Water Treatment Handbook by ADIL

Water Treatment Hand Book

PREFACE Aqua Designs was started with the mission of providing eco friendly solutions which will be useful for individuals, industries and also to nature. Since its inception, Aqua Designs has offered successful solutions on environmental perspective which has created a unique place in the industrial sector. The vision of MD Mr. Suthakar is to spread the message of harvesting water, reducing its usage, recycling and reuse. This vision transformed into collection of data on water and its uses and sharing this knowledge with one and all in order to make this world a lively place to live. .......... and hence this book. With best compliments from S. Suthakar Managing Director – Aqua Designs

ABOUT US Aqua Designs – Offers A to Z solutions for water and waste water treatment. A one Stop Shop for all types of consultancies in water and waste water management. Aqua Designs commitment to the environment, keeps it in the forefront of product innovations, purification and recycling technologies. Aqua Designs provides water solutions for Institutions, Industry, Municipal Authorities, and Commercial and Public properties. The Company boasts of the widest range of specialty water-related products and services that are ISO 9001:2000 certified by RINA of Italy. Aqua Designs was the proud recipient of the prestigious Award for The “Best Upcoming Water Company 2006 – 2007”given by the magazine Water Digest in association with UNESCO, NDTV Profit & WES-Net India in order to acknowledge those persons and Organizations, who have contributed toward water and its industry. Aqua Designs was also the proud winner of the Awards for “Best Water Treatment Project – Industrial 2007-2008” & “Best Water R&D and Technological Breakthrough 2007-2008” instituted by Water Digest. For the year 2008-2009, Aqua Designs added one more feather in its cap. It bagged two more Awards instituted by the Water Digest for the categories Best Consultancy & Best Water Conservation IT Park showing its strength in IT Sector using MBR Technology. A proven track record of offering A – Z solutions was appreciated and the Best Consultancy Award is the proof for that. The Company has excellent marketing and sales team with a cumulative experience beyond 100 years. It is one of the major reason for Aqua Designs entering big corporate and Multi National Companies. Due to its expertise the Company is able to offer competitive Designs and proposals, which keeps the competitors at bay .This proven technology has made the company one of the front runners in this field.

Aqua Designs success depends on its human resources. From Designs, Proposals, Projects, Erection and commissioning to operation and maintenance, it has proved its capability in the market which gives them a clear edge over others in the market. Aqua Designs is supported by its own State-of-the-Art Laboratory for testing water, waste water, air & stack samples both for physiochemical and microbiological parameters as per PCB norms and IS standards. We have the facility to monitor stack emissions and ambient air quality...The facility is certified under ISO 9001:2000. The Laboratory handles and supports all in house requirements; specific client needs and also offers Pilot Plant studies. Aqua Designs provides services starting from EIA to Designs to implementation of Projects to Operation & Maintenance to Supply of Specialty Chemicals to run the operations and finally to analyze the various products of the treatment using its Laboratory facility. Aqua Designs also has its own chemical manufacturing and fabrication facilities to support its growing needs in business. Aqua Designs was formed with the sole intention of suggesting eco friendly solutions for Industries and Municipalities. The vision was to provide solutions to varied sectors in par with the developed nations. Aqua Designs not only offers the concepts and design to their customers, but also stay with the customer and successfully operate the scheme for years. The customer satisfaction has lead Aqua Designs to be successful in various types of Industries ranging from Petrochemicals, Automobile, Food and Beverages, Breweries and Distilleries, Chemicals, Electronics, Power Industries etc. Aqua Designs believes only in continual improvement. It keeps offering innovative solutions to its customers. One such is the concept of Membrane Bio Reactors technology for treating the Sewage. Aqua Designs has now set a trend such that big IT Parks have started using MBR Technology. Aqua Designs is leaping forward like a giant and nothing can stop it. In the near future it aspires to be a Global leader. Aqua designs “believes in Better the Best” and this has made everything possible.

CHAPTER 1 Impurities in Water................................ ................................................................ ......................

1

CHAPTER 2 Filters ................................................................ ................................ ...........................................

8

CHAPTER 3 Iron Removal Filters ................................ ................................................................ .....................

13

CHAPTER 4 Ion Exchange ................................ ................................................................ ................................

17

CHAPTER 5 Softener ................................................................ ................................ .......................................

36

CHAPTER 6 Membrane System................................ ................................................................ .......................

40

CHAPTER 7 Steam Boiler ................................ ................................................................ ................................

49

CHAPTER 8 Cooling Water Treatment................................ ................................ ................................ .............

62

CHAPTER 9 Pumps ................................................................ ................................ ..........................................

79

CHAPTER 10 Raw Water Treatment ................................ ................................................................ .................

84

CHAPTER 11 Industrial Waste Water Treatment ................................................................ ..............................

92

CHAPTER 12 Chemical Cleaning................................ ................................................................ ........................

97

WATER SAMPLE TEST PROCEDURES ................................................................ ........................ 107 Phenolphthalein (P) Alkalinity Test Procedure ................................ ................................ ........ 109 Total (M) Alkalinity Test Procedures ................................................................ ....................... 110 Conductivity Test Procedure ................................ ................................ ................................... 112 pH-Electrometric Method Test Procedures ................................................................ ............. 113 Total hardness Test Procedures ................................................................ .............................. 114 Sulphite testing procedure ................................ ................................ ...................................... 115 Chloride Test Procedure ................................ ................................ ................................ .......... 116 Checking Acid Solution Strength for Cleaning ................................ ................................ .......... 117

UNITS AND MEASUREMENT CONVERSION ...................................................... 118 BASICS................................................................ ................................ ..................................... 119

CHAPTER 1

01

Impurities in Water Water impurities Impurity in water technology is a relative term. For example Hardness is not considered as an impurity in drinking water but in industrial water treatment it leads to scaling of equipment and hence considered as an impurity. Common impurities in water, their effect and method of removal are as follows: Impurities

Can clog pipelines and equipment can choke Ion exchange resin and RO membranes

Coagulation, and filtration

Color

Indication of organic, iron etc. and can be harmful to the unit operation ahead.

Coagulation, settling filtration, followed by activated carbon filter.

Organic matter

Can foul Ion exchange resins membranes and may be detrimental to process.

Coagulation, setting, filtration, followed by activated carbon filtration.

Bacteria

Will depend upon the type of bacteria, can induce corrosion and also harmful to RO membrane.

Coagulation, filtration, setting and super chlorination, UV, ozonation

Iron

Red water, corrosion, deposit, interferes with dyeing, bleaching etc.

Aeration, coagulation, filtration, filtration through Manganese Zeolite

pH

High pH or low pH can both induce corrosion.

Ion exchange, addition of acid or alkali.

Calcium, Magnesium (Hardness)

Scaling, cruds with soap interfere with dyeing and also harmful to other process.

Ion exchange Lime Soda

Turbidity Suspended silica

02

Method of removal

Effect

setting

WATER TREATMENT HAND BOOK

Impurities

Effect

Method of removal

Sodium

Unharmful when low in concentration, increase TDS, high concentration can induce corrosion.

Ion Exchange through cation H+ resin. Reverse Osmosis

Bicarbonates, Carbonates, Alkalinity, Hydroxide (Alkalinity)

Corrosion, foaming and carry over

Acid addition Ion Exchange by WAC Resin Split stream by hydrogen cation resin Degassification after step 2 and 3

Sulphate

Scaling if associated with Calcium, harmful in construction water.

Ion Exchange Reverse Osmosis Evaporation Electrolysis.

Chloride

Corrosion

Ion Exchange Reverse Osmosis Evaporation Electrodylasis.

Nitrate

Normally not found in raw water. Harmful in food processes (especially baby food).

Ion Exchange Reverse Osmosis

Silica

Scaling and deposition on equipment.

Ion Exchange

Carbon Dioxide

Corrosion

Open aeration, Degasification, and Vacuum deaeration.

Hydrogen Sulphide

Corrosion

Aeration, filtration through Manganese Zeolite, aeration plus chlorination.

Oxygen

Corrosion

Deaeration Addition of chemicals likes sodium sulphite or hydrazine.

03

Impurities

Effect

Method of removal

Ammonia

Corrosion especially of Copper and Zinc

Aeration Hydrogenations exchange if ammonia is present in Ionic form.

Free chlorine

Corrosion

By adding chemicals Activated carbon

Definition of Terms Total Cations= TC= Ca++ + Na+ all as CaCO3 Total Anions=TA=T Alkalinity + Cl + SO4-- + NO3 all as CaCO3 Total Hardness=TH= Ca++ + Mg++ as CaCO3 Total Alkalinity=T.Alk= HCO3 - + CO3-- + OH- all as CACO3 EMA= Cl- + SO4-- + NO3- all as CaCO3 Total Acid Ions=EMA + CO2 + SiO2 all as CaCO3 Total electrolyte=TE=TC=TA Total dissolved solids=TDS=TE + SiO2 Total electrolyte: Electrolytes are strongly ionized compounds. TE is numerically equal to either TC or TA (not some of both). SiO2 and CO2 being weekly ionized are not included in total electrolyte. Leakage: Electrolyte or silica passing through the demineralizing unit due to incomplete ion exchange. Conductivity: The ability of a solution to carry current. Conductivity measurement is used to indicate the purity of water. It is measured as micro mhos or micro siemens/cm. Resistivity: Resistivity is a measurement used for ultra pure water. Its unit is megohm. Resistivity is reciprocal of conductivity

Water Analysis Format The following format which has been shown is for ease of designing calculation where total cation or anion can be easily seen, matched for correction of analysis and also for designing the Ion Exchange units. Water testing laboratories normally do not give analysis for many ions in CaCO3 units; example Chloride ion, given as Chloride (mg/liter) which should be converted to CaCO3ppm units, by multiplying by 1.41. Similar other ions, which are not mentioned in CaCO3 units, should be converted to CaCO3 units.

04

WATER TREATMENT HAND BOOK

Substance

Symbol

Example

Calcium

Ca++

125

Magnesium

Mg++

Sodium

Substance

Symbol

Example

Bicarbonates

HCO3-

150

105

Carbonates, Hydroxides

CO3-OH-

0 0

Na+

100

Chlorides

Cl-

100

Potassium

K+

0

Sulphate Nitrate

SO4-No3-

80 0

Total Cation

TC

330

Total Anions

TA

330

Total Hardness

Ca + Mg

230

Alkalinity

HCO3- + CO3-- + OH-

150

Equivalent Mineral Acidity

ClSo4– No3-

180

SiO2 Co2

20 15

All the above are expressed as ppm CaCO3 Iron

Fe express ed in mg/liter as Fe

0.5

Silica Carbon Dioxide

Substance Turbidity Colour Total Dissolved Solids Suspend Solids Acidity/Alkalinity

Unit NTU Hazen Ppm Ppm pH

Example 5 NTU 5 Hazen Unit 350 ppm 20 ppm 7.3

05

Conversion Factors for conversion to Calcium Carbonate (CaCO3)

Ions

Symbol

Ionic weight

Equivalent weight

To convert to CaCO3 multiply by

CATIONS

06

Aluminum

Al+++

27.0

9.0

5.56

Ammonium

Nh4 +

18.0

18.0

2.78

Barium

Ba ++

137.4

68.7

.728

Calcium

Ca+

40.1

20.0

2.49

Copper

Cu++

63.6

31.8

1.57

Hydrogen

H+

1.0

1.0

50.0

Iron (Ferrous)

Fe++

55.85

27.8

1.80

Iron (Ferric)

Fe+++

55.85

18.6

2.69

Magnesium

Mg++

24.3

12.2

4.10

Manganese

Mn++

54.9

27.5

1.82

Potassium

K+

39.1

39.1

1.28

Sodium

Na+

23.0

23.0

2.17

WATER TREATMENT HAND BOOK

Ions

Symbol

Ionic weight

Equivalent weight

To convert to CaCO3 multiply by

ANIONS Bicarbonate

Hc03-

61.0

61.0

0.82

Bisulphate

HSO4-

97.1

97.1

0.515

Bisulphite

HSO3 -

81.1

81.1

0.617

Carbonate

Co3–

60.0

30.0

1.67

Chloride

Cl-

35.5

35.5

1.41

Fluoride

F-

19.0

19.0

2.63

Hydroxide

OH-

17.0

17.0

2.94

Nitrate

No3-

62.0

62.0

0.807

Phosphate (monovalent)

H2PO4-

97.0

97.0

0.516

Phosphate (divalent)

HOP4–

96.0

48.0

1.04

Phosphate (trivalent)

Po4—

95.0

31.7

1.58

Sulphate

So4–

96.1

48.0

1.04

Sulphide

S–

32.1

16.0

3.12

Sulphite

So3–

80.1

40.0

1.25

07

CHAPTER 2

08

WATER TREATMENT HAND BOOK

Filters Basic Operation of Filter The basic operation of Pressure Filter, Dual Media Filter and Activated Carbon and iron removal filters is same. All Units operate in down flow mode, where the water enters from the top, percolates through the media and treated water is collected from the bottom.

Sequence of Operation u Service: The water to be filtered enters from the top of the shell, percolates downward through the media and is drawn off from the bottom. u Backwash: The water enters from the bottom of the vessel, passes through the media and is drained from the top. This is called BACKWASH and it is done to carry the dirt accumulated on the top. Generally back washing is done once in every 24 hrs or when the pressure drop exceeds 8 psi. (0.5 kg/cm2). Rinse : The water enters from the top passed through the media and is drained off from the bottom.

Dirty Water Raw Water

Filter Media

Filter Media Collecting System Collecting System

Treated Water

Raw Water Backwash

Note When activated carbon is installed in a vessel, it should be soaked for 12 to 24 hours to remove trapped air and back washed to remove fines and stratify the bed. A necessary maintenance item, periodic back washing removes solids trapped in the carbon bed, as well as fine carbon particles. Since the dechlorination reaction oxidizes the carbon surface, which slowly breaks down the carbon structure, back washing is especially important in de-chlorination applications. Frequency is determined by the solids content of the feed water. Tests on activated carbon dechlorination systems indicate that regular back washing of carbon beds helps preserve the dechlorination and filtering efficiency. By back washing regularly and expanding the carbon by at least 30 percent, fouling or binding of the carbon bed does not occur.

09

CAUTION Wet activated carbon removes oxygen from air. In closed or partially closed containers and vessels, oxygen depletion may reach hazardous levels. If workers must enter a vessel containing activated carbon, appropriate sampling and work procedures for potentially low-oxygen spaces should be followed as required by salutatory requirements.

Thumb rules for designing a filter Calculate area of vessel by required volumetric flow rate and the velocity as mentioned in the following table. Area (m2) = Volumetric Flow Rate (m3/hr)/ Velocity (m/hr) (1) Based on above calculated area calculate diameter of the vessel by the following formulae: Diameter (m) = [Area (m2)/ 0.785] ½ (2) Parameters

Dual Media Filters

Sand Filters

Activated Carbon

Velocity (m3/m2/hr)

7.5 – 12

12-20

15-20

Effective size of Media (mm)

0.45 - 0.6 (fine sand)

0.65 - 0.76 (Anthracite)

0.35 - 0.5

Uniform coefficient

1.6 max

1.85

100 140 180 240 300 430 650 950 1250 16,000 1/5 < 11 1.3 – 1.9 1–3 3–5 7 24(600)

Inches (mm)

>200 >450

mm mm M/hour

14 (200) kg/cm2(psi)

1-2 138-1000

M/sec kPa

Detention Parameters for Sedimentation coagulants in Water treatment Type of Treatment

Overflow Rate M3/M2/day

Detention Time hours

for

various

Channel Loadings M3/M/Day

Alum coagulation

20-30

2-8

150-220

Iron coagulation

28-40

2-8

200-275

Lime-soda coagulation

28-45

4-8

200-275

91

CHAPTER 11

92

WATER TREATMENT HAND BOOK

Industrial Waste Water Treatment Industrial Pretreatment Processes The treatment of industrial wastewater involves the same processes as those used in the treatment of civil water. However, because of specific compositions, the systems tend to vary. The chemical-physical type processes are especially important for the removal of inorganic matter. The basic processes used are

Wastewater Unit operation Unit Operation

Physical

Chemical

Biological

Screening Comminution Flow equalization Sedimentation Flotation Granular –medium Filtration Precipitation Adsorption Disinfection Dechlorination Other Chemical Processes Activated sludge Process Aerated Lagoon Trickling Filters RBC Pond Stabilization Anaerobic digestion Biological nutrient removal

Physical u Screening is removal of coarse solids by use of a straining device. u Sedimentation is gravity settling of pollutants out of the wastewater. u Flotation is the use of small gas bubbles injected into the wastewater,

which causes pollutant particles in the wastewater to rise to the surface for subsequent removal. Air stripping is removal of volatile and semi-volatile organic u compounds from wastewater by use of airflow.

93

Chemical Neutralization is adjustment of alkalinity and acidity to the same u concentration (pH 7). Precipitation is addition of chemicals to wastewater to change the u chemical composition of pollutants so that the newly formed compounds settle out during sedimentation. Coagulation is use of chemicals to cause pollutants to agglomerate u and subsequently settle out during sedimentation. Adsorption is use of a chemical, which causes certain pollutants to u adhere to the surface of that chemical. Disinfection is use of a chemical (or other method such as ultraviolet u radiation) to selectively destroy disease-causing organisms. (Sterilization is the destruction of all organisms.) Breakpoint chlorination is the addition of chlorine to the level that u chloramines will be oxidized to nitrous oxide and nitrogen, and chlorine will be reduced to chloride ions.

Biological Air activated sludge is an aerobic process in which bacteria consume u organic matter, nitrogen and oxygen from the wastewater and grow new bacteria. The bacteria are suspended in the aeration tank by the mixing action of the air blown into the wastewater. This is shown schematically in Figure 1. There are many derivations of the activated sludge process, several of which are described in this section. High purity oxygen activated sludge is an aerobic process very similar u to air activated sludge except that pure oxygen rather than air is injected into the wastewater. Aerated pond/lagoon is an aerobic process very similar to air activated u sludge. Mechanical aerators are generally used to either inject air into the wastewater or to cause violent agitation of the wastewater and air in order to achieve oxygen transfer to the wastewater. As in air activated sludge, the bacteria grow while suspended in the wastewater. Trickling filter is a fixed film aerobic process. A tank containing media u with a high surface to volume ratio is constructed. Wastewater is discharged at the top of the tank and percolates (trickles) down the media. Bacteria grow on the media utilizing organic matter and nitrogen from the wastewater. Rotating biological contactor (RBC) is a fixed film aerobic process u similar to the trickling filter process except that the media is supported horizontally across a tank of wastewater. The media upon whom the bacteria grow is continuously rotated so that it is alternately in the wastewater and the air. Oxidation ditch is an aerobic process similar to the activated sludge u process. Physically, however, an oxidation ditch is ring-shaped and is equipped with mechanical aeration devices.

94

WATER TREATMENT HAND BOOK

Pollutant Bio-Chemical Oxygen Demand (BOD)

Pretreatment Processes Activated Sludge Trickling filter or RBC Aerated lagoon Oxidation ditch

Total Suspended Solids (TSS)

Sedimentation Screening Flotation Chemical precipitation

Nitrogen

Nitrification/denitrification Air stripping Breakpoint chlorination

Phosphorus

Chemical precipitation Biological treatment Air stripping

Heavy metals

Biological treatment Chemical precipitation Evaporation Membrane process

Fats, Oil and Grease (FOG)

Coagulation Flotation Biological treatment Membrane process

Volatile Organic Compounds

Air stripping Biological treatment Carbon adsorption

Pathogens

Chemical disinfection UV radiation ozonation

95

Pretreatment Process

Items to Look for in the Field for Efficient Operation

Physical Screening

No blinding or clogging of screens, no excessive build-up of material on the screen

Sedimentation

Low flow rate, no short circuiting of flow, no floating sludge, scum removal if appropriate

Centrifugation Air stripping

No scaling of packing and piping, or freezing problems at low temperatures

Chemical Neutralization

pH monitoring, automated chemical feed, adequate mixing

Precipitation

Automated chemical feed system, adequate mixing & contact timer

Coagulation

Automated chemical feed system, adequate mixing & contact timer

Adsorption

Efficient means of regeneration is key to performance

Disinfection

Automated chemical feed system, adequate mixing & contact timer

Biological

96

Activated sludge

Fine bubble aeration, even distribution of air and mixing, dissolved oxygen concentration monitoring, air flow turndown capability, no bulking/floating sludge

Trickling filter

Method for positive air circulation, even & periodic dousing of filter media

Rotating biological contactor (RBC)

Steady shaft rotation

WATER TREATMENT HAND BOOK

CHAPTER 12

97

Chemical Cleaning General Guidance Chemical cleaning of water systems can be divided into two classifications: preoperational and remedial. Pre-operational cleaning is performed to prepare the water-contacted metal surfaces to receive chemical treatment, which provides protection from scale, corrosion, and microbiological growth. Remedial cleaning is performed to restore water systems that have been fouled with scale, corrosion products, and microbiological growth due to inadequate or ineffective water treatment. Cleaning, particularly remedial cleaning is often performed by outside contractors familiar with cleaning procedures, techniques, and safety. It should be noted that if the water system is significantly scaled, the chemical treatment program was obviously inadequate and was not properly designed, set-up, controlled, or applied. After cleaning has been completed, the chemical treatment program and QC program must be improved so the same problem does not recur. Use of a well-designed QA program would have produced identification and notification of potential and developing problems before they became serious. Pre-operational cleaning is often performed by contractors responsible for the fabrication of the water system before turning it over to the military installation. Water system operations personnel must assess the effectiveness of any cleaning process that has been performed.

Pre-Operational Cleaning Pre-operational cleaning can be performed on all new systems or pieces of equipment installed in any existing system, including new boiler tubes or new chiller copper tube bundles. New piping and coils will usually be contaminated with materials such as mill scale, rust, oil, and grease resulting from the fabrication, storage, and installation of the equipment. Pre-operational cleaning is performed to remove these materials and prepare metal surfaces to receive corrosion protection from chemical treatment. Pre-operational cleaning agents that are used include detergents, wetting agents, rust removers, and dispersants. These cleaning agents have a pH in the range of 9 to 11. Water systems containing piping or components constructed of galvanized steel and aluminum should not be subjected to procedures that require high pH (greater than 8.5) because this would contribute to initiating corrosion of these surfaces. The requirement for performing a pre-operational cleaning process is usually written into the specification for new construction of a water system that must be performed by a mechanical contractor. The mechanical contractor is required to perform the work as directed in the specifications. However, if the specifications are not appropriate for the specific system, including consideration of all system metallurgy, the cleaning process may contribute to corrosion to mild steel, galvanized steel, copper, or aluminum, or it may result in incomplete cleaning of dirty and corroded metal surfaces. A qualified inspector should review the specifications or qualified independent consultant to ensure that cleaning agents and procedures have been specified appropriately.

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WATER TREATMENT HAND BOOK

Remedial Cleaning Remedial cleaning is performed to restore a water system that is fouled with scale, corrosion products, or microbiological biomass due to inadequate or ineffective waters treatment. The problem could have resulted from using improper chemical technology, failure to maintain treatment levels within control parameters or the failure of pre- treatment equipment. The cleaning agents used for remedial cleaning usually include acids, chelants, neutralizing agents, and specialty cleaning chemicals.

Safety and Environmental Issues Remedial cleaning may pose safety issues for personnel handling acids, caustics, and various chemicals. There could also be environmental concerns associated with chemical disposal. Inexperienced personnel should not perform the chemical cleaning of an industrial water system.

Contracting Cleaning Services For some cleaning jobs, such as large boilers and cooling towers, it may be advisable to engage a service company specializing in chemical cleaning. If the cleaning service is contracted, it is vital that adequate lines of communication be established, and that safety procedures employed by the service company comply with military regulations. An orientation meeting should be scheduled between military installation personnel and the service company representatives. At that time, the scope of the work can be defined, proper procedures initiated, and the nature of the hazards described thoroughly. The use of proprietary cleaning chemicals or chemical formulations may be involved; disclosure of the use and nature of these chemicals should be made at the orientation meeting. Military policies and restrictions can also be explained.

Reasons for Cleaning Maintenance of an effective water treatment program is essential to minimize scale and corrosion problems in industrial water systems; however, scale and deposits that form will require remedial cleaning (descaling). If not removed, these scale and water-caused deposits may impact the safety of operations personnel, interfere with heat transfer, and cause excessive damage to, or destruction of, the water-using equipment. Cleaning is not appropriate for the removal of deposits when corrosion of the system has advanced to the point where a large number of leaks may result from the removal of the deposits.

Types of Deposits The deposits that occur in water systems can be inorganic mineral salts and corrosion products or organic (oily) or biological in nature. Deposits range in composition from very dense crystalline structures, to very porous and loosely bound materials, to gelatinous slimes. Most of the deposits formed from water constituents consist of corrosion products such as iron and copper oxides, mineral scales, or mixtures of these materials.

99

Waterside Deposits Located in Heat Exchangers Water deposits located in heat exchangers are usually carbonate-based scales, while steamside deposits may be a mixture of metallic oxides and organic residuals from lubricating oil, particularly where reciprocating-type engines are used. In steam systems, the oxides are usually iron and copper, resulting from aggressive condensate. Microbiological deposits may form in cooling systems from bacterial or algae growths, or from decomposition products of various microorganisms.

Boiler Deposits Boiler deposits may take various forms. In low-pressure boilers using a relatively hard feedwater, deposits are essentially calcium and magnesium, silicates, sulfates, carbonates, phosphates and hydroxides, plus some organics. Deposits may also contain considerable amounts of silica, iron, and copper. These deposits can be spongy or porous or relatively hard and glasslike. Deposits of the latter characteristic occur where silica is present in appreciable quantities in the boiler water. Deposits in medium-pressure to high-pressure boiler systems usually are mixtures of iron and copper oxides and phosphates. Dense deposits may tend to form in high-heat transfer areas. Considerable quantities of sludge-type accumulations may be found in downcomers, mud drums, waterwall headers, crossover tubes, and areas of low water circulation in the boiler.

Remedial Cleaning Procedure Cleaning procedure information and procedures presented in this Chapter are general in nature and must be modified to fit specific applications. Because contractors perform most cleanings, these procedures are provided only for general information.

Cleaning Methods There are two methods generally adopted for cleaning 1. Mechanical 2. Chemical

Mechanical Methods Mechanical methods are the oldest techniques used for removing deposits. To perform an adequate mechanical-type cleaning, the equipment to be cleaned may need to be partially or entirely dismantled. Even when equipment is dismantled, some areas may be extremely difficult to reach and clean. Chemical cleaning has largely replaced mechanical process equipment cleaning as the most satisfactory method of removing deposits; however, mechanical methods such as wire brushing, tumbling, scraping, and abrasive blasting with sand and grit are still employed in special applications.

Chemical Methods In this method acid or alkali is generally used for cleaning. At times there are other chemicals which are also used for cleaning.

100

WATER TREATMENT HAND BOOK

Cleaning Agents Cleaning agents may be broadly classified as being acid, alkaline, organic, or solvent cleaners. There is no general or universal cleaner that removes all deposits. The selection of a solvent or cleaning agent is based on the material's ability to remove or dissolve the deposit, as well as on cost considerations, safety hazards, and the effect of the cleaning material on the metals involved. General Guidance and Procedures for Preparing Cleaning Solutions General guidance and procedures for preparing cleaning solutions of inhibited hydrochloric (muriatic) acid and inhibited sulfamic acids are provided in paragraphs below. Inhibited acid contains special chemical inhibitors that prevent the acid cleaner from attacking the base metal while allowing the acid to remove the unwanted corrosion product or scale deposit. Hydrochloric (Muriatic) Acid Inhibited hydrochloric (muriatic) acid in strengths of 5 to 20% is very effective for removing calcium scale and iron oxide; however, for most applications, a 10% solution is adequate. The following formulation is for a 10% hydrochloric acid solution. It can be used for removing scale consisting primarily of carbonates with lesser amounts of phosphates, sulfates, and silicates. This type of scale is typically found in a steam boiler system containing copper alloys that has been treated with a phosphate-based program. Depending on the specific descaling application, some of these ingredients can be omitted from the formulation. Example Procedure for 10% Solution The following is an example procedure that can be used to make 3785 liters (1000 gallons) of a 10% solution: 1. Add 1079 liters (285 gallons) concentrated (36% strength) hydrochloric acid, American Society for Testing and Materials (ASTM) E 1146, Specification for Muriatic Acid (Technical Grade Hydrochloric Acid), to approximately 2271 liters (600 gallons) of water. 2. Add the proper amount of a corrosion inhibitor, Military Specification MIL-I17433, Inhibitor, Hydrochloric Acid, Descaling and Pickling, recommended by the manufacturer to the diluted acid solution. The inhibitor must be compatible with hydrochloric acid and must not precipitate under any condition during the cleaning operation. 3. In a separate tank containing about 284 liters (75 gallons) of water: 4. Add 39 kilograms (85 pounds) of the chemical (1,3) diethylthiourea to complex any copper and keep it from depositing. Do not use the diethylthiourea as the corrosion inhibitor required in paragraph 92.2.1(step 2) above. 5. Add 55 kilograms (120 pounds) of ammonium bifluoride, technical grade, to help dissolve certain iron and silica scales. 6. Add 3.79 liters (1 gallon) of wetting agent, Add the dissolved diethylthiourea, ammonium bifluoride, and wetting agent to the diluted acid solution. Add sufficient water to obtain 3785 liters (1000 gallons).

101

Carbonate Deposits. Carbonate deposits dissolve rapidly in hydrochloric acid, with evolution of free carbon dioxide. The escaping carbon dioxide tends to create some circulation or agitation of the acid, which ensures the continual contact of fresh acid with the scale. Once the carbonate has been dissolved from a mixed deposit, a loose, porous structure may be left behind. This residual material can be effectively removed from the equipment either mechanically or by washing with highpressure water.

Phosphate Deposits The removal of phosphate deposits can usually be accomplished by using hydrochloric acid; however, phosphate deposits have a tendency to dissolve rather slowly. To minimize the total cleaning time, a temperature of 49 to 60 °C (120 to 140 °F) is usually necessary to remove a predominantly phosphate scale.

Metallic Oxides Most metallic oxides found in deposits can be removed with hydrochloric acid. The rate of dissolution is a function of temperature and solution velocity. If copper oxides are present on steel surfaces, special precautions are needed to prevent copper metal plate-out on the steel.

Silica and Sulfate Scale Heavy silica and sulfate scale is almost impossible to remove with hydrochloric acid. Special chemicals and procedures are required to remove this scale.

Hydrochloric Acid Limitations Hydrochloric acid is not used to clean stainless steel because the chloride ion in the acid solution may cause pitting or stress corrosion cracking. Hydrochloric acid is not used for removing scale from galvanized steel surfaces since the galvanizing will corrode. Aluminum is not cleaned using hydrochloric acid.

Sulfamic Acid Sulfamic acid is an odorless, white, crystalline solid organic acid that is readily soluble in water. An inhibited sulfamic acid compound, in a dry powder form, is available. A 5 to 20% solution (2 to 9 kilograms to approximately 38 liters of water [5 to 20 pounds to approximately 10 gallons of water]) is used for removing scale from metal surfaces. The following information pertaining to sulfamic acid should be considered. u ?Carbonate deposits are dissolved in sulfamic acid in a similar manner as in hydrochloric acid. All the common sulfamate salts (including calcium) are very soluble in water. u The dry powder form of sulfamic acid is safer to handle than a liquid solution of hydrochloric acid; however, aqueous solutions of sulfamic acid are much slower in action and require heating to remove scale. The sulfamic acid solution is heated to a temperature in the range of 54 to 71 oC (130 to 160 oF) to obtain the same fast cleaning time that is achieved by using hydrochloric acid at room temperature. Sulfamic acid is more effective on sulfate scale than hydrochloric acid.

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u Inhibited sulfamic acid, used at temperatures up to 43 oC (110 oF), will not corrode galvanized steel. Its use is recommended for removing scale in cooling towers, evaporative condensers, and other equipment containing galvanized steel. In general, sulfamic acid can be applied to equipment while it is operating but should be drained from the system after a few hours, and the concentration of the normally used corrosion inhibitor should be increased several-fold to protect the metal surfaces. u ?Commercially prepared descaling compounds consisting of concentrated or diluted inhibited acid (containing 7 to 28% of the acid and inhibitor) may be purchased under various trade names at prices 4 to 30 times the cost of the ingredients themselves if purchased as generic chemicals. u ?Advertisements of some of these products may contain claims that the acid does not attack cotton clothing and skin. These claims are usually based on a very dilute solution of the acid that causes a minimal attack on clothes and skin; however, the cost of the cleaning process may be increased because a higher quantity of dilute product may be needed. Be aware that handling acid in any strength must be performed with considerable care, caution, and adherence to safety procedures. u The cost of diluted acid is expensive; therefore, concentrated acid of government specifications should be purchased and diluted to usable strengths. The necessary corrosion inhibitors can be added to the dilute acid solution. Users of small quantities of acid cleaners (possibly less than 38 liters [10 gallons] of diluted acid per year) may not be able to justify purchasing undiluted acid and spending the time, cost, and effort to prepare the cleaning solution. Cleaning Preparation u The unit to be cleaned must be isolated from other parts of the system. For systems that cannot be isolated by the closing of valves, isolation may be accomplished using rubber blankets, wooden bulkheads with seals, inflatable nylon or rubber bags, rubber sponge-covered plugs, or blind flanges and steel plates with rubber seals. u Decide whether to clean using a soaking process or by circulating the cleaning solution. In either case, temporary piping or hose lines will be required to connect the cleaning solution mixing tanks or trucks to the unit, with return lines to tanks or drains. Proper precautions and adequate provisions must be made to protect equipment, isolate control lines, replace liquid level sight glasses with expendable materials, and provide suitable points for checking temperatures. u The entire cleaning procedure/process must be developed in detail before starting chemical cleaning operations. Factors to be considered include: the methods for controlling temperatures; the means of mixing, heating, and circulating the chemical solution; proper venting of dangerous gases from equipment to a safe area.

103

Methods for Removing Scale Removing scale may be accomplished by circulating the inhibited acid solution through the equipment or by soaking the equipment in a tank of inhibited acid. Before starting any descaling process, check the acid to make sure it is properly inhibited. You may check the acid by placing a mild steel coupon into a beaker containing the prepared, diluted acid. You should notice no reaction around the coupon. If you observe a reaction generating hydrogen gas bubbles around the coupon, add more inhibitor.

Recirculating Cleaning Process for Boilers The following example is an appropriate procedure for cleaning small boilers or other systems using a hot recirculating inhibited acid solution: 1. Fill the boiler or system with preheated (71 to 77 oC [160 to 170 oF]) dilutes inhibited acid solution. 2. Allow the dilute inhibited acid solution to remain in place for 8 hours. Circulate the acid solution for approximately 15 minutes each hour at a rate of about 3.15 liters per second (50 gallons per minute) to ensure good mixing. 3. Keep the temperature of the acid solution preheated at 71 to 77 oC (160 to 170 oF). Measure and record the temperature at least once every 30 minutes. 4. Check and record the acid strength at least every hour 5. Drain the system by forcing the acid solution out using 276 to 345 kilopascals (40 to 50 pounds per square inch gauge) nitrogen; follow Specification A-A-59503, Nitrogen, Technical, Class 1. If leaks develop when the system is under nitrogen pressure, you must use an alternate method for removing the acid, such as pumping. 6. Fill the boiler with preheated (65 to 71 oC [150 to 160 oF]) water and soak at this temperature for 15 minutes. 7. Drain under nitrogen pressure of 276 to 345 kilopascals (40 to 50 pounds per square inch gauge). 8. Prepare this mild, acid-rinse solution: Add 7.57 liters (2 gallons) of hydrochloric acid (ASTM E 1146 or IS 226) for each 3785 liters (1000 gallons) of water. Also add corrosion inhibitor, in the amount recommended by the manufacturer. 9. Fill the boiler with the preheated (71 to 77 oC [160 to 170 oF]) mild acidrinse solution and soak for 30 minutes. 10. Drain the mild acid-rinse solution under nitrogen pressure at 276 to 345 kilopascals (40 to 50 pounds per square inch gauge). Maintain a positive pressure of nitrogen in the boiler to prevent outside air from leaking inside. 11. Fill the boiler with the passivating solution preheated to 65 to 71 oC (150 to 160 oF), circulate for 10 minutes, and hold in the boiler at 65 to 71 oC for an additional 30 minutes. Drain and rinse boiler until the pH of the rinse water is pH 8 to 10.

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Circulating Method without Heat The steps below describe a typical process for descaling smaller equipment, such as enclosed vessels or hot water heater coils, without heating the inhibited acid solution: 1. Note that an acid cleaning assembly may consist of a small cart on which is mounted a pump and an 18.9- to 189-liter (5- to 50-gallon) steel or polyethylene tank with a bottom outlet to the pump. 2. Install sill cocks at the bottom of the water inlet of the heat exchanger and the top of the water outlet so that a return line can be connected directly from the acid pump and from the heat exchanger to the acid tank. 3. Prepare an inhibited acid cleaning solution 4. Pump the acid solution into the heat exchanger through the hose connection. Continue circulation until the reaction is complete, as indicated by foam subsidence or acid depletion. 5. If the scale is not completely removed, check the acid strength in the system If the acid strength is less than 3%, add fresh acid solution and continue circulation until the remaining scale is removed. Usually an hour of circulation is adequate. 6. Drain the heat exchanger. 7. Neutralize remaining acid by circulating a 1-% sodium carbonate (soda ash) solution {about 3.6 kilograms per 38 liters (8 pounds per 100 gallons)}for about 10 minutes. 8. Rinse thoroughly with water until the pH of the rinse water is pH 8 to 10.

Fill and Soak Method 1. 2.

Prepare an inhibited dilute acid solution in a container of suitable size. Depending on the item to be cleaned and the types of scale involved, you may want to place an agitator (mixer) in the tank or install a pump outside the tank to circulate the acid solution. A method to heat the acid may be required, such as a steam coil. All equipment must be explosion-proof and acid-resistant. 3. Immerse the item to be cleaned in the dilute acid solution. Continue soaking until the reaction is complete as indicated by foam subsidence or acid depletion. 4. If the scale is not completely removed, check the acid strength. If it is less than 3%, add additional acid and continue soaking the items until the remaining scale is dissolved. Usually 1 to 2 hours of soaking is adequate. 5. Remove item from tank. 6. To neutralize remaining acid, immerse the item in a 1% sodium carbonate (soda ash) solution (about 3.6 kilograms per 38 liters [8 pounds per 100 gallons]) for 2 to 3 minutes. Rinse the item thoroughly with water.

105

Checking Acid Solution Strength The initial strength of the dilute inhibited acid will vary from 5 to 20%, although 10% is typical. The strength of the acid decreases since acid is consumed in dissolving the scale. The strength of the acid solution should be measured periodically during a cleaning operation. When the acid strength falls below 3%, the solution may be discarded since most of its scale-dissolving capability will have been used. Use the following procedure to check the acid strength:

Apparatus: 1. 2. 3. 4. 5.

Burette, 25 milliliters (0.8 ounce) automatic (for sodium hydroxide solution) Bottle, with dropper, 50 milliliters (2 ounces) (for phenolphthalein indicator solution) Graduated cylinder, 10 milliliters (0.3 ounce) Casserole, porcelain, heavy duty, 210-milliliter (7.1-ounce) capacity Stirring rod

Reagents: 1. 2.

Sodium hydroxide solution, 1.0 normality (N) Phenolphthalein indicator solution, 0.5%

Method: 1. 2. 3. 4. 5.

Measure 10 milliliters of acid solution accurately in the graduated cylinder. Pour into the casserole. Add 2 to 4 drops of phenolphthalein indicator solution to the casserole and stir. Fill the automatic burette with the 1.0 N sodium hydroxide solution; allow the excess to drain back into the bottle. While stirring the acid solution constantly, add sodium hydroxide solution from the burette to the casserole until color changes to a permanent faint pink. This is the endpoint. Read the burette to the nearest 0.1-milliliter (0.003-ounce).

Results: For hydrochloric acid: Percent hydrochloric acid = milliliter of 1.0 N sodium hydroxide x 0.36. For sulfamic acid: Percent sulfamic acid = milliliter of 1.0 N sodium hydroxide x 0.97

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WATER SAMPLE TEST PROCEDURES

107

WATER SAMPLE TEST PROCEDURES Purpose of Testing Testing of industrial water is done to determine the amount of treatment chemicals in the water so that dosage levels can be properly regulated. These tests are the only known means of having reliable operations, as far as the water is concerned.

Testing Techniques Accurate test results depend on following good basic laboratory procedures and techniques. 1.

2.

3.

4.

5.

Water analyses require certain chemical apparatus. These are scientific instruments and are to be treated as such. The apparatus should be HANDLED WITH CARE! It is necessary to keep everything in GOOD ORDER at all times. Have a place for everything and everything in its place! Be sure all bottles are properly labeled and avoid mixing bottles! All bottles should be tightly closed. Keep any reserve stock of solutions and reagents in cool, dark place. All equipment and apparatus should be kept CLEAN! Unless this is done, the tests will not be reliable and errors will be introduced. Thoroughly rinse and dry all glassware immediately after use. If color apparatus are employed, do not expose to heat or to direct sunlight. If any liquid is spilled on any of the equipment or apparatus, wipe off at once and dry. MEASURE CAREFULLY! The apparatus are precision instruments that are capable of very fine measurements. The results will be “off” if improper amounts of samples are taken, if incorrect volumes of solution are added, if the burette is not read correctly, of if the methods prescribed on the following pages are not performed exactly as written. The SUSPENDED MATTER OR SLUDGE will generally settle to the bottom if the sample is allowed to stand before testing. The clear water can then be used for the tests, making it unnecessary to filter (except for specific tests). Theoretically, all water analyses should be made at 77oF (25oC); however, no appreciable error will be introduced if the test is made between 68 and 86oF (20 to 30oC). In general, the shorter the time between the collection and the analysis of the sample, the more reliable will be the results.

When the water sample color interferes with the analysis, it may be necessary to filter the sample through activated charcoal, except for the sulfite and nitrite tests.

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Phenolphthalein (P) Alkalinity Test Procedure APPARATUS: Graduated Cylinder, 50 ml, Plastic Bottle, w/Dropper (for Phenolphthalein Indicator) 2 oz Casserole, Porcelain, Heavy Duty, 200 ml Capacity Stirring Rod, Plastic REAGENTS: Standard Sulfuric Acid Solution, N/50 Phenolphthalein Indicator Solution, 1 percent METHOD: Measure the amount of water to be tested in the graduated cylinder. The amount should be based on the expected results of the test according to the following: u Pour into the casserole. u Add 6 drops of Phenolphthalein Indicator Solution to the casserole and stir. If the water does not change to a red color, there is no phenolphthalein alkalinity present and the “P” reading is reported as “zero.” If the water does change to red color, “P” alkalinity is present and the test should be continued. u Squeeze the rubber bulb to force the Standard Sulfuric Acid Solution from the bottle to fill the burette just above the zero mark; then allow the excess to drain back automatically into the bottle. u While stirring the water constantly, add Standard Sulfuric Acid slowly from the burette to the casserole until the red color disappears and the water resumes the original color of the sample before the Phenolphthalein Indicator Solution was added. This is the end point. Read the burette to the nearest 0.1-ml. u RESULTS: The P alkalinity (ppm as CaCO3) is calculated as follows: P alkalinity (ppm as CaCO3) = (ml acid) x (factor) P Alkalinity Expected, As CaCO3

Sample Size

Factor

Less than 100

50ml

20

More than 100

20ml

50

EXAMPLE: 4.3 ml of N/50 sulfuric acid were required to change the color of a 50 ml sample of water from red to colorless: P alkalinity = 4.3 x 20 = 86 ppm as CaC

109

Total (M) Alkalinity Test Procedures APPARATUS: Burette, 10 ml, Automatic (for N/50 Sulfuric Acid) (item 1001) Graduated Cylinder, 50 ml, Plastic (item 1004) Bottle, w/Dropper (for Mixed Indicator) 2 oz (item 1005) Casserole, Porcelain, Heavy Duty, 200 ml Capacity (item 1003) Stirring Rod, Plastic (item 1006) REAGENTS: Standard Sulfuric Acid Solution, N/50 (item 2001) Mixed Indicator Solution, (item 2036) METHOD: Measure the amount of water to be tested in the graduated cylinder. The amount should be based on the expected results of the tests according to the following: u Pour into the casserole. u Add 10 drops of Mixed Indicator Solution to the casserole and stir. If the water changes to a light pink color, free mineral acid is present. There is no mixed indicator alkalinity, and the “M” reading is reported as “zero.” If the water changes to a green or blue color, “M” alkalinity is present and the test should be continued. u Squeeze the rubber bulb to force the Standard Sulfuric Acid Solution to fill the burette to just above the zero mark; then allow the excess to drain back automatically into the bottle. u While stirring the water constantly, add Standard Sulfuric Acid Solution slowly from the burette to the casserole until the green or blue color changes to light pink. This is the end point. Read the burette to the nearest 0.1-ml.

M Alkalinity Expected, As CaCO3

Sample Size

Factor

Less than 100

50ml

20

More than 100

20ml

50

RESULTS: The M alkalinity (ppm as CaCO3) is calculated as follows: M alkalinity (ppm as CaCO3) = (ml acid) x (factor)

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EXAMPLE: 5.9 ml of N/50 sulfuric acid were required to change the color of a 50 ml sample of water from green to light pink: M alkalinity = 5.9 x 20 = 118 ppm as CaCO3 NOTES: u If the end point color is difficult to see, repeat the entire test using 15 drops of Mixed Indicator Solution. u Just before the end point is reached, the green or blue color fades to a light blue color and then becomes light pink. The end point is the first appearance of a permanent pink color. Value of P & M

Bicarbonate

Carbonate

Hydroxide

Total

Alkalinity

Alkalinity

Alkalinity

Alkalinity

Alkalinity

P= Zero

M

Nil

Nil

M

P< 1/2M

M-2P

2P

Nil

M

P=1/2M

Nil

2P

Nil

M

P>1/2M

Nil

2(M-P)

2P – M

M

111

Conductivity Test Procedure Apparatus Conductivity Meter & cell In general, there are two types of conductivity meters. One has an electrode that is put into a cell containing the water to be tested. The other has a small cup mounted on the meter into which the water to be tested is poured. Either type of meter may be automatically temperature compensated, or the meter may require a temperature correction. The meter may indicate TDS or conductivity as micromhos, but either measurement represents the same characteristic of the water sample. Where the meter is designed to give either measurement, it is important to always use the same measurement to avoid an error. Thermometer Beaker Graduated cylinder

Procedure Determine the cell constant if necessary, either directly with a standard potassium chloride solution (say 0.002N) or by comparison with a cell the constant of which is known accurately. (In the later case, the concentration and nature of the electrolytes in the liquid which is used for the comparison should be the same and should be similar respectively to those of the liquids with which the cell is likely to be used in practice. Use some of the samples to washout the conductivity cell thoroughly. Fill the conductivity cell with the sample. Measure the conductivity in accordance with the instruction of the instrument manufacturer.

Results Depending upon the type of meter used, the results are read as either conductivity in micromhos or TDS in ppm. The relationship between these measurements when these procedures are used is as follows: TDS, ppm = 0.66 x Conductivity, micromhos Conductivity, micromhos = 1.5 x TDS, ppm.

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pH-Electrometric Method Test Procedures Apparatus pH Meter, Complete Beaker, 150 ml, Heavy Duty Plastic (3 each) Wash Bottle, 500 ml, Heavy Duty Plastic Reagents Standard pH Buffer Solution, pH-4 Standard pH Buffer Solution, pH-7 Standard pH Buffer Solution, pH-10 METHOD: Carefully follow the procedures provided with the pH meter. They should be similar to the following: u Turn the meter from “standby” to “on” position. u Standardize instrument by immersing the electrode(s) into two different Standard pH buffer Solutions in the test beaker as follows: (a.) Place electrode(s) in pH-7 Buffer Solution and adjust the meter to read pH-7.(b). Place electrode(s) in the second pH Buffer Solution, either the pH-4 or pH-10, depending on the suspected range of the unknown sample to be tested, and adjust the meter to the same pH. u Remove electrode(s) and thoroughly wash with distilled or condensate water. u Immerse the electrode(s) in the water sample and turn the meter to “test” or “pH” position and read meter. u Rinse the electrodes with distilled or condensate water and turn the instrument to the “standby” position. Do not turn off. Notes: u When not in use, keep the glass electrodes soaking in a pH-4 Buffer Solution. u When not in use, keep the plastic cap on the reference electrode. Some reference electrodes must be kept full of electrolyte. Follow the instrument instructions on this.

113

Total hardness Test Procedures Introduction Hardness is defined as the sum of the calcium and magnesium ions in water expressed in milligrams per liter (or ppm) as calcium carbonate. Hardness tests should be done on softeners to make sure they are functioning and deaerator water to make sure no contamination is occurring. This test is based on the determination of the total calcium and magnesium content of simple by titration with a sequestering agent in the presence of organic dye sensitive to calcium and magnesium ions. The red to blue color change endpoint is observed when all calcium and magnesium ions are sequestered. Hardness tests should be conducted on water softeners and condensate but not on boiler water as elevated iron concentrations can lead to chemical interference and poor test results.

Reagent required Hardness Reagent 0.01 M Hardness Buffer Hardness Indicator Powder

Procedure u Rinse the graduated cylinder and beaker or a test tube with the sample to be tested. Fill the graduated cylinder to 50 mL and add this water to the beaker or a test tube u If hardness is expected to be greater than 100 take a 50 ml sample and if less than 100 then the sample can be of 20 ml u Add 5 drops of Hardness Buffer to the beaker using the plastic pipette. Swirl to mix. u Add 1 spoon of Hardness Indicator Powder. Swirl to dissolve completely. The sample will turn red if hardness is present. If the sample is blue, the hardness level is completed to be zero. u If the sample colour is purple or red, add standard hardness titrating solution slowly from the burette to the beaker until the purple or red colour changes to blue. This is the end point. Read to nearest 0.1 ml

Calculation u For a 50 mL sample, ppm Hardness as CaCO3 = mL of Hardness Reagent X 20. u For a 20 mL sample, ppm Hardness as CaCO3 = mL of Hardness Reagent X 50.

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Sulphite testing procedure Introduction Sulfite is used in boiler feedwater conditioning to prevent oxygen pitting by the removal of dissolved oxygen. It is necessary to maintain an excess sulfite level to ensure rapid and complete oxygen removal. This test is based on the reaction of sulfite with iodine in acidic solution. The iodide-iodate titrant generates iodine in the acidic solution. This iodine is consumed in a reaction with excess sulfite. At the endpoint, excess iodine combines with the indicator to form a blue colour.

Reagents required Iodide-Iodate Reagent N/40 Acid Starch Indicator Powder Phenolphthalein Indicator

Procedure u Rinse the graduated cylinder and beaker or a test tube with the sample to be tested. Fill the graduated cylinder to 50 mL and add this water to the beaker or a test tube u If sulphite is expected to be greater than 100ppm take a 50-ml sample and if less than 100 ppm then the sample can be of 20 ml u Add 1 drops of Phenolphthalein Indicator to the beaker using the plastic pipette. Swirl to mix. u If the sample remains colourless proceed with step 5. If the sample turns pink add Acid Starch indicator Powder one, 1gram at a time until the sample becomes colorless. Swirl to mix between each addition of indicator. u Fill the Titration Burette to the zero mark with Iodide-Iodate Reagent N/40. Add the reagent slowly to the Erlenmeyer flask with constant stirring. Continue to titrate until a permanent blue color develops in the sample. Read the titrated volume from the burette.

Calculation For a 50 mL sample, Ppm sulphite as CaCO3 = mL of Iodide-Iodate Reagent X 20. For a 20 mL sample, Ppm sulphite as CaCO3 = mL of Iodide-Iodate Reagent X 50.

115

Chloride Test Procedure Apparatus: Burette, 10 ml Automatic (for Mercuric Nitrate Solution) Graduated Cylinder, 50 ml, Plastic Casserole, Porcelain, Heavy Duty, 200 ml Capacity Stirring Rod, Plastic Bottle, w/Dropper, 2 oz (for Chloride Indicator Solution)

Reagents Standard Mercuric Nitrate Solution, 0.0141 N Chloride Indicator Solution Standard Sulfuric Acid Solution, N/50

Procedure u Measure the amount of water to be tested in the graduated cylinder. The amount should be based on the expected results of the tests according to the following: u Pour into the casserole. u Add 1.0 ml of Chloride Indicator Solution to the water in the casserole and stir for 10 seconds. The color of the water should be a green-blue color at this point. u Add the standard Sulfuric Acid Solution a drop at a time until the water turns from greenblue to yellow. u Squeeze the rubber bulb to force the Standard Mercuric Nitrate Solution from the bottle to fill the burette just above the zero mark; then allow the excess to drain back automatically into the bottle. While stirring the sample constantly, add Standard Mercuric Nitrite Solution slowly from the burette to the casserole until a definite purple color appears. This is the end point.(The solution will turn from green-blue to blue a few drops from the end point.) Read the burette to the nearest 0.1-ml.

Results The Chloride, in ppm C1, is calculated as follows: Chloride, ppm C1 = (ml of Mercuric Nitrate – 0.2) x factor.

Example 11.2 ml of 0.0141 N Mercuric Nitrate Solution was required to change the color of a 50-ml sample of water from a green-blue to purple. Chloride = (11.2 – 0.2) x 20 = 220 ppm) Chloride Expected as Cl

116

Sample Size

Factor

Less than 20 ppm

50ml

10

More than 20 ppm

20ml

20

WATER TREATMENT HAND BOOK

Checking Acid Solution Strength for Cleaning The initial strength of the dilute inhibited acid will vary from 5 to 20%, although 10% is typical. Since the acid is consumed by dissolving the scale, the strength of the acid decreases. The strength of the acid solution should be measured periodically during a cleaning operation. When the acid strength falls below 3%, the solution may be discarded since most of its scale-dissolving capability will have been used. Use the following procedure to check the acid strength:

Apparatus: Burette, 25 milliliters (0.8 ounce) automatic (for sodium hydroxide solution) Bottle, with dropper, 50 milliliters (2 ounces) (for phenolphthalein indicator solution) Graduated cylinder, 10 milliliters (0.3 ounce) Casserole, porcelain, heavy duty, 210-milliliter (7.1-ounce) capacity Stirring rod

Reagents: Sodium hydroxide solution, 1.0 normality (N) Phenolphthalein indicator solution, 0.5%

Method: u Measure 10 milliliters of acid solution accurately in the graduated cylinder. u Pour into the casserole. u Add 2 to 4 drops of phenolphthalein indicator solution to the casserole and stir. u Fill the automatic burette with the 1.0 N sodium hydroxide solution; allow the excess to drain back into the bottle. u While stirring the acid solution constantly, add sodium hydroxide solution from the burette to the casserole until color changes to a permanent faint pink. This is the endpoint. Read the burette to the nearest 0.1-milliliter (0.003-ounce).

Results: For hydrochloric acid: Percent hydrochloric acid = milliliter of 1.0 N sodium hydroxide x 0.36 For sulfamic acid: Percent sulfamic acid = milliliter of 1.0 N sodium hydroxide x 0.97

117

Units and Measurement conversion

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WATER TREATMENT HAND BOOK

BASICS Length 1 m = 39. 37 " | in = 3,281 ' | feet 1 in | " = 25.40 mm = 2,540·10-2 m 1 ft | ' = 304. 8 mm = 0.3048 m Area 1 m² = 10.76 ft² = 1550 in² 1 ft² = 9,290·10-2 m² 1 in² = 6,452·10-4 m² Volume 1 m³ = 6,102·104 in³ 1 m³ = 35.31 cf | ft³ = 264.2 US Gallon 1 cf | ft³ = 2,832·10-2 m³ = 28.32 Liter | dm³ 1 in³ = 1,639·105m³ = 1,639·10-2 Liter | dm³ 1 US Gallon = 3,785·10-3 m³ = 3,785 Liter | dm³ 1 UK Gallon = 4,546·10-3 m³ = 4,546 Liter | dm 1 mn3 Air=38.04 SCF Air=1.292 kg Air 1 SCF Air =2,629·10-2 mn 3 Air=3,397·10-2 kg Air Density 1 kg/m³ = 6.243·10-2 lb/ft³ 1 lb/ft³ = 16.02 kg/m³ Mass 1 kg = 2.205 lb | lbs 1 lb | lbs = 0.4536 kg Velocity 1 m/s = 3.281 ft/s 1 m/s = 196.9 ft/min | FPM 1 FPM = 5.080·10-3 m/s 1 ft/sec. = 0.3048 m/s Volume Flow 1 m³/h = 0.5885 CFM | ft³/min 1 CFM = 1.699 m³/h 1 SCFM = 1.577 mn 3/h Air (only) Mass Flow 1 kg/h = 2.205 lb/h 1 lb/h = 0.4536 kg/h

119

Pressure 1 bar = 14.50 psi 1 bar = 100.0 kPa 1 bar = 0.9869 Atm. 1 mbar = 0.7501 mm Hg | Torr 1 mbar = 10.20 mm WG 1 mbar = 100.0 Pa 1 psi | lbf/in² = 6,895·10-2 bar 1 psi | lbf/in² = 6,804·10-2 Atm. 1 psi | lbf/in² = 6,895 kPa Kinematic Viscosity 1 Pa·s = 1.000 cP 1 Pa·s = 0. 6720 lb/ (ft·s) 1 cP = 1,000·10-3 Pa·s | Ns/m² 1 cP = 1,000·10-3 kg/ (m·s) 1 lb/ (ft·s) = 1.488 Pa·s 1 lb/ (ft·s) = 1488 cP | mPa·s Temperature °C | Celsius = 5 · (°F – 32) / 9 °F | Fahrenheit = 32 + 9 · °C / 5 Heat Content & Energy 1 kJ | KN·m = 0.9478 Btu 1 kJ | KN·m = 0.2388 Kcal 1 Btu = 1.055 kJ 1 Btu = 0.2520 Kcal 1 kcal = 4,187 kJ 1 kcal = 3.968 Btu 1 kWh = 859.8 Kcal Heat Load | Power 1 kW = 3412 Btu/h 1 kW = 859.8 Kcal/h 1 Btu/h = 2,931·10-4 kW 1 Btu/h = 0.2520 Kcal/h 1 kcal/h = 1,163·10-3 kW 1 kcal/h = 3.968 Btu/h 1 Boiler HP = 9.81 kW Specific Heat 1 kJ/ (kg·K) = 0.2388 Btu/ (lb·°F) 1 kJ/ (kg·K) = 0.2388 kcal/ (kg·°C) 1 Btu/ (lb·°F) = 4,187 kJ/ (kg·K) 1 kcal/ (kg·°C) = 4,187 kJ/ (kg·K)

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WATER TREATMENT HAND BOOK

Common conversion factors for ion exchange calculation Capacity To Convert Kgr/ft3 (as CaCO3) Kgr/ft3 (as CaCO3) Kgr/ft3 (as CaCO3) g CaCO3/litre g CaO/litre

Multiply by

To g CaO/Litre g CaCO3/Litre eq/litre Kgr/ft3 (as CaCO3) Kgr/ft3 (as CaCO3)

1.28 2.29 0.0458 0.436 0.780

Flow Rate To Convert U.S.gpm/ft3 U.S.gpm/ft2 U.S gpm BV/min

To BV/hr M/hr M3/hr U.S. gpm/ft3

Multiply by 8.02 2.45 0.227 7.46

Pressure drop To Convert PSI/ft

To MH2O/M of Resin G/cm/M

Multiply by 2.30 230

Density To Convert

To

Multiply by

Lbs/ft3

gm/litre

16.0

Rinse requirement To Convert U.S. gal/ft3

To BV

Multiply by 0.134

121

Water Equivalents One U.S. gallon One U.S. gallon One U.S. gallon One U.S. gallon One U.S. gallon One U.S. gallon water One cubic foot One cubic foot of water One litre/second One cubic meter per hour One kgr / sq. cm One Pound/1000 gel One inch/minute rise rate One cubic meter One cubic meter One cubic meter

Water Analysis Conver-sion table

Kilogr ains per cubic foot Kgr/ cu.ft

.1

.0583

.07

.0004

.001

.1

.0583

.07

.0004

1

100

58.3

70

.435

.01

1

.583

.7

.00436

Grams per Liter gms/L

1

1

.001

1

1

1 gram per litre(1m /litre)

1000

1000

1 Parts per hundred thousand 1pt /100 0000)

10

10

Parts per hund-red thous and pts/ 100000

Grains per British Imp gallon grs/Im gal

Milli-grams per liter mg/L

1 milli gram per litre (1mg /litre)

0.1337 cubic foot 231 cubic inches 0.833 British Imp gallons 3.785 Liters 3785 cubic cm (Milliliters) 8.33 Pounds (Lb) 7.48 U.S. gallons 62.43 Pounds 15.9 (US) gal/Min 4.4 (US) gal/min 14.2 pounds/sq. inch 120 parts per million 0.625 gpm/sq.ft 1000 liter 264.2 U.S gallons 220 British Imp gallons Grains per U.S. gallons grs/U.S gal

Parts per million (ppm)

1 Part per million (1 ppm)

122

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WATER TREATMENT HAND BOOK

Water Analysis Conversion Table for Units Employed: Equivalents Water Analysis Conver-sion table

Parts per million (ppm)

Milli-grams per liter mg/L

Grams per Liter gms/L

17.1

17.1

.017

14.3

14.3

1 Kilograin per cubic foot (1 kgr /cu.ft)

2294

1 Parts per million (1 ppm)

Parts per hund-red thous and pts/ 100000

Grains per U.S. gallons grs/U.S gal

Grains per British Imp gallon grs/Im gal

Kilogr ains per cubic foot Kgr/ cu.ft

1.71

1

1.2

.0075

.014

1.43

.833

1

.0052

2294

2.294

229.4

134

161

1

1

0.1

.0583

.07

.1

.0560

.020

10

1

0.583

0.7

1

0.560

.20

1 Grain per US gallon (1 gpg)

17.1

1.71

1

1.2

1.71

0.958

.343

1 English or Clark degree

14.3

1.43

.833

1

1.43

0.800

.286

10

1

.583

.7

1

0.560

.20

17.9

1.79

1.04

1.24

1.79

1

.357

1 Grain per U.S gallon(1 gr/U.S gal) 1 Grain per British Imp gal-lon (1 gr /Imp gal)

1 Part per hundred thousand (1 pt /100000)

1 French Degrees (1.French) 1 German Degrees (1 German)

123

Indian standard grade for the commonly used regeneration chemicals

IS Number

Regeneration Chemicals

124

Hydrochloric Acid

IS 265

Sulphuric Acid

IS 266

Sodium Hydroxide

IS 252 (Tech/Rayon Grade 46% lyes) IS1021 (Pure Grade - Flakes)

Sodium Carbonate

Is251 (Tech Grade)

Sodium Sulphite

Is251 (Tech Grade)

Sodium chloride

IS 297 (Tech Grade)

Alum

Is260 (Tech Grade)

WATER TREATMENT HAND BOOK

Brief List of Reference Betz Handbook Demineralization by Ion exchange – S. Applebaum – Academic press Reverse osmosis by Zahid Amjad – Van Nostrand Reinhold (NY) Membrane Manual –Dow Chemical Company Army Engineering Publications- Public bulletin No. 420-49-05 CIBO Energy efficiency handbook WARE Boiler book on-line “Chemical Treatment of Cooling Water in Industrial Plants”by Timothy Keister (Basic Principals and Technology) ProChemTech International, Inc. Brockway, Pennsylvania Glegg handbook Water and Wastewater by Hammer and Hammer Dorfner, K., Ion Exchangers, Properties and Applications, Ann Arbor Science, Ann Arbor, Michigan, 972 Kunin, R., Ion Exchange Resins, Robert E. Krieger Publ. Co., Huntington, N.Y., 1957 Nachod, F. C. and Schubert, J., editors, Ion Exchange technology, Academic Press, New York, N.Y., 1957 Water treatment technology program Report no 29 Pure water handbook by osmonics "Pretreatment of Industrial Wastes," Manual of Practice No. FD-3 Public Works Technical Bulletin 420-49-21 Boiler water treatment lessons learned Public Works Technical Bulletin 420-49-22 Cooling water treatment lessons learned (Published by the U.S. Army Installation Support Center) International site for Spirax Sarco Industrial Water Treatment Primer TYNDALL AFB, FL 32403-6001 Sedifilt.com Web site of N.E.M Business Solutions Website of Portland water bureau How to Manage Cooling Tower Water Quality by Ken Mortensen in RSES journal _5-03pd And many more

125

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