Excreta and Household Wastewaters - IntroductionGlobal Water, Sanitation and Hygiene
ENVR 890 Section 003ENVR 296 Section 003
Mark D. SobseyFebruary, 2006
Household Human Wastes and Wastewaters
Excreta and Graywater– Definitions and Properties
Excreta: Human feces and urineManaged in different ways:
Direct disposal on land or in waterDirect use as fertilizer, soil conditioner and for aquaculturePre-treatment prior to use Dilution with water to convey (sewage) for disposal or use
Direct use of untreated (raw) sewageTreatment and discharge to land or waterTreatment and reuse (agriculture, aquaculture, horticulture,
industrial and civil useGraywater: Other wastewater from human activity
Not directly from human fecs and urineWastewater from washing, bathing, etc
Contains human wastes and exudates
Managing Human Excreta - Options• “Dry” Collection:
– Open defecation– Collect in a container
• e.g., chamber pot
– Discharge to the environment w/ or w/o Rx
• Latrines – several kinds– Treat or dispose of or both– Separate feces and urine;
• Then, treat/store, use, dispose to the environment
Managing Human Excreta - Options
• Semi-wet (or semi-dry)
• Use some water
• Pour-flush toilets and other low water use systems
Managing Human Excreta - Options
• Wet Systems– On-site Septic Systems– Other On-site systems
• Soak pits
– Sewerage– Sewage treatment systems
Human Excreta – Resource or Risk?
Nitrogen (N) 4.5Phosphorous (P) 0.6Potassium 1.0Organic matter(as BOD)
35
• Human excreta as a potential resource• Contains nutrients (N, P, K, and organic matter)• Nutrients and organic matter are:
•Detrimental in water, esp. surface water•Eutrophication, anoxia, fish kills
• Beneficial on land•Fertilizer, soil conditioner, land stabilizer
• Widely used as a fertilizer and soil amendment in both developed and developing countries• Potential for excreta misuse and environmental pollution is great without proper attention to management plans and human behavior considerations
Annual Amounts/Person, Kg
Nutrient Content of Human Excreta • Rich source of inorganic plant nutrients: N, P K and organic matter • Daily human excretion: ~30 g of C (90 g of organic matter), ~ 10-12 g
N, ~ 2 g of P and 3 g of K. • Most organic matter in feces most N and P (70-80 %) in urine. K
equally distributed between urine and feces.
0
20
Organicskg COD/ (Person·year)
12.3
3.6
14.1
VolumeLiter / (Person·year)
10.0
00 –
200
.00
0 l
500 l 50 l
sour
ce:
Ott
erpo
hl
0
6
Nutrient contentkg N,P,K / (Person·year)
N
P
K
0.8
5.3
1.0
Composition of Household Waste and Wastewater
greywater urine faeces
• of no major (or less) hygienic concern/risk• volumetrically the largest portion of wastewater• contains almost no (or less) nutrients (simpler
treatment)• may contain spent washing powders etc.
3. greywater
• less hygienically critical (less risk)• contains the largest proportion of nutrients
available to plants• may contain hormones or medical residues
2. urine
• hygienically critical (high risk)• consists of organics, nutrients and trace elements• improves soil quality and increase its water
retention capacity
1. feces
characteristicfraction
Characteristics of Human Wastes
sour
ce:
Dra
nger
t, 1
998
Fertilizer Equivalence of Yearly per Capita Excreted Nutrients and Fertiliser Requirements for Producing
250 kg of Cereals
0
1
2
3
4
5
6
N N P P K K
Nu
trie
nt
(kg
)
cerealrequirements
faeces
urine
Fertilizer Potential of Human Excreta
treatment
utilisation
substances faeces(brownwater)
anaerobic digestion,
drying, composting
biogas, soil
improvement
constructedwetlands, gardening,
wastewater ponds, biol.treatment, membrane-
technology
greywater (shower,
washing, etc.)
irrigation,
groundwater- recharge ordirect reuse
urine (yellowwater)
liquid or dry fertiliser
hygienisation by storage or
drying
Options for Excreta and Greywater Utilization
