Water Testing Procedure Handbook
Our Water Test Book Cover CONTROL METHODS AND Required EQUIPMENTS and recommended Analytical Methods, Recommended Analytical Equipment, Composition Of Reagents, Preparation Of Sample & Care Of Equipment, METHODS (Titration Methods, Colorimetric Methods, Photometric Methods, Expression of Analytical Results, Equivalent Per Million (epm), calculation of Dissolved Solids by EPM)
CONTROL METHODS AND EQUIPMENT ::: Why RXSOL WATER TEST BOOK is Required ?
In industrial water conditioning, chemical analyses are necessary to govern the treatment processes. Water treatment without control analyses would be useless and sometimes harmful. For control purposes, a complete analyses of the water is usually not required. For, example, in sodium zeolite softening the important determinations are hardness and chloride. The hardness test is used to determine the end of the softening cycle the chloride test determines the end of the rinse cycle. A complete water analyses to control a zeolite softener would be pointless. Similarly, in lime or lime soda softening the important tests are hardness, phenolphthalein alkalinity, and methyl orange alkalinity. These three tests provide proper control of the softener under normal circumstances. Due to residence times in precipitation processes, it is sometimes necessary to test the influent water in addition to the effluent. For control, the alkalinity, hardness and calcium should be monitored in the influent.
When the proper tests have been selected, the analyses must be conducted by some responsible person at the plant because the results determine adjustments required in chemical treatment. Treatment methods and practices should be checked by complete analyses at periodic intervals by the supervising laboratory. However, the actual daily control of any treatment process should be in the hands of the plant personnel. The tests must be conducted promptly after sample collection so that the chemical nature of the sample is unchanged and any treatment adjustment necessary can be placed into effect without delay. While many processes require more frequent tests and treatment adjustment, the minimum frequency is usually once daily.
Recommended Analytical Methods
In this book, all recommended test methods are those which are the most applicable for control analyses by the plant personnel. These methods have been selected for their simplicity, rapidity and convenience with minimum sacrifice of accuracy. While suitable for use by an experienced chemist, the tests also can be employed by personnel with no formal chemicals training.
Methods are given for those tests commonly conducted for the control of various softening processes; internal boiler water treatment and the conditioning of industrial cooling water. Tests made infrequently, or under unusual circumstances, such as sodium, potassium, fluoride, boron, etc. have been omitted. No tests have been included for bacteriological or sanitary purity.
The recommended test methods in this book are adopted, for the most part, from such authoritative works as the “Annual Book of ASTM Standards”, published by the American Society for Testing Materials and “Standard Methods for the Examination of Water and Wastewater”, published jointly by the American Public Health Association, American Water Works Association, and the Water Pollution Control Federation. The referee methods published in these references are intended to be the most precise and accurate known. It is recommended that these publications be consulted where further information is needed or in cases in which the utmost precision and accuracy are required, such as for research work or where litigation may be involved.
Recommended Analytical Equipment
In titration methods, only common laboratory glassware is usually required. However, in colorimetric work, a wide variety of comparators and photometers are commercially available, while color comparators or photometers, photometer measurements are more sensitive, selective, accurate and precise.
Commercial photometers are relatively inexpensive and are suitable for most industrial control water analysis.
Composition of Reagents
The chemical reagents specified, such as “Sulfuric Acid, Concentrated” under the individual tests should all be reagent grade laboratory chemicals. Where standardized reagents have been specified, the composition of these reagents is shown under the section of this book entitled “Composition of Prepared Reagents”. However, standardized reagents should be prepared only in a well-equipped laboratory, under the supervision of an experienced chemist. It is advisable to purchase standardized reagents from laboratory supply house if complete laboratory facilities are not available for their preparation.
Preparation of Sample
If the results obtained from an analyses are to be valuable, it obviously is necessary to secure a sample that is truly representative of the condition of the water at the point at which the sample was obtained. For example, in sampling from a boiler, the sampling point should be blown thoroughly before the sample is taken. It is desirable to sample the boiler from the continuous blow down rather than from gauge column. It is also important to secure the sample with as little flashing of steam as possible, using a cooling coil for this purpose. In the case of a sample from a tap or valve, the water should be run for a few minutes before collecting. Sampling points should always be selected to secure a representative sample rather than from a “dead spot.” The sample should be collected in a clean container which has been rinsed several times with the water to be sampled.
The sample should be cooled to room temperature (60 to 80oF) and any suspended matter permitted to settle. Analysis is made on the clear supernatant liquid. Other necessary precautions have been noted under the individual tests.
Care of Equipment
Too much emphasis cannot be placed on the necessity for keeping the apparatus clean at all times to obtain accurate results. Bottles and containers should be cleaned carefully after each using. Apparatus used in chelant testing should be of plastic instead of glass and must be kept free of hardness and other contamination.
All measuring apparatus such as pipes and graduate cylinders should be carefully rinsed before using, preferably with a portion of the water to be tested. Flasks, casseroles and similar vessels in which titration are made should be rinsed with distilled water, but a portion of the water to be tested may be used if distilled water is not available.
Titration Methods
Historically, the most common method of plant control analyses was by titration. This method of testing is based on the use of a buret from which an amount of standard solution is added to the sample until an “endpoint” is reached. The endpoint usually is a color change.
For plant use, automatic burets should be employed. Automatic burets of varying capacity are commercially available. The automatic feature consists of a reservoir for “automatic filling of the buret, and some are also constructed to start each titration at a “zero” reading.
Always use the same buret for any given standard solution. Always arrange buret in some standard order to avoid confusion.
If automatic burets are employed, fill the reserve with standard solution to be used, first rinsing the reservoir bottle and the buret with a small amount of the solution. Larger automatic burets are often equipped with a flexible plastic reservoir bottle. This type of buret is filled by squeezing the bottle until the reagent rises above the “zero” mark and then releasing the pressure.
In smaller automatic burets (2 and 3-ml capacity), a reservoir beside the buret is controlled by the buret stopcock. In one position of the stopcock the buret fills into the titration vessel.
In titrating from any buret, be certain the outlet tip is filled with solution before starting a titration. The reading of the liquid level in either a burette or a graduated cylinder should always be made at the bottom of the curved surface, called the “meniscus”.
This illustration is typical of the appearance of a meniscus in an ordinary buret or a graduated cylinder. In some automatic burets, the center tube slightly affects the curvature of the meniscus.
Burets used in plant should be protected against breakage and maintained in a position ready for use. Most plants have found the use of a test cabinet containing all the equipment to be most satisfactory.
However, in protect laboratories, offices, or similar areas, a simple titration stand for holding the buret is satisfactory.
Colorimetric Methods
Colorimetric tests are particularly useful for plant control because they are simple. These methods are based on the development of a color in the sample, which is proportional to the concentration of the substance to be determined. The concentration present in the sample is determined by comparison with color standards.
The historical method of color comparison was with the use of Nessler tubes. These tubes are available in matched sets made from uniformly drawn tuning. Nessler tubes are used in color comparison work by comparing the color produced by the unknown sample with the color of standard solutions of different concentrations, after treatment with the color developing reagents. Since standard solutions of known concentration must be prepared for each set of tests, Nessler tubes are not adapted to rapid control analyses.
For color comparison work in control water analyses, it is recommended that one of the several types of commercial color comparators be used. Color comparators are available in which the color standards are sealed in glass ampoules. Other comparators use colored glass or plastic disc as standards. Still other commercially available comparators combine sealed glass ampoule standards with reagent containing ampoules. When the tip of the reagent ampoule is broken in the sample solution, the vacuum draws up a specific volume of unknown to mix with the reagent. The unknown ampoule is then compared to the sealed standards. Units of this type are preferred to Nessler tubes for control purposes.
Photometric Methods
As water treatment problems and the methods for their solution have grown more complex, there has arisen the need for more accurate analytical determinations not only in laboratory and research analyses, but in some cases for routine plant control.
One of the most useful tools available to the analyst in this search for more sensitive methods is the filter photometer. In general terms, a photometer can distinguish differences in color intensity not apparent to the human eye and can consistently provide a reliable reproducible reading. In addition, a spectrophotometer can measure light absorption in the ultraviolet and infrared ranges, not visible to the human eye. A flame accessory for the spectrophotometer normally is used in the determination of minute quantities of such elements as sodium, lithium and potassium.
Principle of Operation. White light, passing through a solution, is partially absorbed. The unabsorbed portion produces a sensation of color to the human eye. The strength of depth of this color varies as the intensity of the unabsorbed light.
A photocell can be used to measure the intensity of the unabsorbed light, thus determining the light absorptive capacity of the solution. Consequently, with photometers it is the light absorptive properties of the solution which are measured. The instrument does not measure color, but instead the intensity of light transmitted through the solution.
Photometers operate by responding to the unabsorbed light which is passed through the solution in the absorption cell and which strikes a photocell. The photocell transforms the light into an electric current which is proportional to the intensity of the light. This current is measured by a microammeter, to produce a reading on the dial. For solutions following Beer’s law, the dial reading thus obtained is proportional to the intensity of the color in the solution, which in turn is proportional to the concentration of the ion being measured.
In analytical measurement, it is desirable to measure the light absorptive capacity of the solution at a wavelength where there is maximum light absorption by the solution. Instead of passing white light through the solution in the absorption cell, filters are used which absorb all light except that the desired wave length. By using such a properly selected filter, maximum sensitivity can be obtained. Theoretically, for the most precise work monochromatic light (light of one wavelength only) should be used. Spectrophotometers can produce nearly monochromatic light, but normally are too expensive and fragile for plant control. Filter photometers use glass filters which pass light in a narrow range of wavelength only.
Application in Water Analyses. As previously mentioned, the use of photometers is most pertinent where greater accuracy is desired than is possible with visual color comparators that use fairly wide spaced standards, For example, if the phosphate content of the boiler water is controlled between 30 to 60 PPM as PO the use of conventional color comparator is satisfactory and there is no need for the additional accuracy secured by a photometric method. However, where phosphate may be controlled between 3 to 6 PPM is some once through cooling water systems or within narrow limits in some high pressure boiler water, the photometric method provides many advantages.
Some titration methods for chromate in cooling water systems are subject to interference by various contaminants. The diphenylcarbazide test is preferred because of its freedom from such interference. Comparator methods using fixed standards are unsatisfactory because the reagent rapidly deteriorates. The photometric method possesses such a high degree of accuracy that even when high dilutions of the sample are made, no significant error is introduced.
Similarly, for those situations where small concentrations of nitrate, copper, iron, sulfate and other species are significant, the use of photometric method is advisable.
With photometric methods it is important to be aware of the effect of temperature on color development. With practically any test there is a definite effect of temperature on color intensity and consequently on the photometer dial reading. To secure reliable result, all samples should be tested at the same temperature used in preparing the calibration curve, namely room temperature. The normal variation in room temperature is not significant in most tests. However, where the utmost accuracy is required, all standardization and testing should be conducted at exactly the same temperature.
Other Equipment and Methods
There are other methods of analyses which are important to the water treatment engineer, but which are too tedious and complicated to lend themselves to plant control.
Such methods as flame photometry, atomic absorption spectrophotometry, X-Ray fluorescence and diffraction and other are important in the laboratory. However, there are other special instruments which may be required for plant control for certain tests, for example, the turbidimeter. Where turbidity is an important control, such an instrument is desirable.
Another special instrument which is important in plant control is the conductivity meter. This instrument measures electrical conductance which is proportional to dissolved solids. The method of test is particularly important in the control of boiler blowdown and as a check on steam and condensate purity.
Finally the battery or line operated pH meter is recommended where greater accuracy in pH measurement and alkalinity titration is required.
Expression of Analytical Results
In the analysis of a water sample, it is necessary to determine the presence of various substances usually found in extremely small amounts. The expression of results in percentage would require the use of cumbersome figures. For this reason the results of a water analysis usually are expressed in parts per million (ppm) instead of percentage. One part per million equals one ten thousandth of one per cent (or 0.0001%).
One part per million means one part in a million parts. For example, one ounce in a million ounces of water. It makes no difference what units are used as long as the relationship between the substance reported and the water is the same. As a further example, one part per million does not equal one pound in a million gallons of water since the units are not equivalent.
Just as the use of percentage is avoided in figure of parts per million when reporting the results of a water analyses, there are circumstances which may make the use of parts per millions somewhat cumbersome. When elements are present in minute or trace quantities, the use of parts per million results in decimal values. It is therefore more convenient to use parts per million (0.001 ppm). For example, in conducting studies of steam purity using a sodium content, values as low as 0.0001 ppm are more conveniently reported as 1.0 ppb.
All the analytical methods in this book contain the calculations required to obtain results in parts per million (ppm).
Test procedures and calculations of results are based on the milliliter (ml) rather than the more common cubic centimeter (cc) The defined distinction between the two terms is so slight that it has no practical significance, but technically the expression milliliter is preferred in this work. By definition, a milliliter is the volume occupied by one gram of water at 4c in vacuo, whereas a cubic centimeter is the volume enclosed within a cube one centimeter on each side. (1 ml =1.000028 cc).
Equivalent Per Million (epm)
Another unit sometimes used in reporting water analyses on an ion basis is the term equivalent per million (epm). This method is closely allied to the use of parts per million and consists in reducing all constituents to a common denominator chemical equivalent weight.
The use of equivalent per million is not recommended for normal plant control. Parts per million is a simpler form of expressing results and is accepted as the common standard basis of reporting a water analysis. However, whenever extensive calculations must be performed, the use of equivalents per millions greatly simplifies the mathematics since all constituents are on an equivalent weight basis. The remainder of this section provides a discussion of parts per million and equivalent per million for those who desire a working knowledge of these methods of expression for purpose of calculations.
A part per million (ppm) is a measure of proportion by weight and is equal to a unit weight per million unit weights of solution. Control testing is conducted without measuring the density of the solution.
Therefore, in common practice ppm has come to mean unit weight by volume which would be required to give a million unit weights of solution (e.g. milligram per liter 0.001g/1000g). For common solutions and suspensions, this poses no great inaccuracy since the density of the solutions is approximately one. Caution should be taken in measuring very dense or very light solutions, however. For example, the suspended solids content of a dense sludge from a classifier underflow may exceed one million “ppm” expressed in units of mg. But closed cooling systems using high preparations of organic solvents in water often have densities significantly less than 1 gram per milliliter.
An equivalents per million (epm) is a unit chemical equivalent weight per million-unit weights of solution. Again, the volume equivalent of the million unit weights is almost invariably used, and the precautions are the same as described above. Concentration in epm is calculated by dividing concentration in ppm by the chemical equivalent weight of the substance or ion. This unit is also referred to as milligram equivalents per kilogram or milliequivalents per liter.
The concept of ppm and epm are commonly combined in normal reporting of water analysis, and many different constituents are frequently reported on a common unit weight basis. For example, calcium (equivalent weight = 20.0) is reported in terms of CaCO3 (equivalent weight =50.0) - calcium as CaCO3. The test for calcium is calibrated in terms of CaCO3, so the conversion factor
2.5 (50.0 ¸20.0) need not be used. Likewise hardness, magnesium, alkalinity and free mineral acids are also usually reported in terms of CaCO3; the value reported is the weight of CaCO3 that is chemically equivalent to the amount of material present. Among these substances, ionic balances may be calculated. When constituents are the same unit weight basis, they can be directly added or subtracted. For example, ppm total hardness as CaCO3, minus ppm calcium as CaCO3 equals ppm magnesium as CaCO3. Note, however, that ppm magnesium as Mg equals 12.2 (magnesium equivalent weight) ¸ 50.0 (CaCO3 equivalent weight) times the ppm magnesium as CaCO3. In every case, it is necessary to define the unit weight basis of the results -“ppm alkalinity as CaCO3” or “ppm sulfate as SO4” or “ppm silica as SiO2”. Where the unit weight basis is different, calculations must be based on the use of chemical equations or equivalents per million
The following rules illustrate where epm can be used and where ppm must be used. In general, where an exact chemical formula is known, either ppm or epm may be used. When such knowledge is lacking, ppm must be used.
The concentration of all dissolved salts may be expressed either in ppm or epm of the individually determined ions.
Two or more ions of similar properties whose joint effect is measured by a single determination may be reported either in ppm or epm. For example, total hardness, acidity and alkalinity.
The concentration of undissolved or suspended solids should be reported in ppm only.
The concentration of organic matter should be reported in ppm only.
The concentration of dissolved solids (by evaporation) should be expressed as ppm only.
Total dissolved solids by calculation may be expressed either in ppm or in epm.
Concentration of individual gases dissolved in water should be reported in ppm. The total concentration of each gas when combined in water may be calculated to its respective ionic concentration in either ppm or epm.
Calculation of Dissolved Solids by epm
Starting with a reasonably complete water analyses, dissolved solids may be calculated by means of epm. In a complete water analyses, the negative ion epm will equal the positive ion epm. Where there is an excess of negative ion epm, the remaining positive ion epm usually is assumed to be sodium or potassium, or both, and for the sake of convenience generally is considered to be sodium. Where there is an excess of positive epm, the remaining negative epm usually is assumed to be nitrate provided the analyses is rather complete.
To calculate dissolved solids, convert the various constituents from ppm to epm and total the various cations (positively charged ions) and anions (negative ions). The cations should equal the anions. If not, add either sodium (plus) or nitrate (minus) to balance both columns. Then convert each component to ppm as the individual ionic weight and sum to a total in order to obtain ppm dissolved solids.
In the example shown to convert 150 ppm calcium as CaCO3 to epm, divide by 50 (the equivalent weight of calcium carbonate) and obtain 3.0 epm. To convert 96 ppm sulfate as SO4 to epm, divide by 48 (the equivalent weight of sulfate) and obtain 2.0 epm. After balancing the cations and anions by the addition of sodium, convert to ionic ppm by multiplying the epm by the particular ionic equivalent weight. For example, to convert 3.0 epm calcium to ppm calcium as Ca, multiply by 20 (the equivalent weight of calcium) and obtain 60 ppm calcium as Ca. To obtain the ppm dissolved solids, total the individual ions.
These are fiew topics, which is described in our RXSOL Water Test Book - ( Book is available for SALE )
1.ACIDITY(FREE MINERAL) TITRIMETRIC METHOD (0-200 PPM)
2.ALKALINITY (TITRIMETRIC METHOD 0-200 PPM)
3.ALUMINIUM (ERIOCHROME CYNINE R METHOD 20-300 ppb)
4. AMMONIA (PHOTOMETRIC METHOD 0.2 ppm)
5. CALCIUM (TITRIMETRIC METHOD 0-200 ppm as CaCO3)
6. FREE CARBON DIOXIDE: (DIRECT TITRATION METHOD, 0-100 ppm)
7. CHLORIDE (MOHR METHOD 0-200ppm)
8. FREE CHLORINE (DPD PHOTOMETRIC METHOD 0.4 ppm)
9. CHROMATE, TITRATION METHOD 10-100 ppm as CrO4 & PHOTOMETRIC METHOD (0-30 ppm as CrO4)
10. TOTAL CHROMIUM, PHOTOMETRIC METHOD (0 TO 30-PPM AS CrO4)
11. CONDUCTANCE OF BOILER WATER
12. CONDUCTANCE OF STEAM CONDENSATE
13. COPPER PHOTOMETRIC METHOD (0-5 ppm)
14. EDTA CHELANT DEMAND, TITRIMETRIC, PHOTOMETRIC METHOD AND NTA CHELANT DEMAND TITRIMETRIC METHOD
15. HARDNESS, TITRATION METHOD (0-2000 ppm)
16. HYDRAZINE, PHOTOMETRIC METHOD (0-0.3ppm)
17. IRON PHENANTHROLINE METHOD (0-2 ppm)
18. NITRATE BRUCINE, COLORIMETRIC PROCEDURE (0-30 ppm)
19. CADMIUM REDUCTION METHOD
20. NITRITE DIRECT TITRATION METHOD (0-230 ppm)
21. DISSOLVED OXYGEN, WINKLER METHOD (0-0.8 ppm O2)
22. pH, GLASS ELECTRODE METHOD
23.ORTHOPHOSPHATE & TOTAL INORGANIC PHOSPHATE & TOTAL PHOSPHATE PHOTOMETRIC METHOD (0-10ppm as PO4)
24. SOLUBLE SILICA, PHOTOMETRIC METHOD (0-4 ppm & 0-50 ppm SiO2)
25. SULFATE, TURBIDIMETRIC PHOTOMETRIC METHOD (0-50ppm)
26. SULFITE, TITRIMETRIC METHOD (0-100ppm)
27. TURBIDITY
28. ZINC PHOTOMETRIC METHOD (0-3 ppm)
MICROBIOLOGY OF COOLING WATER
INTRODUCTION & SAMPLING FOR MICROBIOLOGICAL ANALYSIS
TOTAL VIABLE COUNT (TVC)
(Summary of Method, sample requirements, procedure)
SULFATE REDUCING BACTERIA (SRB)
(Summary of Method, procedure, MPN Table)
IRON OXIDISING BACTERIA (IOB)
(Summary of Method, sample requirements, procedure)
ALGAE
Equipments required for testing & Procedure
MICROBIOLOGICAL WATER ANALYSIS FORMAT
Also covers Standard solution preparation method :
Acetic Acid Sodium Acetate Buffer
Alkaline Potassium Iodide
Aluminium standard
Ammonium Molybdate Solution & Ammonium standard
Ascorbic Acid Solution
Barium Chloride, 10%
Bromothymol Blue Indicator
Brucine Reagent
Calcium Indicator & Calcium Standard Solution, 50 ppm as CaCO3
Chelant Blank Reagent, Chelant Demand Reagent P1, P2, P3 & P4, Chelant Indicator No.1, 2, & 3
Chelant Liquid Buffer
Chromate Reagent & Chromate Standard
Chromium Reagent
Conductivity Standard
Copper Reagent P1, P2 & Copper Standard
DPD Indicator
Disodium Ethylenediamine Tetraacetate (EDTA) solution, 0.01M
EDTA Standard solution & EDTA Titrating solution
Eriochrome Cyanine R Dye Indicator
Glycerol Sulfate Solution
Hardness Buffer Reagent ; Hardness indicator ; Hardness Titrating Solution, 1 ml = 1 mg CaCO3
Hydrazine reagent A, B, C & D ; Hydrazine standard
Hydrochloric acid, 0.02N; Hydrochloric acid, 2%; Hydrochloric acid, 10%; Hydrochloric acid, 50 %
Hydrochloric acid, 3%
Iodide crystals
Iron reagent & Iron standard
Manganous sulfate
Methyl orange indicator & Methyl purple indicator
Molybdate Reagent
NTA Standard Solution & NTA Titrating Solution
Nessler Reagent
CAUTION: TOXIC AVOID INGESTION
Neutral Barium Chloride Solution
Nitrate Standard
Nitric Acid, 10 %
Orthophenenthroline Reagent
Phenolphthalein Indicator
Phosphate Buffer Solution & Phosphate Standard
Potassium chromate indicator ; Potassium Iodide-Iodate, 1 ml=0.5 mg SO3 ; Potassium Permanganate, 0.1N ;
Potassium Permanganate Solution
Silica Standard & Silica Nitrate, 1 ml = 1 mg Cl
Sodium Carbonate, 0.02N & Sodium Carbonate, 0.045N
Sodium Fluoride Solution, 3% ; Sodium hydroxide 1.0N ; Sodium hydroxide, 14N ; Sodium Sulfite Solution ;
Sodium Thiosulfate, 0.1N
Stannous chloride reagent
Starch Indicator
Starfamic Indicator & Starfamic Acid
Sulfate Standard & Sulfite Indicator
Sulfuric Acid, 0.02N ; Sulfuric Acid, 1.0N ; Sulfuric Acid, 6.0N ; Sulfuric Acid, 5% ; Sulfuric Acid, 10%
Sulfuric Acid, 30% ; Sulfuric Acid, 50%
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