### Notes from Site Visit at A2A’s Centrale di Monfalcone on April 1 , 20 11

EPA conducted a site visit at A2A’s Centrale di Monfalcone ( Monfalcone ) located in

Monfalcone

, I taly on Friday

, April 1 , 20 11 to learn about the operations at the plant , specifically

the flue gas desulfurization ( FGD ) system and the FGD wastewater treatment system

. Process flow diagrams of the FGD wastewater treatment system are included as Attachment 1 to th ese

notes

.

These notes describe the information collected during the site visit. Table 1, at the end of these notes, identifies the site visit participants.

Plant Overview

**•** 

### Monfalcone operates four electric generating units. Units 1 and 2 burn both coal

and fuel oi l, while Units 3 and 4 burn only fuel oil. The table below contains some general information on the operation of each steam electric generating unit at the

time of the site visit

.

Unit Installation

Date Capacity (MW) Particulate

Control NOx Control SO 2 

### Control

1 196 5 165 Electrostatic Precipitator (ESP) Overfire air Wet FGD

2 1970 171 ESP Overfire air Wet FGD

3 19 83 320 ESP Overfire air None

4 1984 320 ESP Overfire air None [QUESTION FOR MONFALCONE: Does the plant operate selective catalytic reduction (SCR) or selective noncatalytic reduction (SNCR) systems on any of the units?]

**•** 

### On average, Monfalcone burn s 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 content 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 stormwater and plant wastewater. The

efflu ent from this treatment system is discharged.

**•** 

### Monfalcone also has the capability to burn biomass, but it can only account for 5 percent of the fuel used at any given 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 con tractor to take the fly ash off site.

**•** 

### Monfalcone operates a completely dry bottom ash system. Plant personnel stated that they used to operate with a wet hopper, but they converted to a completely dry system. The bottom ash is pneumatically conveyed to silo (separate silo from

### Page 2

fly ash). According to plant personnel, the plant generates approximately 100,000 tons of bottom ash each year. Of that, approximately 1,000 tons is disposed of in a landfill and the other 99,000 tons is marketed for reuse. [QUE STION FOR

MONFALCONE: What is the bottom ash marketed for? Is the landfill located

onsite or offsite? ]

**•** 

### The plant operates a once

- through cooling water system

.

Flue G as Desulfurization (FGD) System

**•** 

### Monfalcone operates double

- contact flow limestone force d oxidation FGD systems on Units 1 and 2 that were designed by Mitsubishi. A limestone slurry is sprayed upward from the bottom of the absorber 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 source of the scrubber ma ke up water.

**•** 

### The FGD systems operate with a chlorides level between 10,000 and 30,000 ppm. The maximum design chlorides level is 50,000 ppm. The FGD system operates with approximately 30 percent solids in the absorber.

**•** 

### The blowdown from the scrubbers is approximately 3 to 4 cubic meters per hour

. The blowdown is transferred directly to vacuum belt filters; it is not transferred to hydroclones prior to dewatering. The plant washes the gypsum as it is applied to

the belt filters. The moisture content of the gypsum is typically 12 percent. Monfalcone does not market the gypsum. The plant pays a contractor to take the gypsum from the plant.

**•** 

### A portion of the filtrate from the vacuum belt filters is recycled back to the FGD system. The remainder is sent to the FGD wastewater treatment system.

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 using clarification and softening to reduce suspended solids, calcium, magnesium, and heavy metals. The second step

involves the use of a two

- stage evapora tion and crystallization system.

### Page 3

**•** 

### 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 wastewater 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 provide 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 soften the water and reduce the calcium and magnesium prior to the evaporation system. 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 sen t to the evaporation system.

**•** 

### The underflow from the clarifier is transferred to a sludge holding tank and then either recycled to the secondary reaction tank or sent to a filter press. The filtrate from the filter press is transferred to the intermediate tank. [QUESTION FOR MONFALCONE: How does the plant dispose of the filter press solids?]

**•** 

### From the intermediate tank, some of the wastewater is recycled back to be mixed

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

r emainder of the water is transferred to the evaporation system.

**•** 

### The FGD wastewater first passes through a plate heater where the process condensate heats the FGD wastewater. The plant then adds hydrochloric acid to

the heated water and transfers this str eam 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. 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 introduced to the shell side of the brine concentrator (i.e., the outside of the tubes), al ong with additional make

- up steam. The temperature difference between the compressed vapor and the brine solution causes the compressed vapor to transfer heat to the brine solution, which flashes to a vapor. As heat is transferred to the brine, the compre ssed vapor cools and

condenses as distilled water.

**•** 

### The condensed vapor from the brine concentrator is collected and transferred to a condensate tank. Within this tank, some additional steam vapor is returned to the

system . The remaining condensed water is either recycled back to the compression portion of the system to be reused as steam or it is pumped through

### Page 4

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 brine concentrator, while a small amount is continuously 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 exchanger where the plant uses steam to heat the slurry prior to it reentering the crystallizer. The heat from the slurry enter ing the crystallizer vap orizes some of the water in the crystallizer . Th is steam vapor exits the top of the crystallizer and is transferred to an air condenser, where air is used to cool the steam. This cooled steam, along with the condensed steam from the heat exchanger, is tra nsferred to a condensate tank. Some of the vapor in the tank is combined with the steam exiting the crystallizer to be cooled in the air condenser. The remaining condensed water is a process condensate stream.

**•** 

### Some of the slurry from the bottom of the c rystallizer is transferred through the heat exchanger where it is heated with steam 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 evaporatio n 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 the Oberlin filter presses where the crystallized solids are dewatered. The filtrate from the filter presses is transferred to the mother liquor tank and recycled to the crystallizer. The crystallized solids are collected in bags. The plant pays a German company to remove these solids

, which are use d as mine fill. Plant personnel stated t hat

, in 2009, the plant generated approximately 350 tons of crystallized solids.

**•** 

### Monfalcone transfers the condensate from the FGD treatment system to the demineralizer system . Following treatment in the demineralizer system ( reverse osmosis )

, it is used a s make up for the boiler.

Sampling

**•** 

### As part of the site visit, EPA had planned 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 rece ived at the plant in time for EPA to collect the samples during the visit. Therefore, plant representatives collected the samples at a later

date following instructions provided by EPA (see Attachment 2) . The plant representatives shipped t he samples to the EPA

- contract laboratories for analysis

.

**•** 

### Samples were collected from the following waste streams (see Attachment 1 for identification of the waste streams in the process flow diagrams):

### Page 5

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

o Condensate from brine concentrator (process stream 35

– after plate heater); and

o Condensate from crystallizer (process stream 39).

**•** 

### Table 2 presents the analytes for which EPA requested Monfalcone to collect samples and the analytical methods that were use d for the analysis.

**•** 

### Plant representatives collected the 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 long er cold by the time they were returned to the plant, EPA coordinated with the plant to only re ship the metals and mercury samples to the laboratories. Therefore, EPA does not have any results for the classical analytes.

**•** 

### Table 3 presents the analytical re sults for each of the three waste streams.

### Page 6

Table 1. Site Visit Attendees

Name Organization (Representing) Telephone E

- mail

Leonardo Mainardis A2A (+39) 0481749269 l eonardo.mainardis@a2a.eu

Javier Ceballos HPD (+34) 944914092 j avier.ceballos@veoliawater.com

Mikel Garcia HPD (+34) 944914092 mikel.garcia@veoliawater.com

Ron Jordan EPA/Office of Water (202) 566

- 1003 jordan.ronald@epa.gov

T.J. Finseth ERG (Contractor to EPA) (703) 633

- 1698 thomas.finseth@erg.com

Tracey Footer ERG (Contractor to EPA) ( 919 ) 468

- 7952 tracey

. footer @erg.com

### Page 7

Table 2 . Analytical Methods

Parameter Method Number

Classicals

Chemical o xygen d emand (COD) EPA 410. 4

Total s uspended s olids (TSS) SM 2540 D

Total d issolved s olids (TDS) SM 2540 C

Sulfate EPA 300.0

Chloride EPA 300.0

Ammonia as n itrogen EPA 350.1

Nitrate/ n itrate as n itrogen EPA 353.2 Total Kjeldahl n itrogen (TKN) EPA 351.2

Total p hosphorus EPA 365. 1

Total and Dissolved Metals Mercury EPA 1631 E

A ntimony, a rsenic, 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 200.7

### Page 8

ND

– Not detected (number in parentheses is the quantitation limit).

4

– MS and/or MSD did not meet laboratory criteria, but sample concentration is four times greater than the 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 3. Analytical Results, Monfalcone

Analyte Units Method Influent to FGD

Wastewater Treatment Condensate from Brine

Concentrator Condensate from Crystallizer

Aluminum ug/L 200.7 1600 ND (200) U ND (200) J

Antimony ug/L 200.8 4.1 ND (2.00) U ND (2.00) U

Arsenic ug/L 200.8 4.7 ND (4.00) U ND (4.00) U

Barium ug/L 200.7 470 ND (20.0) U ND (20.0) U

Beryllium ug/L 200.7 ND (2.00) U ND (2.00) U ND (2.00) U

Boron ug/L 200.7 220000 B

, 4 700 B 710 B

Cadmium ug/L 200.8 100 ND (4.00) U ND (4.00) U

Calcium ug/L 200.7 6400000 4 630 460

Chromium ug/L 200.8 11 ND (8.00) U ND (8.00) U

Cobalt ug/L 200.7 26 ND (20.0) U ND (20.0) U

Copper ug/L 200.8 8.2 ND (4.00) U ND (4.00) U

Iron ug/L 200.7 1300 ND (200) U ND (200) U

Lead ug/L 200.8 3.2 ND (2.00) U ND (2.00) U

Magnesium ug/L 200.7 830000 4 ND (400) J ND (400) J

Manganese ug/L 200.7 3000 4 ND (20.0) J ND (20.0) J

Mercury ng/L 1631E 10300 3.76 9.93

Molybdenum ug/L 200.7 ND (40.0) J ND (40.0) U ND (40.0) U

Nickel ug/L 200.8 160 F ND (4.00) U ND (4.00) U

Selenium ug/L 200.8 120 ND (4.00) U ND (4.00) U

Silver ug/L 200.8 ND (2.00) F

, U ND (2.00) U ND (2.00) U

Sodium ug/L 200.7 820000 4 32000 36000

Thallium ug/L 200.8 4.7 ND (2.00) U ND (2.00) U

Tin ug/L 200.7 ND (200) U ND (200) U ND (200) U

### Page 9

ND

– Not detected (number in parentheses is the quantitation limit).

4

– MS and/or MSD did not meet laboratory criteria, but sample concentration is four times greater than the 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 3. Analytical Results, Monfalcone

Analyte Units Method Influent to FGD

Wastewater Treatment Condensate from Brine

Concentrator Condensate from Crystallizer

Titanium ug/L 200.7 76 ND (20.0) U ND (20.0) U

Vanadium ug/L 200.8 25 ND (10.0) U ND (10.0) U

Zinc ug/L 200.7 270 ND (40.0) U ND (40.0) U