Separating Inflow Reduction From Infiltration Removal Using Simple Tools Frederick Bloetscher, PhD, PE Florida Atlantic University
For Florida: Inflow Stormwater discharged directly into sewers from roof drains and stormwater runoff Infiltration Groundwater that enters the sewer through defective pipes, joints, connections, & manholes Inflow creates hydraulic issues and SSOs Both overload collection systems & reduces treatment efficiency Function of age
Symptoms of a problem: Sewer Higher than Water Sales?
Symptoms of a Problem Sewer Flows v. Rainfall We can see …..INFLOW!!!
Symptom Sanitary Sewer Overflow
Sewer flow peaks during rain events. The size of the storm event matters. A larger storm event will create more inflow. During storm events, wastewater flow is linearly related to rainfall. Based on an analysis of flow vs. rainfall graphs from pre and post construction activities inflow reduction will be calculated. Inflow
INFLOW Inflow
INFLOW Inflow BASEFLOW + INFILTRATION
INFLOW Inflow
Cover / Frame Inflow Frame / Chimney Infiltration Rain or Shine Water Table Inflow Solutions – Low tech Protocol – Seal Manhole Frame/Cone Connection
Sealing the Manholes Plus Correct Dish!!!
Smoke the System!!!
LDL Plugs for Cleanouts Broken or Removed
Results - LS 52 – Cooper City – Inflow Correction Only
Results - LS 53 Cooper City – Inflow Correction Only
Results - LS 54 Cooper City – Inflow Correction Only
Results - Dania – System
Community % Change (Pre Vs. Post) Dania Beach (2006 vs. 2009)-31.9% Cooper City (2011 vs. 2013)-62.8% Savings for Inflow Removal
Midnight Run! flow. 2 inch wide flow, 1/4 in deep at 2 ft/s = gpm flow. 3 inch wide flow, 1/2 in deep at 2 ft/s = flow. 4 inch wide flow,.75 in deep at 2 ft/s = 4.675gpm flow. 6 inch wide flow, 1.25 in deep at 2 ft/s = 28.05gpm flow. 8 inch wide flow, 4 in deep at 2 ft/s = gpm
Concurrently Inspect Manholes
Report MH 1-11MH MH 1-15 MH MH 1-30 MH MH 1-30 MH MH 1-31 MH MH 1-4 MH MH 1-40 upstrea m8150LS FM? MH 1-41 MH MH 1-42 MH MH 1-5 MH MH 1-6 MH MH 161 lateral20.35
Map = note only 20% of pipe needs to be investigated – avoided cost was $1.2 M in tving and cleaning in Dania Beach
Next Phase Once Stormwater inflow is out…. Pipelines…
Groundwater vs Base+Infiltration
Base + Infiltration increases with time
Infiltration
A comparison of slopes developed the following findings: 2006 Slope2009 SlopeTotal % Change% Change/Year x0.5558x25.4%8.5% In total Dania Beach experienced a 25.4% increase in infiltration between 2006 and Based on the findings above it is assumed that without any improvements utilities can expect approximately an 8.5% increase in infiltration per year. Infiltration
Work to reduce infiltration within the sewer collection system was initiated in 2012 in Dania Beach. In order to compare infiltration following pre and post-construction, flow values between 2012 and 2013 were compared. Infiltration Correction
Baseline increase in inflow was calculated to be 14.1% per year. Baseline increase in infiltration was calculated to be 8.5% per year. Percent decrease in Inflow was 54.8% Percent decrease in infiltration was nearly 30% w point repairs Overall with both efforts, Dania Beach ADF 3.4 to 2.4 MGD from 2005 – 2014 despite adding 0.2 MGD of concentrate to sewer system Results
Based on information provided by the city of Hollywood, Dania Beach currently pays $2.98/1,000 gallons. Assume 850 Manholes, 60 Miles of pipe Cost Analysis Assume 800 MHInflowInfiltration Sewage Reduced (gallons) 18,348,01172,706,566 Amount Saved($55,044)($216,665) Cost$472,000$772,000 Cost/1000 gallon$22.72$7.64 BUT… Avoided Cost($1,200,000)$0 Cost/1000 gallon($42.68)$7.64
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