MEMORANDUM 

TO: Public Record for the Effluent Guidelines Program Plan 2009/2010 

FROM: TJ Finseth, ERG 

DATE: 10 February 2009 

SUBJECT: Notes from EPA Meeting on June 5, 2008 with HPD/Veolia Water Solutions and 

Technologies to Discuss FGD Wastewater Treatment 

EPA and ERG participated in a meeting with HPD/Veolia Water Solutions and Technologies 

(VWS) on June 5, 2008 to discuss treatment technologies for FGD wastewaters. The following 

people participated in the meeting: 

HPD/VWS 

Bill Shaw 

Jeff Brosdal 

EPA 

Ron Jordan 

Josh Hall 

ERG 

Deb Bartram 

TJ Finseth (via phone) 

This memorandum summarizes the meeting discussion points. The presentation that HPD 

presented during the meeting is provided as an attachment to the memorandum. 

EPA Study Background 

 EPA explained that they are reviewing the Effluent Guidelines for the Steam 

Electric Power Generating Industry to determine if revisions to the guidelines are 

warranted. EPA stated that they have been studying the industry for several years 

now, but had a broad focus at the beginning of the study and now they are 

focusing on FGD, ash sluice, and coal pile runoff wastewaters. 

Company Overview 

 HPD explained that they have a parent company, Veolia Environnement, which 

has the following four company sectors: 

— Veolia Water; 

— Veolia Environmental Services; 
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November 6, 2008 

Page 2 

— Veolia Energy; and 

— Veolia Transportation. 

 Part of the Veolia Water sector is Veolia Water Solutions and Technologies 

(VWS). HPD explained that this is the technological division of Veolia Water 

and focuses on municipal and industrial customers. 

 HPD is a subsidiary of VWS and focuses only on industrial customers. 

 HPD stated that they provide innovative process solutions utilizing evaporation 

and crystallization technologies, and they are the largest evaporation/ 

crystallization company in the world. 

 HPD also provides ceramic membrane technology (CeraMem®) through their 

HPD Membrane Technology Center, located in Waltham MA. 

 HPD has several offices around the world and has approximately 150 employees. 

 HPD has experience in multiple industrial sectors, including chemical processing, 

power generation, oil and gas, ethanol/biofuel, and pulp & paper. 

 HPD stated that they are capable of providing complete turnkey solutions to their 

customers, including both designing and building systems. 

FGD Wastewater Treatment Options 

 HPD has focused its efforts on FGD wastewater treatment associated with wet 

limestone forced oxidation systems, which, according to HPD, accounts for 80 to 

90 percent of the wet FGD scrubbers. 

 [CBI information has been removed from this document.] 

 HPD provides evaporation and crystallization technologies for the treatment of 

FGD wastewater, which achieves zero-liquid discharge. 

 HPD stated that the other treatment technologies currently available to power 

plants include physical/chemical/biological treatment which produces a discharge 

to surface waters. 

 The physical/chemical treatment systems are capable of removing suspended 

solids and heavy metals. The biological systems are capable of removing BOD, 

nitrogen, and some heavy metals. In addition, the biological systems typically 

require a solids removal step to remove the suspended solids prior to the 

biological treatment step. 

 The physical/chemical/biological treatment systems do not remove chlorides or 

dissolved solids from the wastewater. In addition, they do not recover clean water 

for reuse at the plant. HPD also stated these systems typically have a large 

footprint, and a high chemical demand. 

 HPD stated that some power plants are afraid of evaporation technologies for the 

treatment of FGD wastewater because the industry has the perception that it is 

expensive, difficult to operate, and challenging. 

History of Evaporation at Power Plants 

 According to HPD, falling-film evaporators (brine concentrators) have been used 

at power plants for the treatment of cooling tower blowdown since the 1970’s. 

The brine concentrator, which is discussed in more detail later in the notes, 

produces a quality distillate stream that can be reused by the plant and a 

concentrated brine stream. The use of a brine concentrator followed by a 
Memorandum 

November 6, 2008 

Page 3 

crystallizer or a spray dryer to evaporate the remaining water in the concentrated 

brine stream results in zero liquid discharge (ZLD). 

 HPD stated that there are 50 to 75 brine concentrators treating cooling tower 

blowdown from power plants in the U.S. HPD stated that most of these 

applications are in the West (i.e., along the Colorado River, in California, or the 

southwest). HPD stated that they believe that all new power plants built in 

California will be permitted as zero liquid discharge and will have to eliminate 

direct discharge of cooling tower blowdown. 

 HPD stated that plants in those areas are using evaporators because they need to 

conserve water as well as prevent salt water discharges to the rivers. 

 HPD stated that reverse osmosis could also be used to treat cooling tower 

blowdown, but it is not a ZLD system and therefore would have a discharge. 

 HPD stated that the ZLD systems treating cooling tower blowdown are capable of 

achieving high concentration factors. The concentration factor of the system 

represents the factor by which the stream is concentrated, meaning that a 

concentration factor of four will produce a concentrated brine stream where the 

pollutant concentrations are four times higher than the influent because there is 

four time less (75% less) water in the concentrated brine stream. HPD stated that 

the higher the concentration factor, the more water that can be recovered. HPD 

estimated that approximately 95% of the cooling tower blowdown water can be 

recovered as quality distillate, which is equal to a concentration factor of 20. 

FGD Wastewater Treatment Issues 

 HPD stated that treating FGD wastewater with a ZLD system is more difficult 

than treating cooling tower blowdown because of the chemistry of the FGD 

wastewater. HPD stated that FGD wastewater contains higher levels of TDS, 

chlorides, suspended solids, heavy metals, boron, ammonia, and COD. In 

addition, the primary salt in cooling tower blowdown is sodium, compared to 

calcium and magnesium in FGD wastewater. Finally, FGD wastewater is 

saturated in gypsum. 

 The differing wastewater chemistries between the FGD wastewater and cooling 

tower blowdown have the following impacts on the design for treating FGD 

wastewater: 

— High levels of TDS (20,000 - 40,000 mg/L): restricts the concentration 

factor achieved by the brine concentrator. In addition, it prevents the use 

of reverse osmosis because the wastewater is already above the osmotic 

pressure limits. 

— High levels of chlorides (10,000 – 30,000 mg/L): has the potential to cause 

pitting or stress cracking in the evaporator; therefore, noble materials of 

construction are required. 

— High levels of suspended solids: has the potential to build up and clog the 

system; therefore, pretreatment is required to remove the solids. [CBI 

information has been removed from this document.] 

— Gypsum at saturated levels: will precipitate out of solution as water is 

evaporated, which would cause scaling on the evaporator equipment; 

therefore, a seeded slurry of calcium sulfate crystals needs to be fed to the 

system to prevent scaling. 
Memorandum 

November 6, 2008 

Page 4 

— High levels of heavy metals, boron, ammonia, and COD: These chemicals 

can interfere with the seeded slurry, as well as contaminate the distillate 

produced. 

— Calcium and magnesium salts: These salts are aggressive acid salts which 

require noble materials of construction. In addition, these salts have a 

high boiling point rise as they become more concentrated; therefore, 

additional power is required to achieve these higher temperatures. 

Brine Concentrator System Design for FGD Wastewater 

 HPD uses falling-film evaporators, also known as a brine concentrator, in the 

design of the ZLD systems because they have a high heat transfer coefficient, 

which requires less surface area to achieve the same heat transfer. Because less 

surface area is needed, the equipment is smaller. Additionally, brine 

concentrators allow a large amount of surface area to be packed efficiently in a 

small space, making a smaller footprint for the system. 

 In the brine concentrator, the FGD wastewater is pumped to the top of the brine 

concentrator and a pair of distribution plates disperse the liquid evenly among the 

heat transfer tubes. The heat transfer tubes are approximately two inches in 

diameter and are thin-walled to improve heat transfer. The tubes are typically 

about 50 feet long. Because the tubes are thin, they are vulnerable to pitting and 

cracking. HPD usually constructs the tubes out of titanium due to its strength, 

good heat transfer properties, and corrosion resistance. HPD stated that titanium 

cannot be used in waste streams with high fluoride concentrations. Waste streams 

with high concentrations of fluoride can be addressed by substituting titanium 

with inconel or similar alloys. 

 As the liquid enters the heat transfer tubes, it creates a film along the inside walls 

of the tube. This film allows for better heat transfer to occur. HPD prevents the 

liquid from flooding the tubes by controlling the flow rate within the tubes and the 

level of the combined feed and concentrate at the bottom of the brine 

concentrator. 

 As the liquid flows down the heat transfer tubes, steam condenses along the 

outside of the heat transfer tubes. The steam transfers its heat to the liquid inside 

the tubes and some of the water is thereby evaporated to steam and continues 

flowing downward in the tubes along with the remaining liquid. In addition, the 

steam on the outside of the tubes condenses and falls to the bottom of the brine 

concentrator where it is collected and recovered as a quality distillate. 

 When the vaporized water reaches the bottom of the brine concentrator, it exits 

the heat transfer tubes and begins flowing upward, thereby separating from the 

liquid. This vapor then passes through a mist eliminator, which removes any 

entrained liquid from the vapor. The mist eliminator allows the vapor to pass 

through, but the water is entrapped and falls back downward into the bottom of 

the brine concentrator. 

 The vapor is then sent to a compressor to compress the vapor, which raises its 

saturation temperature. This compressed vapor is used as the steam in the brine 

concentrator, and eventually becomes the quality distillate. This process is known 

as mechanical vapor compression. 
Memorandum 

November 6, 2008 

Page 5 

 HPD uses the mechanical vapor compression system in the design of the ZLD 

systems because it is energy efficient. Because the heat of vaporization from the 

water vapor is recovered and recycled by vaporizing additional liquid, the only 

input to the system is the electrical energy used to run the compressor. HPD 

stated that the energy input to a mechanical vapor compression evaporator is 30 to 

60 BTU/lb distillate, compared to 1,000 BTU/lb distillate for a steam-driven 

evaporator. 

 HPD stated that steam is needed in the mechanical vapor compression system 

during the cold start up to begin the process. 

 HPD stated that they also use seeded slurry in the brine concentrators that are 

treating FGD wastewater to control scale formation. The seeded slurry consists of 

adding calcium sulfate seed crystals to the circulated liquid. 

 The low solubility salts will precipitate out of the circulated liquid as it becomes 

more concentrated. The seeded slurry causes these salts to preferentially 

precipitate out onto the seed crystals instead of precipitating onto the heat transfer 

tube walls. 

 HPD uses a hydroclone to recycle the seeded slurry within system. The 

concentrated stream leaving the brine concentrator is sent to a hydroclone where 

the solids (seed crystals) are separated from the liquid. The seed crystals are 

recycled back to the brine concentrator, and the liquid continues to the next step 

in the process. 

 HPD stated that there are some constituents within the FGD wastewater that can 

interfere with the seeded slurry; however, HPD stated that it was proprietary 

information. HPD stated that this was the reason that the AES Milliken (Cayuga) 

ZLD system did not operate properly. 

 In addition to the brine concentrator, HPD typically has a feed tank, a feed 

preheater, and a deaerator that operate within the system. The feed tank is used to 

add an acid to the waste stream to convert the calcium carbonate to carbon 

dioxide and add an anti-scalant. The feed preheater uses the distillate stream to 

heat the feed to its saturation temperature. The deaerator uses steam vented from 

the brine concentrator to strip the noncondensables (e.g., carbon dioxide, oxygen) 

from the feed stream. [CBI information has been removed from this document.] 

 HPD stated that the brine concentrator does require cleaning over time. HPD 

stated that the brine concentrator can be chemically cleaned, or the tubes can be 

hydroblasted to remove build up. HPD stated that the system is usually cleaned 

as part of a plant shutdown, one to two times per year. 

 HPD stated that the brine concentrator is typically designed for a 30-year lifetime. 

Options for Treating FGD Wastewater 

 HPD stated that there are currently two different options available for treating 

FGD wastewater with an evaporator system. The first is to evaporate the FGD 

wastewater directly (Option 1). The second is to evaporate the FGD wastewater 

following a softening pretreatment step (Option 2). 

 For Option 1, the FGD wastewater would need to undergo a solids removal step 

prior to the brine concentrator. The wastewater would then go to the brine 

concentrator, which would operate similar to the one described previously. 
Memorandum 

November 6, 2008 

Page 6 

 HPD stated that the brine concentrator for an Option 1 system can typically 

concentrate the stream 4 to 5 times, which would recover 75 to 80 percent of the 

water. HPD stated that the system is limited by the TDS and the boiling point rise 

of the calcium salt. As the calcium salt becomes more concentrated in the water, 

the boiling point for the solution rises, which requires more power to evaporate 

the liquid. 

 The Option 1 system is based on calcium and magnesium chemistry, which means 

that a crystallizer cannot be used for the final drying stage because calcium 

chloride won’t crystallize. Therefore, the Option 1 system will typically use a 

spray dryer for final drying. In the spray dryer, the liquid is sprayed downward 

into a large chamber and hot air (created from burning a fuel, typically natural 

gas) evaporates the liquid and the remaining salt particulates are collected at the 

bottom of the chamber. 

 The dry salt generated from this process is hygroscopic, which means that it will 

readily take up and retain moisture. To prevent issues with handling the salt, it is 

typically bagged immediately after it is generated and then disposed. 

 [CBI information has been removed from this document.] 

 For Option 2, the FGD wastewater is pretreated with lime and soda ash to remove 

the solids in the wastewater and to convert the chemistry in the water from 

calcium and magnesium based to sodium based. 

 [CBI information has been removed from this document.] 

 The Option 2 system uses the same design for the brine concentrator system as the 

Option 1 system. The brine concentrator will achieve a similar concentration 

factor as achieved for Option 1 (4 to 5 times); however, because the wastewater is 

based on sodium chemistry, the boiling point rise will be less, which will require 

less energy. 

 The Option 2 system has the capability to use a crystallizer for the final drying 

stage because of the sodium-based chemistry. The crystallizer will generate a 

sodium chloride by-product and the solids will be landfilled. 

 HPD stated that Option 2 typically looks better economically because of the 

reduced power consumption from the use of a crystallizer versus a spray dryer. 

HPD’s New Option for Treating FGD Wastewater 

 HPD recently developed a new evaporation technology to treat FGD wastewater. 

 HPD stated that the new technology is a single stage system that can treat the 

FGD wastewater directly. 

 HPD stated that no pretreatment is required for the system. The only input to the 

system, other than the FGD wastewater, is the electrical energy. The solid 

product is produced in the evaporator and there is no need for crystallizer, spray 

dryer, or further processing. The output from the system is the recovered quality 

distillate and a stable solids product that requires dewatering from a centrifuge or 

filter. 

 HPD stated that the system is commercially ready, but they are waiting for the 

patent approval before it is made publicly available. 

 HPD stated that the capital cost for the system is approximately 25% less than a 

physical/chemical system. The O&M costs are expected to be comparable to a 

physical/chemical system, but with 60 percent reduction in system footprint. 
Memorandum 

November 6, 2008 

Page 7 

The Future for ZLD Systems Treating FGD Wastewater 

 HPD stated that the U.S. is installing approximately 40 wet scrubbers per year. 

HPD stated that China is adding scrubbers at an even faster rate. 

 HPD stated that with the Option 1 and Option 2 ZLD systems available, probably 

only 10% of the new scrubbers will use a ZLD technology for the treatment of the 

wastewater. 

 HPD stated that ZLD systems are typically easier to operate at larger power plants 

because there is less swing in the plant’s loading. 

 HPD stated that the cost and the unfamiliarity of the ZLD system are the two 

biggest reasons why plants aren’t installing ZLD systems to treat FGD 

wastewater. HPD stated that there is no reason for the plants to spend the extra 

money on the ZLD system at this time. 

 [CBI information has been removed from this document.] 

 A ZLD system provided by Veolia/HPD has been installed at Monfalcone in Italy 

At the time of the June 5 meeting, the ZLD system was in the process of starting 

up. The evaporators were running on water but were not expected to receive 

scrubber purge until early July. This system uses softening, followed by 

evaporation, followed by a crystallizer. 

ZLD Technology for IGCC plants 

 There are four IGCC plants operating in the world currently. Three of the plants 

use ZLD systems to treat the gasifier wastewater. 

 HPD stated that the IGCC plants have a clarifier right after the gasifier to remove 

the solids from the gasifier water. HPD stated that the brine concentrator is 

located after the clarifier. 

 HPD stated that the water characteristics of the IGCC wastewater are different 

than the FGD wastewater, especially the chlorides concentrations. [CBI 

information has been removed from this document.] 

Additional Contacts 

 HPD stated that Larry Gunari is knowledgeable about the power industry and 

treatment options for various waste streams, as well as treatment options for reuse 

of waste streams. Larry’s phone number is (937) 238-3965. 

 HPD stated that Terkel Christensen, Kruger A/S is a contact for the MetClean® 

system. Terkel’s phone number is +45-3957-2474 and his e-mail is 

tcc@kruger.dk.