Chloramine Production & Monitoring in Florida’s Water Supply Systems

Robert D. McVay

ource waters in many areas of the state weeks, during which superchlorinating with contain elevated levels of total organic car - free is used to destroy problematic or - Robert McVay, P.E., is the bon (TOC) which combines with free ganisms and unstable conditions in the water trainer for the Florida Rural Water Associa - Schlorine to produce disinfection byproducts system. When this happens, DBPs often exceed tion. His duties include assisting water (DBPs). These compounds are regulated at 80 regulatory limits, sloughing of pipeline growth treatment systems that experience disinfec - parts per billion and 60 parts per billion for total and sediments can occur, and customers re - tion byproduct problems and troubleshoot - trihalomethanes and haloacetic acids. Meeting ceive high concentrations of chlorine, often re - ing small- and medium-size water these low regulatory limits can be difficult when sulting in taste and odor complaints. treatment plants in Florida. This article was free chlorine is used as a . Fortunately, the use of chloramines and the presented as a technical paper at the With the increase in regulatory attention control of problems in the distribution system FSAWWA Fall Conference in November such as the new Stage 2, Initial Distribution follow predictable patterns that can be identified 2007. System Evaluation, rules that require all pub - and corrected before conditions deteriorate to a lic water supply systems to report elevated point where problems occur. This article exam - DBP values, and given the problems meeting ines the concepts in the formation and the use of current rules, many water treatment systems chloramines and suggests pre-emptive tech - distribution system. The purpose of second - have elected to switch to chloramines as their niques to identify the status of deteriorating con - ary disinfection is to provide enough disinfec - secondary disinfectant. ditions and implement corrective actions to keep tant to prevent bacteriological growth. Chloramination, or producing chlorine the chloramination process under control. The It is useful to review the mechanisms of by adding in the presence of free work supporting these recommendations was how free chlorine and chloramines are made chlorine, has been used by many water treat - performed in a Florida Department of Environ - in the disinfection process. When free chlorine ment systems for a number of years for con - mental Protection-sponsored study for the Lake (Cl 2) is initially added to water, it goes through trolling the production of DBPs. The process City Florida Water System conducted in 2008. a series of chemical actions and eventually of forming chloramines is well understood splits into two components: hypochlorous acid and consists of adding ammonia in the pres - Understanding Chlorine Addition (the active compound that forms the DBPs) ence of free chlorine in a ratio of about 3-5 for Primary Disinfection and the hypochlorite ion. milligrams per liter (mg/l) free chlorine to 1 Although both hypochlorous acid and mg/l of ammonia. DBPs are formed when chlorine, in the the hypochorite ion provide disinfection, the Unfortunately, switching water systems form of hypochlorous acid formed in the dis - hypochorous acid that is formed is much from free chlorine to chloramine creates new infection process, is allowed to contact natu - stronger than the ion. The amount of and unexpected problems. Attempting to find rally occurring organic material. To control hypochlorous acid or the hypochlorite ion an explanation for what is occurring is not the production of DBPs effectively, three formed is completely dependent on pH. These easy, and when problems grow worse, the sys - methods can be employed: relationships are shown in Figure 1. tem operator is left with no other option than 1) Remove the organic precursors that are re - As can be seen from the curve, when the to switch back to free chlorine disinfection and active with the chlorine. pH of the water is around 7.5, a value near most performing a “burn.” 2) Decrease the amount of hypochlorous acid Florida groundwaters, the relative concentra - A burn is a process that lasts several available for the reaction. tions of hypochlorous acid is around 50 per - 3) Decrease the time of contact between the cent. If pH is lowered, more hypochlorous acid is available and more DBPs form at a faster rate. Figure 1 organic material and the acid. Generally, operators will accomplish all Conversely, when pH is increased, the 100 these objectives by moving chlorine dosing available hypochlorous acid is lower and DBP 90 points to locations that allow some precursor formation will be slower. As the pH ap - 80 removal to occur within the plant and then proaches 8, the relative portion of the hypochlorous acid is about 20 percent. 70 OCl - lower free chlorine concentrations to only those 60 levels needed to meet regulatory requirements. Above a pH of 9, most of the chlorine is 50 When in-plant strategies are not success - in the form of the less effective hypochlorite 40 ful, many systems have chosen to reduce the ion, and disinfectant ability will be about 1 HOCl 30 amount of hypochlorous acid available for re - percent of the disinfectant power compared to 20 action within the distribution system by the acid form. Raising pH does have a signifi - cant drawback: As the amount of hypochlor - 10 switching to chloramine as a secondary disin - ous acid is reduced, disinfection ability is 0 fectant. Free chlorine or other disinfectant is used to provide primary disinfection and meet reduced accordingly. 4 5 6 7 8 9 10 11 initial disinfectant demand, and chloramine is The practical significance of this fact in Continued on page 18 pH used as the secondary disinfectant, i.e., in the 16 • APRIL 2009 • FLORIDA WATER RESOURCES JOURNAL be naturally present. FREE CHLORINE This oxidation-reduction reaction will proceed to completion until all inorganic sub - 0.2 0.6 1.0 2 3 5 7 10 PPM 8.5 strate is consumed. Within this range, free chlorine may be added to the water without producing any significant DBPs. This concept is important because many Florida water 8 sources contain iron, hydrogen sulfide, and background ammonia—all inorganic-de - manding substances that can be oxidized with p chlorine without producing significant DBPs. 7.5 H Between segments 2 and 3, there are no Temper ature 25o C longer any unreacted inorganic compounds in Alkalinity100 mg/l the water, and oxidation of organic contami - 7 TDS 500 mg/l nants that produce DBPs will now occur. To prevent this undesirable situation, many water treatment plants with DBP problems have switched to the use of chloramines. Chlo - 6.5 ramine is produced by adding 1 mg/l ammo - 550 600 650 700 750 800 850 900 nia to a ratio of between 3 mg/l to 5 mg/l measured free chlorine. ORP mV Note that when the chlorine to ammonia ratio exceeds about 5 mg/l chlorine to 1 mg/l ammonia, t he production of other chloramine Figure 2: Breakpoint Chlorination Curve and Chloramine Development products besides occurs si - multaneously with a decrease in the measured total chlorine residual concentration. These re - actions result in additional chlorine demand. Continued from page 16 they follow the general pattern illustrated in Note that when the 5:1 ratio is exceeded, water treatment is that free chlorine residual Figure 3. Note that between the segments la - monochloramine (NH 2Cl) is being converted does not indicate microbial inactivation un - beled 1 and 2, free chlorine has been added but into dichloramine (NHCl 2), and finally as less pH is accounted for. This limitation can be no chlorine residual of any kind is shown on more chlorine is added, the dichloramine is avoided when the hypochlorous acid compo - the left Y-axis because within this range, the converted to nitrogen trichloride before off nent is measured directly, which can be ac - chlorine is reacting with inorganic con - gassing as nitrogen. complished by the use of an ORP meter. stituents in the water such as iron, manganese, The most desirable form of chloramine is An ORP meter will provide an estimate hydrogen sulfide, and any ammonia that may Continued on page 20 of the inactivation power of chlorine at any given pH. An ORP value of 650 mV has been used since mid-1980 for municipal drinking water in Europe to maintain high oxidative ) E F D S S S S S D D S conditions in water distribution systems. N L I E E E O C E C E D C I I I B A N Y N Y N M I I N N N N Figure 2 illustrates how this value relates A M O U O R A A O M M L A I E I R R O O G A A G T G T T R A F to current Florida Department of Environ - P R R R R A S S V O M L O O O O A E E M R A mental Protection residual requirements for O L L R R D D R O E U C H H O O L O E Y E D C C L free chlorine in a water distribution system. At L I F G L H R N I H H S T N F C D D I R E C C R

ORP values between 500 and 600 mV, bacter - N N E C R O L A A A U M L P

ial inactivation will occur but it will require A D O H E S C U ( much longer contact time to be effective. R D Y I

To understand how chlorine forms DBPs B S with a source water that contains chlorine-de - E >8:1 T R N manding substances, it is necessary to develop I E O P a breakpoint chlorination curve. An example is N I 5:1 >5.5:1 K A R

illustrated in Figure 3, where the X-axis shows E O R FREE B the amount of free chlorine added continu - L 4:1 AV AILABLE ously to a source water sample and the Y-axis H RESIDUAL shows the total chlorine residual present. C Total chlorine is in a combined form (Y 3:1 axis) until all the inorganic and organic demand COMBINED RESIDUAL is satisfied. In other words, until the initial inor - ganic demand has been oxidized, no hypochlor - CHLORINE ADDED ous acid is available for organic reactions. The reactions shown on the breakpoint Figure 3: Breakpoint Chlorination Curve Showing affects of Various Chlorine-to- curve are unique for each water system, but Ammonia Ratios

18 • APRIL 2009 • FLORIDA WATER RESOURCES JOURNAL Figure 4: Production of Various Species of material and thus produce more DBPs. Con - Chloramine by Increasing Chlorine Doses versely with chloramine, if significant excess residual is not maintained, the chloramine will 8 have a tendency to break down, which can lead l a

N to loss of disinfection ability, the formation of - u 4 DBPs, slime growth, and nitrification. d i H 6 The substances that cause disinfectant de - s N

e NHCl 2 mand are indicative of the source water qual - g R ity. These are also the compounds that

m 4 e /

2 typically cause water quality customer com - n l i -

r HOCl + OCl

C plaints. Most source waters contain a variety o l

g 2 of both inorganic and organic contaminants h NH 2Cl m whose chlorine demand can be identified with C NCl 3 a simple jar test without knowledge of the 0 types of concentrations of the contaminants. 0 2 4 6 8 10 12 14 16 A disinfection “jar test” is a simple proce - dure in which a known concentration of chlo - rine, such as the approximate 5.25 percent Chlorine Dose, mg Cl 2/mg NH 4-N household bleach, is used to make a chlorine dosing“standard.” To facilitate calculations, add Continued from page 18 ial resistance to the added . 5 ml of the bleach to 1 liter of de-ionized water to make an approximate 200-mg/l standard so - monochloramine (NH 2Cl) and it will pre - When ammonia is added to water con - dominate below the 5:1 free-chlorine-to- taining hypochlorous acid, the production of lution. Check the concentration of the standard ammonia ratio . As the amount of free chlorine chloramines occurs instantaneously with the by adding 5 ml to 1 liter if de-ionized water. The exceeds the 5:1 ratio, dichloramine is produced rate of reaction controlled by pH. The reaction free chlorine concentration should register on a and the total chlorine residual will fall off ap - rates are shown in Table 1. The arrow indicates DPD meter near 1 mg/l free chlorine. proaching zero total residual at point 4 on the the range of Florida source waters that are typ - Once the standard’s concentration is de - breakpoint curve. ically between a pH of 6.8 and 7.8. In this range, termined with the meter, it can then used to If additional free chlorine is added beyond chloramine production is instantaneous. dose 1-liter source water samples in 2.5-ml, 5- point 4 on the curve, then “breakpoint,” or the ml, and 10-mg/l increments. The combined point where free ammonia will be released to the Determining Chlorine Demand and free residual chlorine levels are then meas - ured after 15 minutes to develop the classic atmosphere, will be reached. The figure shows for Your Water System that breakpoint chlorination is reached at a ratio breakpoint chlorination curve. of free chlorine to ammonia at a ratio of about It is imperative that water systems iden - The chlorine demand test will provide the 10:1, resulting in the formation of nitrogen gas, tify their chlorine demand so free chlorine operator with a good estimate of the chlorine- nitrate, and nitrogen chloride, as well as dosage can be minimized at the plant and demanding substances that are available im - hypochlorous acid and the hypochlorite ion. chlorine residuals can be maintained in the mediately and will identify the minimum Point 4 on the curve represents the point distribution system at the 0.20 mg/l free chlo - chlorine dose that can be added to achieve where free chlorine or hypochlorous acid and rine or 0.60 mg/l chloramine levels required breakpoint. This is important because exces - the hypochlorite ion can be measured in a by the state of Florida. sive chlorine being added will increase the pro - water treatment plant or in a water distribu - When performing DBP analysis on their duction of DBPs within the treatment plant. tion system as free chlorine. When chloramine finished water at the plant, operators at many is used as a secondary disinfectant, hypochlor - systems find that after implementing the con - Estimating Chlorine Demand ous acid is not present. trols described above, DBPs produced at the Using Known Contaminant It is important that the chlorine be added plant are at least 25 percent less than those Concentrations prior to the ammonia. Ammonia is a nutrient, produced in the distribution system. Excessive and adding it to water prior to the chlorine free chlorine residuals in the distribution sys - Chlorine demand also can be estimated will encourage biological growth and bacter - tem increase the reaction rates with organic Continued on page 22

Table 1: Time to 99 Percent Conversion of Chlorine to Monochloramine Table 2: Determin - ing Chemical De - mand from Source Water Laboratory Analysis

20 • APRIL 2009 • FLORIDA WATER RESOURCES JOURNAL Natural Degradation previously. When 2.5 mg/l of monochlo - ramine is maintained, it has been found to im - of Monochloramine (NH 2Cl) pede nitrification significantly. Three degradation equations for mono - chloramine that occur in any water system are Monitoring Chloramine Levels shown below. Note that in each case that the in Water Distribution System end product is either ammonia or the ammo - nium ion that both contribute to nitrification. Monitoring chloramine residuals is es - sential to avoid loss of disinfection, nitrifica - Equation #1: Autodecomposition tion, and biofilm growth in the distribution - 3NH 2Cl → N2 +NH3 +Cl + 3H+ system. Direct measurement of free chlorine and total chlorine residual is always the pre - Equation #2: Oxidation of Organic Matter ferred method of determining the concentra - .1C 5H7O2N + NH 2Cl + .9H 20 → tions and the type of disinfectants present, but - - - .4CO 2 + .1HCO 3 +1.1 NH4 + Cl it does not necessarily identify a problem con - dition unless other indicators are present. Equation #3: Reduction by Nitrite Conventional methods of identifying Table 3: Oxidative States of Common - - NH 2Cl + NO 2 +H 20 → NH3 + NO 3 + HCl Oxidants Used in Water Treatment chloramine breakdown and nitrification episodes include noting reduced disinfection All of these forms of degradation of residual; DO depletion; reduction in pH and monochloramine are exacerbated by long de - alkalinity; the presence of ammonia, nitrate, tention times such as in dead-end pipes or in Continued from page 20 and nitrite; and the increased growth of het - storage tanks. Most water system operators do by using the laboratory or field sampling kit erotrophic bacteria. Unfortunately, identifica - not know the residence times in their distri - values for eight contaminants that are signifi - tion of these constituents are all indicators that bution systems. Studies have found that many cant in demanding chlorine: iron, manganese, a problem is in progress and possibly out of average-size water distribution systems have hydrogen sulfide, ammonia, organic nitrogen, control, so more predictive methods must be residence times that exceed 12 days in some nitrite, and total organic (TOC). Table employed as are discussed in the following places. In some smaller systems, residence 2 illustrates how to use these laboratory values paragraphs. times as high as 24 days are not uncommon. to determine chlorine demand. These residence times are more than adequate This method provides a quick check on to favor monochloramine degradation. Maintaining a Highly Oxidative the chlorine demanding-substances. Note that Since the mechanisms of the degradation (ORP) Environment the demand exerted by very small concentra - of chloramine are well known, it is recom - tions of naturally occurring ammonia is ex - in a Water Distribution System mended that water distribution systems target tremely high and will dominate the demand a 2.5-mg/l level in stagnant areas of the distri - Nitrification is unlikely at high oxidative for free chlorine. It is not uncommon for bution system to avoid the problems discussed states, since these states tend to inhibit the or - Florida source waters to contain some meas - urable ammonia. Also note that the demand for organic substances is typically less than 10 percent of the demand total and can be estimated by using a representative value of 5 mg-C/l for TOC if unknown. Organic nitrogen can be ig - nored when evaluating groundwater.

Chloramine Disinfectant Mechanisms

The ability of chloramine to inactivate pathogens begins to degrade relatively early in a distribution system. This process occurs within a few days after the monochloramine is applied and is known as autodegradation. For each 3 moles of monochloramine de - graded, 1 mole of ammonia will be released. The degradation will continue to occur the longer the chloramines are detained. This is the reason that water systems are encouraged to flush. If organic material is present in the distri - bution system, chloramines will oxidize organic contaminants in the water, releasing ammonium. Both autodegradation and organic reactions favor the start of nitrification because ammonia is released into the distribution system. Figure 5

22 • APRIL 2009 • FLORIDA WATER RESOURCES JOURNAL Figure 6: ORP Values for Chloramine Degradation in a Water Distribution System

ORP NH 2Cl Oxidant Condition Monitoring MV Ranges and Bacterial Growth Parameters 1. Desired ORP Range to inhibit Nirtrification. 2. ORP Range Supporting Nitrification and 4 Growth of AOB. 1 Highly Oxic 3. ORP Range Where Nitrification is Occur - 600 Residual Level > 2.5 PPM 5 ring and NOB Supported. No AOB Growth 4. Drop in DO level indicating conditions for Nitrification or Nitrification may have 500 started. > 2.0 PPM 5. Drop in pH/alkalinity level indicating that 2 6 Nitrification is imminent or beginning. 400 6. Detection of NH 3 in this range indicates that Aerobic Level Nitrification Process has begun. < 1.0 PPM AOB Growth 7 7. Detection of NO 2 in this range indicates 3 Mature Nitrification Process. 300 Note: Monitoring Parameters (4, 5, 6 and 7) are useful relative to initial ORP signature. 200 Aerobic Transition Level The upper range of chloramine residual sug - NOB Growth gested (2.5 mg/l) inhibits bacterial activity; 100 amounts of chloramine below these levels are in a range where bacteria can grow with less inhibition. 0 ganisms necessary for the process to occur. To Expected ORP Ranges for chloramine is highly unlikely to occur. minimize microbial growth, therefore, high Chloramination of Finished Water Where oxidation potentials are low or oxidative, or ORP, states should be maintained dropping, conditions favor nitrification or ni - as previously discussed. Figure 6 shows the various ranges of chlo - trification may already be occurring. Thus, All disinfectants used in water treatment ramines that can be expected in finished well these relationships provide a quantitative inactivate microbes by oxidation. Each disin - water and how these values inhibit nitrifying method for determining the state of the oxi - fectant used in water treatment has a relative organisms. Chloramine concentrations are dation reactions and the trend toward unde - oxidation potential that increases the oxidative shown in ranges, not in numeric values, because sirable low concentrations of disinfectants that state beyond the level possible using oxygen. the temperature, chemistry, water quality, and are occurring in a water distribution system at The oxidative states for common oxidants pH of each water will differ and thus the ORP is any point in time. used in water treatment are shown in Table 3 best used for determining acceptable chloram - Nitrification takes place best in a situation in relation to the oxidation power of oxygen. ination ranges that result in adequate combined where ammonia is available with elevated tem - Note that all oxidants used in water treatment chlorine residual and water system stability. peratures when the pH is between 7.0 and 8.0, have higher oxidation potentials than oxygen. ORP is thus an indicator of the status of but it can occur within a much wider pH chlroramine degradation at any point in time. range under slower conditions. Decay of chlo - Using ORP to Help Determine Monitoring ORP allows operators to predict ramine provides a source of ammonia and Chloramine Degradation the rate of chloramine degradation and take thus nitrification is fairly common in water steps to prevent further ORP reductions that distribution systems in Florida that use this Use of ORP monitoring in a water distri - will favor nitrification. disinfectant. bution system, in combination with other water The higher values of monochloramine quality parameters, provides a good indica - produce elevated ORP values near 500 mV, Bacterial Significance tion—or snapshot in time—of the stability of which can effectively inactivate microbes with in Nitrification the current system. An ORP measurement pro - longer detention times than are needed with free vides an initial signature of the water system’s chlorine. The stability of the oxidation state in a There are two types of ubiquitous bacte - condition, and ORP values can then be used to water system will depend on the concentration ria that participate in the nitrification reaction. determine how fast a condition is deteriorating. of pollutants or reducers in the finished water. The first is classified as an aerobic oxidizing The range of values provided by an ORP When high concentrations of monochlo - bacteria (AOB). In this reaction, ammonia is can indicate a problem. When ORP is used in ramine are added, bacterial inhibition will oxidized to the nitrite form (NO2 -). Nitrite, as combination of the other water quality pa - occur as long as a highly oxic state exists. If or - we saw in the chlorine demand example, ex - rameters, it provides a quantitative method for ganic material is available, the monochloramine erts a chlorine demand of five times its con - determining if distribution problems can be will be destroyed, as shown by the equations in centration. This situation will result in rapid expected before they occur, giving the operator the previous section. Thus, high oxidation states loss of disinfection residual. time to adjust. (high mV) are indicative of an environment As more ammonia is oxidized, the alka - where nitrification and rapid degradation of Continued on page 24

FLORIDA WATER RESOURCES JOURNAL • APRIL 2009 • 23 Continued from page 23 Lowered oxidation conditions in a water Proactive Chloramine Monitoring linity in the water is consumed and the pH will system also promote the growth of biofilm— drop. A drop in pH is thus an indicator that active bacteria that include both AOB and NOB. Water systems can avoid creating the con - nitrification is occurring. The conditions for These and other bacteria that proliferate under ditions for nitrification by water system mon - nitrite conversion require a lower oxidation lowered oxidation conditions further compli - itoring and taking pre-emptive actions such as concentration as shown in the figure above. cate the problem in maintaining a chloramine flushing or increasing chloramine levels to en - These bacteria are known as nitrogen oxidiz - residual in the water distribution system. sure that adequate oxidative conditions are ing bacteria (NOB). maintained to prevent bacterial growth. In monitoring system parameters within the Lake City Water System, temperature was a simple, often-overlooked parameter that pro - vided good chloramine degradation correla - tion. The temperatures taken along the water’s route from the water treatment plant to a water storage tank are shown in Figure 7. It became clear that water temperature was being affected by a local water storage tank that was dominat - ing water volume in the immediate area. These pipeline temperature readings clearly indicate correlation with storage tank fluctua - tions. Additional sampling of chloramine con - centrations with known tank fluctuations provided the results shown in Figure 8. The chloramine degradation conditions identified in Figure 8 were easily corrected by plant management by ensuring better cycling in water storage tanks during periods of low peak demand.

Flushing to Increase Chloramine Effectiveness

The most common method of maintain - Figure 7: Lake City, Florida—Chloramination and Nitrification Study, FRWA 2008, ing chloramine residual within a water system Temperature Correlations at remote locations is to ensure adequate turnover of the water. Unfortunately, a flush - ing program for a distribution system can be very labor intensive. Manufacturers have de - veloped automated flushing valves for this purpose, as shown in Figure 9. Flushing can be an effective method for moving fresh chloramine and improving the oxidative state in a water distribution system,

Figure 8: Lake City, Florida—Chloramination & Nitrification Study, FRWA 2008, Figure 9: Automatic Flushing Valve Chloramine/Tank Fluctuation Relationships COURTESY KUPFERLE FOUNDRY CO.

24 • APRIL 2009 • FLORIDA WATER RESOURCES JOURNAL Figure 10: Chloramine Residual Benefits 0.050 – - Achieved by Increasing pH in the Water - 0.045 –-

Distribution System ) - - M 0.040 – - m - ( - 0.035 –

e - but it should not be attempted without devel - - n - i - oping a flushing plan that identifies the 0.030 –- m - amount of water needed for flushing and the a - r 0.025 –- time the pipe segment needs to be flushed to o - l - achieve any degree of success in increasing h –-

c 0.020 chloramine residual. Generally a flow velocity - o - of 3 fps is needed to move sediment. n 0.015 –-

o - To increase chloramine residual, generally - M - a full pipe volume must be displaced to achieve 0.010 – - any benefits. In most cases, the flushing needs - 0.005 –- only to move water and not sediment. An ef - - – – – – – – – – – –

------fective flushing program generally must move 0.000 –- only enough water to increase chloramine 0 20 40 60 80 100 120 140 160 180 residual to a target value. Concentration should be confirmed by field testing using a Time (hours) DPD meter and flushing kept to a minimum to avoid wasting water. of free chlorine to ammonia to produce some eration should be given to its impact on the dichloramine to disrupt conditions favoring wastewater treatment system. Batch treatment Effective Flushing Methods nitrification in extremely warm weather. is not practical because of the initial dose re - for Achieving Increased Dichloramine will provide a buffer as a more quired to build residual and the possibility of Chlorimine Residuals effective disinfectant but can also result in cus - corrosion byproduct sloughing off and being tomer complaints of taste and odor; however, flushed into customer plumbing. • Flush three pipe volumes or until the disin - its use may preclude a burn out. fectant residual is restored (usually between 1 Managing Chloramines and 3 volumes of the stagnant main section). Adjusting pH for Maintaining • Flush until color and turbidity are restored Chloramine Residuals in It is highly recommended that systems to normal levels (usually 0.5 NTU or less). Water Distribution Systems using chloramine establish programs for mon - • Flush at a rate that keeps the main pressure itoring total chlorine, ammonia, nitrite, tem - above 35 psi. Another method used successfully by perature, alkalinity, ORP, and pH—all • To minimize water loss, flush for the least water systems to maintain chloramine residu - parameters that can be measured using sim - amount of time needed. als is to maintain an alkaline pH. The limita - ple, low-cost field kits. The relationships tions here are that very few systems have the among various water quality changes on chlo - Methods for ability to adjust pH without adding an addi - ramine stability are shown in Table 4. Controlling Chloramine tional treatment process. The effects of raising It is highly recommended that the opera - Breakdown & Nitrification pH are shown in Figure 10. tor establish signatures in critical areas of the A pH increase is effective for maintaining water system and monitor the parameters sug - Raising chloramine levels to above 2.5 chloramine residuals because it slows ammo - gested to observe trends in chloramine break - mg/l is the best way to impeded nitrification, nia release from chloramine degradation. down before conditions are allowed to but sometimes this is not possible. State drink - deteriorate. Historical information is most ing water rules prohibit chloramine concen - Use of Blended Phosphates valuable in predicting the likely occurrence of trations in a distribution system from for Chloramine chloramine breakdown, and the pre-emptive exceeding 4.0 mg/l. Residual Protection measures identified in this article are recom - In some cases where distribution systems mended especially in warmer weather. are several miles long with low demand, a 2.5- Some smaller systems have gained similar mg/l residual can be maintained only by using benefits by using a blended phosphate as a se - References: an additional chloramine dosing facility lo - questering agent. The blended phosphate works cated closer to the problem area. Attempting to by sequestering both unreacted inorganic met - 1. Robert Spon, RR Spon and Associates, control the concentration at a remote location als and any corrosion products produced by Chloramines, Breakpoint Chlorination and to above 2.5 mg/l will require a concentration bacterial action within the water distribution DBP Control, , Presentation at the 2006 greater than 4.0 mg/l leaving the water plant. system. This action is thought to reduce chlo - FDEP Drinking Water Annual Meeting, St. To circumvent the problems with chlo - ramine degradation and chemical activity. Augustine, Florida, July 2006 ramine degradation, using higher chloramine Phosphates, however, must be controlled 2. Control of Biofilm Growth in Drinking residuals in warmer months is recommended. to minimum dose levels, since they are a nu - Water Distribution Systems, Seminar Pub - “Burn outs” (switching to free chlorine for 30 trient. Typically, dosage is limited by the water lication, USEPA, June 1992 days) may be minimized or eliminated if nitrifi - hardness and the amount of iron present in 3. Water Quality and Treatment, A Handbook cation conditions are prevented from occurring. the water supply. of Community Water Supplies, McGraw Hill, Some systems choose to push the ratios When using blended phosphates consid - Continued on page 26 FLORIDA WATER RESOURCES JOURNAL • APRIL 2009 • 25 Table 4: Using Chemical Parameters to Determine Effectiveness of Chloramines in a Water Distribution System

Continued from page 25 American Water Works Association, 1999 4. Alternative Disinfection Guidance Manual, Alternative Disinfectants and Oxidants, USEPA, April 1999 5. Charlotte D. Smith, Monitoring for Nitrifi - cation Prevention and Control, Manual 56, AWWA, 2003 6. Small Water System Operation and Mainte - nance, A Field Study Guide, California State University, Sacramento, 1999 7. Trevor Suslow, Oxidation Reduction Poten - tial (ORP) for Water Disinfection Monitor - ing, Control and Documentation, University of California, Publication 8149 8. Introduction to ORP as the Standard for Postharvest Water Disinfection Monitoring, UC Davis Vegetable Research Center 9. Troy Hamberger, Methods of Controlling Nitrogen Using ORP, Florida Rural Water 12. D.L. Harp, Specific and Effective Methods in Chloraminated Drinking Water Systems, Association, White Paper for Controlling Chloramination of Waters, M56, AWWA, 2006 10. Sensorex, Technical Education Series, What Hach Chemical Company, 2007 15. Robert McVay P.E, Chloramination and is ORP?, http://www.sensorex.com, 2007 13. Jacques M. Steinninger, PPM or ORP: Nirification Study, Lake City Florida, Pres - 11. Flushing Programs and Hydrant Mainte - Which Should Be Used?, Swimming Pool entation at the 2008 FDEP Drinking Water nance, Texas Commission on Environ - Age and Spa Merchandiser, Nov. 1985 Annual Meeting, Orland, Florida, August mental Quality, 2007 14. Fundamentals and Control of Nitrification 2008 

26 • APRIL 2009 • FLORIDA WATER RESOURCES JOURNAL