Factors influencing exfiltration processes in sewers.

Area of Science:

• Environmental Engineering
• Water Resources Management
• Civil Engineering

Background:

• Exfiltration from sewerage systems is a significant issue.
• New legislation may mandate identification and rectification of sewer exfiltration sources.
• Accurate leakage rate assessment is crucial for water service providers.

Purpose of the Study:

• To investigate the influence of sewage solids and sediments on exfiltration rates.
• To develop and utilize specialized exfiltration test apparatus.
• To provide a more realistic understanding of sewer leakage.

Main Methods:

• Described exfiltration test apparatus.
• Conducted experiments using actual sewage.
• Analyzed the impact of solids and sediments on leakage.

Main Results:

• Previous estimates of exfiltration leakage rates were often too high.
• Sewage solids and sediments exhibit a "self-repairing" action in defects.
• Recorded exfiltration rates as low as 0.1% of sewer flow for defects up to 6mm.

Conclusions:

• The self-repairing action of sewage significantly reduces exfiltration.
• Exfiltration rates are lower than previously estimated.
• Water service providers should consider these findings for accurate leakage assessment.