What is faecal sludge ?

Faecal sludge are residues extracted from onsite or decentralized sanitation systems (various type of latrines and septic tanks).
They consist of dissolved matters, settleable and floating solids. Depending on their origin, they can have very heterogeneous compositions. We can classify them in 2 big groups:

• Sludge from septic tanks (called septic sludges) that are generally highly concentrated, especially in dissolved solids (COD greater than 10 g/L)
• Sludge from single pits or latrines that are mostly low concentrated (COD around 2 g/L)

Average characteristics of faecal sludge :

References: IRSTEA, 2013 

Due to this heterogeneous composition, faecal sludge treatment is more or less difficult depending on the final objective, particularly for dissolved pollution.