PATIENT DOING ? MWEA L AB P RACTICES S EMINAR M AY 2013 Presented - - PowerPoint PPT Presentation

COLLECTION SYSTEM HEALTH – HOW IS THE

PATIENT DOING?

MWEA LAB PRACTICES SEMINAR – MAY 2013

Presented by: Carey Bond, PE

AGENDA

Brief History (In Time) - Collection Systems Collection System Components The Stakes Methods to Evaluate & Protect Real World Applications Questions

May 2013

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Stephen Hawking quotes: “It is all right to make mistakes; nothing is perfect because with perfection, we would not exist” “Life would be tragic if it weren't funny.”

HISTORY OF OUR COLLECTION SYSTEMS

 Early-Mid 1800’s – open sewers/gutters used to convey

waste in urban areas

 Mid-late 1800’s – first (combined) buried pipe systems

constructed in large cities (e.g. NYC, Chicago)

 Pipe materials initially used – brick, clay, iron, even wood

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HISTORY OF OUR

COLLECTION SYSTEM

 1930s-1970s - Improvements to sewer design &

management methods, including separate systems for storm (typ. straight to receiving water) & sanitary (conveyed to modern treatment facility)

 Currently 16,000+ sewer systems in the U.S.  Approx. 740,000 miles of public sewer & 500,000 miles

• f private laterals in the U.S.

 Modern materials & equipment:  RCP, PVC, DIP, HDPE  Directional drilling

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THE STAKES

Inadequate collection system protections

What’s at stake?

Typ. Collection System Value ≈ WWTP Value

Damage to the POTW Collection System

 Often unseen damage as components are buried/below

ground

 Interrupted service  Emergency repairs  Expensive & often unplanned costs  Replacement $0.4 to $0.6M/mile

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COLLECTION SYSTEM COMPONENTS

Gravity Sewers  Min. diameter 8” (Modern design standard)

 Materials: vitrified clay pipe –VCP (older),

reinforced concrete pipe-RCP, PVC, DIP

 Considerations: Flow, depth/surface loads,

corrosion potential, slope, groundwater table

Force Mains`  Min. diameter typically 4”  Materials: PVC, DIP, HDPE  Considerations: Flow, operating pressure/pressure

surge, abrasion/wear, corrosion, soil conditions

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COLLECTION SYSTEM COMPONENTS

Manholes/Structures  Min. diameter 4’

 Materials: pre-cast or cast-in-place concrete,

fiberglasss reinforced plastic (FRP)

 Considerations: Depth, #/size of connecting pipes,

access needed

Pump or Lift Stations  Types: submersible (most common), suction lift,

dry well/wet well

 Considerations: Flow, system pressure & velocity,

wet weather flows, solids, grit, owner preference

 Associated Components: valves – shut-off, check,

air release, electrical gear, emergency power

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May 2013

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Typical Submersible Lift Station

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Typical Suction Lift Station

THE STAKES

 Many Collection systems are in poor condition  ASCE 2013 Report Card gave national sewer infrastructure a grade of “ D+ ”  Know your collection system: 

Be familiar with your community’s master sewer system map, GIS version? Even better!! Request a copy.



Discuss with your IPP coordinator and DPW co-workers to gain insight on system specifics



Age – where are oldest components?



Identify long FMs, material types, high-strength input locations (typ. commercial and industrial customers,)



Corrosion prone segments – where are the customer odor complaints?

 Lift stations locations  Long forcemain runs and what structures they discharge to  Long sewer runs without many connections (i.e., low flows, long

detention times)

 Areas of sewers near surface waters or where groundwater table is

known to be high(er).

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Sept 2012

EXAMPLE MASTER SEWER MAP

UNDERSTANDING COLLECTION SYSTEM ISSUES

Wastewater treatment starts during

collection & conveyance

Rate of (early) “treatment” depends on:

 BOD Strength  Time  Temperature  Presence of oxygen  Velocities in sewers & FMs – enough to move solids?  Solids Retention Time (SRT)  Attached growth ‘slime’ layer

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METHODS TO EVALUATE & PROTECT

Evaluation of Collection System Chemistry:

 5-day Biological oxygen demand (BOD5) Chemical

• xygen demand (COD)

 Dissolved oxygen  pH  Temperature  Oxidation Reduction Potential (ORP)  Sulfates/Sulfides  Hydrogen sulfide  Fats, Oils & Greases – FOG  Odor sniffing

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METHODS TO EVALUATE & PROTECT

BOD5 & COD

 Primary measure of wastewater strength  BOD5 measures D.O. needed by aerobic

biological organisms to break down organic material over 5-day period

 COD oxidizes nearly all organic compounds to

provide ‘bigger picture’ on wastewater strength

 Typ. domestic wastewater BOD5 – 150 to 300

mg/L

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METHODS TO EVALUATE & PROTECT

BOD5 & COD

Typ. ratio of COD to BOD: 1.4 to 1.8 If COD ratio is higher, indicates potential

non-domestic wastewater source(s)

COD test simpler, quicker to obtain result High strength wastewater > 500 mg/L

BOD/COD can deplete dissolved oxygen, i.e., higher risk environment for hydrogen sulfide generation  corrosion

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EXAMPLES FOR COD TESTING

Examples where COD test would be the better

indication of wastewater strength to identify & protect the POTW:

 e.g. pickle waste with BOD15 caused odor/corrosion at Bay

County WWTP

 e.g tannery waste with BOD20 caused upsets in Grand

Haven

 e.g tannery, leachate and other wastes accelerated

corrosion/ collapse & plugging in Rockford trunk sewer

 e.g. biodiesel byproduct with high BOD20 affected

treatment at the Bangor treatment lagoons (pass through, interference and odors!)

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METHODS TO EVALUATE & PROTECT

Dissolved Oxygen (D.O.)

Easy, portable test helped by recent

improvements in sensor technology

Provides quick analysis of potential for

corrosion forming conditions

D.O. levels less than 0.5 - 1mg/L could

prompt additional evaluation (e.g., grab sample for COD test, ORP test)

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METHODS TO EVALUATE & PROTECT

pH

Easy, portable grab test (can be same

meter as used for D.O. or ORP)

pH levels less 5 s.u. are a concern Dischargers must maintain pH >5 per

federal regulations (40CFR Part 403 Pretreatment Stds)

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METHODS TO EVALUATE & PROTECT

Temperature

 Easy, portable grab test typically indicated

• n meters for D.O., pH, ORP

 Warm temperatures >80F provide sewer

environment for accelerated biological activity, decreased D.O. levels, i.e., precursors for corrosion

 Wastewater temp >104F prohibited 40CFR

Part 403 Pretreatment Stds)

 Colder wastewater 50-55F could indicate

significant groundwater infiltration or surface water inflows

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METHODS TO EVALUATE & PROTECT

Oxidation Reduction Potential (ORP)

 Easy, portable grab test  ORP measured in millivolts  Historical uses: treating plating wastewater

(e.g., Chrome VI to Chrome III reduction), confirmation of adequate disinfection in drinking water supply, groundwater quality assessments

 Aerobic conditions typically a +value, while

anaerobic conditions a –value

 Reducing environments another precursor to

potential corrosion

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METHODS TO EVALUATE & PROTECT

Sulfates

 Typical levels in domestic wastewater is 20-50

mg/L

 Some industries discharge higher concentrations  Sulfates can contribute to hydrogen sulfide

levels if introduced to low or zero oxygen environments where sulfur reducing bacteria convert sulfate to hydrogen sulfide

 Sulfate control (e.g., local limit) can help limit

this potential sulfide generation

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H2S ISSUES – SULIFIDE IN YOUR SYSTEM

Hydrogen sulfide is major source of odors and

corrosion in collection systems.

H2S H2S H2S H2S

Hydrogen sulfide smells like rotten eggs, but

quickly numbs the sense of smell.

Concrete, steel and Iron pipes and structures are

susceptible to this corrosion.

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H2S ISSUES – BACKGROUND ON CORROSION

Corrosion:  Direct – immediately caused by wastewater discharge  Less direct – caused, with many interacting factors Microbial Induced Corrosion (MIC)  Anaerobic bacteria produce hydrogen sulfide gas in

sewers, lift stations, force mains

 Hydrogen sulfide feeds acid producing bacteria  Acid reduces the pH of the concrete sewers & MHs

corroding and weakening them

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H2S ISSUES – BACKGROUND ON CORROSION

Key Factors in bacteria growth, odor & corrosion

 High BOD/COD >300-500 mg/L  Warm Temperatures  Long Retention Times  Turbulence (i.e., develop aerobic conditions)  Solids deposition  Higher Sulfate Concentrations

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H2S ISSUES – BIOCHEMICAL REACTIONS



Three General Steps or Phases

• 1. Dissolved oxygen, then nitrate ‘chewed up’ with BOD
• 2. Sulfate & organics converted to odorous H2S and
• ther organic odorous compounds
• 3. Hydrogen sulfide released from water, converted to

Sulfuric Acid…corrosion



Conversion by thiobacillus aerobic bacteria:



H2S + 2O2  H2SO4 (Strong acid) summary equation

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May 2013

H2S ISSUES – BIOCHEMICAL REACTIONS

In the presence of anaerobic bacteria:

 SO4

• 2 + Organic Matter  HCO3-1 + H2S

 H2S(aq) = HS-1 + H+ (Mild acid)

Conversion by thiobacillus aerobic bacteria:

 H2S + 2O2  H2SO4 (Strong acid)

….HALT ANY ONE STEP…STOP THE CORROSION!

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May 2013

OVERVIEW OF METHODS

TO EVALUATE EXISTING CONDITIONS & NEEDS

Map the collection system for “travel time”,

vulnerable pipe materials, location of high strength etc. wastewater

Log odor complaints – great clue! Conduct a H2S survey; Odaloger equipment

measures H2S in vapor form

Guideline action level is ~20 ppm H2S vapor Rule of thumb 20 ppm vapor ~ 0.5 mg/L H2S

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FOG ISSUES

asdf

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FOG – PREVENTATIVE/CORRECTIVE MEASURES

Identify specific dischargers

 Restaurants need grease traps & interceptors  CCTV necessary on the Hot Spot FOG segments

Not all FOG is created equal!

 SUO needs to address different types of FOG  Polar, non-polar, solid at 45°F, liquid at 45°F  Do hexane extractable FOG test (Method 1664 A)

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FOCUS ON SPECIFIC FOG /CORRECTIVE MEASURES

Consider Polar HEM FOG

Solidifies at 45F and causes plugging in the

sewer = MOST IMPORTANT

Many Soaps are in this category = LEAST

IMPORTANT as biodegradable

Consider Non-Polar HEM FOG

 Petroleum? Pass-through potential at the POTW

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FOCUS ON SPECIFIC FOG /CORRECTIVE MEASURES

 Example Review:  Total HEM concentrations were in the ____ range. Evaluate the

speciation of the Oil/grease components:

 The cooled, “floatable” free oil samples were ____. Compare to the

local limit developed to protect against oil/grease.

 The total “non-polar” oil/grease concentration (floatable & emulsified

• ils) was _____. Compare to the local limit developed to protect

against oil/grease.

 A substantial portion of the “HEM” is “polar”, known as

biodegradable or ‘soluble’, thus compatible with biological treatment and unlikely to clog up the sewer system.

 The grab samples ranged from ___ to ___ mg/L, average result would

be ___ mg/L +/- __ mg/L

 -photos  -Petroleum: 58-13=45% non-polar, emulsified  -Free/floatable Oil 13% non-polar, free  -Polar “not oil” 42% (hexane extractable includes 40-

80mg/L soap compounds, glycols, biodegradable constituents = BOD)

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REAL WORLD APPLICATIONS

H2S – Odor & Corrosion Fats, Oils, & Grease Solids settling in sewers; SRT > HRT

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REAL WORLD APPLICATIONS – H2S ISSUES

Your nose knows! If it stinks – it corrodes!

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H2S ISSUES – CASE STUDIES

 Northport, MI

 FM with long residence time due to seasonal low

flows; domestic wastewater

 North Kent Sewage Disposal System

 Industrial contributors: Tannery, Landfill, Papermill

 Davenport Sewage System

 Industrial contributor: Food Processor

 Martin Michigan (SIU permit due to flow, system impact)

 Long FM and resulting residence time: SRT>HRT  Industrial contributors: none

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May 2013

NORTHPORT, MI

Est. Avg. BOD = 300 mg/L (indv. grinders stations) Avg. sulfate = 30 mg/L* FM Length = ~2 miles (3” dia.) Temperatures: 50-55°F Retention Time = several days during offseason

*Typical medium strength wastewater, Metcalf & Eddy 35

May 2013

NORTHPORT, MI

Odor complaints began approx. 1 year after

construction

FM & Sewer was PVC (protected) but concrete MHs

at risk.

Mobile chemical dosing station used to identify best

location to feed nitrate-based chemical to stop sulfate to sulfides conversion in anaerobic conditions in FM

RESULTS: successful H2S control to <10ppmv and

• dor complaints eliminated

*Typical medium strength wastewater, Metcalf & Eddy 36

May 2013

NORTH KENT SEWER*

Avg. BOD = 4700 mg/L Avg. sulfate = 1800 mg/L Sewer Length = ~8 miles Temperatures: 39°C papermill, 14°C landfill Retention Time = 0.25 to 0.5 days

*Based on data collected 4-1-97 thru 4-5-97 for Kent County 37

May 2013

NORTH KENT SEWER SYSTEM

Result: odor along route, sewer collapsed in

1995-97, replacement sewer

Failure attributed to hydrogen sulfide/biofilm

sulfuric acid corrosion on concrete pipe

Hydrogen sulfide attributed to rapid

degradation of high strength, high temperature wastewater

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May 2013

DAVENPORT, IOWA

Avg BOD = 2000 to 4000 mg/L Avg Sulfate = N/A (likely >250 mg/L) Sewer Length = ~3 miles Temperatures: 38°C food processor Retention Time = ~0.2 days

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May 2013

DAVENPORT, IOWA SEWER

Result: 2 mile sewer collapse, 1996 Failure attributed to hydrogen sulfide induced

corrosion on concrete pipe

Hydrogen sulfide attributed to rapid

degradation of high strength, high temperature wastewater

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May 2013

MARTIN, MI

Avg BOD = 275 mg/L Avg Sulfate = ? (likely 40 to 60 mg/L) Sewer Length = ~5 miles Temperatures = 18-20C Retention Time = liquid est. at 3 to 5 days, solids

• est. at >10 years (scouring velocity problem)

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May 2013

MARTIN, MI

Result: Odors in Plainwell, sewer collapse at

Sherwood St, 1997

Failure attributed to hydrogen sulfide induced

corrosion on concrete pipe

Hydrogen sulfide attributed to the biological

degradation of settled solids in the sewer, inadequate velocity to convey solids

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May 2013

H2S ISSUES – PROTECTIVE MEASURES

Limits in your Sewer Use Ordinance

 H2S vapor phase limit – MH head space monitoring  Plainwell example <10 ppmv, with language in the

SUO that ties H2S formation back to high strength

Nitrate chemical addition

 Provide an alternate food source for the sulfide

reducing bacteria

 Bioxide ($$ brand name) or generic  Successfully deployed in Northport, MI

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H2S ISSUES – PROTECTIVE MEASURES

Identify & map out hot spots in your system

 Review collection system – focus on areas with long

forcemains, long SRTs

 Identify drop MHs, LS, and other areas with high

turbulence

 Test for low DO, high H2S vapor (use OdaLogger or

similar), high BOD, high temperature

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H2S ISSUES – PREVENTATIVE MEASURES

Design practices to mitigate H2S formation

 Higher velocities needed for re-suspension of settled

solids – 2 ft/sec isn’t going to cut it!!

 Consider multiple pump locations  Design for daily FM flushing – larger wet well volume  Multi-hill re-design (Town of Lagro, Indiana)

 Increased pump size/flow  Multiple pumps running to achieve flushing flows/velocities  Wet well volume large enough to index solids over/down FM

hills – allow for re-suspension of the solids using >3.5 fps vs. traditional 2 fps design

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H2S ISSUES – CORRECTIVE MEASURES

What to do in an old system with potential

for big H2S/Corrosion??

 FM Flushing - where FM problems are not readily

solved (e.g. large diameter, low velocity, multiple hills, long)

 Martin to Plainwell FM – flushing produced slug

loading 5500 mg/L BOD, 7700 mg/L TSS (significant)

 Flushing maintenance events need to be managed:

“Special event” permit, including coordinated timing and approval requriements with POTW

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H2S ISSUES – CORRECTIVE MEASURES

What to do with a long or large forcemain

that has potential for big H2S/Corrosion??

 <<insert photos of Hampton LS here>>

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H2S ISSUES – CORRECTIVE MEASURES

Manhole/structure rehabilitation options:

 Manhole lining  Epoxy paints, mortars  Polyurethane elastomeric coatings

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OTHER THOUGHTS

 Please follow your facility’s safety manual/procedures when

working in and around sanitary sewer system structures

 If not properly trained, team up with DPW personnel that have

received their safety training for confined space entry

 Use multi-gas sensor (LEL, H2S, O2) to check spaces for safe

atmosphere levels

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QUESTIONS?

Carey Bond, P.E. Fleis & VandenBrink Engineering 800.494.5202

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Sept 2012