case study - Purafil

CASE STUDY FOR 

THE SILVAN 

DISINFECTION PLANT 

PURAFIL ® 

FIRST 

IN CLEAN 

AIR 

www.purafil.com 

PURAFIL ESD PREVENTS 

ACCIDENTAL CHLORINE RELEASES 

FOR THE SILVAN DISINFECTION PLANT 

ABOUT THE SILVAN DISINFECTION PLANT 

Located in the mountains outside Melbourne, the Silvan Disinfection Plant was classified 

under state government legislation as a major hazard facility. 

THE PROBLEM 

According to plant project manager Stephen Answerth, 

"Melbourne Water was required to reduce the risk of a chlorine 

release ‘so far as practicable.'" 

Plant representatives considered using wet scrubbers, which 

were less expensive but required more maintenance and could 

harm humans, wildlife, and the environment. 

PURAFIL PROVIDES THE SOLUTION 

To prevent accidental chlorine (Cl 2 ) releases, Silvan opted to use 

a Purafil Emergency Gas Scrubber (EGS) that measured 10 feet 

in diameter by 15 feet tall and held 25,000 pounds of CSO 

media. Local Purafil representative James McIntosh (Airepure 

Australia) facilitated their request. 

In the event of an unintentional Cl 2 emission, the EGS follows 

these steps to eliminate the gas from the air: 

1) Released Cl 2 is drawn into the scrubber through a blower and 

contacts dry-scrubbing media. 

2) Media react with Cl 2 and permanently convert the gas to 

non-toxic solids. 

3) Clean air is discharged to the outdoors with a Cl 2 concentration 

of less than 5 parts per billion. 

The EGS requires significantly less maintenance than a wet 

scrubber. It does not need heaters for outdoor applications, 

and it has just one moving part--a blower. Instead of using liquid 

caustic, the EGS neutralizes Cl 2 with dry-scrubbing media, 

which are highly porous, spherical pellets that permanently 

transform the gas into harmless solids. As long as media do not 

react with Cl 2 , they do not need to be replaced; they only 

require occasional testing to determine remaining life and to 

project change-out dates. Non-toxic and non-hazardous, 

media do not require special handling and can be disposed in 

landfills. 

"The dry scrubber was selected because it is a simpler system 

and does not involve having liquid caustic soda on-site," 

Answerth said. 

ABOUT PURAFIL ESD 

For more than 15 years, Purafil ESD has been the premier single-source 

provider of clean air to over 100 North American 

and European clients. A division of Purafil, Inc., Purafil ESD 

manufactures a broad range of dry-scrubbing media and systems 

that remove odorous, toxic, and corrosive gases at water 

and wastewater applications. 

Purafil ESD's Emergency Gas Scrubber (EGS) removes the contents 

of a fully-loaded chlorine (Cl 2 ) or sulfur dioxide (SO 2 ) 

cylinder in a worst-case release scenario and discharges less 

than 5 parts per billion. The EGS works in temperatures ranging 

from -40 degrees to 200 degrees Fahrenheit. 

In the event of a release, the EGS draws Cl 2 /SO 2 -laden air 

through a bed of dry-scrubbing media. The gases react irreversibly 

with the media's chemical impregnant, and the products 

of this reaction are solid salts that can be disposed of in 

common landfills. 

PURAFIL ® EMERGENCY GAS SCRUBBER 

Purafil, Inc. • 2654 Weaver Way, Doraville, Georgia, 30340, U.S.A. • www.purafil.com • tel: (770) 662-8545 • (800) 222-6367 

© Purafil 2006 CsStdy--Silvan-01 

ISO 9001:2008

CASE STUDY 

FOR 

T H E D E T R O I T WAT E R 

T R E AT M E N T P L A N T 

FIRST 

IN CLEAN 

AIR 

A B O U T T H E S P R I N G S W E L L S W A T E R T R E A T M E N T P L A N T 

P U R A F I L 

P R E V E N T S AC C I D E N TA L 

C H L O R I N E R E L E A S E S 

FOR THE DETROIT WATER 

TREATMENT PLANT 

Springwells Water Treatment Plant is a 540 million gallon per day (mgd) surface water 

treatment plant located in a mixed residential and light industrial area on the west side of 

Detroit. The largest freshwater treatment plant in Michigan, Springwells draws water from 

the Detroit River, disinfects it with chlorine, coagulates it with alum, and filters it through 

high-rate dual-media rapid sand filters. Plant output feeds a distribution system serving 

approximately 125 communities and 4.3 million consumers. Built in 1931, the original plant 

was a combined treatment plant and pumping station of 340 mgd capacity. An additional 

200 mgd capacity was added in 1958 for a total design capacity of 540 mgd. 

T H E P R O B L E M 

Because source waters are low in organic content, 

Springwells disinfects the water with liquid chlorine, 

which is stored in one-ton containers. The plant 

previously used a sodium hydroxide wet-scrubbing 

system to neutralize chlorine gas in the event of an 

accidental release. However, this system contained 

a messy, highly corrosive lye solution that was 

hazardous to system operators and attacked piping, 

valves, and pump seals. Keeping the wet scrubber 

operational required extensive maintenance, and the 

system ultimately fell into disrepair, with only the 

fans working in its last days. 

P U R A F I L P R O V I D E S T H E S O L U T I O N 

When Springwells replaced their entire chlorine 

storage and feed facility, they purchased a Purafil 

Emergency Gas Scrubber (EGS) from local 

representative Ryan Forbes (Hi-Tech Environments). 

The EGS "dwarfed the former wet scrubbing 

system," said Richard Pernal, filtration supervisor. 

"With nearly a tenfold increase in storage and feed 

capacity, special emphasis was given to reliability 

and safety. A sister plant in our system had 

upgraded to a Purafil dry scrubber earlier with 

favorable results. With our system upgrade, the 

same Purafil scrubber was specified." 

The EGS requires significantly less maintenance than 

a wet scrubber. It does not need heaters for 

outdoor applications, and it has just one moving 

part – a blower. Instead of using liquid caustic, the 

EGS neutralizes chlorine with dry-scrubbing media, 

which are highly porous, spherical pellets that 

permanently transform the gas into harmless solids. 

As long as media do not react with chlorine, they do 

not need to be replaced; they only require 

occasional testing to determine remaining life and 

to project change-out dates. Non-toxic and nonhazardous, 

media do not require special handling 

and can be disposed in landfills. 

According to Pernal, "The Purafil EGS has been 

especially trouble free. There are no corrosive 

liquids to handle, no valves to foul, no spills to 

contain. The scrubber's operation is checked on a 

weekly basis by testing our chlorine detectors with 

a calibration gas. Our local Purafil representative 

periodically visits to sample the dry-scrubbing 

media for analysis." 

Pernal has nothing but praise for the dry scrubber. 

"Our system looks and performs today as well as 

day one, with virtually no maintenance. The 

maintenance savings are great, and operations has 

a system that is not dangerous to operate. We're 

very happy with our EGS." 


© Purafil 2007 CsStdy--Detroit WWTP-01 

ISO 9001:2008

A B O U T T H E E G S 

P U R A F I L D R Y- S C R U B B I N G M E D I A 

Purafil's Emergency Gas Scrubber (EGS) removes the 

contents of a fullyloaded 

chlorine (Cl 2 ) or 

sulfur dioxide (SO 2 ) 

cylinder in a worst-case 

release scenario and 

discharges less than 5 

parts per billion. The 

EGS works in 

temperatures ranging 

PURAFIL 

from -40 degrees to 200 

® CHLOROSORB MEDIA 

degrees Fahrenheit. 

In the event of a release, the EGS draws Cl 2 /SO 2 -laden 

air through a bed of dry-scrubbing media. The gases 

react irreversibly with the media's chemical impregnant, 

and the products of this reaction are solid salts that can 

be disposed in common landfills. 

· System media are UL Classified. 

· System media are immediately available for instantaneous reaction. 

· Spent media are landfill acceptable before and after use. 

A B O U T P U R A F I L 

For over 40 years, Purafil’s gas-phase media has protected 

environments from corrosive, toxic, irritant and odorous gases. Purafil, 

Inc. is the world leader in innovating, designing, engineering, and 

manufacturing gas-phase air filtration systems, atmospheric and 

reactivity corrosion monitors, and UL classified granular media. Purafil 

maintains nearly 40,000 global installations in industrial, commercial, 

municipal, high purity, mission critical (data centers and server rooms), 

power generation, and preservation facilities. 

Call Purafil at 1-800-222-6367 for assistance with your air quality 

concerns or visit our Web site at www.purafil.com. 


© Purafil 2007 CsStdy--Detroit WWTP-01 

ISO 9001:2008


THE CITY OF RICHLAND’S COLUMBIA 

RIVER WATER TREATMENT PLANT 

PURAFIL ® 

FIRST 

IN CLEAN 

AIR 


PURAFIL PERFORMS SUCCESSFUL RETROFIT 

FOR THE CITY OF RICHLAND’S 

WATER TREATMENT PLANT 

ABOUT THE CITY OF RICHLAND WATER TREATMENT PLANT 

The City of Richland’s Columbia River Water Treatment Plant (WTP) was built and put into operation in the fall of 1963, supplementing 

a system of wells that were constructed by the Federal government in the 1940’s. Richland’s WTP is a direct filtration surface water 

treatment plant designed to treat a maximum flow of 30 million gallons a day. The plant is one of three water treatment sites operated 

and maintained by Richland Water. The system presently serves a population of approximately 50,000. The WTP handles surface water 

in a series of treatment processes, including coagulation, chlorination, and filtration. Chlorine disinfection may occur both before and 

after filtration depending on the surface water conditions. Chlorine usage during the summer months can exceed 500 pounds per day. 

THE PROBLEM 

In 1996, the WTP went through a plant expansion that 

doubled the rated capacity from 15 mgd to 30 mgd. The 

renovation included construction of a chlorine handling 

facility and the installation of a wet chlorine scrubber 

with a designated emergency generator. The emergency 

scrubber developed leakage problems and ended up 

being drained and shipped out for repairs twice in a 

four-year period. Caustic wet scrubbers use large 

amounts of chemicals to operate and also require much 

more maintenance than dry scrubbers; and because 

they use harsh chemicals, they are also subject to very 

strict guidelines. The plant operators also noticed 

caustic freezing issues that would render the scrubber 

inoperable during very cold periods of the winter 

months. 

Crystallized caustic found in the wet scrubber during the retrofit 

In 2006, Richland Water completed construction of a 

new multiple phase Ultraviolet Disinfection Facility 

(UVDF). This facility was designed to use chlorine for 

contact time and residual detection to ensure 

maximum disinfection. Since the disinfection facility 

was storing large amounts of chlorine, they decided to 

invest in a more efficient emergency standby 

equipment to prevent accidental chemical releases. 

Based on their previous experience with wet scrubbers, 

Richland Water incorporated a Purafil dry Emergency 

Gas Scrubber (EGS) to the UVDF. Seeing the benefits of 

using Purafil’s EGS, Richland Water decided to replace 

the failing wet scrubber at the WTP with a dry scrubber. 


At first, the city considered switching the 

wet scrubber to a brand new Purafil 

dry 1-ton capacity scrubber. 

When the plant operators 

contacted Purafil’s local 

representative, Treatment 

Equipment Company, they 

learned about the capability to 

retrofit existing wet chlorine 

scrubbers to dry scrubbers using 

Chlorosorb ® Ultra Media. 

Purafil Water-Wastewater Market Manager, Colin 

Christie, provided a competitive quote to complete the 

retrofit. Due to the significant cost savings and the 

capabilities of Richland Water’s staff to perform the 

work in-house, the plant managers decided to turn 

their existing installation into an efficient, low 

maintenance dry scrubbing system. Purafil project 

engineers worked closely with the WTP staff to make 

the retrofit a success. 

Chlorosorb ® Ultra Media 


© Purafil 2012 CsStdy--RLD- 01 

ISO 9001:2008

CUSTOMER SATISFACTION 

Richland Water’s staff was able to perform all the 

required labor. With the guidance of Purafil’s project 

engineers, all questions and issues regarding the 

project were dealt with in a timely manner. Thanks to 

the support and efforts of Purafil and its 

representatives, the project was completed on time and 

under budget. Based on the approved budgeted 

amount for the project, Richland Water saved 

approximately $70,000 by retrofitting its existing 

installation using Purafil’s expertise. 

Richland WTP’s Water Manager, John Finch, told Purafil, 

“Having owned and operated two different types 

of scrubbers, I know for a fact that the Purafil dry 

scrubber is much easier to operate and maintain.” 

Retrofitted scrubber at the water treatment plant 

Thanks to its successful retrofit, Richland water 

treatment plants are currently only using dry scrubbers. 

DRY SCRUBBERS VERSUS WET SCRUBBERS 

Dry scrubbers have several advantages over 

conventional wet scrubbers. For instance, dry scrubbers 

require significantly less maintenance than wet 

scrubbers. They have just one moving part—a blower. 

No need to hassle with pumps, spray nozzles, or pH 

controls! 

Dry scrubbers are much 

safer, too. Instead of 

using toxic caustic liquid, 

they neutralize gases 

with non-toxic dryscrubbing 

pellets. These 

pellets are called media, 

and they permanently 

transform gases into 

harmless solids. Unlike 

caustic liquid scrubbers 

which require staff to Purafil Emergency Gas Scrubber 

regurlarly measure the 

total amount of gas that can be fed in the scrubber, the 

media inside dry scrubbers are immediately available 

for instantaneous reaction, regardless of the gas load 

rate. 

Purafil’s dry emergency gas scrubber discharges less 

than 25 parts per billion, whereas wet scrubbers 

discharge 1-4 parts per million. 

PURAFIL’S PATENTED RETROFIT PLAN FOR 

WET TO DRY CONVERSION IS AS EASY AS 1, 2, 3! 

STEP 1: 

Remove Caustic Material 

Remove the three-panel lid. 

Drain and dispose of liquid caustic from reservoir and reaction chamber. 

Remove recirculation pump and pipe. 

STEP 2: 

Modify Existing Scrubber 

STEP 3: 

Install Purafil Chlorosorb ® Ultra Media 

Remove and dispose of tower packing material. 

Cut out internal fiberglass walls and barrier between reaction chamber and liquid reservoir. 

Install aluminum posts and secure to external fiberglass walls. 

Install perforated, aluminum media screens and secure to posts. 

Install Purafil ESD Chlorosorb Ultra dry chemical media between media screens. 

Replace three-panel lid and plug holes. 


© Purafil 2012 CsStdy--RLD - 01 

ISO 9001:2008


MOCCASIN BEND WASTEWATER 

TREATMENT PLANT 

PURAFIL ® 

FIRST 

IN CLEAN 

AIR 


PURAFIL EGS PREVENTS TOXIC 

CHLORINE GAS RELEASE 

FOR THE CITY OF CHATTANOOGA 

MOCCASIN BEND WWTP CUSTOMER SATISFACTION 

“We installed a Purafil [emergency chlorine] gas scrubber in 2000 [to comply with] our risk management plan,” explains 

Jerry Stewart, City Director of Waste Resources for the City of Chattanooga which oversees Moccasin Bend Wastewater 

Treatment Plant (WWTP). “It’s been nine years and we never had to use it. The day finally came and it performed as 

advertised.” 

As a plant operator attempted to switch the chlorine cylinders, a potentially catastrophic chlorine leak occurred. Although 

the plant operator escaped the chlorine leak and did not sustain injury, the WWTP implemented its emergency response 

plan; the Chattanooga Fire Department hazardous waste unit responded to the site; an Incident Command Structure was 

established; and the plant site and surrounding areas were secured; and the local chlorine supplier’s emergency response 

team was called to access and shut off the leaking one-ton chlorine cylinder Fortunately, the risk was minimal; and Stewart 

reported, the plant’s emergency gas scrubber “neutralized all of the chlorine that leaked out of the one-ton cylinder.” 

THE PROBLEM 

Wastewater treatment plants combine four primary steps 

to process sewage: liquid handling, solid handling, pump 

stations and plant maintenance. During the liquid 

handling process, chlorine (Cl 2 ) is used to treat the 

cleaned wastewater. 

Facilities storing large quantities of chlorine, typically in 

one or more one-ton cylinders, must invest in emergency 

standby equipment to prevent accidental chemical 

releases. The U.S. Environmental Protection Agency’s 

(EPA) Risk Management Program for Chemical Accident 

Release Prevention “requires regulated facilities to 

develop and implement appropriate risk management 

programs to minimize the frequency and severity of 

chemical plant accidents.” In addition, “a performancebased 

approach towards compliance with the risk 

management program rule is required.” 

If a toxic gas release from a one-ton cylinder were to 

occur, the thermodynamic properties of chlorine suggest 

that approximately 400 lbs of liquid chlorine would flash 

into vapor and the remaining contents of the cylinder 

would spill out as a liquid at its boiling point. According 

to the American Water Works Association (AWWA) Risk 

Management Program (RMP) Guidance, the outer limit of 

the impact area, in a chlorine release, is drawn at a fivemile 

radius in all directions from the point of impact. 

EGS is designed to neutralize an initial 400 lbs in the first 

minute and any additional chlorine at a rate of 80 

lbs/min thereafter, which exceeds the requirements of the 

Uniform Fire Code. 

Instead of using toxic, liquid caustic to neutralize gases, 

the EGS uses non-toxic, dry-scrubbing medium. This 

medium’s chemisorptive process removes chlorine by 

means of adsorption, absorption and chemical reaction. 

Chlorine gas is trapped within the medium pellet where 

an irreversible chemical reaction changes the chlorine 

gas into a harmless solid. 

During the chlorine leak at Moccasin Bend, Purafil ESD’s 

EGS immediately began to disinfect the chlorine gas, 

minimizing the risk to the worker and the community. 

Gary Williams, Occupational Safety Specialist admits, “It’s 

an emotional thing when you think that someone could 

have died.” 

This unit and site are prime examples of the benefits of 


In 2000, Moccasin Bend officials purchased a Purafil ESD 

FOC-1, fiberglass EGS with Chlorosorb ® dry-scrubbing 

medium and installed it adjacent to the chlorination 

room. Purafil ESD’s dry-chemical EGS is designed to 

contain the entire contents of a fully loaded 1-ton 

chlorine cylinder in a worst-case release scenario. The 

PURAFIL ® ESD FIBERGLASS ONE-TON (FOC-1) 

EMERGENCY GAS SCRUBBER (EGS) 

PURAFIL ® ESD CHLOROSORB ® ULTRA DRY- 

SCRUBBING MEDIA 


© Purafil 2009 CsStdy--Moccasin Bend-01 

ISO 9001:2008

an EGS with dry-scrubbing media. The dry-scrubbing 

medium within the 

unit is non-toxic, 

non-hazardous, 

maintenance-free, 

UL Classified, and 

most importantly, it 

can effectively help 

to save the priceless 

elements of a 

community. Stewart 

contends, “The 

biggest thing [the 

EGS] did for us was 

turn a [potentially] 

CHLORINE TANKS WITHIN MOCCASIN BEND WWTP’S 

CHLORINE ROOM 

major chlorine incident into a minor one. We were able 

to shut the gas off without it escaping to surrounding 

areas.” 

For years, Moccasin Bend WWTP’s officials have 

underscored safety. The chlorine room’s sensors were 

installed to measure a leak of 1 part per million (ppm), 

which will activate an alarm and seal the building to 

contain the gas. These preventative measures are vital to 

guard against a worst-case scenario leak. In 2004, 

Moccasin Bend professionals also conducted the largest 

regional chlorine drill with the Chattanooga Fire 

Department to enact proper procedures during a 

simulated leak. 

Purafil is proud to have played an integral role in 

protecting the Moccasin Bend community. The EGS filled 

with the original Chlorosorb medium remained 

unchallenged for nearly 10 years. When the leak 

occurred, it performed as specified without any 

evidence of medium degradation due to age or 

environmental conditions. When the “all clear” 

signal was given and the Chlorosorb in the EGS 

was removed, all indications were that the unit 

performed properly and it successfully withstood 

the toxic exposure. Moccasin Bend WWTP recently 

ordered 23,000 pounds of new Chlorosorb Ultra 

media, which has a minimum removal capacity of 

15% by weight and the capacity to remove up to 

3450 pounds of chlorine. 

National Historic Landmark and a Native American Burial 

Ground. 

According to The Friends of Moccasin Bend National Park, 

a nonprofit organization, the area represents the 

historical Native essence of Chattanooga. Its place in 

history, which predates the Common Era, has been 

chronicled with life and its necessity for potable water. 

Subsequently, the wastewater treatment plant was built 

in the 1960s and bears the same name. Moccasin WWTP 

serves 250,000 people, treats 140 million gallons of 

water per day (MGD) and has a maximum hydraulic 

capacity of 220 MGD. 

ABOUT PURAFIL ESD 

Purafil ESD’s EGSs are more advantageous than toxic, 

liquid wet scrubbers. Purafil introduced an easy Retrofit 

Plan for Liquid Caustic Scrubbers transform wet scrubbers 

and protect wastewater facilities and their communities 

from potential risk. 

Purafil ESD is the premier single-source manufacturer of 

clean air products throughout North America and Europe. 

A division of Purafil, Inc., Purafil ESD manufactures a 

broad range of dry-chemical media and scrubbers that 

remove odors, prevent toxic gas releases, and corrosion of 

electronics. 

Call Purafil ESD at 1-800-222-6367 for assistance with 

your air quality concerns or visit our Web site at 

www.purafil.com. 

MEDIA LIFE ANALYSIS AFTER RELEASE 

ABOUT THE SITE 

The Tennessee River and Cumberland Escarpment 

intersect to form the historical Moccasin Bend in 

Chattanooga. The 925-acre area’s significant 

development and relevance for its original Native 

American inhabitants span more than 10,000 years. 

In fact, residents and historians, alike, have lobbied 

to preserve Moccasin Bend for more than 20 years. 

In turn, the plush grounds nestled within the 

Chickamauga and Chattanooga National Military 

parks have also been deemed an Archaeological District 

among the National Register of Historic Places, a 

PURAFIL ENGINEERS DESIGN SYSTEMS TO HANDLE MORE THAN A ONE-TON CHLORINE RELEASE. 

FIELD ANALYSIS SHOWS THAT AFTER THE RELEASE IT STILL HAS OVER 10% LIFE REMAINING. 

THE MEDIA LIFE ANALYSIS (MLA) SHOWN ABOVE DEPICTS THE PURAFIL CHLOROSORB MEDIA 

AFTER THE RELEASE WITHIN THE FOC-1 UNIT LOCATED AT THE MOCCASIN BEND WWTP, WHICH 

GENERATES 5,000 CFM. 


© Purafil 2009 CsStdy--Moccasin Bend-01 

ISO 9001:2008

case study - Purafil

Create successful ePaper yourself

Delete template?

Save as template?