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Ventilation, Odor and Corrosion Control for Large Diameter Collection Systems

September 6, 2012

James P. Pistilli, P.E.

Chief Engineer - Wastewater Services

Office of Macomb County Public Works Commissioner

James Joyce, P.E.

Senior Technical Director

V&A Consulting Engineers

Organization

� Introduction

�Sampling and Monitoring Program

�Modeling

Sulfide Modeling

Corrosion Modeling

Ventilation Modeling

�Recommendations

�Fan Testing and Results

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OMID-MID System

Work Tasks

� Sample wastewater and collect data on sulfide generation areas, hydrogen sulfide gas concentrations and headspace air pressure

� Perform sulfide modeling to identify problem generation areas, optimize the sampling effort and estimate corrosion rates

� Identify “hot spots” where odor and corrosion is severe or could become severe

� Evaluate technologies to control sulfide generation, reduce corrosion and control odor release

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SAMPLINGSAMPLING

Sampling and Monitoring Program

� Preliminary screening of dissolved sulfide and headspace H2S to identify likely problem areas

� Continuous H2S monitoring using OdaLog dataloggers

� Five days of grab sampling at screened locations to measure wastewater sulfide, pH, ORP, temperature

� Selected samples for BOD, sulfate

� Continuous monitoring of headspace air pressure

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Monitoring Program

H2S Gas Datalogger Output

Field Analysis of Sulfide Samples

Preliminary Screening of Metering Stations

�Site inspection and man-entry of major metering stations

�Concrete pH

�Headspace H2S

�Wastewater sulfide, pH, ORP, temperature

�Reduced sampling locations to ~25 for more detailed monitoring

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Conclusions from Sulfide Data

� Majority of sulfide is generated in Lakeshore Interceptor, Clintondale FM, and Romeo Arm along 15-Mile Rd

� Some sulfide in upstream end of Garfield Arm (MA-S-2) but most is lost due to oxidation, reactions with concrete, dilution

� Relatively little sulfide in Oakland and Avon Arms

� About half of the sulfide entering the Edison Corridor is formed in Lakeshore Interceptor and Clintondale Force Main. Remainder formed in deposits along Romeo Arm

Mass Balance of Sulfide in Oakland-Macomb Interceptor System

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INSPECTION

INSPECTION PROCEDURE

�ENTER METER VAULTS

�TAKE SURFACE pH

�PROBE SURFACES

�ESTIMATE SURFACE LOSS

�PHOTOGRAPH CORROSION

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OC-S-2 Influent Sewer

RC-S-1 Meter Vault

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ST-S-1 Meter Vault

ST-S-3 Meter Vault

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ST-S-3 Dropshaft

Illustrates the effect of ventilation dynamics

CT-S-3 Meter Vault Corrosion

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CT-S-3 Effluent Corrosion

FR-S-1 No Corrosion

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ST-S-4 Shaft Corrosion

Note Missing Steps

VENTILATION

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NATURAL SEWER VENTILATION

FRICTION DRAG BETWEEN THE MOVING WATER AND THE SEWER AIR CAUSES THE AIR TO MOVE DOWNSTREAM AT A FRACTION OF THE VELOCITY OF THE WATER

DROPSHAFT VENTILATION

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VENTILATION OF METER VAULTS

MODELING

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Corrosion Modeling

�PREDICTS FUTURE CORROSION RATES

�ALLOWS CORROSION FORECASTING

�HELPS TARGET WORST CORROSION AREAS

CORROSION MODELING

Sample Location S2-

Conc. Flux

(mg/l) (g/m2-hr) in/yr in/100 yrs in/yr in/100 yrs

Lakeshore Int

PCI-42A CH-S-2 0.6 0.0048 0.0020 0.20 0.0274 2.74

PCI-14 HR-S-2 1.1 0.0032 0.0014 0.14 0.0183 1.83

PCI-13 Clintondale PS 1.4 0.0046 0.0020 0.20 0.0267 2.67

Garfield/Romeo

PCI-45 MA-S-2 0.4 0.0034 0.0015 0.15 0.0196 1.96

18 Mile

PCI-25 ST-S-6 0.4 0.0050 0.0021 0.21 0.0290 2.90

Romeo Arm/15 Mile

PCI-12A W of Garfield 1.0 0.0052 0.0022 0.22 0.0297 2.97

PCI-12A MC-S-1 2.5 0.0133 0.0057 0.57 0.0764 7.64

Oakland Arm

PCI-8 ST-S-3/ST-S-2 0.4 0.0041 0.0017 0.17 0.0234 2.34

Edison Corridor

PCI-7 15 Mile 0.5 0.0052 0.0022 0.22 0.0298 2.98

PCI-5 Toepfer 0.5 0.0053 0.0023 0.23 0.0304 3.04

Cavg Cmax

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Ventilation Modeling

�Predicts Airflow in Sewers and Tunnels

�Predicts Areas of Positive Pressure and Odor Release

�Allows Sizing of Air Treatment Facilities at Specific Locations

VENTILATION MODELING

FRICTION DRAG AIRFLOW MODELING TO PREVENT PRESSURIZATION

Flow Diameter Slope d/D

(cfs) (in.) Actual Worst Case

Lakeshore Int

PCI-42A 6.0 42 0.040% 0.39 320 336

PCI-14 10.0 132 0.020% 0.13 1614 5042

PCI-13 14.0 132 0.020% 0.15 1983 5042

15 Mile Int

PCI-15C 1 14.0 60 0.508% 0.19 1565 3104

PCI-15C 2 14.0 60 0.158% 0.26 1181 1731

PCI-15C 3 14.0 60 0.034% 0.38 766 803

PCI-15C 4 14.0 60 0.080% 0.31 981 1232

PCI-15C 5 14.0 60 0.109% 0.28 1080 1438

Garfield/Romeo

PCI-45 15.0 72 0.063% 0.26 1252 1777

18 Mile

PCI-25 6.0 42 0.150% 0.28 475 652

Garfield/Romeo

PCI-24 21.0 108 0.048% 0.19 2313 4574

PCI-12A 1 26.0 126 0.023% 0.21 2745 4776

Romeo Arm/15 Mile

PCI-12A 2 40.0 132 0.021% 0.25 3509 5167

PCI-37 43.0 96 0.021% 0.41 2156 2210

PCI-12A 3 43.0 132 0.021% 0.26 3634 5167

Oakland Arm

PCI-10B 45.0 96 0.220% 0.23 4335 7153

PCI-10A 45.0 96 0.220% 0.23 4335 7153

Avon Arm

PCI-11B 1 5.0 36 0.250% 0.27 406 558

PCI-11B 2 5.0 36 0.100% 0.34 308 353

PCI-11B 3 5.0 48 0.100% 0.23 477 760

PCI-11B 4 5.0 36 0.380% 0.24 451 687

PCI-11B 5 5.0 36 0.100% 0.34 308 353

PCI-11B 6 5.0 42 0.120% 0.27 411 583

PCI-11B 7 5.0 48 0.060% 0.26 415 588

PCI-11B 8 5.0 48 0.060% 0.26 415 588

PCI-11B 9 5.0 48 0.120% 0.22 501 832

PCI-11B 10 5.0 42 0.120% 0.27 411 583

PCI-11B 11 5.0 48 0.060% 0.26 415 588

Oakland Arm

PCI-9 50.0 105 0.160% 0.23 4712 7747

PCI-8 62.0 114 0.060% 0.29 4573 5907

Edison Corridor

PCI-7 107.0 153 0.068% 0.25 9363 13783

PCI-6 110.0 153 0.068% 0.26 9392 13783

PCI-5 112.0 153 0.068% 0.26 9410 13783

Airflow (cfm)

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RECOMMENDATIONS

Sulfide Control Evaluation

� Major target areas –♦ Lakeshore Interceptor

♦ Clintondale FM

♦ Romeo Arm along 15-Mile Rd

� Flow in Lakeshore–Clintondale system is approx. 14 cfs

� Flow in Romeo Arm is 43 cfs

� Chemical treatment of Lakeshore–Clintondale flow is economically viable

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Screened Chemical Sulfide Control Options

Chemical Advantages Disadvantages

Iron Salts Economical, versatile Price fluctuations. Cannot reduce sulfide below 0.3 mg/L

Nitrate Safe to handle, effective High cost

Magnesium hydroxide Safe to handle, effective Not economical for sulfide levels <5 mg/L

Iron-Peroxide (proprietary)

Turn-key operation Higher unit cost reflects maintenance, monitoring

Lakeshore/Clintondale Sulfide Control

�Chemical feed station at upstream location – $125,000

�Chemical dosing and O&M – $80,000/yr

�Conduct minimum 30-day demonstration with ferrous chloride

�Alternative: complete turn-key operation with iron-peroxide process or iron alone.

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Ferrous Chloride Dosing Facility

� Metering pumps and timers to vary dosage

� Secondary containment necessary

� Corrosive chemical

Romeo Arm Sulfide Control

�Monitor solids build-up in interceptor

�Remove debris and solids at regular intervals

�Continue to monitor sulfide levels in wastewater

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TYPICAL DROPSHAFT CORROSION

DROPSHAFT/TUNNEL PROTECTION

TUNNEL

DIAMETER

MIN.

PROTECTED

DISTANCE

MIN.

PROTECTED

DISTANCE

MIN.

PROTECTED

DISTANCE

MIN.

PROTECTED

DISTANCE

(in)(Diameters

Downstream)

(Feet

Downstream)

(Diameters

Upstream)

(Feet

Upstream)

60 80 400 6 30

72 65 390 5 30

84 55 385 5 35

96 45 360 5 40

108 40 360 5 45

120 35 350 4 40

132 30 330 4 44

144 25 300 4 48

156 20 260 4 52

168 20 280 4 56

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METER VENTILATION

SHAFT EDUCTION DOMINATES CAUSING NO METER CHAMBER CORROSION

METER VENTILATION

TUNNEL PRESSURE DOMINATES AND METER CHAMBER CORRODES

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RECOMMENDED VENTILATION

� Lower Lakeshore Interceptor (between HR-S-2 and Clintondale PS) (5,000 cfm)

� Mid-Garfield Arm (around 18 Mile Road) (5,000 cfm0

� Mid-Oakland Arm (between UT-S-1 and ST-S-1 (8,000 cfm)

� Near or just downstream of Garfield at 15 Mile road (5,000 cfm)

� Edison Corridor at the upstream end of PCI-7 (15,000 cfm)

Recommended Air Treatment

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EXAMPLE VENTILATION BIOFILTER

RECOMMENDED VENTILATION

�Maintain a negative pressure in interceptors

�Reduce H2S concentration in interceptors

�Dry portions of the pipe to reduce corrosion

�Reverse ventilation air direction to prevent meter corrosion

�Control odor releases from interceptors

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VENTILATION COSTS

ITEM 5000 CFM 8000 CFM 15000 CFM

In-Ground Organic Media

Biofilter $250,000 $400,000 $750,000

Fan $9,000 $14,000 $24,000

Site Improvements $15,000 $15,000 $15,000

Utilities $5,000 $5,000 $5,000

Ductwork $5,000 $7,500 $10,000

SUBTOTAL $284,000 $441,500 $804,000

Engineering and

Contingencies @ 20% $56,800 $88,300 $160,800

TOTAL CAPITAL COST $340,800 $529,800 $964,800

Electricity $11,000 $15,000 $27,000

Water $500 $750 $1,400

Maitenance $6,000 $7,000 $8,000

TOTAL O&M COST $17,500 $22,750 $36,400

Media Replacement

(~Every 5 years) $35,000 $55,000 $100,000

CAPITAL COST

O&M COST

PERIODIC COSTS

RECOMMENDATIONS SUMMARY

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METER CHAMBER REHABILITATION

SUMMARY RECOMMENDATIONS + COSTS

RECOMMENDATION LOCATIONINTERCEPTOR

SYSTEMUNIT COST

CAPITAL

COST

ANNUAL

O&M COST

Chemical Addition (Ferrous

Chloride)

Lakeshore

InterceptorMID --- $125,000 $80,600

Magnesium Hydroxide

(Corrosion Protection)

Meter

ChambersOMID-MID $0.75/ft2 --- ---

5,000 cfm In-Ground

Organic Media Biofilter

Lakeshore

InterceptorMID --- $340,800 $17,500

5,000 cfm In-Ground

Organic Media BiofilterGarfield Arm MID --- $340,800 $17,500

8,000 cfm In-Ground

Organic Media Biofilter

Oakland

ArmOMID --- $529,800 $22,760

5,000 cfm In-Ground

Organic Media Biofilter

Garfield @

15 MileMID --- $340,800 $17,500

15,000 cfm In-Ground

Organic Media Biofilter

Edison

CorridorOMID --- $964,800 $36,400

CIPP Rehab

Meter

Chamber

Dropshafts

OMID-MID $30/ft2 --- ---

Spiral Wound Lining RehabMain

InterceptorsOMID-MID $35/ft2 --- ---

PHASE 1

PHASE 2

PHASE 3

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FAN TESTING

Supplemental Fan Testing

�Fan Testing was recommended to identify the actual performance of ventilation and odor treatment facilities before sizing

�Fan Testing was performed at two locations in the MID system♦ 15 Mile at Garfield Road

♦ Clintondale Pump Station at the end of the Lakeshore Interceptor

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Purpose

�Proper Sizing of Ventilation is Difficult♦ Fan testing recommended in complicated systems

♦ Provides quantitative confirmation of calculations

�Fan testing provides basis of design:♦ Air extraction point

♦ Most Economical airflow extraction volume

�Simulates the depressurization effects of a proposed VPOC facility

Methodology

� Air extracted at potential OCF site♦ Varying airflow to determine

optimum capacity

� Pressure monitoring before, during, and after test

� Data provides basis to determine the zone of influence the OCF will have

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Pressure Monitoring

�Pressure differential between sewer headspace and atmosphere

�Differential pressure reflects sewer ventilation dynamics

�Monitors record pressure in the range of +/- 2.0 inH2O

Instrumentation

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MID Case Study

15 Mile and Garfield Road

�Downstream of known odor complaints

�11’ Diameter Interceptor

�Upstream of Diameter Constriction

EQUIPMENT SET-UP

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Methodology

� Two 12,500 cfm Fans @ 8” S.P.♦ Speed controlled using VFDs

� Testing Conducted at Four Speeds♦ Varied every 30 minutes to 1

hour

♦ 50% - 100% Speed

� Airflow Measured Using Hotwire Anemometer

Clinton Drive PS Fan Test Setup

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Fan Test Setup

Fan Test Setup

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Fan Test Results - Garfield

Fan Test Results - Clintondale PS

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QUESTIONS?

OMID-MID SAMPLING LOCATIONS

OMID MID

NORTH GRATIOT INTERCEPTOR

CH-S-1

OC-S-2 CH-S-2

RC-S-2 LAKESHORE INTERCEPTOR

UT-S-1 CH-S-5

ST-S-1 HR-S-1

ST-S-3 HR-S-2

35705 Dodge Park HR-S-3

ST-S-2 CT-S-2

Clintondale PS

15 MILE ROAD INTERCEPTOR

RC-S-1 CT-S-4

SY-S-1 GARFIELD ARM

MA-S-2

SY-S-3

Edison Corr at 15 Mile ST-S-6

Edison Corr at 14 Mile CT-S-3

ST-S-4 ROMEO ARM

Edison Corr at 10 Mile CT-S-1

Edison Corr at Toepfer FR-S-1

ST-S-5

MC-S-1

OAKLAND ARM

AVON ARM

EDISON CORRIDOR