Fishbeck, Thompson, Carr & Huber, Inc.

Controlling POTW

Pass-Through/Interference

Due to Compatible Pollutants

Jerald O. Thaler, P.E.

Option 3

Treatment at POTW

with Excess Capacity

The Captive Loading Conundrum

Many WWTPs experiencing lower flows and

loads, leaving available capacity

Many WWTPs also have local limits which are: Uniform not-to-exceed concentrations

Applied to all nondomestic users, whether or not they

discharge the particular pollutant

Result = “captive loading” (on paper)

that cannot be accessed

Objective

If a POTW has available capacity, determine

how to achieve:

Accommodating special needs of SIUs

Enhancing revenues

Ann Arbor WWTP (Ann Arbor .com)

Using Available Capacity to Accommodate Special Needs of SIUs

Special Allocation Limits (SALs)

Releasing captive loading via SALs can:

Assist industries with special needs

Promote local economy and protect jobs

Improve asset utilization

SALs most applicable to compatible pollutants Treatable via existing system

Generally safe from toxic overloading

Special Allocation Limits (SALs)

Extension of traditional local limits

Option to allow alternate user-specific limits

At discretion of WWTP management

Provides ultimate in allocation flexibility

Rapidly gaining acceptance in State

Ann Arbor

Bay City

Flint

Genesee County

Lansing

Wyoming

Current Example #1

Dairy facility considered locating in community Requested applicable local limits

Assessed need and cost of pretreatment system

Decided to instead locate in Indiana

WWTP has available capacity

To improve economic development opportunities in future, now implementing SALs

Current Example #2

Existing landfill expanding in community

Involved major capital investment

Would require expensive pretreatment system to meet

ammonia local limit

WWTP has available capacity

To “subcontract” ammonia treatment to WWTP,

now implementing SALs

Traditional Local Limits

MAHL = not-to-exceed mass to protect WWTP

MAIL = portion of MAHL available to SIUs

Allocate MAIL over total SIU flow

SAL-based Local Limits

Set aside portion of MAIL as reserve

Allocate remaining MAIL over total SIU flow

If assigned to SAL, deduct excess loading from

reserve

USEPA Position on SALs

May select any allocation method producing

enforceable local limits which: Prevent pass-through and interference

Comply with prohibitions in Federal regulations

Subject to review by approval authority

MDEQ Position on SALs

Legal authority in Sewer Use Ordinance

Constraints Total influent mass cannot exceed MAHL

Total allocated mass cannot exceed MAIL

Assigned limit cannot exceed any applicable CSL

Important to have accurate and up-to-date

MAHLs/MAILs

Approvable written procedures

Example SAL Procedures

Local Limit (CLCL LIM) = 1,000 mg/L

Surcharge Threshold (CSURCH) = 250 mg/L

Background (CBKGD) = 110 mg/L

Classification for

BOD5

A

B

C

X…

(misc. other) B

where: X - Discharger to be regulated via SAL

Significant Industrial User

Acme Manufacturing

USA Automotive, Inc.

Standard Plating

Smith Foods

Discharge Flow,

gal/day

50,000

100,000

25,000

250,000

75,000

where: A - Surcharging Specific Discharger (>CSURCH & <CLCL LIM)

where: B - Nonsurcharging Specific Discharger (>CBKGD & <CSURCH)

where: C - Nonspecific Discharger (<CBKGD)

METROPOLITAN WWTP

INDUSTRIAL PRETREATMENT PROGRAM

Step 1 – Classify Dischargers

Status of Status ofApproved Approved

MAHL MAIL

Maximum Allowable Headworks Loading (MAHL) 16,500 lb/day

- Safety Factor @ 10% of MAHL 1,650 lb/day

- Background 9.500 mgd @ 110 mg/L 8,710 lb/day

Maximum Allowable Industrial Loading (MAIL) 6,140 6,400 lb/day

- Septage 0.000 mgd @ 1,000 mg/L 0 0 lb/day

- Allocated to SIUs 2,890 2,890 lb/day

Remaining 3,250 3,510 lb/day20% 21% of MAHL

MAIL

Fraction

Acme Manufacturing 50,000 gpd @ 1,000 mg/L 420 lb./day 7%

USA Automotive, Inc. 100,000 gpd @ 250 mg/L 210 lb./day 3%

Standard Plating 25,000 gpd @ 110 mg/L 20 lb./day <1%

Smith Foods 250,000 gpd @ 1,000 mg/L 2,080 lb./day 34%

… (misc. other) 75,000 gpd @ 250 mg/L 160 lb./day 3%

Allocated to SIUs 2,890 lb./day

X

B

A

B

C

SIU

Classification

Significant

Industrial User

Allocated

Discharge Flow

Allocated

Concentration

Allocated

Discharge Mass

BOD5

METROPOLITAN WWTP

INDUSTRIAL PRETREATMENT PROGRAM

MASS ACCOUNTING FOR

Example SAL Procedures

Step 2 – Check MAHL/MAIL Status

Status of Status ofApproved Approved

MAHL MAIL

Maximum Allowable Headworks Loading (MAHL) 16,500 lb/day

- Safety Factor @ 10% of MAHL 1,650 lb/day

- Background 9.500 mgd @ 110 mg/L 8,710 lb/day

Maximum Allowable Industrial Loading (MAIL) 6,140 6,400 lb/day

- Septage 0.000 mgd @ 1,000 mg/L 0 0 lb/day

- Allocated to SIUs 4,980 4,980 lb/day

Remaining 1,160 1,420 lb/day7% 9% of MAHL

MAIL

Fraction

Acme Manufacturing 50,000 gpd @ 1,000 mg/L 420 lb./day 7%

USA Automotive, Inc. 100,000 gpd @ 250 mg/L 210 lb./day 3%

Standard Plating 25,000 gpd @ 110 mg/L 20 lb./day <1%

Smith Foods 250,000 gpd @ 2,000 mg/L 4,170 lb./day 68%

… (misc. other) 75,000 gpd @ 250 mg/L 160 lb./day 3%

Allocated to SIUs 4,980 lb./day

BOD5

METROPOLITAN WWTP

INDUSTRIAL PRETREATMENT PROGRAM

MASS ACCOUNTING FOR

Classification Discharge Flow Concentration Discharge MassIndustrial User

SIU Significant Allocated Allocated Allocated

A

B

C

X

B

Example SAL Procedures

Step 3 – Select Appropriate SAL

Using Available Capacity to Enhance Revenues

Surcharges with SALs

Extra-strength surcharges recover cost to

treat concentrated wastes

Not penalty or fine

Use SAL as basis for calculating surcharge Condition of agreement

Subcontracting portion of treatment capacity

Often less expensive than pretreatment

Extra-Strength Surcharges

Applicable only for compatibles

Basis Threshold concentration (mg/L)

Surcharge rate ($/lb)

Example Assuming 250 mg/L threshold and $0.20/lb rate, surcharge for SIU discharging 0.25 mgd at 1,000 mg/L:

Surcharge Threshold

Should represent “normal” domestic sewage

Set by sampling of background location,

basis of design, and/or literature values

Not same as local limit

Metcalf & Eddy, Inc., Wastewater Engineering, 1991

Pollutant

Medium

Strength

mg/L

High

Strength

mg/L

BOD5 190 350

TSS 210 400

Ammonia-N 25 45

Total-P 7 12

Surcharge Rates

Represent incremental treatment cost over

“normal” domestic waste

Important to have accurate and up-to-date

representation of O&M costs

MWEA IPP Committee Survey

Pollutant

POTWs with

Surcharge

(N=49)

Median

Rate

$/lb

Range of

Rates

$/lb

BOD5 100% 0.19 0.01-0.50

TSS 98% 0.17 0.01-0.73

Ammonia-N 31% 0.41 0.14-4.98

Total-P 86% 1.51 0.27-4.79Complied by Mr. Jack Keys, ca. 2000

Surcharge Rates

Wide range in survey was surprise

Traditional calculation approach

Rule-of-thumb estimates

Surveys of other communities

Assumed cost breakdown factors

New method needed

Improve accuracy; more site-specific

Straightforward updates

New Surcharge Rate Method

Apply state-of-the-art O&M Cost Software to

simulate effect of load increases

From results, calculate corresponding

surcharge rate

O&M Cost

Software

0

1

2

3

4

5

0 1 2 3 4

lb/d

ay

0

1

2

3

4

5

0 1 2 3 4

$/d

ay

0

1

2

3

4

5

0 1 2 3 4lb/day

$/d

ay

slope (Δ$/Δlb) = surcharge rate

O&M Cost Software

Selected CapdetWorks® (Hydromantis, Inc.)

Wide range of unit operations for wastewater and biosolids

Specify system configuration and influent quality, obtain: Steady state mass balance, with recycle streams

Detailed O&M cost breakdown

Windows-based; user friendly

Case Study -- Ionia WWTP

System Configuration

CapdetWorks®

Case Study -- Ionia WWTP

O&M Cost Breakdown

Case Study -- Ionia WWTP

Load Increase Simulations

BOD5

+0

+50

+100

+150

+0 +250 +500 +750

Nondomestic User Loading (lb/day)

O&

M C

ost ($

/da

y)

Slope ($/lb) = 0.11

TSS

+0

+50

+100

+150

+0 +250 +500 +750

Nondomestic User Loading (lb/day)

O&

M C

ost ($

/da

y)

•

Slope ($/lb) = 0.22

Ammonia-N

+0

+25

+50

+75

+0 +30 +60 +90

Nondomestic User Loading (lb/day)

O&

M C

ost ($

/da

y)

•

Slope ($/lb) = 0.22

Total-P

+0

+25

+50

+75

+0 +5 +10 +15

Nondomestic User Loading (lb/day)

O&

M C

ost ($

/da

y)

Slope ($/lb) = 4.43

Case Study -- Ionia WWTP

Summary

Observations Low cost to treat BOD5, TSS, and Ammonia-N

High cost to treat Total-P

Previously overcharging for BOD5 and TSS

Parameter Previous

Surcharge Rate $/lb

Updated Surcharge Rate

$/lb

BOD5 0.50 0.11

TSS 0.50 0.22

Total-P -- 4.43

Ammonia-N -- 0.22

Example SAL/Surcharge Revenue

Allocated Flow = 250,000 mgd

Surcharge Rate = $0.20 /lb

Extra-Strength BOD5 Surcharge – Smith Foods

METROPOLITAN WWTP

$0

$10,000

$20,000

$30,000

$40,000

0 500 1,000 1,500 2,000 2,500

Mo

nth

ly C

har

ge

Discharge Concentration, mg/L

CS

AL

CL

CL

LIM

CT

HR

ES

H

CB

KG

D

Perspective

SALs can release captive loading Still protect against pass-through and interference

Promote local economy/jobs by assisting SIUs with special needs

Surcharges combined with SALs can enhance revenues Use SAL as basis for surcharge (i.e., “subcontracting”

portion of treatment capacity)

Important to have accurate and up-to-date MAHLs/MAILs and surcharge rates

Questions & Discussion

Michigan Residents Are Stewards for

20% of the Earth’s Usable Fresh Water

NASA

Fishbeck, Thompson, Carr & Huber, Inc.

Thank You!