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Iowa City Wastewater Expansion

Planning for Nutrients and Flood

Mitigation

Candice Bark, P.E., Jay Brady, P.E.

March 20, 2012

Project Overview

• Iowa City has two plants – North and South

• Older North Plant was flooded in 2008

• South Plant needs to be expanded to allow

decommissioning of the North Plant and for

future city growth

• Economic Development Administration (EDA)

and State of Iowa grants along with City sales

option tax is funding the $40 million project

Consulting Team

Stanley Consultants

Brown and Caldwell

Iowa City, Iowa

Project Overview • City of Iowa City sewer system serves 70,000

people. City population is 69,000 people.

• Major contributors:

– Proctor and Gamble (Health Care Products)

– University of Iowa (31,000 students and major

research institution,

– University of Iowa Hospitals and Clinics

• Major economic center in eastern Iowa

NORTH WWTP

SOUTH WWTP

Iowa River

Napolean Park

Lift Station

North Plant Overview

• Trickling filter plant – parts stem from 1935

• Raw sludge pumped to South Plant

• Location adjacent to city downtown

commercial district in flood prone area

• Long range planning from 1990s envisioned

migration of treatment to South Plant

North Plant – 2008 Flood

North Plant – 2008 Flood

North Plant – 2008 Flood

Napolean Park Lift Station

South Plant

Existing South Plant Design Flows

and Loads

Avg Max

Month

Max Day PHWW

Flow (mgd) 6 10 25 60

BOD5 (lb/d) 16,554

TSS (lb/d) 17,000

TKN (lb/d) 2,940

Existing Combined North and South

Plant Flows and Loads

Avg Max

Month

Max Day PHWW

Flow (mgd) 8.0 18.6 33.1 44.9

BOD5 (lb/d) 21,643

TSS (lb/d) 22,075

TKN (lb/d) 4,665

2025 Design Flows and Loads

Avg Max

Month

Max Day PHWW

Flow (mgd) 10 24.2 43/30 62/30

BOD5 (lb/d) 32,658

TSS (lb/d) 34,385

TKN (lb/d) 6,311

Design WLA

Pollutant Monthly Limit (lb/d) Max Day (lb/d)

CBOD5 25 mg/l 40 mg/l (7-day)

TSS 30 mg/l 45 mg/l (7-day)

NH3N Avg Max Avg Max

Month mg/l mg/l lb/d lb/d

January 12.4 16.6 2,857 4,111

February 14.1 15.8 3,234 3,877

March 6.4 15.9 1,470 3,952

April 4.6 16.6 1,060 4,192

May 3.9 16.1 905 4,051

June 2.7 15.3 620 3,181

Design WLA - NH3N

NH3N Avg Max Avg Max

Month mg/l mg/l lb/d lb/d

July 2.8 18.6 633 2,560

August 2.5 17.1 577 2,709

September 3.0 17.6 700 2,933

October 6.4 16.7 1,476 4,200

November 7.9 15.6 1,825 3,923

December 9.3 17.0 2,145 4,275

Why Look at Nutrient Removal for Iowa

City?

Existing process already allows partial dentrification

Use of nitrate in anoxic selector minimizes filaments

and reduces oxygen use

Anti-Degradation Analysis Pollutants of Concern

include Nitrogen and Phosphorus

High Potential for future nutrient limits

Planning Challenge: Nutrient Limits

not Set

Potential Total Nitrogen: <3 to 10 mg/l

Potential Total Phosphorus: 0.1 to 1 mg/l

Nutrient policy is being developed

Implementation likely in 5 years

Planning Effluent Quality

Parameter Base case Future

Phosphorus 1.0 mg/L 0.1 or 0.3 mg/L

Ammonia Current mass

loadings

Current mass loadings or

mussel toxicity

Total N 12 mg/l 5 or 10 mg/L

Phosphorus Removal

Two Main Approaches

Biological P Removal using P accumulating

organisms

Chemical Removal with iron salts, alum, or lime

Biological Phosphorus Removal

Consistent Removal to 1 mg/l Possible with adequate VFAs, COD, and Influent P

Phosphorus Removal Below

1 mg/l by Chemical Feed

0.5 to 1 mg/l: Chemical Feed with Filtration

O.1 to 0.5 mg/l: Chemical Feed with Flocculating

Clarifiers and Filtration or Membrane Separation

Filtration

Low Level Phosphorus Removal

Technologies

FeCL3

Filter

Membrane

FeCl3FeCl3

PolymerPolymer

AlumAlum

AlumAlum

Clark County

BioP

Rock Creek

AlumAlum

Alum

Alum

AlumAlum

AlumAlumAlum

Blue Plains

CARBONFeCl3 FeSO4

CARBONCARBONFeCl3FeCl3 FeSO4FeSO4

Filter

Low Level Phosphorus Removal

Technologies

Tertiary sedimentation with

flocculation

BioP Alum

Polymer

Waste Sludge

to Sewer

BioP AlumAlum

PolymerPolymer

Waste Sludge

to Sewer

Iowa Hill

FeCl3

FeCl3

BioP

FeCl3FeCl3

FeCl3FeCl3

BioP

FeCl3

BioP

FeCl3FeCl3

BioP

F Wayne Hill

Cauley Creek

Filter

Low Level Phosphorus Removal

Technologies

Ballasted Sedimentation

•Densadeg/Actiflo

Low Level Phosphorus Removal

Technologies

BioP Alum

Polymer

Waste Sludge

to Sewer

BioP AlumAlum

PolymerPolymer

Waste Sludge

to Sewer

Iowa Hill

FeCl3

FeCl3

BioP

FeCl3FeCl3

FeCl3FeCl3

BioP

FeCl3

BioP

FeCl3FeCl3

BioP

F Wayne Hill

Cauley Creek

Membranes

•MBR, post-clarifiers/filters

Others :CoMag; BluePRO,

Total Nitrogen Removal

Total Nitrogen = NH3N + NO3 + Org N

1st Step Nitrification: Biological Conversion of NH3N

to NO3

2nd Step Denitrification: Biological Conversion of

NO3 to NOx/N2

Nitrification Process Implications

• High Oxygen Requirement:

– 4.6 lbs O2 per lb of NH3N

• Consumes Alkalinity

– 7.14 lb Alkalinity per lb NH3N

• Nitrifier Sensitivities

Activated Sludge Plant Alternatives

– Add aeration tanks (AT) to extend SRT √

– Bioaugmentation √

– Integrated Fixed Film Activated Sludge (IFAS) √

– Chemically enhanced primary treatment (CEPT)√

Nitrification – Ammonia removal

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Denitrification Process Implications

• Use of NO3 as electron donor can reduce O2

use by up to 25 percent

• Denitrification Process yields alkalinity

– 3.57 lb Alkalinity per lb NO3

• Tail End or 2nd Stage Denitrification generally

needs supplemental carbon – methonal or

ethanol

Combined N & P Flow Schemes

A2O/Phoredox

5-Stage Bardenpho

Combined N & P Flow Schemes

Separate Stage Denitrification with

External Carbon

36

RETURN ACTIVATED SLUDGE

ORGANIC

CARBON

AEROBIC ANOXIC AEROBIC CLARIFIER CLARIFIER

RETURN SLUDGE

Dentrification

Activated sludge

Deep Bed

filtration

Biologically

activated filters

(Biostyr, Biofor)

Whole Plant BioWin Model

Zone 1

Digesters

FSTPST

Zone 2

Aeration BasinsEffluent

RDT

Belt Press

EQ Basins

Dewatered Cake

South Influent

Digester

North Plant Solids

Solids EQ

Ferric

Aeration Basins

Selected Alternative: BAR/MLE

Birth of the BAR process: Need for High

Rate Nitrification: Constrained Sites

Appleton, WI

(Originator: Parker at Brown and

Caldwell)

Prague, Czech Republic

(Originator: Wanner at

Prague Institute)

The BAR Process

4

0

CLARIFIER

RETURN ACTIVATED SLUDGE

PRIMARY

EFFLUENT

EQUALIZED AMMONIA

LADEN FILTRATE

FROM DEWATERING

Pros

•Well proven

•Not “commercial”

•Reduced Ammonia Loading to

Main Process

•Continual Nitrifier Seeding of

Main Process

•Through bioaugmentation

mainstream tank size reduced

Con

•Alkalinity supplementation

unless stopping at nitrite in N/DN

plants

•High rate designs do not

produce lowest effluent

ammonia levels

Bioaugmentation

R = Reaeration or

Regeneration

Biosolids

Storage

BAR Addition/ Additional Cells in

Aeration Basin

Additional Blower Capacity

Questions/Discussion