NPDES ENFORCEMENT SECTION

1
NPDES ENFORCEMENT SECTION
DENNIS BENSON, BRANCH MANAGER, NPDES ENFORCEMENT
SECTION
2
Inflow and Infiltration

• ITS NOT JUST ABOUT SSOs

3
Inflow and Infiltration

• SOLIDS WASH OUT
• Peak Hydraulic loads overcome the settling rate
  in the secondary clarifiers causing biomass
  (mixed liquor) to be washed out of the plant.
• Solids in chlorine contact chamber
• Solids in receiving stream

4
Inflow and Infiltration

• SOLIDS WASH OUT
• MLSS levels reduced (F/M ratio out of whack,
  settling characteristics changed)
• BOD removal efficiencies greatly reduced
• Large loading violations

5
Inflow and Infiltration

• Disruption of food to microorganism ratio
• Wash out
• Very weak influent sewage
• F/M disruption can result in reduced removal
  efficiencies, pin flock, or sludge bulking

6
Inflow and Infiltration

• Loss of Alkalinity
• Approximately 7.1 parts alkalinity are required
  to remove 1 part ammonia.
• Disruption of nitrification process.
• Ammonia violations until nitrification process
  restabilized.

7
Inflow and Infiltration

• Temperature and pH Shocks
• Inflow can bring large volumes of water to the
  treatment plant with significantly different
  temperature and/or pH than the water in the
  treatment plant. Bacteria like fairly static
  conditions, so these shocks reduce treatment
  efficiency.
• Effluent violations
• Violation of removal standard

8
Inflow and Infiltration

• High Velocity of Wastewater Causes Scouring of
  Sewer Lines
• Levels of Grit and Grease to treatment plant
  increase significantly

9
Inflow and Infiltration

• Grit
• Abrasion of pumps and other surfaces
• Settles in tight layers which is difficult to
  remove and leads to loss of capacity.
• Grease
• Accumulates on equipment
• Low pH values
• Disruption of oxygen exchange

10
Inflow and Infiltration

• Toxic Runoff
• Inflow from certain industrial facilities can
  have high levels of toxic pollutants.
• These toxic pollutants can pass through the
  treatment plant or cause interference.

11
Inflow and Infiltration

• Increased energy cost
• High volumes of water to pump and treat
• Increased maintenance cost
• Lots of mechanical equipment have maintenance
  schedules based upon usage
• Shortened life of equipment

12
Inflow and Infiltration

• Dont try to solve your SSO problem by just
  building bigger facilities. Have an active
  program to eliminate I I.