Transcript Excreta and Household Wastewaters - Introduction Global Water, Sanitation and Hygiene ENVR 890 Section 003 ENVR 296 Section 003 Mark D.

Excreta and Household
Wastewaters - Introduction
Global Water, Sanitation and Hygiene
ENVR 890 Section 003
ENVR 296 Section 003
Mark D. Sobsey
February, 2006
Household Human Wastes and
Wastewaters
Excreta and Graywater– Definitions and Properties
Excreta: Human feces and urine
Managed in different ways:
Direct disposal on land or in water
Direct use as fertilizer, soil conditioner and for aquaculture
Pre-treatment prior to use
Dilution with water to convey (sewage) for disposal or use
Direct use of untreated (raw) sewage
Treatment and discharge to land or water
Treatment and reuse (agriculture, aquaculture, horticulture,
industrial and civil use
Graywater: Other wastewater from human activity
Not directly from human fecs and urine
Wastewater 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?
• 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
Nitrogen (N)
Phosphorous (P)
Potassium
Organic matter
(as BOD)
4.5
0.6
1.0
35
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.
Composition of Household
Waste and Wastewater
20
14.1
12.3
5.3
6
3.6
K
Organics
P
kg COD/ (Person·year)
0
N
0.8
1.0
Nutrient content
500 l
50 l
Volume
Liter / (Person·year)
greywater
urine
faeces
source: Otterpohl
kg N,P,K / (Person·year)
0
Characteristics of Human Wastes
fraction
characteristic
1. feces
• hygienically critical (high risk)
• consists of organics, nutrients and trace elements
• improves soil quality and increase its water
retention capacity
2. urine
• less hygienically critical (less risk)
• contains the largest proportion of nutrients
available to plants
• may contain hormones or medical residues
• 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
Fertilizer Potential of Human Excreta
Fertilizer Equivalence of Yearly per Capita Excreted
Nutrients and Fertiliser Requirements for Producing
250 kg of Cereals
6
cereal
requirements
4
faeces
3
2
urine
1
0
N
N
P
P
K
K
source: Drangert, 1998
Nutrient (kg)
5
Options for Excreta and Greywater Utilization
urine
(yellowwater)
faeces
(brownwater)
treatment
hygienisation by
storage or
drying
anaerobic
digestion,
drying,
composting
utilisation
liquid or dry
fertiliser
substances
biogas,
soil
improvement
greywater
(shower,
washing, etc.)
constructed
wetlands, gardening,
wastewater ponds, biol.
treatment, membranetechnology
irrigation,
groundwaterrecharge or
direct reuse