Reusing Bio-Solids Harvested from Septage and Sewage

In 2023, Centre for Science and Environment (CSE) published two reports that assessed the performance and effectiveness of 47 faecal sludge treatment plants (FSTPs) and 14 sewage treatment plants (STPs) across India. These reports represent the first of its kind evaluation done at this scale in India as well as globally. What these reports found:

• FSTPs demonstrate comparable effectiveness to STPs in terms of reducing biochemical oxygen demand (BOD) and chemical oxygen demand (COD). Both FSTPs and STPs face challenges in reducing COD and pathogens
• The initial separation of solids from wastewater in FSTPs leads to a significant reduction of BOD and COD in separated wastewater. The subsequent treatment of wastewater depends on volume and regulatory reduction targets.
• Harvested bio-solids from septage and sludge, whether from FSTPs or STPs, are nutrient-rich, but also carry a high pathogen load and potential heavy metal content.
• Currently, there are no prescribed standards for reusing these harvested bio-solids.
• Harvested bio-solids do not meet the compost standards outlined in the Fertilizer Control Order (FCO) due to failure to meet the carbon/nitrogen ratio requirement.
• High pathogen levels in harvested bio-solids are linked to moisture content.

As India strives to move beyond ODF, there is an urgent need for developing effective treatment systems for septage and sewage. With Odisha leading the way in urban wastewater treatment infrastructure, particularly through implementation of low-cost nature-based nonsewered faecal sludge treatment systems, it serves as an exemplary state for others to follow. CSE is organising a workshop in Odisha to, therefore, to carry forward the learnings and discussion on reuse of bio-solids harvested from treatment systems.

For more details, contact:

SUMITA SINGHAL
Programme Manager
Water Programme, CSE
Email: sumita.singhal@cseindia.org
Phone: +91 8884646146