Final Notes from Site Visit at A2A’s Centrale di Monfalcone on April 1, 2011

EPA conducted a site visit at A2A’s Centrale di Monfalcone (Monf alcone) located in Monfalcone, Italy on Friday, April 1, 2011 to learn about the operations at the plant, specifically the flue gas desulfurization (FGD) system and the FGD wastewater trea tment system. Process flow diagrams of the FGD wastewater treatment system are included as Attachment 1 to these

notes.

These notes describe the information collected duri ng the site visit. Table 2, at the end of these notes, identifies the site visit participants.

Plant Overview

 Monfalcone operates four electric gene rating units. Units 1 and 2 burn both coal and fuel oil, while Units 3 and 4 burn only fuel oil. Table 1 contains some general information on the operation of each steam electric generating un it at the time of

the site visit.

Table 1. Steam Electric Generating Unit Operations

Unit Installation

Date Capacity (MW) Particulate

Control NOx Control SO 2 Control

1 1965 165 Electrostatic Precipitator (ESP) Overfire air Wet FGD

2 1970 171 ESP Overfire air Wet FGD

3 1983 320 ESP Overfire air None

4 1984 320 ESP Overfire air None

 On average, Monfalcone burns 2,400 to 2,600 tons of coal per day in Units 1 and

2. Monfalcone burns a Russian bituminous coal with a sulfur content between 0.3 and 0.4 percent. The maximum sulfur conten t of the coal is 1 percent. The plant stores 30 to 45 days worth of coal on site . The coal pile runoff at the plant is collected in sumps and transferred to a physical/chemical precipitation wastewater treatment system that receives other storm water and plant wastewater. The effluent from this treatment system is discharged.

 Monfalcone also has the capability to bur n biomass, but it can only account for 5 percent of the fuel used at any gi ven time, based on permit restrictions.

 Fly ash from Units 1 and 2 is handled dry and sent pneumatically to a single silo. The silo has a capacity of 2,000 tons of fly ash. Monfalcone generates approximately 200 to 300 tons of fly ash per day; therefore, the silo has the capacity for eight to ten days of storage. Monfalcone currently pays a contractor to take the fly ash off site.

 Monfalcone operates a completely dry botto m ash system. Plant personnel stated that they used to operate with a wet h opper, but they converted to a completely dry system. The bottom ash is pneumatically conveyed to silo (separate silo fromPage 2

fly ash). According to plant personnel , the plant generates approximately 100,000 tons of ash (both fly and bottom ash). The amount of bottom ash generated is approximately 20,000 tons each year. Of th e bottom ash generated, approximately 500 tons is disposed of in an off-site landfill and the other 19,500 tons is marketed for reuse. The bottom ash is marketed for the preparation of concrete or cement,

as a substitute for trass or Santorin earth, which are natural pozzolanas.

 The plant operates a once-th rough cooling water system.

Flue Gas Desulfurization (FGD) System

 Monfalcone operates double-contact fl ow limestone forced oxidation FGD systems on Units 1 and 2 that were designe d by Mitsubishi. A limestone slurry is sprayed upward from the bottom of the absorb er to react with the sulfur dioxide in the flue gas as the slurry is moving upward and as it is falling back down to the

reaction tank.

 Monfalcone purchases a dry limestone dust and does not use ball mills on site. The plant does mix the limestone with well water to generate the slurry used in

the absorber.

 Monfalcone uses well water as the so urce of the scrubber make up water.

 The FGD systems operate with a chlori des level between 10,000 and 30,000 ppm. The maximum design chlorides level is 50,000 ppm. The FGD system operates with approximately 30 percen t solids in the absorber.

 The blowdown from the scrubbers is appr oximately (8 to 12) cubic meters per

hour. The blowdown is transferred direc tly to vacuum belt filters; it is not transferred to hydrocyclones prior to dewa tering. The plant washes the gypsum as it is applied to the belt filters. The moistu re content of the gypsum is typically 12 percent. Monfalcone does not market th e gypsum. The plant pays a contractor to take the gypsum fr om the plant.

 A portion of the filtrate from the vacuum belt filters is recycl ed back to the FGD system. The remainder is sent to the FGD wastewater treatment system.Page 3

FGD Wastewater Treatment

 Diagrams of the FGD wastewater flow and treatment system are included as

Attachment 1.

 The FGD wastewater treatment system uses a two-step process to treat the FGD

wastewater to achieve zero discharge of wastewater from the system. In the first step, the FGD wastewater is pretreated us ing clarification and softening to reduce suspended solids, calcium, magnesium, and heavy metals. The second step involves the use of a two-stage evap oration and crystallization system.

 The filtrate from the vacuum belt filters is transferred to a reaction tank where the plant adds lime to raise the pH to 11 S.U. The plant does not operate an equalization tank prior to the reaction tank.

 From the primary reaction tank, the wastewat er is sent to a second reaction tank. The plant does not add any chemicals to this reaction tank, but some of the sludge from the downstream clarifier is recycled to the tank to provi de nucleation sites for the precipitation of additional solids.

 The effluent from the second reaction tank is transferred to the clarifier where the plant adds ferric chloride, polyelectrolyte, and sodium carbonate (soda ash) to the

wastewater. The soda ash is used to so ften the water and reduce the calcium and magnesium prior to the evaporation syst em. Calcium and magnesium lead to larger boiling point rise in the system , which requires additional energy.

 The overflow from the clarifier is transferred to the intermediate tank prior to being sent to the evaporation system.

 The underflow from the clarifier is transf erred to a sludge ho lding tank and then either recycled to the seconda ry reaction tank or sent to a filter press. The filtrate from the filter press is tr ansferred to the intermedia te tank. The plant generates approximately 1,100 tons of filter press soli ds each year. Of that, approximately 200 tons is disposed of in a landfill and the other 900 tons is marketed for reuse (e.g., for the preparation of fertilizer).

 From the intermediate tank, some of the wa stewater is recycled back to be mixed

with the sodium carbonate to create the mixt ure that is used in the clarifier. The

remainder of the water is transf erred to the evaporation system.

 The FGD wastewater first passes thr ough a plate heater where the process

condensate heats the FGD wastewater. The plant then adds hydrochloric acid to

the heated water and transfers this stream to the deaerator. The hydrochloric acid reacts with the carbonate to generate carbon dioxide, which is vented to the atmosphere.

 The wastewater is then fed to the sump of the falling-film brine concentrator.Page 4

Brine from the sump is pumped to the top of the brine concentrator and enters the heat transfer tubes. While falling down the heat transfer tubes, part of the solution is vaporized and then compressed and intr oduced to the shell side of the brine concentrator (i.e., the outside of the t ubes), along with additional make-up steam. The temperature difference between the compressed vapor and the brine solution causes the compressed vapor to transfer h eat to the brine solution, which flashes to a vapor. As heat is transferred to the brine, the compressed vapor cools and

condenses as distilled water.

 The condensed vapor from the brine concentr ator is collected and transferred to a condensate tank. Within this tank, some additional steam vapor is returned to the system. The remaining condensed wate r is either recycled back to the compression portion of the system to be reused as steam or it is pumped through the plate heater where it transfers its heat to the incoming FGD wastewater and at the same time cooling the condensate stream.

 The concentrated brine slurry from the brine concentrator tubes falls into the sump and is recycled with the feed back to the top of the brin e concentrator, while

a small amount is continuous ly withdrawn from the sump and transferred to the crystallizer system.

 The brine is combined with the slurry recirculation from the bottom of the crystallizer and transferred to a heat exch anger where the plant uses steam to heat the slurry prior to it reentering the crysta llizer. The heat from the slurry entering the crystallizer vaporizes some of the wate r in the crystallizer. This steam vapor exits the top of the crystallizer and is tran sferred to an air cond enser, where air is

used to cool the steam. This cooled st eam, along with the condensed steam from the heat exchanger, is transferred to a condensate tank. Some of the vapor in the tank is combined with the steam exiting th e crystallizer to be cooled in the air condenser. The remaining condensed wa ter is a process condensate stream.

 Some of the slurry from the bottom of th e crystallizer is tran sferred through the heat exchanger where it is heated with st eam and fed back to the crystallizer. The heat transferred to the slurry allows the water present in the slurry to evaporate and exit the crystallizer as steam. The ev aporation of the water also concentrates the solids present and allows the solids to crystallize. There is a continuous bleed of the slurry from the crystallizer that is fed to a filter press, where the crystallized solids are dewatered. The filtrate from the filter presses is transferred to the mother liquor tank and recycled to the cr ystallizer. The crystallized solids are collected in bags. The plant pays a Ge rman company to remove these solids, which are used as mine fill. Plant personnel stated that, in 2009, the plant generated approximately 350 tons of crystallized solids.

 Monfalcone transfers the condensate fr om the FGD treatment system to the demineralizer system. Following treatment in the demineralizer system (reverse osmosis), it is used as make up for the boiler.Page 5

Sampling

 As part of the site visit, EPA had pl anned to collect wastewater samples to

characterize the untreated FGD wastewater and the condensate streams generated from the wastewater treatment system. Due to delays in customs, the sampling materials were not received at the plant in time for EPA to collect the samples during the visit. Therefore, plant repres entatives collected the samples at a later date following instructions provided by EPA (see Attachment 2). The plant representatives shipped the samples to the EPA-contract laborato ries for analysis.

 Samples were collected from the followi ng waste streams (see Attachment 1 for

identification of the waste streams in the process flow diagrams):

o Influent to FGD wastew ater treatment system (process stream 1);

o Condensate from brine concentrator (process stream 35 – after plate heater); and

o Condensate from crystalliz er (process stream 39).

 Table 3 presents the analytes for whic h EPA requested Monfalcone to collect samples and the analytical methods that were used for the analysis.

 Plant representatives collected th e requested samples on April 14, 2011.

 The samples were shipped by the plant representatives, but they did not pass customs and were returned to the plant. Because the classical analytes were no longer cold by the time they were returned to the plant, EPA coordinated with the plant to only reship the metals and mercury samples to the laboratories. Therefore, EPA does not have any re sults for the classical analytes.

 Table 4 presents the analytical result s for each of the three waste streams.Page 6Table 2. Site Visit AttendeesNameOrganization (Representing)TelephoneE-mailLeonardo Mainardis A2A (+39) 0481749269leonardo.mainardis@a2a.euJavier Ceballos HPD (+34) 944914092javier.ceballos@veoliawater.comMikel Garcia HPD (+34) 944914092mikel.garcia@veoliawater.comRon Jordan EPA/Office of Water(202) 566-1003 jordan.ronald@epa.govT.J. Finseth ERG (Contractor to EPA) (703) 633-1698 thomas.finseth@erg.comTracey Footer ERG (Contractor to EPA)(919) 468-7952 tracey.footer@erg.comPage 7

Table 3. Analytical Methods

Parameter Method Number

Classicals Chemical oxygen demand (COD) EPA 410.4 Total suspended solids (TSS) SM 2540 D
Total dissolved solids (TDS) SM 2540 C

Sulfate EPA 300.0

Chloride EPA 300.0 Ammonia as nitrogen EPA 350.1

Nitrate/nitrate as nitrogen EPA 353.2 Total Kjeldahl nitrogen (TKN) EPA 351.2 Total phosphorus EPA 365.1

Total and Dissolved Metals Mercury EPA 1631E Antimony, arsenic, cadmium, chromium, copper, lead, manganese, nickel, selenium, silver, thallium, and vanadium EPA 200.8 with collision cell

Aluminum, barium, beryllium, boron, calcium, cobalt, iron, magnesium, molybdenum, sodium, tin, titanium, and zinc. EPA 200.7Page 8ND – Not detected (number in parentheses is the quantitation limit).4 – MS and/or MSD did not meet laboratorycriteria, but sample concentration is fourtimes greater thanthe matrix spike amount, so control limits are not applicable.B – Analyte was found in the blank and sample.F – MS and/or MSD not within laboratory control limits.J – Result measured above the MDL, but less than the quantitation limit.U – Result below the MDL. (Number shown in parentheses is the quantitation limit).Table 4. Analytical Results, MonfalconeAnalyteUnitsMethodInfluent to FGDWastewater TreatmentCondensate from BrineConcentratorCondensate fromCrystallizerAluminum ug/L 200.7 1600 ND (200) U ND (200) JAntimony ug/L 200.8 4.1 ND (2.00) U ND (2.00) UArsenic ug/L 200.8 4.7 ND (4.00) U ND (4.00) UBarium ug/L 200.7 470 ND (20.0) U ND (20.0) UBeryllium ug/L 200.7 ND (2.00) U ND (2.00) U ND (2.00) UBoron ug/L 200.7 220000 B, 4 700 B 710 BCadmium ug/L 200.8 100 ND (4.00) U ND (4.00) UCalcium ug/L 200.7 6400000 4 630 460Chromium ug/L 200.8 11 ND (8.00) U ND (8.00) UCobalt ug/L 200.7 26 ND (20.0) U ND (20.0) UCopper ug/L 200.8 8.2 ND (4.00) U ND (4.00) UIron ug/L 200.7 1300 ND (200) U ND (200) ULead ug/L 200.8 3.2 ND (2.00) U ND (2.00) UMagnesium ug/L 200.7 830000 4 ND (400) J ND (400) JManganese ug/L 200.7 3000 4 ND (20.0) J ND (20.0) JMercury ng/L 1631E 10300 3.76 9.93Molybdenum ug/L 200.7 ND (40.0) J ND (40.0) U ND (40.0) UNickel ug/L 200.8 160 F ND (4.00) U ND (4.00) USelenium ug/L 200.8 120 ND (4.00) U ND (4.00) USilver ug/L 200.8 ND (2.00) F, U ND (2.00) U ND (2.00) USodium ug/L 200.7 820000 4 32000 36000Thallium ug/L 200.8 4.7 ND (2.00) U ND (2.00) UTin ug/L 200.7 ND (200) U ND (200) U ND (200) UPage 9ND – Not detected (number in parentheses is the quantitation limit).4 – MS and/or MSD did not meet laboratorycriteria, but sample concentration is fourtimes greater thanthe matrix spike amount, so control limits are not applicable.B – Analyte was found in the blank and sample.F – MS and/or MSD not within laboratory control limits.J – Result measured above the MDL, but less than the quantitation limit.U – Result below the MDL. (Number shown in parentheses is the quantitation limit).Table 4. Analytical Results, MonfalconeAnalyteUnitsMethodInfluent to FGDWastewater TreatmentCondensate from BrineConcentratorCondensate fromCrystallizerTitanium ug/L 200.7 76 ND (20.0) U ND (20.0) UVanadium ug/L 200.8 25 ND (10.0) U ND (10.0) UZinc ug/L 200.7 270 ND (40.0) U ND (40.0) U