AGENDA WAYS TO PROTECT YOUR WASTEWATER COLLECTION SYSTEM

Transcription

1 WAYS TO PROTECT YOUR WASTEWATER COLLECTION SYSTEM MWEA IPP SEMINAR SEPTEMBER 2012 Presented by: Carey Bond, PE AGENDA History of Our Collection Systems The Stakes Frontlines IPP Staff The Issue Methods to Evaluate & Protect Real World Applications Local Limits Considerations (H2S) Questions 2 1

2 HISTORY OF SANITARY 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 3 HISTORY OF SANITARY COLLECTION SYSTEMS, CONT D 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 of private laterals in the U.S. Modern pipe matls & equipment: RCP, PVC, DIP, HDPE Directional drilling 4 2

3 THE STAKES Inadequate collection system protections What s at stake? Damage to the POTW Collection System Often unseen damage it s all buried Interrupted service Emergency repairs Expensive & often unplanned costs Replacement $0.4 to $0.6M/mile (Plus costs for road restoration where applicable) POTW = Publically Owned Treatment Works 5 THE STAKES, CONT D Many collection systems are in poor condition ASCE 2009 Report Card gave national sewer infrastructure a grade of D- So what grade would your community s collection system get? 6 3

4 FRONTLINES IPP STAFF Industrial pretreatment staff are on the frontline of protecting their community s POTW, not only at the WWTF but also the collection system - sewers, MHs/structures, and lift stations. IP staff have central intel on high-strength or high solids/fog discharges, odor complaints, back-ups that are all important knowledge in protecting the collection system 7 FRONTLINES IPP STAFF Know your collection system: Be familiar with your master sewer system map, request a working copy (hard copy &/or electronic) Assist with keeping sewer map updated Identify long FMs, material types, high-strength input locations, low-flow/long travel time sections, as part of a vulnerability analysis Highlight or color-code corrosion/odor-prone segments 8 4

5 9 THE ISSUE Most historic IPPs did not address the need to protect: Sewers from corrosion, odors, solids deposition MHs/Lift Stations from corrosion, odors, solids deposition Historically IPP/Local Limits programs have focused mostly on effects at the treatment plant Typ. Collection System Value WWTP Value 10 5

6 THE ISSUE, CONT D Wastewater treatment starts during collection & conveyance Rate of (early) treatment depends on: BOD Strength Time (during conveyance) Temperature Presence of oxygen Solids Retention Time (SRT) Attached growth slime layer 11 ADDRESS THE ISSUE Consider Local Limits to protect: Interference with collection (any action, discharge or material that interferes) Plugging that can cause uncontrolled release (permit violations) Corrosion & collapse that can cause uncontrolled release (permit violations) 12 6

7 OVERVIEW OF METHODS TO EVALUATE EXISTING CONDITIONS & NEEDS Identify a non-domestic user as significant per IPP regulations. Issue a permit with specific limits. Map the collection system for travel time, vulnerable pipe materials, location of high strength wastewater, etc. Log odor complaints; Conduct a H2S survey; Develop SUO language to protect the entire POTW from damage 13 LOCAL LIMITS CONSIDERATIONS Reevaluate BOD, TSS limits as needed to protect the collection system (sewer segments will vary) e.g. gelatin factory in Davenport IA accelerated corrosion/ collapse & plugging with in trunk sewer COD needs to be defined & utilized when BOD5 test is not adequate to identify or 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 within Rockford trunk sewer e.g. biodiesel byproduct with high BOD20 affected treatment at the Bangor treatment lagoons (pass through, interference and odors!) 14 7

8 LOCAL LIMITS CONSIDERATIONS CONT D Sulfides generated due to high(er) strength BOD or COD Include discharges that contribute to generation of hydrogen sulfide Include high strength discharges that rapidly biodegrade Sulfides discharged due to manufacturing process (e.g. tanneries, landfills) 15 REAL WORLD APPLICATIONS H2S Odor & Corrosion Solids settling in sewers; SRT > HRT Fats, Oils, & Grease 16 8

9 REAL WORLD APPLICATIONS H2S ISSUES Your nose knows! If it stinks it corrodes! 17 H2S ISSUES SULIFIDE IN YOUR SYSTEM Hydrogen sulfide is major source of odors and corrosion in collection systems. H 2 S H 2 S H 2 S H 2 S 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 (PVC & HDPE are not) 18 9

10 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 19 H2S ISSUES BACKGROUND ON CORROSION, CONT D Key Factors in bacteria growth, odor & corrosion High Biochemical Oxygen Demand, >300 mg/l Warm Temperatures Long Retention Times Solids deposition Higher Sulfate Concentrations Turbulence or Agitation (i.e., source of O2 for aerobic conditions) 20 10

11 LOCATIONS OF TURBULENCE (INTRO OF O2) 21 H2S ISSUES BIOCHEMICAL REACTIONS Three General Steps or Phases: 1 st Step - Dissolved oxygen, then nitrate chewed up with BOD 2 nd Step - Sulfate & organics converted to odorous H2S and other organic odorous compounds 3 rd Step - Hydrogen sulfide released from water, converted to Sulfuric Acid corrosion 22 11

12 23 H2S ISSUES BIOCHEMICAL REACTIONS In the presence of anaerobic bacteria: SO Organic Matter HCO H 2 S H 2 S(aq) = HS -1 + H + (Mild acid) Conversion by thiobacillus aerobic bacteria: H 2 S + 2O 2 H 2 SO 4 (Strong acid) summary equation.halt ANY ONE STEP STOP THE CORROSION! 24 12

13 OTHERWISE CORROSION RESULTS 25 CORROSION RESULTS 26 13

14 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 27 NORTHPORT, MI Est. Avg. BOD = 300 mg/l (indv. grinders stations) Avg. sulfate = 30 mg/l* FM Length = ~2 miles (3 dia.) Temperatures: F Retention Time = several days during offseason due to seasonal population 28 *Typical medium strength wastewater, Metcalf & Eddy 14

15 NORTHPORT, MI Odor complaints began approx. 1 year after construction FM & Sewer was PVC (protected) but concrete MHs at risk. Was an odor issue/nusiance Mobile chemical dosing station used to identify best location to feed nitrate-based chemical to stop sulfate to sulfides conversion (by anaerobic bacteria) RESULTS: successful H2S control to <10ppmv and odor complaints eliminated 29 NITRATE CHEMICAL FEED STATION 30 15

16 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 31 *Based on data collected thru for Kent County NORTH KENT SEWER SYSTEM Result: odor along route, sewer collapsed in , 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 32 16

17 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 33 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 34 17

18 REAL WORLD APPLICATIONS SOLIDS SETTLING IN SEWERS OR FORCEMAINS 35 SOLIDS SETTLING IN SEWERS/FMS CASE STUDY Martin Michigan SIU permit due to flow, system impact Long FM and resulting residence time: SRT>HRT Industrial contributors: none 36 18

19 MARTIN, MI Avg BOD = 275 mg/l Avg Sulfate =? (likely 40 to 60 mg/l) Sewer Length = ~5 miles Temperatures = 18-20C Conveyance Time = liquid est. at 3 to 5 days, solids est. at >10 years (scouring velocity problem) 37 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 Corrosion also occurred at each air release valve location along the forcemain 38 19

20 H2S ISSUES PROTECTIVE MEASURES 40 CFR 403 Requires -- Protection from substances that will harm the collection system Requires Control measures be implemented Develop Local Limits in your Sewer Use Ordinance H2S vapor phase limit MH head space monitoring H2S liquid phase limits 39 H2S ISSUES PROTECTIVE MEASURES Develop SUO provisions, Surcharge Limits General statement: e.g. Prohibited: Discharge of substances and/or discharge of wastewater under conditions that contribute to the formation of hydrogen sulfide at liquid phase levels greater than 0.5 mg/l or vapor phase levels greater than 10 ppmv measured in a downstream manhole. Specific Local Limits: e.g. Hydrogen sulfide (liquid phase) <0.3 mg/l BOD <300 mg/l ** ** subject to demonstration of H2S vapor formation 40 20

21 H2S ISSUES PROTECTIVE MEASURES Develop SUO provisions, Surcharge Limits Considerations: Broad flexibility required Every high-bod discharge needs independent evaluation Odors & corrosion might not be due to an industry Like the WWTP, each part of the Collection System has a BOD capacity that needs evaluation 41 H2S ISSUES PROTECTIVE MEASURES Nitrate chemical addition Provide an alternate food source for the sulfide reducing bacteria Controls hydrogen sulfide odors and corrosion biologically, because of a natural ENERGY PREFERENCE: O 2 > NO 3 > SO 4 Bioxide ($$ brand name) or generic Successfully deployed in the Northport, MI case study Other chemicals such as ferric chloride (& other metal salts), tie up sulfides but doesn t prevent there formation 42 21

22 H2S ISSUES PROTECTIVE MEASURES Identify & Map Out Hot Spots in Your System Review your collection system focus on areas with long forcemains, long SRTs Identify drop MHs, LS, and other areas with high turbulence Elevate BOD/Long Runs Runs with chronic settling of solids Areas uphill of common complaints (clues) Test for low DO, high H2S vapor (use OdaLog or similar), high BOD, high TSS, high temperature 43 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 >4 fps vs. traditional 2 fps design 44 22

23 H2S ISSUES PREVENTATIVE MEASURES What to do with a long or large forcemain that has potential for big H2S/Corrosion or Plugging with Solids /Grit?? Hampton Township Lift Station Example: Designed for flushing velocity of 4 to 6 fps to move solids Multiple pumps so that flushing velocities could be achieved periodically (at least once per day) Wet Well sized so that volume pumped each run cycle would index solids down FM. i.e., pick-up and move solids with sufficient flushing velocity

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25 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 requirements with POTW 49 H2S ISSUES CORRECTIVE MEASURES Manhole/structure rehabilitation options: Cured-in-place liners for sewers Manhole lining Epoxy paints, mortars Polyurethane elastomeric coatings 50 25

26 PROTECTED EPOXY COATED MANHOLE 51 REAL WORLD APPLICATIONS FOG ISSUES asdf Fats, Oils & Greases 52 26

27 FOG PREVENTATIVE/CORRECTIVE MEASURES 40 CFR 403 Includes requirements for controlling Fats, Oils & Greases (FOG) discharges More specifically 403.5(b)(3) Prohibit solid or viscous pollutants in amounts which will cause obstruction in POTW and its collection system 53 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 material (HEM) FOG test (Method 1664 A) 54 27

28 FOCUS ON SPECIFIC FOG /CORRECTIVE MEASURES Consider Polar HEM FOG Portion that solidifies at 45F and causes plugging in the sewer = MOST IMPORTANT Many Soaps are in this category, do not solidify or cause plugging = LEAST IMPORTANT Consider Non-Polar HEM FOG Petroleum? Not a plugging issue but has hazardous potential in collection system and pass-through potential at the WWTP 55 COMPANY ABC EVALUATION Example: Total Oil/grease results were to mg/l range, but what was the speciation of the Oil/grease components? The cooled, floatable free oil samples were to mg/l The total non-polar oil/grease concentration (floatable & emulsified oils) were to mg/l Average of Results: -Petroleum: mg/l non-polar, emulsified -Free/floatable Oil mg/l -Polar not oil mg/l (Polar not oil are hexane extractables including soap compounds, glycols, biodegradable constituents = BOD) 56 28

29 FOG CONCLUSIONS Not all FOG created equal - Need to look at more than just FOG analytical results for some industrial or commercial users Identify polar and non-polar HEM results Polar portion of FOG that solidifies below 45 deg F is portion of FOG that can cause plugging most important Consider that other fractions may contribute to interference or pass-through 57 REFERENCES Tracking Down the Roots of Our Sanitary Sewer Systems website: compiled by John Schladweiler, PE, RLS; Arizona Water Association Website Metcalf & Eddy, Wastewater Engineering: Treatment & Reusue, 2002 North Kent Sewage Disposal System: Sampling and Flow Analysis, Kent County, MI Davenport, Iowa WWTP interviews 58 29

30 QUESTIONS? 59 30