Iron and copper release in drinking-water distribution systems.Introduction
Unlined metal pipes are widely used in drinking-water distribution systems. In the United States United States, officially United States of America, republic (2005 est. pop. 295,734,000), 3,539,227 sq mi (9,166,598 sq km), North America. The United States is the world's third largest country in population and the fourth largest country in area. , more than 60 percent of distribution pipes are composed of cast iron, ductile iron Ductile iron, also called ductile cast iron or nodular cast iron, is a type of cast iron invented in 1943 by Keith Millis. While most varieties of cast iron are brittle, ductile iron is much more ductile, as the name implies. , and steel (McNeill & Edwards, 2001). Copper pipe is a primary material for home plumbing systems. Corrosion of all unlined metal pipes is ubiquitous and can result in a contaminant contaminant /con·tam·i·nant/ (kon-tam´in-int) something that causes contamination.
something that causes contamination. release that adversely affects health and the aesthetic quality of the water.
Corrosion in drinking-water distribution systems results from chemical reactions This is the 18th episode of television drama Men in Trees. It originally aired on June 25, 2007 on the TV2 network in New Zealand as a continuation of season 1. Recap
Marin and Cash have a stew cook off, she admits his is better than hers. between pipe metals (or plumbing fixtures) and finished water; it results in formation of a solid corrosion product: scale. Disruption of the solid scale is undesirable, as more contaminants are typically released until new scale is formed. If the composition of the water frequently varies, the equilibrium between the corrosion scale and the water is disrupted, and contaminant release occurs. Many studies have been done on the formation and properties of corrosion scales to gain insight into corrosion mechanisms as affected by water quality in distribution systems (Blengino, Keddam, Labbe, & Robbiola, 1995; Palit & Pehkonen, 2000; Refait, Abdelmoula, & Genin, 1998; Sarin sarin (zärēn`), volatile liquid used as a nerve gas. It boils at 147°C; but evaporates quickly at room temperature; its vapor is colorless and odorless. , Snoeyink, Bebee, Kriven, & Clement, 2001). These scales can be porous porous /por·ous/ (por´us) penetrated by pores and open spaces.
1. Full of or having pores.
2. Admitting the passage of gas or liquid through pores. or impervious im·per·vi·ous
1. Incapable of being penetrated: a material impervious to water.
2. Incapable of being affected: impervious to fear. . Impervious scales can stop corrosion, but porous scales can accelerate corrosion and increase iron and copper release.
Many water quality parameters, including pH, alkalinity al·ka·lin·i·ty
The alkali concentration or alkaline quality of a substance that contains alkali.
1. the quality of being alkaline.
2. , sulfate sulfate, chemical compound containing the sulfate (SO4) radical. Sulfates are salts or esters of sulfuric acid, H2SO4, formed by replacing one or both of the hydrogens with a metal (e.g., sodium) or a radical (e.g., ammonium or ethyl). , chloride, phosphate, silicates, natural organic matter, dissolved oxygen, disinfectantresiduals, and temperature, can affect iron and copper release under different specific conditions (Boulay & Edwards, 2001; Broo, Berghult, & Hedberg, 1997; Edwards, Schock, & Meyer, 1996; Larson & Skold, 1958; Sander, Berghult, Broo, Johansson, & Hedberg, 1996). The mechanisms involving metal pipe corrosion and corrosion product release, however, are still unclear, and contradictory results have been reported by different researchers.
Because of a lack of well-accepted guidelines for corrosion and metal release control, a pilot study was needed to reveal water quality problems that might occur in a distribution system because of changes in water source and treatment process. Findings from such a study could help utility operators work out effective measures to ensure high-quality drinking water drinking water
supply of water available to animals for drinking supplied via nipples, in troughs, dams, ponds and larger natural water sources; an insufficient supply leads to dehydration; it can be the source of infection, e.g. leptospirosis, salmonellosis, or of poisoning, e.g. for consumers.
With the joint support of the American Water Works Association American Water Works Association (AWWA) is an international nonprofit professional organization dedicated to the improvement of drinking water quality and supply. It was founded in 1881 and, as of 2007, there are approximately 60,000 AWWA members world-wide. Research Foundation (AWWARF AWWARF American Water Works Association Research Foundation ) and Tampa Bay Tampa Bay, inlet of the Gulf of Mexico, 25 mi (40 km) long and 7 to 12 mi (11.3–19 km) wide, W Fla., separated from the Gulf by numerous small islands; it receives the Hillsborough River. St. Water (TBW TBW Total Body Water
TBW Total Body Weight
TBW To Be Written
TBW Tambov (Russia)
TBW To Be Watched
TBW Talking Book World
TBW The Business Workshop (India)
TBW Time-Bandwidth Product ) in Florida, a large-scale pilot study was carried out at the University of Central Florida “UCF” redirects here. For other uses, see UCF (disambiguation).
UCF is a member institution of the State University System of Florida. UCF was founded in 1963 as Florida Technological University with the goal of providing highly trained personnel to support the Kennedy . The purpose was to determine what effect blending finished waters from ground, surface, and saline sources would have on distribution system water quality Treatment and distribution systems were built for this pilot study.
This paper focuses on seven finished waters produced from different treatment systems. The quality of these waters is characterized, and their influences on iron and copper release are interpreted in terms of primary water quality parameters and changing operation conditions.
Water Treatment Systems
Finished waters were produced by seven pilot treatment systems (Table 1). The selection of the treatment processes was based on research interests and the needs of TBW. The integrated membrane system (S2) was selected to provide a point of high water quality. The nanofiltration system (G4) was selected to provide data for a TBW member government that was considering nanofiltration of all treated waters. The softening system (G3) was selected to provide data for a second member government that was considering softening all waters in an existing softening facility. The remaining four systems (G1, G2, S1, and RO) were existing water treatment systems. Source groundwater was drawn from the project site, the Cypress Creek well field in Pasco County, Florida Pasco County is a county located in the U.S. state of Florida. As of 2000, the population was 344,765. The 2006 census estimate according to the U.S. Census Bureau for the county is 450,171.  Its county seat is Dade City, Florida6. . Surface water was transported weekly in a 6,500-gallon stainless steel stainless steel: see steel.
Any of a family of alloy steels usually containing 10–30% chromium. The presence of chromium, together with low carbon content, gives remarkable resistance to corrosion and heat. trailer from the Hillsborough River There are at least two rivers named the Hillsborough River:
Decreased the number of microorganisms on or in an object.
Mentioned in: Isolation , and their pH values were adjusted before distribution.
Some of the finished-water parameters were adjusted to meet TBW standards through the addition of chemicals. Calcium and alkalinity (as sodium bicarbonate sodium bicarbonate or sodium hydrogen carbonate, chemical compound, NaHCO3, a white crystalline or granular powder, commonly known as bicarbonate of soda or baking soda. It is soluble in water and very slightly soluble in alcohol. ) were added to S2 and RO waters, alkalinity was added to S1, and sea salts were added to RO-treated water to simulate the quality of finished water from the TBW Regional Desalination desalination
Removal of dissolved salts from seawater and from the salty waters of inland seas, highly mineralized groundwaters, and municipal wastewaters. Facility.
All requirements for disinfection disinfection,
n the process of destroying pathogenic organisms or rendering them inert.
disinfection, full oral cavity,
n a procedure used to reduce active periodontal disease, usually completed within a certain short time frame. contact time (the time that disinfectant disinfectant, agent that destroys disease-causing microorganisms and their spores. Disinfectants, or germicides, are sometimes considered to be substances applied to inanimate bodies, whereas antiseptics, not so potent, are agents that kill microbes on living things. and water were required to be in contact) were met for free chlorine or ozone, and the water had a total chlorine residual (monochloramine and free chlorine, measured as [Cl.sub.2]) of 4 mg/L before it entered the pipe distribution systems. All finished waters were stabilized with respect to calcium carbonate calcium carbonate, CaCO3, white chemical compound that is the most common nonsiliceous mineral. It occurs in two crystal forms: calcite, which is hexagonal, and aragonite, which is rhombohedral. (CaC[O.sub.3]) by pH adjustment: The waters would neither dissolve preformed solid CaC[O.sub.3] nor form new CaC[O.sub.3].
Construction and Operation of Pipe Distribution Systems
The pipe distribution systems (PDSs) consisted of 18 lines made of PVC PVC: see polyvinyl chloride.
in full polyvinyl chloride
Synthetic resin, an organic polymer made by treating vinyl chloride monomers with a peroxide. , lined cast iron, unlined cast iron, and galvanized gal·va·nize
tr.v. gal·va·nized, gal·va·niz·ing, gal·va·niz·es
1. To stimulate or shock with an electric current.
2. pipes. All the pipes used to make the PDSs were excavated from existing distribution systems. Fourteen PDSs were hybrid lines that consisted of PVC, lined cast iron, unlined cast iron, and galvanized pipes. Four of the 18 PDSs were made of a single material. The PVC, lined-cast-iron, and unlined-cast-iron pipes were all 6 inches (15.2 cm) in diameter, and the galvanized pipe was 2 inches (5.1 cm) in diameter. All 14 hybrid lines had identical components: 20 feet (6.1 m) of PVC, 20 feet (6.1 m) of lined cast iron, 12 feet (3.7 m) of unlined cast iron, and 40 feet (12.2 m) of galvanized pipe.
All PDSs were equilibrated for 144 days, from July 16, 2001, to December 6, 2001, with finished groundwater, which was the historical source. At the end of the equilibration equilibration /equi·li·bra·tion/ (e-kwil?i-bra´shun) the achievement of a balance between opposing elements or forces.
occlusal equilibration period, the background water quality was stable, with 0.1-0.15 mg/L effluent effluent
waste from an abattoir carried away in liquid form. Disposal is a major problem because of the need to avoid pollution of waterways. See aerobic effluent treatment, anaerobic effluent treatment. total iron, 0.8 NTUs turbidity turbidity /tur·bid·i·ty/ (ter-bid´i-te) cloudiness; disturbance of solids (sediment) in a solution, so that it is not clear.tur´bid
The cloudiness or lack of transparency of a solution. , and 10 CPUs (Co-Pt units) of apparent color.
Distribution of finished waters to the PDSs began on December 6, 2001, and continued for one year. The water flowed in a single pass; there was no re-circulation. During the yearlong year·long
Lasting one year.
Adj. 1. yearlong - lasting through a year; "attending yearlong courses"
long - primarily temporal sense; being or indicating a relatively great or greater than average duration or operation period, the finished-water pipeline assignments were switched every three months to minimize experimental error. Therefore, the study could be divided into four operational phases, Phase I through Phase IV, which corresponded well with the four seasons, winter to autumn To Autumn is a poem written by English Romantic poet John Keats in 1819 (published 1820).
Keats was inspired to write To Autumn after walking through the water meadows of Winchester, England, in an early autumn evening of 1819. . In addition, for G3 and G4, the water source blending ratios varied from phase to phase. Moreover, the division into phases made it possible to evaluate the effect of temperature on water quality changes in distribution systems. The PDS (1) (Processor Direct Slot) A single expansion slot on certain, early Macintosh models that was used to connect high-speed peripherals as well as additional CPUs. Providing a channel directly to the CPU, the PDS coexisted with NuBus slots on some models. hydraulic residence time (HRT HRT
hormone replacement therapy
Hormone replacement therapy (HRT)
Also called estrogen replacement therapy, this controversial treatment is used to relieve the discomforts of menopause. ) was five days in Phase I, Phase II, and Phase III Noun 1. phase III - a large clinical trial of a treatment or drug that in phase I and phase II has been shown to be efficacious with tolerable side effects; after successful conclusion of these clinical trials it will receive formal approval from the FDA , except for the last two weeks of Phase III. PDS residual disinfectant dissipated dis·si·pat·ed
1. Intemperate in the pursuit of pleasure; dissolute.
2. Wasted or squandered.
3. Irreversibly lost. Used of energy. too rapidly during the summer because of high temperature. Consequently, the HRT was reduced to two days for the last two weeks of Phase III and until the end of the study. All the PDS lines were flushed once a week during five-day HRT period and once every two weeks during the two-day HRT period. Because of the limited length of PDS lines, the flow velocities In fluid dynamics the flow velocity, or velocity field, of a fluid is a vector field which is used to mathematically describe the motion of the fluid. Definition
The flow velocity of a fluid is a vector field
Copper Loop Corrosion Monitoring
Each of the PDSs was succeeded by a copper loop (new copper pipe) 30 feet (9.1 m) long and 5/8 inch (1.6 cm) in diameter, which contained a lead coupon and simulated home plumbing systems. We monitored these loops for lead and copper to provide information for compliance with the Lead and Copper Rule (LCR See least cost routing. ). The water in the copper loops was typically stagnant stagnant /stag·nant/ (stag´nant)
1. motionless; not flowing or moving.
2. inactive; not developing or progressing. but was periodically flushed in simulation of home use. Samples were collected after a standing period of six hours, as required by the LCR. The corrosion of lead has been reported elsewhere (Tang tang, in zoology
tang: see butterfly fish. , Hong, Xiao, & Taylor, 2006) and is not a subject of this paper.
Sampling and Analysis
We conducted sampling and analysis throughout the whole investigation period in order to establish a detailed database. Some relatively unstable water quality parameters were monitored daily or weekly at the site, including temperature, turbidity, apparent color, dissolved oxygen (DO), free chlorine, total chlorine, and pH. The relatively stable parameters were analyzed less frequently (once every two weeks) in a school laboratory; these parameters included calcium, total iron, alkalinity, sulfate, chloride, conductivity conductivity /con·duc·tiv·i·ty/ (kon?duk-tiv´i-te) the capacity of a body to transmit a flow of electricity or heat; the conductance per unit area of the body.
1. , total dissolved solids Total dissolved solids (often abbreviated TDS) is an expression for the combined content of all inorganic and organic substances contained in a liquid which are present in a molecular, ionized or micro-granular (colloidal sol) suspended form. (TDS TDS
total dissolved solids. ). Copper from the corrosion loops was analyzed once every two weeks in Phase I, Phase II, and Phase IV, and once a week in Phase III.
It needs to be pointed out that the iron release data used in this paper were collected from hybrid pipelines that carried seven different finished waters. The iron release was the sum from both unlined cast iron and galvanized pipes (PVC and lined cast iron pipes did not release iron, as had been proved by preliminary monitoring). Also, the copper release data were associated only with seven finished waters. No blended scenarios are presented in this paper.
Results and Discussion
Characteristics of Finished Waters
Finished water quality depended on source and treatment. Lime softening of the Cypress Creek groundwater produced finished water with low-to-moderate calcium, alkalinity, and TDS. Passing the groundwater through an RO membrane and adding sea salts produced a water with high chloride and low hardness, alkalinity, and total dissolved solids. Coagulation coagulation (kōăg'ylā`shən), the collecting into a mass of minute particles of a solid dispersed throughout a liquid (a sol), usually followed by the precipitation or of the surface water produced a low-alkalinity and high-sulfate water. Phase-average water quality parameters for the seven finished waters are shown in Table 2.
Although all these waters met regulatory limits, there was significant variation in water quality. As noted, G1 water had extremely high alkalinity and calcium, S1 water had extremely high sulfate, and RO water had the highest chloride content. Compared with G1, lime-softened groundwater (G2) had nearly 60 percent less alkalinity and calcium. G3 had the second highest level of sulfate because its source contained treated surface water. S2 had the second highest level of chloride, which came from chemical adjustment. Comparing G3 with G4 and S1 with S2 shows that membrane nanofiltration significantly reduced sulfate levels, from 79 to 6 mg/L and 183 to 12 mg/L, respectively. Since finished waters were stabilized on the basis of CaC[O.sub.3] equilibrium, the average pH values of all waters were kept within a small range, from 7.9 to 8.5.
Table 2 also indicates the water quality variation by season. G3 alkalinity greatly increased during Phase III and Phase IV. G4 alkalinity was much higher in Phase II and Phase IV than in Phase I and Phase III. G3 and S1 sulfate concentrations gradually decreased, from Phase I to Phase IV. These variations were due to the fluctuation of water sources with the season and the difference in treatments required.
Effect of Water Quality on Total Iron Release
Conductivity is related to the types and concentrations of total ions in water and significantly affects corrosion. Within the pH range of drinking water, conductivity is primarily controlled by the major anions (HC[O.sub.3.sup.-], S[O.sub.4.sup.2-], [Cl.sup.-]) and cations ([Ca.sup.2+], [Mg.sup.2+], [Na.sup.+]). As shown in Figure la, conductivity (denoted as [kappa Kappa
Used in regression analysis, Kappa represents the ratio of the dollar price change in the price of an option to a 1% change in the expected price volatility.
Remember, the price of the option increases simultaneously with the volatility. ]) increased linearly with the sum of the major anions (denoted as Ai and including bicarbonate bicarbonate or hydrogen carbonate, chemical compound containing the bicarbonate radical, -HCO3. The most familiar of such compounds is sodium bicarbonate (baking soda). See carbonate. , sulfate, and chloride) over the yearlong operation of the field facility. The unit of Ai, meq/L, means milli-equivalent per liter.
Larson and Skold (1958) studied the corrosion of iron materials and found that sulfate and chloride promoted corrosion, that alkalinity inhibited corrosion, and that the corrosion rate increased as the following ratio (called Larson Ratio, denoted as LR) increased:
LR = ([[Cl.sup.-]] + [S[O.sub.4.sup.2-]])/[[HCO HCO Harvard College Observatory
HCO Hubbard Communications Office (Scientology)
HCO Hearing Carry-Over
HCO Health Care Organization
HCO Helicopter Control Officer
HCO Human Capital Office .sub.3.sup.-]] (1)
In this formula, the unit of measure for all anions is expressed as meq/L. The Larson ratio (LR) was used to correlate with the iron release in this study. Figure 1b shows the correlation of the LR with total iron release for seven finished waters under five-day HRT. Clearly, a significant linear relationship exists between total iron release and the LR. In addition, on the basis of the correlation of conductivity ([kappa]) with anions (Ai) and the correlation of total iron release (Fe) with LR, as shown in Figure 1, the total iron release can also be related to conductivity and bicarbonate concentration:
Fe = 0.0018([kappa]/C) - 0.137/C - 0.07 (2)
where Fe is the total iron release in mg/L, [kappa] is the conductivity in [micro]S/cm, and C is the bicarbonate concentration in meq/L.
Conductivity and alkalinity (within the pH range of drinking water, bicarbonate is the dominant contributor to total alkalinity) can be more conveniently monitored; therefore, Equation 2 can be useful for water quality management.
The average total iron release from the hybrid PDSs receiving one of the seven different finished waters during Phase I, Phase II, and Phase III (a five-day HRT) is shown in Figure 2. It can be seen that the total iron release of these waters differs significantly; the amount of iron release associated with the different waters is, in descending order, as follows: S1 > G3 > RO > S2 > G4 > G2 > G1. The average LR values of these waters over the yearlong operation compared as follows: G1(0.33) < G2(0.66) < G4(0.75) < S2(1.56) < RO(1.99) < G3(2.46) < S1(4.16). This result implies that the LR could be used to proactively evaluate the total iron release in distribution systems with varying water quality.
[FIGURE 1 OMITTED]
[FIGURE 2 OMITTED]
Effect of Changing Operational Conditions on Iron Release
With the different temperatures of the different seasons, the iron release exhibited different behaviors. In Phase III (the summer), the temperature was much higher than in Phase I and Phase II. Linear regression Linear regression
A statistical technique for fitting a straight line to a set of data points. was applied to describe the relationships between the LR and total iron release in low-temperature period (Phase I and Phase II) and high-temperature periods (Phase III) (Figure 3a). The slope of the regression line Noun 1. regression line - a smooth curve fitted to the set of paired data in regression analysis; for linear regression the curve is a straight line
regression curve corresponding to Phase III was significantly greater than that corresponding to Phase I and Phase II. This result indicates that iron release was more sensitive to the LR in Phase III than in Phase I and Phase II.
[FIGURE 3 OMITTED]
In order to maintain disinfectant residuals, the HRT was reduced to two days for the last two weeks of Phase III and Phase IV. Figure 3b shows the iron release trends and the LR under five-day and two-day HRTs. The flow velocity increased with the reduction in HRT. It was observed, however, that iron release decreased with the reduction in HRT. This result indicates that hydraulic scouring scouring
characterized by scour.
a colloquial name for secondary nutritional copper deficiency. was not a dominant contributor to total iron concentration in the PDS effluent waters.
[FIGURE 4 OMITTED]
Copper Release of Different Finished Waters
The water entering each copper loop came directly from the effluent of the corresponding PDS line. Some relatively stable water quality parameters, such as alkalinity, sulfate, chloride, and calcium, did not exhibit significant changes after flowing through PDS lines. Disinfectant residuals and dissolved oxygen, however, decreased markedly after passing through PDS lines (data not shown). The pH values also changed slightly. Statistical methods were used to identify the water quality parameters significantly influencing copper release. The p-values for the correlation between each parameter and copper release are given in Table 3. Obviously, alkalinity and pH are the parameters most significantly related to copper release during all four phases. Factor analysis (data not shown here) demonstrated that alkalinity had a positive linear relationship with calcium (with an average [R.sup.2] value of 0.66). Thus, the effect of calcium on copper release cannot be distinguished from that of alkalinity. Although the copper release is associated with the process of copper corrosion (oxidation oxidation /ox·i·da·tion/ (ok?si-da´shun) the act of oxidizing or state of being oxidized.ox·idative
1. The combination of a substance with oxygen.
2. of metal copper), the total chlorine residual and dissolved oxygen were not detected as significant factors for copper release. The result indicates that copper release behaviors were controlled by the dissolution of the corrosion scales, not by the corrosion rate of metal copper.
Figure 4 shows the correlation of copper release with alkalinity and pH. Copper release increases with increased alkalinity and decreased pH, a result that is in agreement with the findings of Edwards and co-authors (1996). It is also interesting to find that pH variation within the small range of 7.6-8.4 (for PDS effluent waters), which had no significant effect on iron release, had a strong influence on copper release. The sensitivity of copper release to pH suggests that pH adjustment should be taken as a crucial measure for the control of copper levels in copper plumbing systems.
The copper release levels of seven finished waters during the yearlong period are shown in Figure 5a. Obviously, G1 had the highest copper release, while the differences in copper release among other waters were relatively small. The extremely high alkalinity of G1 was responsible for the severity of copper release in that system.
[FIGURE 5 OMITTED]
The roles of sulfate and chloride in copper release were complicated, and the mechanisms involved are still unclear. In our study, sulfate did not under most circumstances significantly affect copper release (Table 3). Chloride correlated significantly with copper release during Phase I, Phase II, and Phase IV, but this effect was mainly due to the negative correlation Noun 1. negative correlation - a correlation in which large values of one variable are associated with small values of the other; the correlation coefficient is between 0 and -1
indirect correlation of chloride and alkalinity. Therefore, the specific effect of chloride on copper release could not be identified. Another aspect of Figure 5a is that during the yearlong experimental period, copper fluctuated much more in the G1 system than in the other systems, although G1 water quality was quite stable. It can be deduced that temperature might affect copper release behavior. The average copper release for G1 and the average temperature changes in different phases are illustrated in Figure 5b. It can be inferred that temperature had a positive correlation Noun 1. positive correlation - a correlation in which large values of one variable are associated with large values of the other and small with small; the correlation coefficient is between 0 and +1
direct correlation with the copper release for G1. The highest copper release for G1 occurred in Phase III (the summer season).
A high positive correlation between total iron release and the Larson ratio was observed, and this result could be applied to predict the potential for iron release in finished waters with different mineral characteristics. Total iron release was more sensitive to the Larson ratio under higher temperatures. Reducing the HRT was an effective method of cutting down total iron release levels in a distribution system. Alkalinity and pH were the two water quality parameters that most significantly affected copper release. Copper release correlated positively with alkalinity and negatively with pH.
With its low alkalinity and high sulfates levels, finished surface water treated by ferric sulfate ferric sulfate or iron (III) sulfate, chemical compound, Fe2(SO4)3, a yellow rhombic crystalline hygroscopic water-soluble salt that decomposes when heated to a temperature of 480°C;. coagulation caused the highest iron release of all the waters. Finished groundwater treated by the conventional method produced the lowest iron release but the highest copper release. The iron release of desalinated water was mainly due to its high chloride concentration and low alkalinity. High temperature could enhance the copper release of finished water with high alkalinity.
The findings of our investigation could be of great significance for utility operation and drinking-water management. When water sources are switched or new treatment processes are introduced, it is necessary to evaluate the corrosivity of the new finished waters with respect to the existing distribution system, with special attention paid to changes in alkalinity, conductivity, and pH.
The indexes traditionally used to assess the chemical stability of finished waters are almost all based on CaC[O.sub.3] equilibrium, which is not effective in predicting iron and copper release in distribution systems. The conductivity and alkalinity ratios may be used as a supplementary index for determination of the chemical stability of the water with respect to metal release from iron-based pipes. If copper pipes are included in the distribution systems, finished water of extremely high alkalinity should be avoided; meanwhile, the pH should also be stringently adjusted and maintained.
The transportation capacity for which the distribution system was designed should match well with the water demand so that water does not stagnate stag·nate
intr.v. stag·nat·ed, stag·nat·ing, stag·nates
To be or become stagnant.
[Latin st for long periods of time. Utility operators and water management personnel can take proactive measures In antiterrorism, measures taken in the preventive stage of antiterrorism designed to harden targets and detect actions before they occur. by adopting alternative water treatment technologies and effective water quality monitoring devices to produce finished waters with high chemical stability.
Acknowledgements: The authors acknowledge the project sponsors AWWARF and Tampa Bay Water. Special thanks go to all the personnel who provided maintenance of the project site and data analysis, both in the field and at the University of Central Florida laboratory.
Corresponding Author: Baoyou Shi, Associate Professor of Environmental Science and Engineering, Chinese Academy of Sciences The Chinese Academy of Sciences (CAS) (Simplified Chinese: 中国科学院; Pinyin: Zhōngguó Kēxuéyuàn), formerly known as Academia Sinica , State Key Laboratory of Environmental Aquatic Chemistry Aquatic chemistry is the study of chemical reactions in aqueous solutions, including acid-base reactions, redox reactions, precipitation reactions, and dissolution reactions. , Research Center for Eco-Environmental Sciences, 18 Shuangqing Road, Haidian, Beijing 100085, China. E-mail: firstname.lastname@example.org.
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1. Something produced in the making of something else.
2. A secondary result; a side effect.
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1. watery; prepared with water.
2. see under humor.
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Baoyou Shi, Ph.D.
James S. Taylor, Ph.D., P.E.
TABLE 1 Finished Waters--Sources and Major Treatment Processes Finished Water Original Source Water Major Treatment Process G1 Groundwater Aeration G2 Groundwater Lime softening, sedimentation, filtration G3 Blended source* Lime softening, sedimentation, filtration G4 Blended source Membrane nanofiltration S1 Surface water Ferric sulfate coagulation, ozonation, biologically activated carbon filtration S2 CSF water** Membrane nanofiltration R0 Groundwater Membrane reverse osmosis (R0) * Blend of finished G1, R0, and surface water after coagulation- sedimentation-filtration. ** Surface water after coagulation-sedimentation-filtration. TABLE 2 Average Water Quality Parameters of Finished Waters During Each Phase Alkalinity* S[O.sub.4.sup.2-] [Cl.sup.-] Phase Finished Water (mg/L) pH (mg/L) (mg/L) I G1 206 8.2 25 30 G2 91 8.1 26 23 G3 51 8.2 108 62 G4 66 8.2 7 55 S1 65 7.9 237 44 S2 67 8.2 11 61 RO 71 8.2 6 99 II G1 210 7.9 25 29 G2 95 8.0 25 27 G3 52 8.1 82 42 G4 105 8.3 6 40 S1 56 7.9 217 41 S2 67 8.1 13 60 RO 69 8.2 5 93 III G1 204 7.9 26 33 G2 87 8.0 25 24 G3 64 8.0 77 54 G4 80 8.1 7 47 S1 61 8.0 160 32 S2 65 8.0 14 69 RO 65 8.0 6 86 IV G1 208 8.0 23 26 G2 89 8.1 25 19 G3 84 8.0 55 42 G4 104 8.3 4 33 S1 60 8.2 124 29 S2 72 8.5 9 76 RO 66 8.3 4 91 Phase [Ca.sup.2+] (mg/L) Conductivity ([micro]S/cm) I 85 508 34 285 46 457 25 285 83 606 25 361 25 389 II 85 545 33 331 31 434 45 355 69 673 24 370 27 445 III 83 582 31 332 31 497 27 345 43 599 27 422 30 449 IV 81 582 32 331 34 479 33 352 32 570 26 462 25 474 * Alkalinity: mg/L of CaC[O.sub.3]. TABLE 3 Statistical-Analysis p-values: Correlations of Copper Release with Water Quality Parameters Phase pH Alkalinity [Cl.sup.-] S[O.sub.4.sup.2-] [Ca.sup.2+] I .000 .000 .003 .023 .000 II .000 .000 .000 0.476 .000 III .000 .000 0.486 0.375 .000 IV .000 .000 .009 0.234 .000 Phase Si[O.sub.2] Total Chlorine Dissolved Oxygen I .011 0.431 0.209 II 0.421 0.246 .048 III .032 .053 .067 IV .002 .032 .044