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Taste and OdorTaste and Odor

NCWOA Spring School

ason Green

Water Treatment Superintendent

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Tastes and Odors in drinking water are the most common and difficult problemsthat confront Operators.

Chlorinous and Earthy odors were found to be the most objectionable odors.Over 80% of utilities treat for taste and odor problems occasionally.

Problems occur locally on a persistent, seasonal, occasional, or infrequentbasis.

Taste and Odor problems are likely to have a significant effect when they occur.First, numerous complaints will be handled. This will create a lot of frustration

for the customers and staff.Water with a taste and odor issue is not desirable by the public and will cause alack of confidence in the water utilitys ability to provide safe, high-quality water.

The secret to successful taste and odor control is to prevent tastes and odorsfrom ever developing. This means control of algae and other microorganisms insource waters and treatment plants through preventive treatment. You musttreat for tastes and odors before the problem occurs.

9.09.0 Importance of Taste and OdorImportance of Taste and Odor

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Considerable headway has been made in the identification of compounds that causetastes and odors. The most common are:

2. Geosmin a natural chemical by-product of various species ofActinomycetes andblue-green algae. Produces earthy odors in the water.

3. 2-Methylisoborneol (MIB) a natural compound produced by various species ofActinomycetes and blue-green algae. This compound imparts a musty odor to thewater.

4. Chlorine the most common disinfectant used in the water industry. It is the mostcommon source of T&O complaints that range from bleach to chlorinous and

medicinal.5. Chloramines when ammonia (NH3) is added to the treatment process, the

formation of odoriferous inorganic chloramines is a potential problem. Thesecompounds are monochloramine, dichloramine, and trichloramine. Thesechloramines cause T&O problems when: Monochloramine levels exceed 5 mg/L,Dichloramine (swimming pool or bleach odor) becomes a problem at levelsbetween 0.9 to 1.3 mg/L, and Trichloramine produces a geranium odor at levels

at 0.02 mg/L or above.6. Aldehydes most common probable associated with aldehydes is the fruity odor

that develops in ozonated water. Aldehydes are formed by the oxidation of aminoacids and nitriles during the treatment process.

9.109.10Specific Taste and Odor CompoundsSpecific Taste and Odor Compounds

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6. Phenols and Chlorophenols phenols in the water supply react withchlorine to form chlorophenols. Pharmaceutical and medicinal T&O are most

often associated with chlorophenols in drinking water.

9.109.10 Specific Taste and Odor Compounds cont.Specific Taste and Odor Compounds cont.

9.119.11 Types of CausesTypes of Causes

According to a 1989 AWWA survey, the major causes of T&O problems are algalblooms in source waters, disinfectants used, and the water distribution system.

Raw water sources, conveyance facilities, treatment plants, chlorination stations,finished water storage reservoirs, distribution systems, and consumer plumbinghave all be identified as potential sources of taste and odor problem.

Actinomycete

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Microscopic organisms are major contributors to T&O problems.Actinomycetes are agroup of filamentous bacteria that grows in sediments, water, and aquatic plant life.

The earthy, musty odors fromActinomycetes are due to formation of Geosmin and 2-methylisoborneol (MIB).Actinomycetes are not detected with routine microbiologicaltests.

Major T&O producing algal groups include: Blue-Green Algae (Cyanophyta), Yellow-Green Algae (Chrysophyceae), Diatoms (Bacillariophyceae), and Dinoflagelates(Pyrrophyta).

Other microorganisms can produce T&O. Sulfur reducing bacteria, a group of

anaerobic bacteria, reduces sulfates to hydrogen sulfide. This produces the rottenegg odor associated with highly polluted water.

Microbial populations can contribute to unpleasant T&O in water in two general ways:as the population grow and multiply, it produces metabolic by-products. The second isdue to the cellular material can also be responsible for complaints. That is why somewater tastes better before treatment due to cellular contents being released into thewater.

The application of an algicide to source water should be considered when: (1) thedominant algae is a T&O producer, (2) algae is not a dominant organism but is knownto be a T&O producer, and (3) sensory or chemical analysis indicates an increase in theodor of the water.

9.1209.120 Biological Growth in Source WatersBiological Growth in Source Waters

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Increased nutrient levels, Euthophication, may result from either natural conditions orfrom human activity in the watershed.

Pollutants normally do not depress oxygen concentrations but the microorganisms

capable of growing from pollutants do. Rapid microbial growth will cause oxygen-poorconditions in polluted waters.

Blooms of photosynthetic algae resulting from increased nutrient concentrations,suitable water temperatures, and favorable sunlight can cause both oxygen depletionand oxygen supersaturation in water during a 24-hour period. During daylight hours,algae produces oxygen via photosynthesis and at night consumes the dissolvedoxygen in the water via respiration.

Photosynthesis a process in which organisms, with the aid of chlorophyll, convertcarbon dioxide and inorganic substances into oxygen and additional plant material byusing sunlight for energy. All green plants grow by this process.

Algae can also effect the pH in the source water. As algae produces O2, CO2 is

removed from the water and the pH increases. During the night when the O2 is

consumed by the algae, the pH will decrease due to the rising level of CO2.

Natural runoff may also lead to T&O by substantially increasing flow velocities.Sediments deposited in the bottom of channels during low-flow periods may beresuspended by scouring action and transported to the treatment plant. Thesesediments may impart septic, musty, or earthy T&O to the drinking water supply.

9.1219.121 Environmental ConditionsEnvironmental Conditions

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1.Municipal Wastewaters - inadequately treated wastewater may enter thetreatment plant due to a process failure, mechanical breakdowns, or overloading ofthe facility. Older Waste Treatment Plants are ineffective in handling large inflows andinadequately treat the wastewater. Individual wastewater disposal systems also

contribute pollutants to the water supply. Septic tanks and leach fields may belocated too close to rivers. Individual systems with poor percolation rates can createsituations where nearly untreated wastewater reaches a municipal source. Theycontribute to T&O by: (1) direct addition of odoriferous compounds, and (2) and theaddition of nutrients that result in algal blooms.

2.Industrial Wastes sometimes present significant T&O problems for downstreamutilities. NPDES requires dischargers to limit chemicals in the effluent, but utilities

downstream of heavily industrialized areas may encounter problems from the totaleffects of all of the facilities discharging upstream.

3.Chemical Spills spills can have a detrimental effect on raw water sources. Theprimary concern from these incidents is the potential toxicity from the spilledchemicals. Most spills are the result from accidents at industrial facilities or duringtransportation. Due to the unpredictability of chemical spills, each facility shouldutilize their Emergency Response Plan to deal with the problem.

* NCDENR SHOULD BE NOTIFIED ASAP IN THE EVENT OF A CHEMICALSPILL *

9.139.13 Human Causes of Tastes and OdorsHuman Causes of Tastes and Odors

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Urban Runoff- During dry periods, oil, grease, gasoline, animal dropping, fertilizer,etc. accumulate and sudden rainfalls wash these contaminates into the water supply.Nitrate concentrations (fertilizers) in the runoff contribute to algal blooms.

Agricultural Wastes Many municipal facilities are located upstream of heavyagricultural areas to avoid contamination from fertilizers, microbial contaminates(Cryptosporidium and Giardia), pesticides, and herbicides. All of these will cause T&Oproblems, as well as, potential health problems. Feedlots, dairies, and commercial pigfarms must comply with NPDES permits to prevent runoffs of animal wastes. Runoffsfrom irrigation operations can also lead to T&O problems due to residuals of pesticides,herbicides, fertilizers, spreading agents, and any microbiological growth in the water.

Housekeeping Plants that have inadequate sludge removal practices will haveissues with T&O due to the sludge turning septic in the plants basins, etc. Plants usingBiological active filters have the potential to form algal blooms due to poorhousekeeping. Failure to prevent water stagnation in the distribution system will alsocause T&O problems. The lack of chlorine residual in stagnant water will allow bacteriaregrowth in distribution lines which results in septic odors and foul tastes.

Household Plumbing Sometimes a customers plumbing is the source of a T&)problem. New construction piping will have a plastic taste, while biological growth instrainers and aerators will have T&O issues. Do not contribute all complaints to thecustomers piping if a widespread event is occurring.

9.139.13 cont.cont.

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Potential Sources T&O problems can originate anywhere and all sources should beinvestigated to determine the source. Once the point of origin is determined, it iseasier to find the underlying cause and develop plans to correct the situation.

Raw Water Sources Use different sampling points to pinpoint where in the raw

water supply the issue is occurring. Once the source is identified, a sanitary survey ofthe source water and its watershed should be conducted. Look for runoff fromagricultural areas, pipelines with potential cross-connections, and nutrients present inthe water.

Treatment Plant look for accumulated sludge and debris, prevent algal blooms ,perform routine cleaning and inspections to prevent T&O problems. Collect samplesfrom various areas within the plant to indentify any potential T&O problems. Operators

should inspect basins and filters for potential biological growth on the walls and filtermedia.

Distribution System Main causes of T&O problems in the distribution system aremicrobiological activity, disinfection residuals and their by-products, organic or mineralcompounds from system materials, and cross connections. Dead-ends and areas of lowflows tend to have the most problems with T&O due to the stagnation of the water.Utilities must be vigilant in requiring and inspecting backflow prevention devices to

prevent cross-connections. Cross connections commonly occur in the following types:(1) a sprinkler supply connected to a non-potable source, (2) potable water used as aseal supply is connected to pump delivering non-potable water, (3) a hose connectedto the house that is left in a swimming pool, (4) a hose connected to a house that isused to apply fertilizers or pesticides, (5) a hose used to flush car radiators

9.29.2 Locating Taste and Odor SourcesLocating Taste and Odor Sources

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Monitoring Program Utilities should develop a program to prevent T&O problemsfrom ever occurring. It is a valuable asset for systems that experience frequent T&Oproblems. A T&O program should include: (1) routine counting and identification ofsource water algal populations and attached algae at the plant, (2) sensory analysis,

such as a taste threshold test, or source and distribution system waters, and plantprofiles.

Raw Water Management Utilities must manage their reservoirs to ensure high-quality water. Monitoring rivers and other tributaries for sources of pollution that mayadversely affect a community water supply are activities that should be conducted aspart of a river management strategy.

Plant Maintenance many plants schedule annual shutdowns to allow inspection

and thorough cleaning of all facilities, especially anything submerged. Another methodis to ensure that the treatment plants ability to treat T&O are functioning properly.Periodic inspection and testing of such equipment is necessary to ensure that it willwork properly when it is needed.

Distribution System Maintenance many systems have areas that are routinelyflushed to prevent T&O problems. Records should be kept to evaluate the effectivenessof flushing. Unidirectional flushing will also help the Utility by removing any biological

growths and eliminate stagnate water. Routine distribution sampling for Coliforms andchlorine residuals can also provide data that gives a snap-shot of the distributionswater quality in developing a flushing program.

9.39.3 Prevention of Tastes and OdorsPrevention of Tastes and Odors

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Methods of Treatment The two main T&O treatment methods are removal anddestruction. Removal techniques include optimumcoagulation/flocculation/sedimentation, degasification, and adsorption. Destruction of

T&O is accomplished by various methods of oxidation.

Improved Coag/Floc/Sed Improving sedimentation is an effective way to removesome T&O problems. Most T&O problems occur during the spring and fall when lakesand reservoirs turnover. Alum has been effective in reducing the organic content in thewater, although turbidity and organic removal may occur at different dosages.

During algal blooms, enhanced coagulation/flocculation can result in longer filter runtimes.

The addition of chlorine to headworks of the plant can increase odor levels by thedestruction of algal cells. Cellular material released by the algal cells and chlorine canform Chlororganic (organic compounds combined with chlorine) compounds whichcan impart an even more objectionable taste to the water.

The degree of success that may be obtained by improving coagulation may be difficultto assess, especially problems of short duration. If it does solve the problem, improvedcoagulation may be simplest and most economical approach available in treating T&Oproblems.

9.49.4 Taste and Odor TreatmentTaste and Odor Treatment

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Description of Process Aeration is the process of mixing air and water throughvarious means. Aeration is only effective in removing gases and organic compoundsthat are VOLATILE (capable of being evaporated or change to a vapor at relativelylow temperatures). Volatile compounds will be noticed as objectionable odors.

The removal of volatile compounds via aeration is known as DEGASIFICATION.Compounds are removed since they exist in lower concentration in the air than thewater. By increasing the aeration rates, the concentration of the objectable may bereduced to levels where they are no longer a problem.

Aeration can also destroy odors by OXIDATION (the addition of oxygen, removal ofhydrogen, or the removal of electrons from an element or compound). This is

effective in reduced inorganic compounds (ferrous iron or manganous manganese).Aeration systems are designed to operate in two ways: air through the water andwater through the air. A process called air stripping combines both by flowingwater over columns of support media while air is pumped through.

Air blowers Air blowers are larger air compressors that supply air under pressure tothe water that is being treated. Effective degasification is accomplished by using verysmall size bubbles to achieve maximum gas transfer.

9.429.42 Aeration Processes and SystemsAeration Processes and Systems

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Cascades and Spray Aerators these are termed waterfall devices since theyoperate like natural waterfalls to aerate the water.

Cascade systems are essentially a series of small waterfalls. The water flows downover a series of tiers, which have a type of medium to increase turbulence and

improve efficiency. Spray aerators work by spraying water through the air to achieve aeration. To be

effective, the water must be dispersed into fine droplets.

Air Stripping air stripping is a process that combines elements of both air blowersand waterfall devices to achieve aeration. This treatment technique is becoming morepopular in removing trace organic contamination (TOCs, etc.).

Air stripping is achieved by flowing water over a support medium or packing that

is contained in a tower while pumping air through the packing in the oppositedirection.

9.429.42 Aeration Process and Systems cont.Aeration Process and Systems cont.

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Types of Processes chemical oxidation is a destructive technique used to controlT&O problems. Objectionable compounds are chemically modified or broken down intoless objectionable by-products. This is the most common method used T&O process.

The four chemicals used are Chlorine (Cl2), Potassium Permanganate (KMnO4),

Ozone (O3), and Chlorine Dioxide (ClO2).

Chlorine to be effective in T&O removal, the Chlorine dose is usually greater thanthe dosage required for disinfection. Easily detected odors, such as fishy, grassy, orflowery odors, can be decreased significantly by increased Chlorine dosages.

The success of chlorination, as a T&O treatment, will depend on the type of odor,the seriousness of the problem, the dose applied, and the contact time betweenchlorine and the water prior to delivery to the customer.

Superchlorination have been used successfully to treat difficult T&O problems.The treated water must be dechlorinated to remove excess chlorine residuals.

Chlorine can be counter-productive by forming Chlorophenolic compounds whenChlorine reacts with Phenolic compounds in the water. These compounds causenoticeable T&O in concentrations 40 to 200 times less than the original phenol.

9.439.43 Oxidative ProcessesOxidative Processes

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Potassium Permanganate potassium permanganate (KMnO4) has been used

for a number of years in water and wastewater treatment. It is a strong chemicaloxidizer that can destroy many organic compounds.

It can oxidize iron, manganese, and sulfide compounds and is used in

aeration for the control of these and other T&O producing substances.

A critical aspect of KMnO4 is color control. It will produce an intense purple

color when mixed with water. When it oxidizes, KMnO4 will turn from purple to

yellow or brown. The final product of the reaction is Manganese Dioxide(MnO2), an insoluble precipitate that can be removed via sedimentation and

filtration. If the color reaches the filters, the customers may experience pink

water and you will experience a headache answering the phones!The most effective injection point is at the inlet of the Plant. This allows anextended contact time for the reaction to produce MnO2 and a somewhat

higher KMnO4 if needed.

An overdose of KMnO4 can be controlled by feeding activated carbon until the

dosage rate has been adjusted.

Typical application rates for T&O control are about 0.3 to 0.5 mg/L, throughthe range reported is from 0.1 to 5 mg/L.

9.439.43 Oxidative Processes cont.Oxidative Processes cont.

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Handling of Potassium Permanganate Permanganate is a dry, crystallineproduct that is best delivered from a dry feeder into a special mixer prior to feeding.Care must used in personal protective equipment and dust removal

Ozone O3 is an unstable form of Oxygen that is an extremely powerful oxidant.

O3 is produced by passing dry air, or oxygen, through a high energy ionizing unit

known as an ozonator. Ozone is very unstable and most be produced onsite fortreatment.

Ozone is a stronger oxidant than chlorine and destroys a wider range of organiccontaminates. Ozone usually does not form objectionable by-products andespecially effective if the T&O problem is industrial in origin.

Chlorine Dioxide ClO2 is another chemical oxidant that is being used more due to

the concern of trihalomethane formation after chlorination.

ClO2 is an extremely strong oxidant that is form by reacting sodium chlorite and

chlorine in a special ClO2 generator. It must be generated onsite since it is an

unstable compound.

Some facilities have experienced T&O problems during the initial trials.

ClO2 has the potential to form unwanted chlorite and chlorate ions. These have

the potential to have health-related effects of these reacted products.

9.439.43 Oxidative Processes cont.Oxidative Processes cont.

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Adsorption is a process of removing materials from water by adding a materialto the water to which T&O producing compounds will attach themselves. This isaccomplished in two ways:

2. The addition of Powdered Activated Carbon (PAC) to the treatment process

3. The use of Granular Activated Carbon (GAC) as a filter medium.

The materials are activated by high temperature and a high pressure steamtreatment. The original sources of carbon include: wood, coal, coconut shells, orbones.

The purpose of the activation is to increase the surface of the particles so thatmore adsorption can take place per pound of carbon. The surface of activatedcarbon may range from 400 to 2000 m2 per gram.

An important consideration is the nature of the porous structure will exert asignificant effect on the success of the treatment. If the pores are too small, thecompounds being treated will not be able to enter the structure. Adsorptionoccurs on the surface and carbon with a greater surface area generally providegreater adsorptive capacity.

Carbon is rated on a basis of a phenol or iodine number. The higher the value,the greater the adsorption value.

9.449.44 Adsorption ProcessesAdsorption Processes

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Description of Process

PAC adsorption is the most common technique used for T&O problems in the US.

PAC has limitations and dosage rates vary from plant to plant.

PAC may be applied to the water at in point in the process prior to filtration. Themost effective feed point is prior to the Plants mixing facilities.

Chlorine and PAC neutralize each other and PAC is less effective after

chlorination. It is not a good practice to apply chlorine and PAC near the samelocation.

KMnO4 is sometimes used with PAC to prevent colored water problems in the

distribution system.

PAC dosages range from 1 to 15 mg/L. Some facilities have used up to 100 mg/Lfor treatment! A GAC (Granular Activated Carbon) filter may be required if thePAC dosage requirements are very high.

9.4419.441 Powdered Activated CarbonPowdered Activated Carbon

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PAC Feed Systems

PAC feed systems may be either dry-type feeders or slurry feeders.

Dry-type Feeders are primarily used in smaller systems or for short-term,occasional incidents.

Slurry (a watery mixture or suspension of insoluble matter) systems requirecontinuous mixing to prevent settling or caking of the carbon. Most treatmentplants clean their Slurry Tanks before each delivery to clean out any foreignmaterials and to visually inspect the equipment.

PAC is a hydrophobic material and water should be sprayed from overhead in the

Slurry Tanks. This overhead spray also helps with dust control, as well as, theinitial mixing of the PAC.

9.4419.441 Powdered Activated CarbonPowdered Activated Carbon

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Dose DeterminationDosage will depend upon the nature of the problem, the concentration of thematerial to be removed, the mixing available, the contact time, and the locationof application point.

Accurate determination of the threshold odor number (TON) of a sample isdifficult to make when several jar tests are run at once. A persons sense ofsmell becomes fatigued after just two or three TON tests and becomedesensitized to the odors present.

One difficulty often overlooked is the problem of measuring the actualconcentration (lbs/gal) of PAC in the slurry tank. Normally, slurry tanks areloaded at the rate of one pound of PAC per gallon of water. Results can beverified by using a Imhoff cone. An Imhoff cone is a clear, cone-shaped containermarked with graduations and is used to measure the volume of settleable solidsin a specific volume.

9.4419.441 Powdered Activated CarbonPowdered Activated Carbon

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Filter performance may be decreased while feeding PAC. Caking of PAC on thefilters can cause shorter filter runs. Removal of PAC from the SedimentationBasins will improve filter run times.

Turbidimeters will NOT warn of the carbon passing through the filters and can

cause dirty water complaints.To determine carbon penetration, a simple method is to collect a one-litersample and pass it through a 0.45 m membrane filter. Any color will be easilyseen on the white filter.

9.44139.4413 Filtration ConsiderationsFiltration Considerations

9.44149.4414 PAC HandlinPAC Handlin

PAC is usually purchased either in individual bags (50 lb) or by the bulk truckload ( up to 40,000 lbs).

PAC produces a lot of dust when handled and the dust must be controlled.

PAC will actively remove oxygen from the air. Appropriate PPE must be used toensure Operator safety during handling. NEVER work alone in a carbon tank.

It is recommended that PAC be stored off the floor on pallets.Carbon is combustible and it should be stored away from other materials. Thisis especially true for KMnO4 and HTH compounds. All electrical outlets and

wiring should be designed for use in a flammable environment.

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Before a T&O treatment regimen is started, the problem must be identified.Communications plays a vital role in the determination of the issue.

Personnel should have a water quality complaint form to fill out. The Operatorcan fill out this document when taking a complaint from a customer.

Customers who contact the utility should be treated courteously andrespectfully, and should be considered a vital resource to help the utility in itsefforts to provide a high quality water for public consumption.

Operator should alert the appropriate personnel when a complaint is received toset up a response.

It is not always necessary to rely on customer complaints for known seasonalevents. Records should be maintained and used to anticipate future T&Oproblems. These records should contain the treatment method used and theresults of the treatments, as well.

9.59.5 Identifying a T&O ProblemIdentifying a T&O Problem

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The first step is to recognize a problem exists and to determine the extentof the problem.

Rule out the customers plumbing if there is not any widespreadcomplaints.

If the entire system is affected, you must determine where the problemoriginates.

Review sample results from different locations throughout the system.This will help to narrow down the possible location of the T&O problem.

Do not waste time evaluating treatment programs that are not availablefor use at your treatment plant.

Once the problem has been identified, determine what treatment orcombination of treatments is effective in reducing or eliminating theobjectionable qualities of the water.

Operators should perform routine collection and counting of algaepopulations in the source water.

The Utility should initiate a public awareness program to educate thecustomers about the T&O issue and what the Utility is doing to correctthe problem.

Prevention is always the best treatment strategy!

9.69.6 Developing a T&O Control StrategyDeveloping a T&O Control Strategy

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Taste and Odor Treatment FormulasTaste and Odor Treatment Formulas

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Thanks for Listening!Thanks for Listening!

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