dc water pumping stations and odor controlconcentrations during the may and july sampling events...
TRANSCRIPT
OBG PRESENTS:
Good Odor Treatment Makes Good NeighborsEvaluation, Piloting, and Design Basis for Wastewater Pumping Stations9/2/16 9-9:30AM Bill Meinert, OBG Laura Knox, DC Water
DC Water Pumping Stations and Odor Control
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Poplar Point Pump Station
New Design Approach
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1,200 LF of 60" influent sewer
55 MGD pump station
Catenary screens
LEED Silver
Carbon odor control
Designed for unmanned, remote operation
3D design tools
15,000-30,000 cfm,99% H2S removal
Main Pump Station
Renovation / Upgrade
Six storm pumps, 400 MGD capacity
Four sanitary pumps
Low area pump station, 10 MGD
Influent mechanical screening
Trunk sewer, inflatable dams, deep tunnel
Odor control …4
20,000 cfm99% H2S removal
O StreetPump Station
Renovation / Upgrade
Six storm pumps
Four sanitary pumps, 45 MGD capacity
Proposed development
Influent mechanical screenings; wash, compact
Trunk sewer, inflatable dams
Odor control …5
10,000 cfm99% H2S removal
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Proposed Development A Higher Standard
Odor Control Evaluation
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Odor Control Evaluation Overview
Field Sampling and Analysis (May and July 2015)• Spring and Summer surveys
NFPA 820 Study (August 2015)• Review existing ventilation• Identify areas with insufficient ventilation for classification
Evaluation of Feasible Odor Control Technologies (May – October 2015)
• Review suitability for Main, O Street, and low area PSs • Identify 2 appropriate technologies for pilot testing
Pilot Test (data collection 9/2/15 to 10/14/15)• Technologies: adsorption with engineered, carbon-based media,
and photoionization• Source: influent gate valve chamber of the Main PS
Evaluations of Solids Removal Operations (November 2015)• Main PS• O Street PS
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Field Sampling
Walkthrough in April 2015
Representative sampling points• 29 locations at Main PS• 18 locations at O Street PS
First survey 2nd week of May 2015 • Spring, intended cooler temps
Second survey 3rd week of July 2015 • Summer, intended hotter weather
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Jerome 631X Analyzer H2S Surveys - Main PS
Location Average H2S Concentration (ppmv) Maximum H2S Concentration (ppmv)
Influent Gate Valve Chamber 2.9 12Sump Room (former LAPS, at double doors) 1.5 4.7Low Area PS (open sewer) 0.166 0.49Lower Screen Room 0.163 0.9Siphon Chamber Room 0.105 0.63Upper Screen Room 0.057 0.34Sanitary Wet Well Gallery 0.014 0.14Main Pump Room 0.010 0.22Exterior Storm Chamber Grates (west side) 0.002 0.016
Jerome 631X Analyzer H2S Surveys - O Street PS
Location Average H2S Concentration (ppmv) Maximum H2S Concentration (ppmv)
Screen Room 0.104 0.61 (west)Inlet to odor control system 0.070 0.14Roof 0.011 0.12 (EF-15)Lower Pump Room 0.003 0.043 (west)Upper Pump Room 0.001 0.005 (west)Loading Dock 0.001 0.003
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OdaLog H2S Concentrations (ppmv)
Location May,Average
May,Peak
July,Average
July,Peak
Main PSInfluent Gate Valve Chamber 0.7 5.2 1.9 26.0Upper Screen Room 0.0 0.1 0.2 2.8Lower Screen Room 0.1 2.8 n/a n/aSiphon Chamber Room 0.0 0.1 0.0 1.2Low Area PS 0.0 1.7 2.0 20.3O Street PSScreen Room, at hoppers 0.0 1.6 0.0 0.4Screen Room, at front of screens 0.0 1.0 0.0 0.3
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Tedlar Bag Odor Analysis - Dilutions to Threshold (D/T)Location May JulyMain PSInfluent Gate Valve Chamber 2,200 14,000Upper Screen Room 850 390Lower Screen Room 1,500 1,100Siphon Chamber Room 3,400 3,300Low Area PS 360 970O Street PSScreen Room, at hoppers n/a 510Screen Room, at front of screens 3,200 110
Summa Canister Samples – RSCs and VOCs
▪ Composite 24-hour samples collected in Silonite-lined Summa vacuum canisters with time-released nozzles analyzed for reduced sulfur compounds (RSCs) and volatile organic compounds (VOCs)
▪ Results indicated low concentrations of various VOCs and the following RSCs: • Carbonyl sulfide (COS): 8.8 to 28 ppbv• Dimethyl sulfide (DMS): 11 to 12 ppbv• Dimethyl disulfide (DMDS): 8.1 to 44 ppbv
Sampling Survey Conclusions
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Concentrations during the May and July sampling events were relatively low
Hydrogen sulfide (H2S) and other compounds present, including dimethyl disulfide (DMDS)
Open wastewater surfaces contributed to odor concentrations
Dilution by increased ventilation reduced concentrations
The Main PS Influent Gate Valve Chamber was chosen for the pilot test, based on highest concentrations during surveys
Odor Control Technologies
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Strategies for Odor Management
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Characteristics of Odorous Compounds
Compound Formula Molecular Weight (g/mol)
Human Detection Limit (ppmv)
OdorDescription
Hydrogen sulfide H2S 34 0.0005 Rotten eggs
Methyl mercaptan CH3SH 48 0.0005 – 0.001 Rotten cabbage
Dimethyl sulfide (DMS) (CH3)2S 62 0.001 Decayed cabbage
Dimethyl disulfide (DMDS) C2H6S2 94 0.0022 Garlic-like
Carbonyl sulfide COS 60 0.055 Burnt rubber
Dilution and Dispersion
Fresh air supply at high exchange rate, for example 12 ACH
Release to atmosphere via tall discharge exhaust stack
Entrain fresh air while moving concentrated process air
Reduce concentrations to below detection limits
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Strategies for Odor Management
Physical Separation
Containment –isolation
Covers and enclosures, e.g. channel covers
Buffer zones
Chemical Addition
Masking
Neutralization
Chemical costs proportional to the
mass flow rate
Liquid-phase Treatment
Air, oxygen injection
Chemical oxidants
Vapor-phase Treatment
Technologies
Chemical scrubbers –chemical oxidation
Biofiltration –biological oxidation,
vs. chemical
Adsorption – activated carbon and related
media
Photoionization / photo catalytic
ionization
Recommendations for Pilot Testing
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Technology Selection
Activated carbon adsorption – best suited for low concentrations and medium air flow rates at Main and O Street
Photoionization – promising alternative
Biofiltration not selected (space, vulnerability to upsets)
Chemical scrubber not selected (higher concentrations and high airflow)
Treatment Units
Two configurations of engineered carbon-based adsorption media and photoionization treatment system
Side by side, same odor source
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Odor Control Pilot Test
19Odor Control Pilot Configuration
Dual Layer Carbon, Blend #1
(500 cfm) (40 fpm)
Dual Layer Carbon, Blend #2
(500 cfm)(40 fpm)
UV Photoionization + Carbon catalyst
(80 cfm) (25 fpm)
Low ppm OdaLogs
Influent(underground gate
valve chamber)
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Dual Layer Carbon, Blend #1
4’ dia. vessel, trailer mounted w/centrifugal fan
Base layer (20 cf; approx. 1.6 ft bed depth)
• PureAir Sulphasorb XL - high performance H2S adsorbing carbon
2nd layer (15 cf; approx. 1.2 ft bed depth)
• PureAir CPS12 Blend – 50/50 blend of high H2S capacity activated carbon and 12% potassium permanganate impregnated alumina, for adsorption, absorption, and oxidation of reduced sulfurs, VOCs
Dual Layer Carbon, Blend #2
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4’ dia. vessel, trailer mounted w/centrifugal fan
Initial configuration
• Triple blend for targeting DMDS removal • (36 cf; approx. 2.9 ft bed depth)
• PureAir 12 (same as in System #1)• PureAir AC-C coconut shell carbon• DMDS adsorbent - new material (“alumina based adsorbent
impregnated with iron chemistry for organic sulfur compounds”)
Modified configuration (last 2 weeks)
Base layer (17 cf; approx. 1.4 ft bed depth)
• PureAir Sulphasorb XL – high performance H2S adsorbing carbon
2nd layer (approx. 20 cf; approx. 1.6 ft bed depth)
• Triple blend - as listed above
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Neutralox unit with 2 ultraviolet light /catalyst modules in series preceded by a preliminary dust filter
Ultraviolet Photoionization + Carbon
Pilot Data Collection and Results
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Data collected for seven-week period, 9/2/15 to 10/14/15
H2S measured, intermittently with Jerome analyzer
and continuously with OdaLogs
Grab samples, weekly in Tedlar bags for odor analysis and
reduced sulfur analysis
Ozone measurements on the discharge of
Neutralox unit for a week
Pilot results odor evaluation memo
Design recommendations based on the pilot testing
Pilot Data Collection and Results
OdaLogs – H2S
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Pilot Data Collection and Results
Tedlar Bag Samples – Odor Analysis
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Pilot Odor Analysis Dilutions to Threshold (D/T)
Location Average Removal Efficiency Minimum Maximum
Influent 8,550 - 440 22,000
Dual Layer Carbon, Blend #1 Discharge 130 98.5% 60 180
Ultraviolet Photoionization + Carbon Discharge 80 99.1% 25 140
Dual Layer Carbon, Blend #2A Discharge 120 98.6% 65 180
Dual Layer Carbon, Blend #2B Discharge 70 99.2% 45 90
Pilot Data Collection and Results
Tedlar Bag Samples – Reduced Sulfurs
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Hydrogen Sulfide (H2S)
Influent H2S concentrations from 160 to 6,300 ppbv, and averaged 2,100 ppbv (2.1 ppmv)
Variations with differing conditions between sampling events, exhaust fan operation in the Chamber, bypass activities, wet weather influence (higher H2S in dry weather), etc.
Dual Layer Carbon, Blend #1 unit removed H2S to non-detect for 4 of 7 weeks, with 2 of 3 remaining achieving >99% removal
Ultraviolet Photoionization + Carbon unit had measurable H2S in the discharge for the first week but removed >99%
Dual Layer Carbon, Blend #2 removed H2S to non-detect for 6 of 7 weeks, with an outlier in Week 3
Pilot Data Collection and Results
Tedlar Bag Samples – Reduced Sulfurs
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Carbonyl Sulfide (COS)
Detected in influent, in discharge of PureAir #2
Increasing COS across the media bed led to reconfiguration, improved removal to non-detect
Carbon Disulfide (CS2)
Not detected, to trace in discharge samples (mainly PureAir #2 prior to reconfiguration)
Methyl Mercaptan (CH3SH)
Detected, successfully treated
Dimethyl Sulfide ((CH₃)₂S; DMS)
Not detected, to trace
Dimethyl Disulfide (C2H6S2; DMDS)
Anticipated, but not detected
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Pilot Conclusions and Recommendations
All three pilot treatment units performed well (averaged 99% removal efficiencies); declaration of a “winner” is dependent on a number of factors
Essentially equivalent outlet odor concentrations (all less than 150 D/T)
H2S loadings were low, most of the other odorous sulfur compounds were below detection limits
Recommended a two media system, PureAir#1 or equal, with a bed of high-H2S capacity media followed by a 50-50 blend polishing layer of 12% permanganate-impregnated alumina and virgin bituminous activated carbon
PureAir #2 contained an experimental media designed specifically for removing dimethyl disulfide, which can be generated in the media bed from the oxidation of methyl mercaptan. Because dimethyl disulfide was detected only once, the use of the experimental media was not justified.
Design Overview
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Review and Screening of Design Alternatives
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Suitability for installation in classified areas
Carbon-based media, constraints for Photoionization type
Configuration
PureAir Filtration Vertical Tube System (VTS), horizontal bed configuration
Photoionization would include connecting an array of modular (7,000-cfm) units
Air Flow Rates for Final Design – O Street PS
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Location Volume (cf) ACH Continuous “Normal” (cfm)
Temporary Emergency (cfm)
Screen Room 40,230Normal 12 8,050Emergency 24 16,100
Compactor Room (24x18x20) 8,640Normal 12 1,730Emergency 24 3,460
Former Scrubber Room 41,496Normal 12 8,300Emergency 24 16,600
Sanitary Wet Well 31,525Normal 12 6,310Emergency 24 12,620
Subtotal 121,891 24,390 48,780Stormwater Wet Well 115,500
Normal 12 23,100 23,100O STREET PS TOTALS 237,391 47,490 71,880
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Discharge Locations and Dispersion Modeling
Discharge Locations and Dispersion Modeling
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High discharge points are favorable – to allow natural air currents to draw away and dilute remaining odor constituent concentrations
Main PS – existing chimney; top of existing unused freight elevator shaft
O Street PS – top floor roof
Additional O.C. Design Considerations
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HVAC coordination, supply / exhaust changes, heat loss
Moisture / grease filters on odor system inlets
Corrosion resistant materials of construction: FRP, SS
Odor control ductwork – FRP recommended (acoustic)
Discharge stack “no loss” cap
Siphon vent carbon filter
Manhole insert scrubbers
HVAC intake carbon filters
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Performance Criteria
H2S removal efficiency
Treatment of reduced sulfurs and other compounds
Odor reduction to low dilutions-to-threshold
Be neighborly!
