SJDO_TE-16 Water Treatment Guide.pdf

TE-16 Water Treatment Guide

INSTRUCTIONS, CONDITIONS, AND NOTICES TO

Table of Contents

1.0 Introduction

2.1 Types of Recirculating Water Loops

2.2 Open Loop Cooling Water System

2.3 Closed Loop Cooling Water Systems

2.4 Steam and Condensate Recirculation Systems

2.5 Closed Loop Hot Water Systems

2.6 Domestic Hot and Cold-Water System

3.1 Water Chemicals Treatment Additives

3.2 Mineral Scale Inhibitor

3.3 Corrosion Inhibitor

3.4 Bacteria Contamination Control

3.5 General Fouling Inhibitor

3.6 Oxygen Corrosion Control

3.7 General Corrosion Control

3.8 Condensate Corrosion Control

4.1 Setting Up a Water Treatment Program

4.2 Open Loop Cooling Water Systems

4.3 Closed Loop Cooling and Hot Water Systems

4.4 Steam and Condensate Recirculation Systems

5.1 Water System Testing

5.2 Water Sampling

5.3 Common Water Chemistry Tests

5.4 Maintenance Parameters

6.1 Alternatives to Chemical Water Treatment

6.2 Pulsed Electromagnetic Fields

6.3 Ozone Generators

1.0 Introduction

This appendix establishes mandatory standards for water in HVAC and domestic water systems in GSA facilities, along with information related to the intent of the standards and guidelines that in most circumstances can be used to construct a water treatment program that will be approved by GSA. Treatment standards are mandatory; procedural instructions in these guidelines are advisory unless required by law or regulation. Subject to GSA approval, maintenance Contractors generally may propose alternative programs where accompanied with sufficient technical data and implementation detail for GSA to determine the likelihood of success of such an alternative program. Any program approved by GSA may be subsequently disapproved if results are unsatisfactory.

Regardless of the complexity or size of a loop, a qualified water treatment Contractor or personnel should be consulted or employed to help the building maintenance personnel develop a water treatment program specific to the needs of each system. The treatment chemicals themselves should be purchased through a licensed supplier that specializes in commercial and/or industrial water systems. Many water treatment chemicals require licenses for specific uses and are regulated by Federal, state, and Local governments. Maintenance Contractors are responsible for selecting and submitting for approval an appropriate program, and for compliance with laws regarding chemical discharge and usage.

Maintenance Contractors are responsible for providing all instrumentation and test equipment necessary to monitor compliance with these standards (e.g., installation of coupon racks or other corrosion monitoring equipment where not already installed).

2.1 Types of Recirculation Water Loops

There are five basic open and closed loop water systems used for the daily operation of commercial buildings.

Each system is vital to the everyday operation of the buildings mechanical systems. The following open and closed loop water systems are described as follows.

2.2 Open Loop Cooling Water System

An open loop cooling water system generally uses cooling towers to cool condenser water that serves chilled water central plants, water source heat pumps and computer room air conditioning units. There are cases where a waterside economizer “free cooling” system is used in place of a chiller to cool condenser water during periods of low ambient conditions. During “free cooling” mode the chilled condenser water is passed through a heat exchanger to cool the closed loop cooling or chilled water loop.

An open loop is exposed to outside contaminants and requires frequent maintenance, chemical tests, and chemical treatment that should be determined by a water treatment Contractor. In general, large systems require chemical tests be performed weekly and a water treatment Contractor to inspect the chemical systems monthly. The four main goals of maintaining an open loop cooling system are; inhibition of mineral scale, corrosion, minimizing bacterial contamination, and general fouling inhibition. See Section

3.0 for a detailed description of cause and effect when using chemical inhibitors.

2.3 Closed Loop Cooling Water Systems

A closed loop cooling water system can either be used for chilled water or condenser water. In a closed loop chilled or condenser water system the cooling water is circulated through the chiller or heat exchanger where it is cooled then pumped through air handlers’ cooling coils, fan coil units, computer rooms units, water source heat pumps, etc.

In view of the fact that a closed loop cooling water system will not be exposed to as much outside containments and no evaporation as in an open loop system, the dissolved mineral concentration in the system will remain relatively constant and there will be virtually no need for blow down. Once the system is filled, every effort should be made to limit the amount of water leakage from seals, water sampling, valve testing and other routine system maintenance. When water leaks out of the system, it will be replaced with untreated makeup water. This water introduces additional minerals and dissolved oxygen into the system. Consistent chemical treatment is sustained with the use of chemical tablet “slug” feed water treatment products.

The treatment program for closed loop cooling water systems requires less frequent testing. The goal of the closed loop program is to inhibit corrosion, inhibit mineral scale formation, and inhibit bacteria growth.

See Section 3.0 for a detailed description of cause and effect when using chemical inhibitors.

2.4 Steam and Condensate Recirculation Systems

Steam systems are closed loop systems that produce either saturated low pressure or superheated high-pressure steam via a steam boiler. The condensate water, with the addition of makeup water, is re-circulated through the steam boiler. A steam system should have an automated water makeup, a mechanical deaerator, condensate pumps, feed water pumps, steam traps, low feed water flame cut off controls and chemical pot feeders for condensate and makeup water treatment. The steam system will be a collection of steam regulators, steam turbines, heat exchanges for heating purposes, or through an absorption chiller to indirectly produce chilled water for space cooling.

The evaporation of water and elevated temperatures cause most of the minerals present in tap water to bond with each other, causing an increase in system mineral concentration. The four main goals to maintaining a steam system is prevention of mineral scale formation, oxygen corrosion, general corrosion, and condensate corrosion. Biocides are not needed in a steam system because bacteria do not grow in high temperature environments. Alternatively, if steam is supplied by a Local utility, then the steam has already been chemically treated and further chemical treatment may not be necessary. See Section 3.0 for a detailed description of cause and effect when using chemical inhibitors.

2.5 Closed Loop Hot Water Systems

A closed loop hot water heating system is not exposed to a great deal of outside containments. Therefore, the dissolved mineral concentration in the system will remain relatively constant and there will be virtually no need for blow down. Once the system is filled, every effort should be made to limit the amount of water leakage from seals, water sampling, valve testing and other routine system maintenance. When water leaks out of the system, it will be replaced with untreated makeup water. This water introduces additional minerals and dissolved oxygen into the system. Consistent chemical treatment is sustained with the use of slug feed water treatment products.

The treatment program for this system is very similar to the closed loop cooling system. The key difference is that hot water systems require more corrosion inhibitor as a result of higher water temperatures. In fact, most hot water systems require two to three times the corrosion inhibitor of closed loop cooling water systems. The goal of a closed loop hot water treatment program is to inhibit corrosion, mineral scale formation, and bacteria growth. See Section 3.0 for a detailed description of cause and effect on using chemical inhibitors.

2.6 Domestic Hot and Cold Water System

A domestic hot and cold water system provides potable water for washing and general domestic use. The water within these systems will contact food, people, or will be consumed, so there is no chemical treatment used for this system to prevent mineral scale or corrosion due to water supplied by the Local utility. The only water treatments used for these systems is the addition of water softeners and filtration systems. The reduction of the corrosive and scaling tendencies of oxygenated hard or softened water is done by repairing leaky fittings and fixtures, limiting the velocity of the circulating water, and/or limiting the operating temperature of the hot water system.

Water Chemicals Treatment Additives

Environmental regulations, handling guidelines and the chemical additives for water systems should be provided by a certified Local water treatment consultant. It is the building operator’s responsibility to ensure compliance with municipal by-laws, and environmental regulations when disposing of chemicals and handling accidental spills. Disposing of chemically treated water into the sewer system must be monitored in blow down logs and not allowed to exceed levels specified by municipal sewage utility by- laws.

The chemical additives suggested herein are organized by class to encompass a variety of chemical additives that are used in open and closed water loops and steam boiler systems.

3.1 Mineral Scale Inhibitor

Mineral scale is the precipitation of dissolved minerals such as calcium carbonate onto the surfaces of the cooling tower, boiler, heat exchangers tubes, and piping. This mineral scale forms an insulating layer on the surfaces that inhibits heat transfer and restricts flow through the system. Mineral scale also promotes corrosion and fouling in open loop and steam systems. All re- circulating water and steam boiler systems should have a mineral scale inhibitor as part of their water treatment program.

Mineral scale inhibitors are separated into two main categories, sludge conditioners and dispersants.

Sludge conditioners are typically used when there is a relatively high concentration of calcium and magnesium in the makeup water. Sludge conditioners are crystal modifiers that allow the minerals to precipitate but interfere with the structure of the crystal to help form a soft sludge that can be easily removed from the steam boiler or cooling tower through blow down. Dispersants are usually polymer- based molecules that help to keep the trace minerals in solution so that they do not precipitate into scale deposits. The mineral scale inhibitors are especially needed when there is little or no pretreatment of the makeup water or when filtration equipment is not reliable. Even with excellent control of the scale inhibitor, chemical scale formation still occurs.

Water treatment consultants use computer models to determine the type of scale inhibitor needed as well as the limits for system pH and total dissolved solids (TDS). These computer models take into account the specific operating parameters of the system and help the water treatment consultant to choose a specific water treatment program that will work.

Open Loop Cooling Water System:

An open re-circulating cooling water treatment program commonly uses a chemical additive that is a combination of a mineral scale inhibitor and a corrosion inhibitor. The type and dosage of mineral scale inhibitor needed is dependent upon the concentration and composition of the minerals in the makeup water, the pH of the cooling water, and the temperature of the cooling water. The overall scale inhibitor program for a cooling water system may consist of a mineral scale inhibitor additive (such as a polymer dispersant), acid for pH control, and limits for the total dissolved solids and/or conductivity of the cooling water. Acid feed and pH control will not be needed in every system.

Steam Systems with Re-circulating Water:

In steam boilers, the buildup of an insulating layer can lead to tube failure and efficiency losses. Calcium and magnesium are the most abundant forms of mineral scale found in a steam boiler system because the solubility of these two minerals decreases as the temperature increases. To minimize the potential for mineral scale formation, most steam boilers have some type of makeup water pretreatment to remove certain minerals from the water before it enters the boiler. The goal of most pretreatment equipment is to minimize the concentration of these two minerals in the makeup water so that there is a less significant chance that they will precipitate and form a crystal scale deposits. Even with good pretreatment, mineral scale inhibitors are needed in all steam boiler systems.

Dispersant mineral scale inhibitor programs are used in steam boilers that have good pretreatment and very low levels of calcium and magnesium in the makeup water. Dispersants are usually only used when the total hardness in the makeup water is greater than 5 ppm consistently. The dispersants are usually a polymer based molecule that helps keep the trace minerals in solution so that they do not precipitate into scale deposits.

Closed Loop Cooling Water and Hot Water (Heating) Systems

In a closed loop system the mineral concentration is relatively stable because very little makeup water is needed. This helps to minimize the need for mineral scale inhibitors. In systems that have poor quality makeup water, with a total hardness above 300 ppm, it is best to pre-treat the water with softeners to remove calcium and magnesium from the makeup water. In most cases, pretreatment of the makeup water is not necessary.

Closed loop cooling and hot water systems should be treated with a polymer dispersant mineral scale inhibitor.

This scale inhibitor is usually combined with a corrosion inhibitor in a one-drum formulation.

3.2 Corrosion Inhibitor

Open Loop Cooling Water Systems:

The corrosion inhibitor chemical treatment protects the metal piping from degradation over time. The type of corrosion inhibitor that is used depends upon the specific metallurgy present in the system as well as the chemistry of the makeup water and pH level in the water. Corrosion inhibitor additives are intended to provide a protective layer on the interior walls of piping which stops the occurrence of corrosion in the system.

A certified chemical water treatment consultant should be contacted to determine the specific type and amount of corrosion inhibitor necessary for each building’s distinct system.

In most cases, there is more than one type of metallurgy in a system, such as galvanized steel, copper, stainless steel, etc. Different metals require distinct chemicals to prevent corrosion, so it is important that the corrosion inhibitor portion of the program have additives that are specific to each type of metal. In most cases, blends of different corrosion inhibitors are used to ensure that all of the metal is protected.

Closed Loop Cooling and Hot Water Systems

Corrosion is the principal concern in a closed loop cooling and hot water systems. There are many different types of corrosion inhibitors available on the market, but the most common products are nitrite based. As with any corrosion inhibitor program, the type of program used is determined by the type of metals used throughout the system. Mild steel systems should be treated with nitrite, molybdate, or phosphonate type inhibitors. Systems containing copper should have some type of azole product.

If bacterial contamination is a problem, Nitrite programs should be avoided. The nitrite corrosion inhibitor can act as a food source for bacteria. The bacteria will convert the Nitrite into Nitrate and Ammonia.

This will destroy the corrosion inhibitor function of the product. A certified chemical water treatment consultant will be able to find the best product for this type of system.

There is one difference between a closed loop cooling and heating systems, which is the dosage of the corrosion inhibitor. The corrosion inhibitor of closed loop hot water system will have dosage 2 – 3 times greater than the dosage for a closed loop cooling water system.

3.3 Bacteria Contamination Control

The control of the bacteria growth is the most important part of an open loop cooling and closed loop cooling and hot water treatment program because bacterial contamination can lead to fouling, mineral scale, and corrosion. Bacterial contamination is controlled through the use of biocides. Below is a description on bacterial contamination control that is used for open loop cooling, closed loop cooling, and closed loop hot water systems.

Open Loop Cooling Water Systems

Open loop cooling water systems are inherently prone to bacterial contamination without a proper water treatment. High bacteria levels in a cooling water system can lead to bio-deposits (algae for example) and increased fouling that can reduce heat transfer in the heat exchangers and cooling tower. The bio-deposits and increased fouling can reduce water flow through the system if there is improper water treatment.

In view of the fact that open cooling water systems are highly susceptible to bacteria growth, the water treatment program should have some type of biocide chemical additive. Biocides kill living organisms and/or bacteria and can be categorized as either oxidizing or non-oxidizing. An oxidizing biocide, when applied at the correct dosage, will kill all types of bacteria. A non- oxidizing biocide targets certain bacteria and will not kill some types of bacteria.

A non-oxidizing biocide can be compared to an Anti-biotic that is used to treat bacterial infections in people.

Over dosing a system or improper usage of a non-oxidizing biocide can create strains of bacteria in the cooling water system that are resistant to the biocide. Limit the program to the use of non-oxidizing biocides alone is never recommended. It is good practice to utilize both an oxidizing biocide and a non-oxidizing biocide to strictly control bacteria contamination. This method is more costly so some building managers chose to only utilize only oxidizing biocides.

The types of oxidizing biocide needed are dependent upon the physical limitations of the facility, safety concerns, costs, and maintained pH of the recirculation water. For example, bromine based oxidizing biocides should be used any time the pH of the water in the system is above 7.5. A water treatment supplier or consultant can provide specific information regarding the different types of oxidizing and non-oxidizing biocides that will suit the needs of your system.

It is important to note that there are both Federal and state laws that regulate the usage and application of biocides for commercial and industrial usage. When choosing a water treatment supplier or consultant, make sure that they are properly licensed and registered in your area to provide guidance on the usage of biocides or pesticides. Also, it is important that you only use biocide products that are specifically approved for use in an open loop cooling water system.

Closed Loop Cooling and Hot Water Systems

It is not uncommon for closed loop systems to experience bacterial contamination, especially if these systems are treated with nitrite. In general, the more makeup water a system needs, the more likely that system is predisposed to bacteria problems. If a closed loop system has a bacteria problem or will not maintain a nitrite residual, there are basically two options to correct the problem. The first solution is to switch the corrosion Inhibitor program to a program that does not contain a food source for bacteria. The second best solution is to utilize non-oxidizing biocides to treat the bacteria problem. A non-oxidizing biocide should be used in a closed loop system because they do not react with the corrosion inhibitors and they do not promote corrosion themselves. An oxidizing biocide will degrade most corrosion inhibitors and they can increase corrosion rates in a closed loop system. It is always best to contact a licensed water treatment consultant that can help you to determine the dosages of biocide needed and which biocide will work for your system.

3.4 General Fouling Inhibitor

A fouling inhibitor is added to an open loop cooling water system when the makeup water contains high levels of suspended particles or turbidity. This includes high levels of dirt, silt, Iron, or other colloidal particles present in the makeup water, which occurs in rare applications. If this is the case, it may be necessary to add a fouling inhibitor additive to the system. These inhibitors are similar to mineral dispersants but are designed to target suspended particles instead of dissolved minerals. Generally, the mineral dispersant treatment program will be sufficient to provide general system fouling inhibition. If the mineral dispersants are not sufficient, contact a licensed water treatment consultant to see if a fouling inhibitor is needed for the system.

3.5 Oxygen Corrosion Control

Steam Systems with Condensate Recirculation

Due to the high temperatures produced by a steam boiler plant, the corrosive reaction between oxygen and carbon steel is greatly increased. The oxygen corrosion in a steam system usually causes internal pipe pitting and can lead to pipe failures and leaks very rapidly. In order to protect the steam system metal from oxygen pitting, it is very important to remove the oxygen from the makeup water using both mechanical deaeration and chemical processes. At room temperature, water normally contains about 9 ppm of dissolved oxygen. As the temperature of the water increases, the solubility of oxygen in the water decreases. A mechanical deaerator is designed to raise the temperature of the feed water to just below boiling so that the oxygen concentration in the water drops from 9 ppm to less than 0.05 ppm. After the makeup water is mechanically depleted of its oxygen content, it is still necessary to reduce it further.

The further reduction in oxygen content is done with an oxygen scavenger chemical, which will reduce the concentration of oxygen to levels below 0.005 ppm.

There are many different types of chemicals used as Oxygen Scavengers. The most common Oxygen Scavenger is Sodium Bi-Sulfite. Contact a licensed water treatment consultant that will decide what product meets all the needs of a given steam system.

3.6 General Corrosion Control

Steam Systems with Condensate Recirculation

A steam system should include an Oxygen corrosion control treatment program along with a general system corrosion control treatment program. A general corrosion control chemical treatment program includes the addition of buffering agents to the boiler feed water to minimize the potential for corrosion throughout the system. This buffering agent is frequently in the form of alkali solution. The alkali species neutralize acids in the water and raise the pH to create a slightly Basic environment that is less corrosive to the metal piping.

Some makeup water has enough natural alkalinity and is able to provide the feed water system with sufficient buffering, to keep the pH of the steam boiler feed water at or above 10.2. When there is not enough natural Alkalinity in the steam boiler feed water, a Caustic chemical should be added to raise the pH above

10.2. A water treatment consultant will be able to test the feed water in the steam system to determine if Caustic feed is needed and what dosage is necessary to raise the pH above 10.2.

3.7 Condensate Corrosion Control

Steam Systems with Condensate Recirculation

The feed water is heated to produce high or low-pressure steam by the boiler. When this occurs some of the alkali solution species will breakdown into Carbon Dioxide (CO2) gas. The CO2 vapor produced will leave the steam boiler, along with the steam and is dissolved into the condensed condensate water, after the energy from the steam is utilized. As the CO2 dissolves into the condensate water, it produces a carbonic acid and will dramatically increase the corrosiveness of the condensate return water. In order to protect the condensate, return piping from corrosion, the condensate must be feed with corrosion control chemicals.

The two most common types of condensate water treatment are neutralizing and filming chemical additives.

A neutralizing chemical additive will neutralize the Carbonic Acid in the condensate water and raise the pH above acidic levels. A filming chemical additive will provide a protective layer on the interior of the piping to keep the condensate return water from actually touching the metal. In most cases a neutralizing chemical additive will tend to be slightly more expensive, but these chemicals are usually more effective.

There are limitations to the type of condensate treatment implemented for steam systems. For example, there are certain treatment programs are restricted if the steam is used for food preparation or direct contact humidification, a treatment product that is approved for use with food preparation or direct contact humidification should be used. Contact a licensed water treatment consultant or supplier for more information regarding which products can be used and for which systems these chemicals are allowed.

4.1 Setting Up a Water Treatment Program

The most important step to setting up a water treatment program is to know what systems are present in the building and what are the requirements for water properties such as pH, conductivity, total dissolved solid (TDS), etc. The water property ranges, definitions and testing schedules are in Section 5. Many of these water chemistry properties can be monitored using stand-alone controllers or global building automation system (BAS) controls. A licensed water treatment consultant should be employed to model the building’s water systems and develop an appropriate treatment plan for each system. There are many treatment plans available; below is a summary of typical plans used for each system, which are used by water treatment consultants in the United States.

4.2 Open Loop Cooling Water Systems

Monitoring conductivity as a measurement of the concentration of Total Dissolve Solids (TDS) is a crucial part of controlling an open loop water system. Conductivity limits should be set by a water treatment consultant and routinely monitored to ensure that mineral scale does not form. Cycles of concentration of the system should not exceed limits set by water treatment consultant. Automated blown down controls with a conductivity meter is recommended for open loop systems. The pH of the water should be routinely monitored especially if an acidic additive is used to control the pH. Corrosion inhibitor residual tests should also be run to verify that the system is receiving the correct dosage. Routine tests should be conducted daily, weekly, or monthly to monitor oxidizing biocide residuals and bacteria concentrations to ensure Micro-Bio levels are under control. In general, bacteria concentrations in the open loop cooling water system should be less than 100,000 cfu/ml (colony forming units per milliliter) at all times.

Corrosion Monitoring should be performed using a real time on-line monitoring device or corrosion coupons with a 90-day rotation schedule. Coupon test results should show mild steel corrosion rates less than 5.0 mils per year (MPY) and Copper Corrosion Rates less than 2.0 MPY at all times.

Recommended Corrosion and Scale Control Programs

Program 1:

Description: Multifunctional Molybdate Based Corrosion Inhibitor and

Dispersant

Function: Corrosion Inhibition, Mineral Scale Inhibition

Components: Molybdate for Mild Steel Corrosion Control

Azole for Copper Corrosion Control Dispersant for Mineral

Scale Inhibition

Form: Liquid

Feed Location: Tower Basin or Header

Control Tests: Molybdate Residual or Test for Tracing Agent if present, Corrosion Monitoring

Program 2:

Description: All Organic Based Multifunctional Corrosion Inhibitor and

Dispersant

Function: Corrosion Inhibition, Mineral Scale Inhibition

Components: Phosphonate for Mild Steel Corrosion Control

Azole for Copper Corrosion Control Dispersant for Mineral

Scale Inhibition

Form: Liquid

Feed Location: Tower Basin or Header

Control Tests: Organic Phosphate Test or Test for Tracing Agent if

Present, Corrosion Monitoring

Program 3:

Description: Zinc Phosphate Multifunctional Corrosion Inhibitor and

Dispersant

Function: Corrosion Inhibition, Mineral Scale Inhibition Components:

Zinc and Phosphate for Mild Steel Corrosion Control

Azole for Copper Corrosion Control Dispersant for

Mineral Scale Inhibition

Form: Liquid

Feed Location: Tower Basin or Header

Control Tests: Ortho-Phosphate or Test for Tracing Agent if present

Program 4:

Description: Stabilized Phosphate Corrosion Inhibitor and Dispersant

Function: Corrosion Inhibition, Mineral Scale Inhibition Components:

Phosphate for Mild Steel Corrosion Control

Azole for Copper Corrosion Control Dispersant for

Mineral Scale Inhibition

Form: Liquid

Feed Location: Tower Basin or Header

Control Tests: Ortho-Phosphate or Test for Tracing Agent if present, Corrosion Monitoring Bacteria Control Programs

Program 1:

Description: Chlorine Bleach Oxidizing Biocide

Function: Oxidizing Biocide

Components: Sodium Hypochlorite

Form: Liquid

Feed Location: Tower Basin

Control Tests: Free Chlorine Residual, Bacteria Monitoring

Program 2:

Description: Stabilized Chlorine Oxidizing Biocide

Function: Oxidizing Biocide

Components: Stabilized Sodium Hypochlorite

Form: Liquid

Feed Location: Tower Basin

Control Tests: Free Chlorine Residual, Bacteria Monitoring

Program 3:

Description: Activated Bromine Oxidizing Biocide

Function: Oxidizing Biocide

Components: Separate Feed of Sodium Hypochlorite

Separate Feed of Sodium Bromide

Form: Both Liquid

Feed Location: Mix together in feed line to activate Bromine then feed to

Tower Basin

Program 4:

Description: Stabilized Bromine Based Oxidizing Biocide

Function: Oxidizing Biocide

Components: Stabilized Bromine

Form: Liquid

Feed Location: Tower Basin

Control Tests: Free Chlorine Residual, Bacteria Monitoring

Program 5:

Description: Solid Chlorine Bromine Tablets

Function: Oxidizing Biocide

Components: Chlorine and Bromine

Form: Solid Tablet

Feed Location: Fed from pot feeder to Tower basin

Program 6:

Description: Solid Chlorine Bromine Tablets

Function: Oxidizing Biocide

Components: Chlorine and Bromine

Form: Solid Tablet

Feed Location: Fed from pot feeder to Tower basin

Program 7:

Description: Isothiazoline

Function: Non-Oxidizing Biocide

Components: Isothiazoline

Form: Liquid

Feed Location: Slug fed to tower basin

Control Tests: Bacteria Monitoring

Program 8:

Description: Glutaraldehyde

Function: Non-Oxidizing Biocide

Components: Glutaraldehyde

Form: Liquid

Program 9:

Description: DBNPA

Function: Non-Oxidizing Biocide

Components: Dibromonitropropianamide

Form: Liquid

Program 10:

Description: Quaternary Amine

Function: Non-Oxidizing Biocide

Components: Quaternary Amine

Form: Liquid

Feed Location: Slug fed to tower basin

Control Tests: Bacteria Monitoring

Program 11:

Description: MBT

Function: Non-Oxidizing Biocide

Components: Methylene-bis-thiocyanate

Form: Liquid

4.3 Closed Loop Cooling and Hot Water Systems

General guidelines for the control of a closed loop cooling or hot water system include the monitoring of the conductivity, pH, corrosion, and micro bio-levels. Water chemistry limits should be set by a water treatment consultant and routinely monitored by maintenance personnel to ensure that mineral scale and corrosion does not occur. Automated make up water controls along with a makeup water meter should be added to the system to maintain a consistent amount of water. The pH of the water should be routinely monitored, especially if an acidic additive is used to control the pH. Corrosion inhibitor residual tests should also be run to verify that the system is receiving the correct dosage. Monthly monitoring of bacteria concentrations to ensure biological organism levels are under control. If biological organism levels are above recommended levels, there could be a point where oxygen is entering the system, i.e. a leak in the system. Corrosion monitoring should be done with iron or copper corrosion coupons with a six month rotation schedule. Coupon test results should show mild steel corrosion rates less than

0.5 mils per year (MPY) and Copper corrosion rates less than 0.2 MPY at all times.

Recommended Corrosion and Scale Inhibition Programs

Program 1:

Description: Multifunctional Molybdate Based Corrosion Inhibitor and

Dispersant

Function: Corrosion Inhibition, Mineral Scale Inhibition

Components: Molybdate for Mild Steel Corrosion Control

Azole for Copper Corrosion Control Dispersant for Mineral

Scale Inhibition

Form: Liquid

Feed Location: Slug feed with Pot Feeder

Control Tests: Molybdate Residual or Test for Tracing Agent if present, Corrosion Monitoring

Program 2:

Description: Multifunctional Nitrite Based Corrosion Inhibitor and

Dispersant

Function: Corrosion Inhibition, Mineral Scale Inhibition

Components: Nitrite for Mild Steel Corrosion Control

Azole for Copper Corrosion Control Dispersant for Mineral

Scale Inhibition

Form: Liquid

Feed Location: Slug feed with Pot Feeder

Control Tests: Nitrite Residual or Test for Tracing Agent if present, Corrosion Monitoring

4.4 Steam and Condensate Recirculation Systems

The water treatment program for a steam and condensate recirculation system should include monitoring for conductivity. Proper Conductivity limits will vary slightly depending upon the type, age, and size of the steam boiler system. The absolute maximum conductivity level for any steam system is 5,500 µmhos.

The alkalinity concentration in the steam boiler should routinely be monitored my maintenance personnel.

There two main types of alkalinity measured in a steam system total (M)-Alkalinity and hydroxide (OH)-alkalinity. The P-alkalinity test is used to measure the portion of M- alkalinity contributed to by Hydroxide (OH)-alkalinity. Barium chloride is added to water samples containing OH-alkalinity then sulphuric acid is added to neutralize the OH, alkalinity is then measured to show the change in alkalinity due to the elimination of OH molecules. P- Alkalinity is used to monitor the condensate return system; to avoid corrosion within the steam boiler OH-alkalinity is measured. Proper chemical dosage for the steam boiler is ensured by running routine chemical residual tests for the oxygen scavenger and internal scale inhibitor.

In addition, it is very important to monitor the chemistry of the steam boilers feed water. Maintenance personnel should test the conductivity of the feed water on a regular basis. If makeup water pretreatment is exists, Maintenance personnel should also test the total hardness level of the feed water.

The remaining tests to be conducted on condensate return for filming Amine residual, or Iron concentration and the condensate pH should be tested to ensure that the system has received the proper chemical dosage.

Further tests can be conducted by a water treatment consultant to determine if dosages should be altered to maintain proper steam, makeup and feed water chemistry.

Recommended Oxygen Scavengers

Program 1:

Description: Sulfite

Function: Chemical Oxygen Scavenger

Components: Catalyzed Sodium Sulfite

Form: Liquid or Powder

Feed Location: Deaerator Drop Leg or Storage Section Control

Tests: Residual Sulfite

Program 2:

Description: Volatile Oxygen Scavenger

Function: Chemical Oxygen Scavenger

Components: Various Types Available

Form: Liquid

Feed Location: Deaerator Drop Leg or Storage Section Control

Tests: DEHA Residual

Recommended Scale Control Programs

Description: Precipitating Phosphate

Function: Sludge Conditioner

Components: Phosphate

Form: Liquid

Feed Location: Boiler Steam Drum or Feedwater line

Control Tests: Conductivity, P Alkalinity, M Alkalinity, OH Alkalinity, Silica, Ortho-Phosphate, Visual Color Test

Program 2:

Description: Polymer Dispersant

Function: Mineral Dispersant

Components: Polymer

Form: Liquid

Feed Location: Boiler Steam Drum or Feedwater line

Control Tests: Feedwater Hardness, Polymer Residual, Silica, OH-Alkalinity, Tracing Agent if available

Program 3:

Description: Chelant

Function: Sludge Conditioner

Components: EDTA Chelant

Form: Liquid

Feed Location: Boiler Steam Drum or Feedwater line

Control Tests: Feedwater Hardness, Chelate Residual, Silica, O-Alkalinity, Tracing Agent if available

Recommended Condensate Corrosion Control

Description: Neutralizing Amine

Function: Raise pH of Condensate

Components: Various Types

Form: Liquid

Feed Location: Steam Header or Boiler Steam Drum Control

Tests: Condensate pH, Condensate Iron

Program 2:

Description: Filming Amine

Function: Provide Protective Barrier for Condensate Piping

Components: Various Types

Form: Liquid

Feed Location: Steam Header or Boiler Steam Drum Control Tests:

Filming Amine Residual, Condensate Iron

Recommended General Corrosion Control (Steam Drum)

Description: Caustic

Function: Increase Alkalinity

Components: Sodium or Potassium Hydroxide

Form: Liquid or Powder

Feed Location: Deaerator storage or Boiler Steam Drum Control

Tests: O-Alkalinity

5.1 Water System Testing

Routine water chemistry tests play an important role in maintaining building water systems; they can be used to anticipate and prevent water’s capacity to accelerate fouling, scaling and corrosion within a mechanical system. Chemical test kits for each building water system are available through most water treatment chemical suppliers or consultants. Section 5.2 lists the most common water tests used and a water treatment consultant can determine if a system requires more rigorous tests.

5.2 Water Sampling

When water samples are taken, they should be isolated from large amounts of mineral buildup, incoming feed water or makeup water and chemical feed points. Samples should be collected during normal operation before system blow down and chemical dosing. When collecting water, allow the samples container to overfill and to avoid sample contamination use sampled water to rinse cap or container. Label the container appropriately and test sample as soon as possible. A licensed water treatment consultant will be able to give advice on chemical testing. However, building maintenance staff should be familiar with specific test procedures that should be provided by the chemical test equipment supplier(s).

5.3 Common Water Chemistry Tests Conductivity:

This test is used to estimate the Total Dissolved Solids (TDS) concentration in a water sample. Conductivity is the measures of electrical conductance in the water. In general 1.0 umhos of conductance is equal to

0.67 ppm of total dissolved solids or minerals. High levels of conductivity increase the scaling potential of the system which depends on water temperature, composition of dissolved solids and interaction with other chemical additives, and the system’s metallurgy.

Cycles of concentration for a water system is measured as the ratio of mineral content (TDS) of system water divided by the mineral content (TDS) of make-up water. High cycles of concentration are an indicator of increased scaling potential. Maintaining high cycles can be done with proper chemical water treatment. Cycles of concentration are mainly monitored in open loop cooling systems and general range from 2 to 14 times the mineral content of the makeup water. The cycles of concentration of a system are completely dependent upon the TDS of the makeup water and the optimum point where corrosion and scale build-up are minimized. A water treatment consultant should specify the optimal cycles for the water system.

pH:

In general, low pH water is corrosive and has a high acidity, a meter reading lower than 7.0. High pH water is prone to scaling and is considered to be alkaline and is specified by a meter reading greater than 7.0 and less than 14. Tests for pH, acidity or alkalinity, are used to monitor chemical treatment product dosages and are used for general troubleshooting of a water system.

Nitrite:

The concentration of Nitrite in a closed loop cooling or hot water system’s water sample is measured to monitor the corrosion inhibitor program. Nitrite is used to passivate metal surface and remove dissolved oxygen resulting in a non-corrosive water system. A water treatment consultant will set the minimum levels of nitrate that need to be maintained.

Sulfite:

This test is a residual oxygen scavenger test used to determine the concentration of sulfite available in a closed loop hot water system. If used as the oxygen scavenger, Sulphite must be maintained at levels between 30-50 mg/L (ppm). When Sulphite levels are not maintained corrosion will occur. Over charging a system with Sulphite will increase the conductivity of the water, corrosively and may cause the growth of sulphate reducing bacteria.

Silica:

Silica testing measures the concentration of Dissolved Silica in a water sample, typically for steam boiler systems. If silica levels are too high and pH is low scaling will occur. Silica can form extremely hard and dense scale on heat transfer surfaces increasing the risk of mechanical failure. Common water test sample points for silica include the boiler drum and the saturated steam.

Corrosion Coupons:

Corrosion coupons are small, slender circular or rectangular pieces of metal (Iron or copper) used to monitor the actual corrosion level in a water system. Typically corrosion coupons are monitored on a 90-day rotation schedule. The original dimensions, thickness, of the coupon are known. When the coupon is removed from the water loop the change in dimensions are noted as the corrosion rate. If the corrosion inhibitor program is effective the coupon’s corrosion rate are below the recommended levels, as specified in Section 5.3.

Bacteria Dip Slide:

This test measures the concentration of bacteria in an open or closed loop cooling water system water sample. A media called “Agar” is wetted with the cooling water then is placed into a tube were Bacteria, yeasts, and fungi are grown. This test is used to confirm that biocide program in an open or closed cooling water system is effective.

Dissolved Iron:

Iron testing is used to monitor corrosion products in a water system. Iron testing is used to either verify that the treatment program is working or to troubleshoot a problem. Dissolved Iron levels should be less than 30 ppm. Increased corrosion problems, leaks, poor heat transfer efficiency, as well as bacteria problems can occur when the dissolved Iron level is high.

Molybdate:

A Molybdate test measures the concentration of Sodium Molybdate in both closed and open loop cooling water systems. A water treatment consultant will state the minimum levels of Molybdate that is needed to maintain the systems’ corrosion inhibitor program.

Organic Phosphate:

This test measures the concentration of organic Phosphate in an open loop cooling water system. This test is needed only if an organic phosphate is used as a corrosion inhibitor. A water treatment consultant will set the minimum levels of organic phosphate that need to be maintained to prevent corrosion.

Ortho-Phosphate:

This test measures the concentration of inorganic Phosphate in a water sample. Ortho- Phosphate is a commonly used in closed loop cooling water and hot water systems as an Iron (ferrous) and non-ferrous alloy corrosion inhibitor. If phosphate is used a minimum concentration of 200 – 300 mg/L (ppm) is required.

Free Chlorine:

A free chlorine test measures the concentration of active oxidizing biocide in a open loop cooling water system. Free Chlorine tests are used to monitor both Chlorine and Bromine and are more accurately described as free halogen tests. These tests are commonly used to monitor the dosage of oxidizing biocide in an open re-circulating cooling water system. Since excessive chlorine concentrations are corrosive, a free chlorine residual of 0.2 to 0.8 ppm is maintained.

5.4 Maintenance Parameters

The following charts list the minimum monitoring requirements for each open loop or closed loop water system. The frequency of the water testing can be increased to better maintain the performance in open loop cooling water, steam boiler, or closed loop system. The chemical test ranges and frequencies given are general and should be clearly defined by a certified water treatment consultant. A water treatment program can be controlled to an optimum level if the system is checked on a daily basis and automated monitoring equipment, such as conductivity and pH meters, are installed.

The operating ranges are mandatory performance standards. The maintenance Contractor must maintain water within these tolerances, unless GSA gives a written waiver for specific reasons. GSA may require more rigorous standards where circumstances dictate. The testing frequencies establish minimum mandatory frequencies. Contractors may test more frequent- ly. Sporadic short-term deviations from operating ranges may not, depending on the terms and conditions of specific Contracts, result in a determination of unsatisfactory Contract perfor- mance where the Contractor takes prompt action to correct the condition.

Open Loop Cooling Water Systems

Chemistry Tests Frequency of Test Operating Ranges

Tower Water Conductivity

Auto Blow down: Weekly, Monthly

Manual Blow down: Daily

160-2400 mmHOS (110-1600 ppm)

Makeup Water Conductivity (Hardness)

Auto Blow down:

Weekly, Monthly

40-600 mmHOS (30-400 ppm) pH Test Daily, Weekly 7.5 to 9.5

Corrosion Monitoring (Coupon Test) Quarterly (3 months) Iron: 2 to 5 mils/ year

Copper: 0.2 to 0.5 mils/ yr

Bacteria Testing Monthly Max: 103 cfu/ml (colony forming units/ ml)

Chlorides Weekly, Monthly Max: 250 ppm as Cl Max: 410 ppm as NaCL

Sulfites Weekly, Monthly 50-100 ppm SO3 80-160 ppm Na2SO3

Corrosion Inhibitor Residual Auto Chem. Feed:

Weekly, Monthly Defined by Consultant

Oxidizing Biocide Residual Auto Chem. Feed:

Weekly, Monthly Defined by Consultant

Closed Loop Cooling Water Systems

Chemistry Tests Frequency of Test Optimum Operating Ranges pH Monthly 7.5-9.5

Total Dissolved Solids (TDS) or Conductivity Quarterly (3 months) Maximum: 2000 ppm or

(2500µS/cm)

Polyphosphates (PO4) Monthly 10- 20 ppm

Sulfites Monthly 50-100 ppm SO3 80-160 ppm Na2SO3

Bacteria Testing Monthly Max: 103 cfu/ml (colony forming units/ ml)

Corrosion Monitoring (Coupon Test) Bi-Annually (6 months) Iron: max. 0.5 mils/ year

Copper: max. 0.2 mils/ yr

Corrosion Inhibitor Residual Monthly Defined By Consultant

Steam Systems with Re-circulating Water

Chemistry Tests

Frequency of Test Optimum Operating

Ranges

Total Hardness Concentration

Daily or 3 times/week

Less Than 2 ppm CaCO3

Feed water pH

10.5-11.5

Feed Water Conductivity or

TDS

Daily or 3 times/week 1500 - 3000 ppm

(2000 – 4000 µS/cm)

Condensate Return pH

8.5-9.5 pH

Condensate Return Conductivity or TDS

Daily or 3 times/week 40 ppm

(50 µS/cm)

Makeup Water Conductivity

Weekly 40-600 mmHOS

(30-400 ppm)

Hydroxide Alkalinity

150-300 ppm CaCO3

Total Alkalinity Auto Chem Feed:

Daily, Weekly

<700 ppm CaCO3

Sulphite

Daily or 3 times/week 30-60 ppm SO3

50 ppm Na2SO3

Steam Drum Scale Inhibitor Residual

Auto Chem Feed:

Defined By Consultant

Steam Drum Oxygen Scavenger Residual

Auto Chem Feed:

Defined By Consultant

6.1 Alternatives to Chemical Water Treatment

There are many alternative non-chemical methods to treating closed and open loop cooling and hot water systems. Not all alternatives on the market have been proven to be effective so carefully consider products that promise too much. The products listed below have been used in many systems and have been an effective means of non-chemical water treatment. There are numerous practical studies that can be referenced, when making a decision for or against either of these non-chemical water treatments.

6.2 Pulsed Electromagnetic Fields

This chemical free water treatment system uses a pulsed electromagnetic field to treat water. The common application of this technology is on open loop water processes subject to scale, corrosion, bio-fouling or bacterial contamination. Typical applications include open process water loops, cooling towers and fountains.

The technology originated in the food and beverage industry as an FDA approved means for water sterilization.

The principal of operation is to generate a pulsating magnetic field around a Section of pipe in the water process system. Each generated electromagnetic wave varies in amplitude and frequency and as the wave decays harmonics are created that can be measured in the megahertz range. It is this harmonic wave that is used to treat the water.

The harmonic wave alters the minerals; i.e. Calcium Carbonates, electrical charge causing the minerals to clump together into finally divide particles; colloidal nucleation. The minerals concentrate due to evaporation and attract each other thus clumping together into fine particles. The minerals then precipitate out of solution as a non-adhesive powder in the cooling tower basin rather than on the inside of the piping and heat transfer surfaces as scale. The powder is then carried off in the water discharged from the cooling tower during blow-down.

This pulsed electro magnetic field technology also has an effect on biological organisms, such as bacteria.

The effect is described by two processes known as electroporation and encapsulation. Electroporation is the electromagnetic pulse causes damage to the cell membrane of biological organisms by repeatedly exposing it to an electromagnetic field. This inhibits the reproductive ability of the bacteria thus exhausting their ability to multiply. Encapsulation is the process of calcium carbonate precipitates surrounding and encapsulating the biological organisms in the condenser water. This prevents bio-fouling and bacteria from accumulating in open water loops. Eliminating the need for oxidizing biocides; which are corrosive substances such as bleach, chlorine and bromine, directly reduces the predominance for corrosion within cooling towers.

The cycles of…