Upgrading Odor Control – and a Plant – in a Shoreline CommunityRichard J. Pope PE, BCEE, Hazen and SawyerThomas J. Lauro PE, Westchester County Department of Environmental FacilitiesFebruary 9, 2017

2

• Lot of Technologies/choices– How to decide?– Vendor claims– Cost-effective

• New Installation– Straightforward

• Retrofit– Maintaining operations CRITICAL

Choosing Odor Control Technologies

• New York– Westchester County– Long Island Sound shore

• Imbedded in suburban community– Residences– Park– Private High School– Potential new

• residential development

4

New Rochelle WWTP

Aerial View of Plant

New Rochelle Wastewater Treatment Plant

• Initial Primary Plant – 1955• Pure O₂ Activated Sludge 1979• New Permit Limits - 2005

– Increased Flow from 13.2 to 20.6 mgd

– Avg TN - 4 mg/l– Cl₂ : 2.0 to 0.5 mg/l

Plant History

• Headworks improvements• Nutrient removal• Enhance odor control

– Reuse/Replace/Additional• UV Disinfection• Current Upgrade $250 million

7

Plant Upgrade

Goal: Maintain “Good Neighbor” status

• Mist Scrubbers– Sludge Processing Bldg– Gravity Thickeners– Sludge Storage Tanks– Truck Load Out

Existing Odor Control at Start of Project

• What are regulatory requirements?• Where are the odors/emissions?• How strong are they?• Does odor impact off-site?• How to mitigate odors?• What air permits are needed?• Will it work?

9

Odor Control ChallengeSeveral Steps:

• NY State Air Regulations– Quality of Life– AAQS for H₂S

• 10 ppb - One hour average• Beyond fence line

– Air Guide 1• Air Toxics• SGC/AGC

10

Step 1 – What are Regulatory Requirements

• Westchester County Permit Program– DOH implements– Construct/Operate permits– Demonstrate compliance

11

Step 1 – What are Regulatory Requirements

Regulations provided road map for Odor Master Plan

• Conducted odor investigation– Multi-day survey– All unit operations– Existing odor control

• Mist Wet Scrubbers– Plant Records

• Influent WW VOCs

12

Step 2 – Where are Odor/ Emissions & How Strong are They?

• Focus on H₂S• Reduced sulfur compounds• CO₂• Odor Parameters

13

Parameters Evaluated

• Odor Strength– Detection Threshold– Recognition Threshold– EN 13725-2003

• Odor Intensity• Hedonic Tone

14

Odor Parameters

• Isolation Flux Chamber– Emission rates

• Evacuation Chamber• Tedlar plastic bags• October sampling time

15

Collecting Samples

Flux Chamber – EPA Sponsored

24"

Plexiglas Dome

SS/Aluminum cylinder

Floatation device

Water surface

Flexible tubing vent

To thermometer

To sampling device

To pressure gauge

Rope to secure Chamber18"

Flux Chamber

17

18

Location Hydrogen Sulfide (ppmv)

D/T (odor units/m3)

Influent Wet Well

0.262 0.52 3,600 3,800

PSTs – Mid Tank

0.183 0.350 1,625 2,600

PSTs – Eff. Launder

3.47 5.80 3,750 5,200

Gravity Thickener

0.987 1.2 3,100 4,800

FST-Mid Tank

0.003 0.003 70 120

FST-Effluent Launder

0.017 0.03 370 610

Sample Results

• Reduced Sulfur Compounds– Carbonyl sulfide– Methyl mercaptan– Dimethyl sulfide– PSTs < 0.01 ppmv– Sludge Processing Bldg < 0.02 ppmv

• Carbon Dioxide– Sludge Processing Bldg = 450 ppmv– Gravity Thickener = 420 ppmv

Sample Results

Parameter Headworks PSTs/SludgeAir Flow Rate (scfm) 18,000 75,000Hydrogen Sulfide, Avg/Max,ppmv

2/5 2/10

Carbon Dioxide, ppmv na 550Organic Reduced Sulfur Compounds, (ppmv)

0.25 0.5

Temperature, ° F 50 na

Odor Control Systems Design Basis

• Headworks Building• Primary Clarifiers (PCs) &

Channels• Solids Processing Building (SPB)• Gravity Thickening Tanks (GTT)• Solids Storage Tanks (SST)• Truck Load Out

22

Plant Odor Sources – Data Based

• TOXCHEM+– Volatile Organic Compounds (VOCs)– Plant simulation– Physical components– Operational components

• WW VOC conc’s – INPUT– Plant recorded inf. data

• Estimates emissions– Rates (Mass/Time)

• at each process unit

23

Estimating Plant Emissions

• Air dispersion model– AERMOD– Odor sampling & TOXCHEM+ data

• Input emission rates• Odor sources

– ID in sampling program• Determine

– Who needs control?– How much?

24

Step 3 – Do Odors Impact Off-Site?

• Plant processes needing control:– Currently controlled

• SST, GTT, SPB, Truck Load Out– New sources

• PC and Channels (influent & Effluent)• Headworks Building

25

AERMOD Results

• Centralized control strategy– Two stations recommended– First :

• Headworks Building– Second :

• PCs and Channels• SST• GTT• SPB• Truck Load Out 26

AERMOD Results

• Odor Control technology review– Wet packed tower scrubber– Biofilter– Biotrickling filter– Activated sludge– Activated carbon– Ionization– Combinations

27

Step 4 – How to Mitigate Odors?

Technologies selected to fit two station, centralized odor control strategy.

• Headworks Building– Biofilter

• Remaining sources– Packed Tower Wet Scrubbers

28

Selected Technolgies

Wet ScrubbersBiofilters

• Very limited space• Operating flexibility• Owners experience with

technology• Plant staff familiarity with

chemicals• CO₂ levels low

29

Why Wet Scrubbing?

• Cost-effective• Right fit• Addresses H₂S & RSC• CO₂ no issue• Low maintenance

30

Why Biofilter?

First biofilter in Westchester County!

• “The Good, the (Not so Good) Bad, & the Ugly”

• Work with Owner & DOH– Educate– Demonstrate

• Site Visit

31

Westchester’s First Biofilter

Change does not always come easy!

• Existing odor control– Two mist wet scrubbers– To Be Replaced!

• New odor control– Two packed tower wet

scrubbers– Install– MOPO

32

Step 5 – How to Install with MOPO

Challenge: Continue odor control while installing new system!

• Develop Strategy• Coordinate

– Engineer/Contractor/Owner• Both systems

– Designed to accept full flow

33

Maintaining Odor Control

• MOPO Strategy– Demo 1 existing mist tower

• Operate second– Install 1 new tower

• Performance test/operate• Connect duct

– Demo 2nd existing mist tower– Install 2nd new tower

• Performance test/operate• Connect duct

34

Maintaining Odor Cont

Plant Biofilters

35

Two of the three biofilter units.Biofiltermedia surface under the cover.

Parameter ValueAir Flow Rate, cfm 18,000

Hydrogen Sulfide Removal w/ Inlet Conc> 10 ppmv

99%

Maximum Exhaust Conc w/ Inlet < 10 ppmv

0.1

Number of Cells 3Contact Time: 2 and 3 Cells On-Line, sec

45/60

Superficial Velocity: 2 and 3 Cells Online, fpm

7/10

Vendor EnvirogenMedia Depth, ft 5Inorganic (ScorFil-High Silica)/Organic (Vamfil-Wood/Bark), ft

2/3

Minimum Inlet Air Temp, deg F 55Makeup Water Rate/Plant Eff, gpm 5

Biofilter Design Parameters

Headworks Biofilter Process Flow Diagram

Biofilters

Acoustical Enclosure and Biofilter Fans

Fans Acoustical enclosure

Heat Exchanger

Humidification Chamber

Spray Nozzle Assembly

Perforated Floor Plates

Biofilter Performance Test

Biofilter Performance Test

Wet Scrubbing Process

Packed Tower Wet Scrubber System

Chemical Feed and Recirculation Pumps

Water Softener, H2S Measurement Equipment

Wet Scrubbers Performance Test

Wet Scrubber No. 1 Performance Test

Wet Scrubber No. 2 Performance Test

• NYState DEC– Part 201 permit

• Certificate of Compliance with all applicable air regulations

• Westchester County DOH– Permits to Construct/Operate

53

Step 6 – What Air Permits Are Needed?

• Systems installed• Passed performance tests• Obtained permits• Operating/Complying with limits

54

Step 7 – Will it Work?

Being a “Good Neighbor” is doable!!!

Month System Avg. H2S Exhaust (ppmv)

April Biofilter 0.001May Biofilter 0.003April Wet

Scrubber0.011

May Wet Scrubber

0.014

Recent Data

56

Speaker Contact Information

Dick PopeHazen and SawyerVice President –

Odor Services LeaderDirect: 212-539-7107Cell: 914-450-6735rpope@hazenandsawyer.com

57