Technical evaluation and optimization of a mobile septage treatment unit

Area of Science:

• Environmental Engineering
• Wastewater Treatment Technologies
• Mobile Treatment Systems

Background:

• Septage and sewage holding tanks require efficient and accessible treatment solutions.
• Existing septage emptying services can be costly and inefficient.
• Onsite treatment systems are needed to manage wastewater at the source.

Purpose of the Study:

• To design, build, and evaluate a mobile septage treatment unit for onsite application.
• To assess the operational and treatment performance of the mobile unit in field conditions.
• To improve the system's capacity and efficiency through iterative design modifications.

Main Methods:

• Construction of a mobile unit using readily available filters (mesh, sand, GAC, microfilter, ultrafilter) on a truck bed.
• Field evaluation at 108 sites in Tamil Nadu, India, processing over 273 m³ of septage across two phases.
• Performance assessment based on removal efficiencies of chemical oxygen demand (COD), total suspended solids (TSS), and total coliform (TC).

Main Results:

• Phase I: High removal efficiencies achieved (83% COD, 75% TSS, 98.4% TC) at 623 L/h.
• Phase II: Improved systems processed septage at higher average flows (1290-2700 L/h) with sustained removal efficiencies (80% COD, 81% TSS, 99% TC).
• Soluble contaminants (soluble COD, NH₃-N) were identified as the primary treatment challenge.

Conclusions:

• The mobile septage treatment unit demonstrates effective removal of solids and bacteria, meeting local discharge standards.
• The system offers a potentially cost-competitive and efficient alternative to traditional septage hauling services.
• Further optimization is recommended to address soluble contaminant removal and site-specific limitations.