How can we estimate faecal sludge generation at household scale?

[Anonymous]

like we know the per capita water supply as per CPHEEO is 135 Lpcd, how can we do it for faecal sludge

[username_1712139132265]

Faecal sludge (FS) can be estimated using two primary methods:
a. Generation-Based Estimation: This method estimates the volume of sludge generated based on user numbers and accumulation rates. It is particularly useful for planning in areas without regular desludging data.

Formula for estimation is based on the following factors:
Faecal Sludge Generation (L/year) = No. of users × Accumulation rate (L/person/year)
Containment Type
Typical Range (L/person/year)

1. Type of containment: Septic tank (with soak pit)
   Typical Range (L/person/year): 30–40
   Source: https://forum.susana.org/214-vault-content-research-and-faecal-sludge-characteristics/22270-sludge-accumulation-rate-in-septic-tank?utm

2. Type of containment: Fully sealed septic tank
   Typical Range (L/person/year): 50–70 Source: https://www.frontiersin.org/journals/water/articles/10.3389/frwa.2023.1130081/full?utm

3. Type of containment: Pit latrine (lined)
   Typical Range (L/person/year): 40–60
   Source: https://link.springer.com/chapter/10.1007/978-981-33-4114-2_27?utm

The value accumulation value can be adopted based on the context adapted in the region, in Indian context, a report published by Centre for Science and Environment, suggest the accumulation rate varies between 70 to 150 litres/person/year. Therefore, any value falling between these upper and lower limits can be considered.

Example:
A 5-member household using a sealed septic tank:
5 (persons)× 60 (L/person/year)= 300 L/year
Over 5 years: 1,500 Litres

b. Collection-Based Estimation:
This method uses actual desludging records from vacuum trucks or manual operators. It measures how much FS is collected and transported, rather than what is theoretically produced.
Formula:
FS Collected (L/HH/year) = (Total Desludged volume (L))/[(Household Served x Years since last emptying)]
A vacuum truck removes 3,000 L from a household every 5 years:
FS Generation = 3000 / 5 = 600 L / year / household