41). 

Negative health effects can result from corrosion of lead, corrosion of copper alloys and solder in water supply systems, and corrosion of copper plumbing in potable water systems. 

Cost effectiveness = Relative effectiveness x dosage x price per weight. The inhibitor dosage rate depends on the local water conditions and temporal factors, such as the time of the year. It should be quantified in terms of percent corrosion inhibition and extension of useful life. Table 4.29 lists inhibitors used in potable water systems. 

TABLE 4.29 Commonly Used Inhibitors in Potable Water systems (45,46)... 

The mechanism of material degradation in sewer pipes is similar to potable water systems. The internal corrosion may be more severe than in potable water because the wastewater is not clean. The winterizing treatments of roads are a source of chloride, which comes into contact with the pipe. Cement-based pipe experiences corrosion of reinforced steel. The corrosion control method consists of using thicker pipe walls, which provide for larger corrosion tolerance and a longer design life. 

Over the past 30 years, many lead-based products have disappeared from use or the use has been greatly diminished. These products include lead-based paints, lead-based anti-knock compounds for automobiles, lead glazes for pottery, lead sealants for wine battles, solder for sealing the seams of steel cans, automobile body solder, solders for potable water systems, solder for sealing copper radiators, chemical tank linings, lead pipes, lead-based metal bearings, lead sealants such as for drain pipes, power and electrical cable sheathing, and ammunition. 

There are two aspects of laboratory plumbing system design, as opposed to operations, which are relevant to safety and health. The first is the capacity of the system to withstand the waste stream which the system may be called upon to handle. The second is the need to prevent the operations within the laboratory facility from feeding back into and contaminating the potable water system that supplies the building. 

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