13 Treatment of Power Industry Wastes Lawrence K. Wang Lenox Institute of Water Technology and Krofta Engineering Corporation, Lenox, Massachusetts and Zorex Corporation, Newtonville, New York, U.S.A. 13.1 INTRODUCTION 13.1.1 Steam Electric Power Generation Industry The steam electric power generation industry is defined as those establishments primarily engaged in the steam generation of electrical energy for distribution and sale. Those establishments produce electricity primarily from a process utilizing fossil-type fuel (coal, oil, or gas) or nuclear fuel in conjunction with a thermal cycle employing the steam–water system as the thermodynamic medium. The industry does not include steam electric power plants in industrial, commercial, or other facilities. The industry in the United States falls under two Standard Industrial Classification (SIC) Codes: SIC 4911 and SIC 4931. There are about 1000 steam electric power generating plants in operation in the United States. Of these plants, approximately 35% generate in excess of 500 megawatts (MW) and approximately 12% generate 25 MW or less. These steam electric power generating plants represent about 79% of the entire electric utility generating capacity, and they generate about 85% of electricity produced by the entire electric utility industry. Within the steam electric power generation industry, plants built after 1970 represent 44% of the total capacity, and plants built before 1960 represent 26% of capacity. “Small units” are defined by the U.S. Environmental Protection Agency (USEPA) as generating units of less than 25 MW capacity. “Old units” are defined as generating units of 500 MW or greater rated net generating capacity that were first placed into service on or before January 1, 1970, as well as any generating unit of less than 500 MW capacity first placed in service on or before January 1, 1974. The term “10-year, 24-hour rainfall event” refers to a rainfall event with a probable recurrence interval of once in 10 years as defined by the National Weather Service. 13.1.2 Power Generation, Waste Production, and Effluent Discharge In the operation of a power plant, combustion of fossil fuels – coal, oil, or gas – supplies heat to produce steam, which is used to generate mechanical energy in a turbine. This energy is subsequently converted by a generator to electricity. Nuclear fuels, currently uranium, are used in a similar cycle except that the heat is supplied by nuclear fusion wastewater discharge. A number of different operations by steam electric power plants discharge chemical wastes. Many wastes are discharged more or less continuously as long as the plant is operating. These include 581 © 2006 by Taylor & Francis Group, LLC wastewaters from the following sources: cooling water systems, ash handling systems, wet- scrubber air pollution control systems, and boiler blowdown. Some wastes are produced at regular intervals, as in water treatment operations, which include a cleaning or regenerative step as part of their cycle (ion exchange, filtration, clarification, evaporation). Other wastes are also produced intermittently but are generally associated with either the shutdown or startup of a boiler or generating unit, such as during boiler cleaning (water side), boiler cleaning (fire side), air preheater cleaning, cooling tower basin cleaning, and cleaning of miscellaneous small equipment. The discharge frequency for these varies from plant to plant. Some or all of the various types of wastewater streams occur at almost all of the plant sites in the industry. However, most plants do not have distinct and separate discharge points for each source of wastewater; rather, they combine certain streams prior to final discharge. Additional wastes exist that are essentially unrelated to production. These depend on meteorological or other factors. Rainfall runoff, for example, causes drainage from coal piles, ash piles, floor and yard drains, and from construction activity. The summary for the steam electric power generating (utility) point source category in terms of the number of dischargers in industry is as follows: . direct dischargers in industry: 1050; . indirect dischargers in industry: 100; . zero dischargers in industry: 10. Current BPT regulations for the steam electric power industry for generating, small and old units can be found elsewhere [1]. 13.2 INDUSTRY SUBCATEGORY AND SUBDIVISIONS Subcategories for the steam electric utility point source category are developed according to chemical waste stream origin within a plant. This approach is a departure from the usual method of subcategorizing an industry according to different types of plants, products, or production processes. Categorization by waste source provides the best mechanism for evaluating and controlling waste loads since the steam electric power plant waste stream source has the strongest influence on the presence and quantity of various pollutants as well as on flow. The breakdown of the stream electric power generation industry into subcategories and subdivisions is based on similarities in wastewater characteristics throughout the industry. The eight broad subcategories and their subdivisions are presented below: 1. Once-through cooling water. 2. Recirculating cooling system blowdown. 3. Ash transport water: . fly ash transport; . bottom ash transport. 4. Low volume wastes: . clarifier blowdown; . makeup water filter backwash; . ion exchange softener regeneration; . evaporator blowdown; . lime softener blowdown; . reverse osmosis brine; 582 Wang © 2006 by Taylor & Francis Group, LLC . demineralizer regenerant; . powdered resin demineralizer; . floor drains; . laboratory drains; . sanitary wastes; and . diesel engine cooling system discharge. 5. Metal cleaning wastes: . boiler tube cleaning; . cleaning rinses; . fireside wash; and . air preheater wash. 6. Ash pile, chemical handling, and construction area runoff coal pile runoffs. 7. Coal pile runoff. 8. Wet flue gas cleaning blowdown. 13.2.1 Once-Through Cooling Water Subcategory In a steam electric power plant, cooling water is utilized to absorb heat that is liberated from the steam when it is condensed to water in the condensers. The cooling water is withdrawn from a water source, passed through the system, and returned directly to the water source. Shock (intermittent) chlorination is employed in many cases to minimize the biofouling of heat transfer surfaces. Continuous chlorination is used only in special situations. Based on 308 data, approximately 65% of the existing steam electric power plants have once-through cooling water systems. 13.2.2 Recirculating Cooling Water Subcategory In a recirculating cooling water system, the cooling water is withdrawn from the water source and passed through condensers several times before being discharged to the receiving water. After each pass through the condenser, heat is removed from the water through evaporation. Evaporation is carried out in cooling ponds or canals, in mechanical draft evaporative cooling towers, and in natural draft evaporative cooling towers. In order to maintain a sufficient quantity of water for cooling, additional makeup water must be withdrawn from the water source to replace the water that evaporates. When water evaporates from the recirculating cooling water system, the dissolved solids content of the water remains in the system, and the dissolved solids concentration tends to increase over time. If left unattended, the formation of scale deposits will result. Scaling due to dissolved solids buildup is usually controlled through the use of a bleed system called cooling tower blowdown. A portion of the cooling water in the system is discharged via blowdown, and since the discharged water has a higher dissolved solids content than the intake water used to replace it, the dissolved solids content of the water in the system is reduced. Chemicals such as sulfuric acid are used to control scaling in the system. Biofoulants such as chlorine and hypochlorite are widely used by the industry. These additives are discharged in the cooling tower blowdown. 13.2.3 Ash Transport Water Subcategory Steam electric power plants using oil or coal as a fuel produce ash as a waste product of combustion. The total ash product is a combination of bottom ash and fly ash. Because the ash Treatment of Power Industry Wastes 583 © 2006 by Taylor & Francis Group, LLC composition of oil is much less than that of coal, the presence of ash is an extremely important consideration in the design of a coal-fired boiler. Improper design leads to the accumulation of ash deposits on furnace walls and tubes, leading to reduced heat transfer, increased pressure drop, and corrosion. Accumulated ash deposits are removed and transported to a disposal system. The method of transport may be either wet (sluicing) or dry (pneumatic). Dry handling systems are more common for fly ash than bottom ash. The dry ash is usually disposed of in a landfill, but the ash is also sold as an ingredient for other products. Wet ash handling systems produce wastewaters that are either discharged as blowdown from recycle systems or are discharged to ash ponds and then to receiving streams in recycle and once-through systems. Ash From Oil-Fired Plants Fly ash is a light material, which is carried out of the combustion chamber in the flue gas stream. The ash from fuel oil combustion is usually in the form of fly ash. The many elements that may appear in oil ash deposits include vanadium, sodium, and sulfur. Ash From Coal-Fired Plants More than 90% of the coal used by electric utilities is burned in pulverized coal boilers. In these boilers, 65–80% of the ash produced is in the form of fly ash. This fly ash is carried out of the combustion chamber in the flue gases and is separated from these gases by electrostatic precipitators and/ or mechanical collectors. The remainder of the ash drops to the bottom of the furnace as bottom ash. While most of the fly ash is collected, a small quantity may pass through the collectors and be discharged to the atmosphere. The vapor is that part of the coal material that is volatilized during combustion. Some of these vapors are discharged into the atmosphere; others are condensed onto the surface of fly ash particles and may be collected in one of the fly ash collectors. 13.2.4 Low-Volume Wastes Subcategory Low-Volume Blowdowns Low-volume wastes include wastewaters from all sources except those for which specific limitations are otherwise established in 40 CFR 423. Waste sources include, but are not limited to, wastewaters from wet scrubber air pollution control systems [2], ion exchange water treatment systems, water treatment evaporator blowdown, laboratory and sampling streams, floor drainage, cooling tower basin cleaning wastes, and blowdown from recirculating house service water systems. Sanitary wastes and air conditioning wastes are specifically excluded from the low-volume waste subcategory. Boiler Blowdown Power plant boilers are either of the once-through or drum-type design. Once-through boilers operate under supercritical conditions and have no wastewater streams directly associated with their operation. Drum-type boilers operate under subcritical conditions where steam generated in the drum-type units is in equilibrium with the boiler water. Boiler water impurities are concentrated in the liquid phase. Boiler blowdown serves to maintain concentrations of dissolved and suspended solids at acceptable levels for boiler operation. The sources of impurities in the blowdown are the intake water, internal corrosion of the boiler, and chemicals added to the boiler. Phosphate is added to the boiler to control solids deposition. 584 Wang © 2006 by Taylor & Francis Group, LLC In modern high-pressure systems, blowdown water is normally of better quality than the water supply. This is because plant intake water is treated using clarification, filtration, lime/lime soda softening, ion exchange, evaporation, and in a few cases reverse osmosis to produce makeup for the boiler feedwater. The high-quality blowdown water is often reused within the plant for cooling water makeup or it is recycled through the water treatment and used as boiler feedwater. 13.2.5 Metal Cleaning Wastes Subcategory Metal cleaning wastes result from cleaning compounds, rinse waters, or any other waterborne residues derived from cleaning any metal process equipment, including, but not limited to, boiler tube cleaning, boiler fireside cleaning, and air preheater cleaning. Boiler Tube Cleaning Chemical cleaning is designed to remove scale and corrosion products that accumulate in the steam side of the boiler. Hydrochloric acid, which forms soluble chlorides with the scale and corrosion products in the boiler tubes, is the most frequently used boiler tube cleaning chemical. In boilers containing copper, a copper complexer is used with hydrochloric acid to prevent the replating of dissolved copper onto steel surfaces during chemical cleaning operations. If a complexer is not used, copper chlorides, formed during the cleaning reaction, react with boiler tube iron to form soluble iron chlorides while the copper is replated onto the tube surface. Alkaline cleaning (flush/boil-out) is commonly employed prior to boiler cleaning to remove oil-based compounds from tube surfaces. These solutions are composed of trisodium phosphate and a surfactant and act to clear away the materials that may interfere with reactions between the boiler cleaning chemicals and deposits. Citric acid cleaning solutions are used by a number of utilities in boiler cleaning operations. The acid is usually diluted and ammoniated to a pH of 3.5 and then used for cleaning in a two-stage process. The first stage involves the dissolution of iron oxides. In the second stage, anhydrous ammonia is added to raise the pH of the cleaning solution to between 9 and 10 and air is bubbled through the solution to dissolve copper deposits. Ammoniated EDTA has been used in a wide variety of boiler cleaning operations. The cleaning involves a one-solution, two-stage process. During the first stage, the solution solubilizes iron deposits and chelates the iron solution. In the second stage, the solution is oxidized with air to induce iron chelates from ferric to ferrous and to oxidize copper deposits into solution where the copper is chelated. The most prominent use of this agent is in circulating boilers that contain copper alloys. When large amounts of copper deposits in boiler tubes cannot be removed with hydrochloric acid due to the relative insolubility of copper, ammonia-based oxidizing com- pounds have been effective. Used in a single separate stage, the ammonia sodium bromate step includes the introduction into the boiler system of solutions containing ammonium bromate to rapidly oxidize and dissolve the copper. The use of hydroxyacetic/formic acid in the chemical cleaning of utility boilers is common. It is used in boilers containing austenitic steels because its low chloride content prevents possible chloride stress corrosion cracking of the austenitic-type alloys. It has also found extensive use in the cleaning operations for once-through supercritical boilers. Hydroxyacetic/formic acid has chelation properties and a high iron pick-up capability; thus it is used on high iron content systems. It is not effective on hardness scales. Treatment of Power Industry Wastes 585 © 2006 by Taylor & Francis Group, LLC Sulfuric acid has found limited use in boiler cleaning operations. It is not feasible for removal of hardness scales due to the formation of highly insoluble calcium sulfate. It has found some use in cases where a high-strength, low-chloride solvent is necessary. Use of sulfuric acid requires high water usage in order to rinse the boiler sufficiently. Boiler Fireside Washing Boiler firesides are commonly washed by spraying high-pressure water against boiler tubes while they are still hot. Air Preheater Washing Air preheaters employed in power generating plants are either the tubular or regenerative types. Both are periodically washed to remove deposits that accumulate. The frequency of washing is typically once per month; however, frequency variations ranging from 5 to 180 washings per year are reported. Many preheaters are sectionalized so that heat transfer areas may be isolated and washed without shutdown of the entire unit. 13.2.6 Ash Pile, Chemical Handling, and Construction Area Runoff Subcategory Fly ash and bottom ash stored in open piles, chemicals spilled in handling, and soil distributed by construction activities will be carried in the runoff caused by precipitation events. 13.2.7 Coal Pile Runoff Subcategory In order to ensure a consistent supply of coal for steam generation, plants typically maintain an outdoor 90-day reserve supply. The piles are usually not enclosed, so the coal comes in contact with moisture and air, which can oxidize metal sulfides to sulfuric acid. Precipitation then results in coal pile runoff with minerals, metals, and low pH (occasionally) in the stream. 13.2.8 Wet Flue Gas Cleaning Blowdown Subcategory Depending on the fossil fuel sulfur content, an SO 2 -scrubber may be required to remove sulfur emissions in the flue gases. These scrubbing systems result in a variety of liquid waste streams depending on the type of process used. In all of the existing FGD (flue gas desulfurization) systems, the main task of absorbing SO 2 from the stack gases is accomplished by scrubbing the existing gases with an alkaline slurry. This may be preceded by partial removal of fly ash from the stack gases. Existing FGD processes may be divided into two categories: nonregenerable FGD processes including lime, limestone, and lime/limestone combination, and double alkali systems. In the lime or limestone FGD process, SO 2 is removed from the flue gas by wet scrubbing with a slurry of calcium oxide or calcium carbonate [3]. The waste solid product is disposed by ponding or landfill. The clear liquid product can be recycled. Many of the lime or limestone systems discharge scrubber waters to control dissolved solids levels. A number of processes can be considered double alkali processes, but most developmental work has emphasized sodium-based systems, which use lime for regeneration. This system pretreats the flue gas in a prescrubber to cool and humidify the gas and to reduce fly ash and chlorides. The gas passes through an absorption tower where SO 2 is removed into a scrubbing solution, which is subsequently regenerated with lime or limestone in a reaction tank. 586 Wang © 2006 by Taylor & Francis Group, LLC The disadvantage of all nonregenerable systems is the production of large amounts of throwaway sludges. Onsite disposal is usually performed by sending the waste solids to a settling pond. The supernatant from the ponds may be recycled; however, according to 308 data, 82% of the plants with FGD systems discharged the supernatant into surface waters. 13.3 WASTEWATER 13.3.1 Characterization Wastewater produced by a steam electric power plant can result from a number of operations at the site. Many wastewaters are discharged more or less continuously as long as the plant is operating. These include wastewaters from the following sources: cooling water systems, ash handling systems, wet-scrubber air pollution control systems, and boiler blowdown. Some wastes are produced at regular intervals, as in water treatment operations that include a cleaning or regenerative step as part of their cycle (ion exchange, filtration, clarification, evaporation). Other wastes are also produced intermittently but are generally associated with either the shutdown or startup of a boiler or generating unit such as during boiler cleaning (water side), boiler cleaning (fire side), air preheater cleaning, cooling tower basin cleaning, and cleaning of miscellaneous small equipment. Additional wastes exist that are essentially unrelated to production. These depend on meteorological or other factors. Rainfall runoff, for example, causes drainage from coal piles, ash piles, floor and yard drains, and from construction activity. A diagram indicating potential sources of wastewaters containing chemical pollutants in a coal-fueled steam electric power plant is shown in Figure 1. Data on wastestream characteristics presented in this section are based on the results of screening sampling carried out at eight plants, verification sampling carried out at 18 plants, and periodic surveillance and analysis sampling carried out as part of compliance monitoring at eight plants. These data were stored on a computerized data file [1]. All waste streams discussed in this chapter were analyzed during the screening program, while the verification program focused on the following waste streams: once-through cooling water, cooling tower blowdown, and ash handling waters. The wastewater characteristics of the various waste streams are discussed in the following sections. Where they are available, only verification data are presented. Where verification data are limited or not available, screening and/or surveillance and analysis data are presented. The data source is clearly indicated in each table and in the text. The following is a summary of all priority pollutants detected in any of the waste streams from steam electric power plants: . Benzene . Chlorobenzene . 1,2-Dichloroethane . 1,1,1-Trichloroethane . 1,1,2-Trichloroethane . 2-Chloronaphthalene . Chloroform . 2-Chlorophenol . 1,2-Dichlorobenzene . 1,4-Dichlorobenzene . 1,1-Dichloroethylene . 1,2-trans-Dichloroethylene . 2,4-Dichiorophenol Treatment of Power Industry Wastes 587 © 2006 by Taylor & Francis Group, LLC Figure 1 Potential sources of wastewater in a stream electric power generation plant. (Courtesy of USEPA.) 588 Wang © 2006 by Taylor & Francis Group, LLC . Ethylbenzene . Methylene chloride . Bromoform . Dichlorobromomethane . Trichlorofluoromethane . Chlorodibromomethane . Nitrobenzene . Pentachlorophenol . Phenol . Bis(2-ethylhexyl) phthalate . Butyl benzyl phthalate . Di-n-butyl phthalate . Di-n-octyl phthalate . Diethyl phthalate . Dimethyl phthalate . Tetrachloroethylene . Toluene . Trichloroethylene . 4,4-DDD . Antimony (total) . Arsenic (total) . Asbestos (total-fibers/L) . Beryllium (total) . Cadmium (total) . Chromium (total) . Copper (total) . Cyanide (total) . Lead (total) . Mercury (total) . Nickel (total) . Selenium (total) . Silver (total) . Thallium (total) . Zinc (total) 13.3.2 Cooling Water In general, wastewater characteristics of once-through cooling water and recirculating cooling water systems are similar. Pollutants discharged from both systems are caused by the erosion or corrosion of construction materials plus the chemical additives used to control erosion, scaling, and biological growth (biofouling). The wastewater generated from a recirculating cooling water system also depends on the design limits for dissolved solids in the system. Erosion The fill material in natural draft cooling towers is frequently asbestos cement. Erosion of this fill material may result in the discharge of asbestos in cooling water blowdown. In a testing program for detection of asbestos fibers in the waters of 18 cooling systems, seven of the 18 sites Treatment of Power Industry Wastes 589 © 2006 by Taylor & Francis Group, LLC contained detectable concentrations of chrysotile asbestos in the cooling tower waters at the time of sampling. Corrosion Corrosion is an electrochemical process that occurs when metal is immersed in water and a difference in electrical potential between different parts of the metal causes a current to pass through the metal between the region of lower potential (anode) and the region of higher potential (cathode). The migration of electrons from anode to cathode results in the oxidation of the metal at the anode and the dissolution of metal ions into the water. Copper alloys are used extensively in power plant condensers, and as a result, copper can usually go into a corrosion product film or directly into solution as an ion or as a precipitate in the initial stages of condensation by tube corrosion. As corrosion products form and increase in thickness, the corrosion rate decreases until a steady state is achieved. Studies indicate that copper release is a function of flow rate more so than of the salt content of the makeup water. Data on copper concentrations in both once-through cooling and recirculatory cooling systems indicate that corrosion products are more of a problem in cooling tower blowdown than in once-through systems discharge. The concentration of pollutants (via evaporation) in recirculating systems probably accounts for most of the difference in the level of metals observed between once-through discharge and cooling tower blowdown. Chemical Treatment Chemical additives are needed at some plants with recirculating cooling water systems in order to prevent corrosion and scaling. Chemical additives are also occasionally used at plants with once-through cooling water systems for corrosion controls. Scaling occurs when the concentration of dissolved materials, usually calcium- and magnesium-containing species, exceeds their solubility levels. The addition of scaling control chemicals allows a higher dissolved solids concentration to be achieved before scaling occurs. Therefore, the amount of blowdown required to control scaling can be reduced. Chemicals added to once-through cooling water to control corrosion or to recirculating cooling water to control corrosion and scaling is usually present in the discharges. Chromium and zinc are the active components of most of the popular corrosion inhibitors. The solvent and carrier components that may be used in conjunction with scaling and corrosion control agents are as follows: . Dimethyl formamide . Methanol . Ethylene glycol monomethyl ether . Ethylene glycol monobutyl ether . Methyl ethyl ketone . Glycols to hexylene glycol . Heavy aromatic naphthalene . Cocoa diamine . Sodium chloride . Sodium sulfate . Polyoxyethylene glycol . Talc . Sodium aluminate . Monochlorotoulene . Alkylene oxide–alchohol glycol ethers 590 Wang © 2006 by Taylor & Francis Group, LLC [...]... pollutants potentially hazardous to the POTW or which may be treated inadequately in the POTW Such treatment methods are numerous, but they generally fall into one of three broad categories in accordance with their process objectives These include pH control, removal of dissolved materials, and separation of phases The following is a summary of end-of-pipe treatment technologies commonly employed in the steam... boiler cleaning operations through its presence in boiler cleaning wastes Cleaning mixtures used include alkaline chelating rinses, proprietary chelating rinses, organic solvents, acid cleaning mixtures, and alkaline mixtures with oxidizing agents for copper removal Wastes from these cleaning operations will contain iron, copper, zinc, nickel, chromium, hardness, and phosphates In addition to these constituents,... Clarification Wastes Clarification is the process of agglomerating the solids in a stream and separating them by settling Chemicals that are commonly added to the clarification process do not contain any of the listed priority pollutants © 2006 by Taylor & Francis Group, LLC Treatment of Power Industry Wastes 599 Table 3A Summary of Priority Pollutants in the Steam Electric Industry Ash Pond Overflow–Intake Information... by Taylor & Francis Group, LLC Treatment of Power Industry Wastes 13. 3.8 611 Wet Flue Gas Cleaning Blowdown The readers are referred to another source for more detailed information regarding wet flue gas cleaning blowdown characteristics and treatment [2,3] 13. 4 WASTE TREATMENT 13. 4.1 End-of-Pipe Treatment Technologies Wastewater effluents discharged to publicly owned treatment facilities are sometimes... wastes from alkaline cleaning mixtures will contain ammonium ions, oxidizing agents, and high alkalinity; wastes from acid cleaning mixtures will contain fluorides, high acidity, and organic compounds; wastes from alkaline chelating rinses will contain high alkalinity and organic compounds; and wastes from most proprietary processes will be alkaline and will contain organic and ammonium compounds Other... identified in the screening program The data are presented in Table 3A and 3B for information of intake and discharge, respectively 13. 3.4 Low-Volume Wastes Low-volume waste sources include water treatment processes that prevent scale formation such as clarification, filtration, lime/lime soda softening, ion exchange, reverse osmosis, and evaporation Also included are drains and spills from floor and yard drains... 5260 m3/MW) The fuel designations in the above surveyed data were determined by the fuel that contributes the most Btu for power generation during the survey The surveyed data also indicate that there were net increases in all of the following compounds: total dissolved solids, total suspended solids, total organic carbon, total residual chlorine, free available chlorine 2,4-dichlorophenol, 1,2-dichlorobenzene,... contaminants Activated carbon, synthetic sorbents are the common adsorbents to be used in the process It may require pH adjustments The process removal efficiency depends on the nature of the pollutants and the composition of the waste Chemical Oxidation This is a process mainly used in power plants for destruction of cyanides using chlorine, hypochlorite salts, or ozone The process removal efficiency is... presentation of the applicable treatment technologies, cost methodology, and cost data are available in the literature [6,7] 13. 6 13. 6.1 PLANT-SPECIFIC EXAMPLES Example 1 Plant 1226 is a bituminous coal-, oil-, and gas-fired electricity plant [1] The recirculator cooling water system in uent was sampled from a stream taken from the river and the effluent from the cooling tower blowdown stream The effluent... used again in the ash sluice stream Table 7 presents the data The following additives are combined with the cooling tower in uent: chlorine (biocide); calgon Cl-5 (corrosion inhibitor); sulfuric acid (scale prevention) The addition is necessary for the control of pipe corrosion © 2006 by Taylor & Francis Group, LLC 616 Wang Table 7 Plant-Specific Treatment Data for Plant 1226 Recirculating Cooling Water . 3.5 and then used for cleaning in a two-stage process. The first stage involves the dissolution of iron oxides. In the second stage, anhydrous ammonia is added to raise the pH of the cleaning solution. the relative insolubility of copper, ammonia-based oxidizing com- pounds have been effective. Used in a single separate stage, the ammonia sodium bromate step includes the introduction into the. sulfur emissions in the flue gases. These scrubbing systems result in a variety of liquid waste streams depending on the type of process used. In all of the existing FGD (flue gas desulfurization) systems, the