32. Inflow and Infiltration

32. Inflow and Infiltration#

Course Website

http://54.243.252.9/ce-3372-webroot/

Readings#

Textbook

Gupta, R.S., 2017. Hydrology and Hydraulic Systems, pp 1-39

Additional Readings

  1. Cleveland, T. G. (2020) Water Systems Design Notes (Sanitary Sewer Systems) to accompany CE-3372, Department of Civil, Environmental, and Construction Engineering, Whitacre College of Engineering. Slides: 28-30)

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Videos#

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Introduction#

Inflow and infiltration (I&I) are critical concepts in the design and operation of sanitary sewer systems. These phenomena increase the volume of wastewater needing treatment, leading to higher operational costs and potential system overflows.

Definitions#

  1. Inflow: Direct connections to sanitary sewers that allow water to enter the system, including:

    • Roof gutters

    • French drains

    • Unauthorized stormwater connections

  2. Infiltration: Leakage into sanitary sewers through:

    • Cracks in pipes

    • High water tables

    • Defective joints and junction boxes

Characteristics of Inflow and Infiltration#

Visualizing I&I#

  • Inflow is often represented in red.

  • Infiltration is represented in blue.

Image Placeholder#

Placeholder for Inflow and Infiltration visualization

Impacts of I&I#

Operational Challenges#

  • Increases in treatment plant loads during wet weather.

  • Overflows in sanitary systems.

  • Additional wear and tear on infrastructure.

Mitigation Measures#

  1. Regular inspection and maintenance of sewer systems.

  2. Prohibition and removal of unauthorized stormwater connections.

  3. Lining or replacing deteriorated pipes to reduce infiltration.

Example Code for I&I Volume Estimation (Placeholder):#

# Placeholder for I&I volume calculation
import numpy as np
inflow_rate = 1000  # gallons per minute
infiltration_rate = 500  # gallons per minute
total_I_and_I = inflow_rate + infiltration_rate
print("Total I&I (gpm):", total_I_and_I)

Regulatory Context#

  • Regulations often require calculations of I&I as part of system design and operational reporting.

  • Design flow must account for I&I during peak conditions.

Example Analysis#

Equation for Peak Flow Design#

[ Q_{total} = Q_{dry} + Q_{I&I} ] Where:

  • ( Q_{total} ): Total peak flow

  • ( Q_{dry} ): Peak dry weather flow

  • ( Q_{I&I} ): Combined inflow and infiltration

Example Calculation:#

#```python
# Example calculation of total flow
peak_dry_flow = 2000  # gallons per minute
I_and_I = 1500  # gallons per minute
total_peak_flow = peak_dry_flow + I_and_I
print("Total Peak Flow (gpm):", total_peak_flow)
#```

Total Peak Flow (gpm): 3500

Monitoring and Management#

Techniques#

  • Flow monitoring: Using weirs, magmeters, or acoustic Doppler profiling.

  • CCTV inspections: Locating and identifying sources of infiltration.

  • Smoke testing: Detecting unauthorized connections.

Image Placeholder#

Placeholder for flow monitoring techniques

This section provides an overview of inflow and infiltration, their impacts, and common methods for analysis and mitigation in sanitary sewer systems. It highlights the importance of proper design and maintenance to minimize these challenges.

End of Section#

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