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

C OLLECTION S YSTEM HEALTH – HOW IS THE PATIENT DOING ? MWEA L AB P RACTICES S EMINAR – M AY 2013 Presented by: Carey Bond, PE

A GENDA  Brief History (In Time) - Collection Systems  Collection System Components May 2013  The Stakes  Methods to Evaluate & Protect  Real World Applications  Questions Stephen Hawking quotes: “ It is all right to make mistakes; nothing is perfect because with perfection, we would not exist” 2 “ Life would be tragic if it weren't funny .”

H ISTORY OF OUR COLLECTION SYSTEMS  Early- Mid 1800’s – open sewers/gutters used to convey waste in urban areas May 2013  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

H ISTORY OF OUR COLLECTION SYSTEM  1930s-1970s - Improvements to sewer design & May 2013 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 materials & equipment:  RCP, PVC, DIP, HDPE 4  Directional drilling

T HE S TAKES  Inadequate collection system protections What’s at stake? May 2013  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 5  Replacement $0.4 to $0.6M/mile

C OLLECTION S YSTEM C OMPONENTS  Gravity Sewers  Min. diameter 8” (Modern design standard)  Materials: vitrified clay pipe – VCP (older), May 2013 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 6

C OLLECTION S YSTEM C OMPONENTS  Manholes/Structures  Min. diameter 4’  Materials: pre-cast or cast-in-place concrete, May 2013 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, 7 air release, electrical gear, emergency power

May 2013 Typical Submersible Lift Station 8

May 2013 Typical Suction Lift Station 9

T HE S TAKES  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. May 2013 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). 10

E XAMPLE M ASTER S EWER M AP Sept 2012 11

U NDERSTANDING C OLLECTION S YSTEM I SSUES  Wastewater treatment starts during collection & conveyance  Rate of (early) “treatment” depends on: May 2013  BOD Strength  Time  Temperature  Presence of oxygen  Velocities in sewers & FMs – enough to move solids?  Solids Retention Time (SRT)  Attached growth ‘slime’ layer 12

M ETHODS TO EVALUATE & PROTECT Evaluation of Collection System Chemistry:  5-day Biological oxygen demand (BOD 5 ) Chemical oxygen demand (COD) May 2013  Dissolved oxygen  pH  Temperature  Oxidation Reduction Potential (ORP)  Sulfates/Sulfides  Hydrogen sulfide  Fats, Oils & Greases – FOG  Odor sniffing 13

M ETHODS TO EVALUATE & PROTECT BOD 5 & COD  Primary measure of wastewater strength  BOD 5 measures D.O. needed by aerobic May 2013 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 BOD 5 – 150 to 300 mg/L 14

M ETHODS TO EVALUATE & PROTECT BOD 5 & COD  Typ. ratio of COD to BOD: 1.4 to 1.8 May 2013  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 15

E XAMPLES FOR COD T ESTING  Examples where COD test would be the better indication of wastewater strength to identify & May 2013 protect the POTW:  e.g. pickle waste with BOD 15 caused odor/corrosion at Bay County WWTP  e.g tannery waste with BOD 20 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 BOD 20 affected treatment at the Bangor treatment lagoons (pass through, interference and odors!) 16

M ETHODS TO EVALUATE & PROTECT Dissolved Oxygen (D.O.)  Easy, portable test helped by recent improvements in sensor technology May 2013  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) 17

M ETHODS TO EVALUATE & PROTECT pH  Easy, portable grab test (can be same meter as used for D.O. or ORP) May 2013  pH levels less 5 s.u. are a concern  Dischargers must maintain pH >5 per federal regulations (40CFR Part 403 Pretreatment Stds) 18

M ETHODS TO EVALUATE & PROTECT Temperature  Easy, portable grab test typically indicated on meters for D.O., pH, ORP May 2013  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 19

M ETHODS TO EVALUATE & PROTECT Oxidation Reduction Potential (ORP)  Easy, portable grab test  ORP measured in millivolts May 2013  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 20

M ETHODS TO EVALUATE & PROTECT Sulfates  Typical levels in domestic wastewater is 20-50 mg/L May 2013  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 21

H2S I SSUES – S ULIFIDE IN YOUR S YSTEM  Hydrogen sulfide is major source of odors and corrosion in collection systems. May 2013 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. 22

H2S I SSUES – B ACKGROUND ON C ORROSION  Corrosion:  Direct – immediately caused by wastewater discharge May 2013  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 23

H2S I SSUES – B ACKGROUND ON C ORROSION  Key Factors in bacteria growth, odor & corrosion  High BOD/COD >300-500 mg/L May 2013  Warm Temperatures  Long Retention Times  Turbulence (i.e., develop aerobic conditions)  Solids deposition  Higher Sulfate Concentrations 24

H2S I SSUES – B IOCHEMICAL R EACTIONS Three General Steps or Phases  1. Dissolved oxygen, then nitrate ‘chewed up’ with BOD May 2013 2. Sulfate & organics converted to odorous H2S and other organic odorous compounds 3. Hydrogen sulfide released from water, converted to Sulfuric Acid…corrosion Conversion by thiobacillus aerobic bacteria:  H 2 S + 2O 2  H 2 SO 4 (Strong acid) summary equation  25