Waste water and its characteristics:
The waste water which is generated from 'kitchens, bathrooms, and other wash areas' is called "Grey water".
The waste water which is generated from 'Toilets' is called "Black water".
The waste water which is generated from 'Toilets' is called "Black water".
Grey water + Black water = Waste water
In general, 80% of water used by the population comes out as waste water. If the water availability is 135 lpcd (Municipal+other sources), we consider 108 lpcd as the waste water generation.General characteristics of waste water is presented as below:
PARAMETER | HIGH | MEDIUM | LOW |
COD Total | 1,200 | 750 | 500 |
COD Soluble | 480 | 300 | 200 |
COD Suspended | 720 | 450 | 300 |
BOD | 560 | 350 | 230 |
VFA (as acetate) | 80 | 30 | 10 |
N total | 100 | 60 | 30 |
Ammonia-N | 75 | 45 | 20 |
P total | 25 | 15 | 6 |
Ortho-P | 15 | 10 | 4 |
TSS | 600 | 400 | 250 |
VSS | 480 | 320 | 200 |
What is Faecal sludge and septage?
The sludge produced by on-site sanitation systems like septic tanks is called "Septage".
The slude produced from pit toilets is called "Faecal sludge".
It is highly polluting than domestic waste water.
Faecal sludge quantity and quality
Supply based: It is estimated that 230 lts of Faecal Sludge is produced per capita per year.
Demand based: No.of septic tank emptying incidents X Capacity of the septic tank cleaning truck
Characteristics of Faecal sludge/septage is presented below:
Constituent All are units but for PH are in mg/l | Average |
PH | 1.5 - 12.6 |
Total suspended solids | 12,862 |
Biochemical oxygen demand | 6,480 |
Chemical oxygen demand | 31,900 |
Ammonia-Nitrogen | 97 |
Faecal sludge Management system (FSM):
 |
| Source: Bill And Gates Foundation |