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22009

September 23,

2009

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Marie E. Tipsord

Hearing Officer

cThQ,V

Illinois Pollution

Control

Board

100

West Randolph Suite

11-500

Chicago, Illinois

60601

Re:

R2008-009,

In The Matter of: Water

Quality

Standards

and Effluent

Limitations

for

the

Chicago Area Waterway

System and the

Lower Des

Plaines River: Proposed

Amendments

to

35

III. Adm.

Code 301,

302, 303 and 304

Dear

Madam Hearing Officer,

This letter

serves as ENVIRON’s

response

on

behalf

of Stepan

Company to Board Member

Dr.

Shundar

Lin’s

question

at the August 13

hearing regarding the

dosage of chlorine

necessary

to

meet the proposed

effluent bacteria standards

at

end of pipe.

The dosage

of

chlorine

determined

by ENVIRON was 70

mg Cl

2!L of wastewater.

In addition

to providing

the exact

chlorine

dose, the

following

comments summarize

ENVIRON’s

general approach

to chlorine

disinfection.

First, the

concept

of chlorine consumption

must be

considered. In typical

wastewater,

there

are

four sources

of chlorine or

hypochlorite consumption,

three of

which compete with

chlorine

availability

for disinfection.

Consequently,

adequate chlorine

must be

added

to satisfy these

sources

of chlorine

consumption and provide

sufficient residual

chlorine to

kill fecal coliform.

These sources

are:

1.

Ammonia-N,

which reacts

with chlorine to form

nitrogen

gas;

2. Oxidizable

organics,

such

as phenols, which

are converted to simpler

organic

constituents and, hopefully,

not converted into

chiorinated—organics;

3.

Oxidizable

inorganics,

such as cyanides, or

sulfides, which are

reduced

to

lower state compounds;

and,

4.

Biological organisms,

including fecal coliforms,

which

are killed in the

presence of sufficient

residual chlorine.

Upon

that

foundation, the calculation

of the chlorine

dose was arrived

in the following

manner.

Stepan’s

wastewater averages

about 2.1 mg/L

of

ammonia-N,

which is a chlorine

consumer,

and

it can range

as high as 3.0 mg/L

of ammonia-N. This will

result

in “breakpoint

chlorination”

to convert

the

ammonia

to

harmless nitrogen gas,

requiring

about

15:1 Cl2 to N (See

Design

Manual

Municipal Wastewater

Disinfection.

Cincinnati: US

EPA Office of

Research and

Development,

1986.

Print).

The theoretical

dosage of chlorine

to convert ammonia

to nitrogen

gas is

47.25 mg/L

[2.1 x 15 x

1.5 (roughly ratio

of maximum to average

ammonia-N

concentration)].

This

leaves approximately

20 mg of CI2

!L

of

wastewater

for disinfection.

From

the

Design of Municipal

Wastewater Treatment

Plants, WEF

Manual of Practice

No.

8 / ASCE

Manual

and Report on

Engineering Practice

No. 76. Alexandria,

VA: Water

Environment

Federation,

1991.

Print, Chapter 14,

Table 14.1: Typical

Chlorine Dosages,

the required

dosage

of chlorine

for disinfecting

municipal

activated sludge

effluent can

be up to 9

mg!L.

Because

of

201

Summit View Drive, Suite 300,

Brentwood, TN 37027

www.environcorp.com

Tel: +1

615.377.4775

Fax: +1 615.377.4976

---

Marie

E Tipsord

-2-

September

23,

2009

the

industrial

nature of

the Stepan wastewater,

there will

most

likely be constituents

that exert

an

additional chlorine

demand (residual

organics surfactants

etc)

Because

this

additional

chlorine

demand

has not been

quantified, a 100%

safety factor

was applied, rounding

the

required

dosage of chlorine

for disinfection

to

20

mgIL. Adding

that amount

of chlorine to

the

amount necessary

to address the presence

of ammonia-N,

which

consumes chlorine,

and

rounding off the

calculations, we

arrived

at 70 mg of CI

2

IL

of wastewater

to achieve

disinfection.

This

dosage of

chlorine is also what

was implicitly reflected

in our cost

calculations,

as the

following calculations

demonstrate:

Design

Flow = 1,100,000

gal/day

The gallons of bleach

solution projected

for disinfection

= 235,883

gal/yr (see

Table

8

of Exhibit

321), which is roughly

646 gallons/day

[235,883/365].

The

bleach

solution is 12.5% bleach

(NaOCI),

so

the bleach/liter

of wastewater

is

approximately

73 mg of NaOCl/L

of wastewater

[646 gals/day

x 12.5%

NaOCl/1,100,646

(gallons

of wastewater plus bleach

solution

in a day)].

Using the molecular

weights

of sodium (Na), oxygen

(0) and

chlorine (Cl), the 73

mg

of NaOCl/L of wastewater

is equivalent

to 51 mg of 0C17

L

of wastewater

and

to 70 mg of Cl

2

/L

of wastewater.

Consequently,

the dosage

of approximately

70 mg of

Cl

2

/L

of wastewater

accounts for

the

presence of ammonia,

susceptible organics/inorganics,

and

a safe residual

for

disinfection

and

served

as the

basis

for our

cost

estimate.

Sincerely,

ENVIRON

International Corporation

Carl E.

Adams Jr., PhD,

PE

Principal