Experimental studies of sewer exfiltration

Area of Science:

• Environmental Engineering
• Wastewater Management
• Fluid Mechanics

Background:

• Wastewater exfiltration from sewer systems is a significant environmental concern.
• Joint integrity and internal pipe conditions, such as sediment buildup, influence leakage rates.
• Understanding these factors is crucial for effective sewer management and infrastructure maintenance.

Purpose of the Study:

• To investigate the impact of joint openings and in-pipe sediment on sewer exfiltration losses.
• To evaluate how flow and hydraulic head affect exfiltration rates under different conditions.
• To assess the effectiveness of simple tracer techniques for quantifying exfiltration and potential tracer adsorption.

Main Methods:

• Conducting experimental tests on a model sewer system.
• Varying hydraulic head and flow conditions during clean-water and sediment-laden tests.
• Utilizing tracer techniques to measure exfiltration volumes.
• Analyzing the physical and chemical properties of in-pipe sediment.

Main Results:

• Exfiltration rates showed exponential relationships with head in clean-water tests.
• Sedimentation altered exfiltration to power-law functions with respect to head.
• Organic sediment, particularly with shredded toilet tissue, effectively sealed joint openings.
• Tracer adsorption by pipe solids was evaluated for its impact on loss quantification.

Conclusions:

• In-pipe sediment can significantly reduce exfiltration, acting as a natural sealant.
• The sealing effectiveness depends on the sediment's composition, with organic materials being more effective.
• Tracer methods are viable for quantifying exfiltration, but potential adsorption must be considered.