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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

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excreta and household wastewaters introduction

Excreta and Household Wastewaters - Introduction

Global Water, Sanitation and Hygiene

ENVR 890 Section 003

ENVR 296 Section 003

Mark D. Sobsey

February, 2006

excreta and graywater definitions and properties
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 feces and urine

Wastewater from washing, bathing, etc

Contains human wastes and exudates

types of human and animal wastes and their systems
Types of Human and Animal Wastes and their Systems

Feces & Urine = Excreta = “Nightsoil” = Slurry = Chamberpot Wastes

    • “Dry” Systems
    • Human (“sanitary”) waste in settings where water use is limited by preference or lack of indoor plumbing for water supply and liquid waste (sewage) disposal.
  • Sanitary or Municipal Sewage – Liquid or “Wet” Systems
    • Typical for human waste in settings where there is piped, household water supply and sanitary waste disposal using water.
  • Agricultural Animal Waste Systems:
    • Liquid or wet systems: use limited amounts of water for waste flushing from animal barns or other high animal density settings (dairy cattle
    • Dry systems: collect manure and urine, sometimes with bedding material by mechanical methods (movers) for storage and treatment
      • Pasture management is typically a dry system
managing human excreta options
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
    • Latrines, cesspools/waste pits
  • Separate feces and urine
    • Then, treat/store (latrines), use or dispose to the environment
managing human excreta options1
Managing Human Excreta - Options
  • Semi-wet (or semi-dry)
  • Use some water
  • Pour-flush toilets/latrines and other low water use systems
    • Needed where water is used for anal cleansing
    • On-site systems needed handle additional water
      • Can be done by infiltration and on-site treatment of semi solid wastes in latrine pits, composting pits, twin-pit pour-flush latrine, etc.
  • Alternatively, collect waste onsite and removed for further centralized or decentralized Rx
managing human excreta options2
Managing Human Excreta - Options
  • Wet Systems
    • On-site Septic Systems
    • Other On-site systems
      • Soak pits
      • Sand filters
    • Sewerage – liquid system to convey sewage off-site
    • Sewage treatment systems (off-site)
      • Subject sewage to physical, biological and chemical treatment processes
        • Separate settlable solids from remaining liquid
        • Biologically degrade ands stabilize organic matter
        • Biologically reduce pathogens
        • Physically and chemically disinfect pathogens
domestic community sanitary sewage
Domestic/Community Sanitary Sewage
  • Human feces and urine diluted in water + other “stuff”
  • ~20-50 grams feces dry weight (100-250 grams wet weight) + 1-1.5 L urine/500-800 L raw sewage
  • Dry weight suspended matter is about 0.1-0.2% (~1-2 grams/L)
      • Most is organic
      • Contains many pathogens, especially larger but also smaller ones
  • Sewage also contains “soluble” organic matter
    • of ten measured directly/indirectly as carbon or biodegradable carbon
    • Smaller microbes are part of the “soluble” matter: viruses + bacteria
human excreta resource or risk
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

Annual Amounts/Person, Kg

nutrient content of human excreta
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







kg COD/ (Person·year)





Nutrient content

kg N,P,K / (Person·year)

Composition of Household Waste and Wastewater

10.000 – 200.000 l

50 l

500 l

Ca. 65-90% of excreta nutrients are in urine as chemical compounds readily accessible to plants

source: Otterpohl


Liter / (Person·year)

greywater urine faeces

characteristics of human wastes
Characteristics of Human Wastes



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

3. greywater

  • 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.
ecological sanitation ecosan
Ecological Sanitation – “Ecosan”
  • A reuse cycle and closed-loop system for excreta
  • Treats human excreta as a beneficial resource
  • Excreta are confined and processed on site until they are free of pathogenic (disease-causing) organisms
  • Sanitized excreta are then recycled by using them for agricultural purposes.
  • Key features of ecosan:
    • Prevent pollution and disease caused by human excreta
    • Manage human excreta as a resource rather than as a waste product
    • Recover and recycle water and nutrients

Ecological sanitation FAQs: http://www.sanicon.net/faq.php3

options for excreta and greywater utilization





washing, etc.)



hygienisation by

storage or


constructedwetlands, gardening,

wastewater ponds, biol.treatment, membrane-technology





liquid or dry







recharge or

direct reuse

Options for Excreta and Greywater Utilization




Ecosan Book: http://www.ecosanres.org/pdf_files/Ecological_Sanitation_2004.pdf

Conventional Domestic/Municipal Sewage Treatment Systems were not Originally Designed for the Purpose of Removing or Destroying Pathogens
  • Emphasis on reducing “nuisance” aspects of sewage: smell, biodegradability (putrescence), vector attraction, etc.
  • Remove settleable suspended matter as solids or “sludge”
    • biologically degrade and stabilize sludge organic matter
  • Oxidize and stabilize non-settleable organic matter and nitrogen in the remaining liquid
    • or denitrify (biologically convert nitrogen to N2 gas)
  • Later (1950s and 1960s), pathogen control was introduced:
    • Disinfect the remaining liquid fraction prior to release
    • Disinfect the remaining solid fraction prior to release
  • Wastewater Reuse – Emerged in the 1970s; water scarcity

Typical Sewage or Community/Municipal Wastewater Treatment Systems

Treated (or untreated) wastewater is often discharged to nearby natural waters; alternatively, it is applied to the land or reclaimed/reused


Land Application of Treated Wastewater:

an Alternative to Surface Water Discharge

conventional community centralized sewage treatment
Conventional Community (Centralized) Sewage Treatment

Pathogen Reductions Vary from: low (<90%) to Very High (>99.99+%)

typical dry excreta management
Typical Dry Excreta Management

Retention of solids

Infiltration of liquids



Polluted groundwater


Conventional „drop and store“ sanitation

When filled, abandon and build and new one.

Poses health risks and is ecologically unsound.

examples of urine diverting toilets
Examples of Urine Diverting Toilets


Dubletten, Sweden

Roediger, Germany

Wost-Man, Sweden


faeces with, urine without flush


faeces without, urine with flush


faeces & urine with flush

GTZ, Mali


faeces and urine without flush

examples of urine diversion toilet slabs
Examples of urine diversion toilet slabs

Urine diverting concrete slab

Composting toilet with urine separation (China)

waterless urinals
Waterless Urinals

vacuum urinal

KfW-building, Germany


Mon Museum, Sweden

South Africa

Tepoztlan, Mexico

examples of composting toilets
Examples of Composting Toilets

Promotes microbial activity at elevated temperature with air, heat, moisture, and some large particles

composting toilet, Germany

(Berger Biotechnik)


examples of composting toilets1
Examples of Composting Toilets

‘Skyloo’, with above-ground vault, Zimbabwe

examples of dehydrating dessiccating toilets
Examples of Dehydrating/Dessiccating Toilets

various dehydration systems (with and without urine separation)

“SolaSan”-prefabricated system, South Africa

“Enviroloo”-prefabricated system, South Africa

Prefabricated dry UD toilets - South Africa

Solar drying toilet, El Salvador


Dehydrating/Dessiccating Toilets/Latrines

  • Goal is to dry the waste, sometimes directing urine away from feces.
  • Use urine separately as a fertilizer.
  • Promote drying, keep the volume of material small; confine feces for 6–12 months.
  • Add ash, lime or other material to feces after each defecation to lower moisture content and raise pH to 9 or higher. Conditions of dryness and ↑ pH promote pathogen die-off.
  • Remove partly treated solid material removed from processing chamber after Rx and storage.
  • Possible further Rx (high temp., composting, alkaline Rx, storage, carbonization/incineration).
on site septic waste treatment systems
On-Site Septic Waste Treatment Systems
  • Wet system with collection into a subsurface tank, separation (settling) and digestion (biological Rx) of solids and discharge of liquid effluent via perforated into subsurface soil for additional Rx.
  • Widely used in rural areas of developed and developing countries.
  • Often fail (eventually) due to poor site conditions, poor installation, lack of maintenance over time.
vacuum systems
Vacuum Systems


vacuum toilets, vacuum urinals, vacuum conductions, pumping station


water saving, concentrated black water collection, decentralised treatment possible (anaerobic)


i.e. Roediger GmbH

membrane rx technology
Membrane Rx Technology
  • Highly effective removal of soluble and biodegradable materials in wastewater stream
  • Selective permeable membrane (pore sizes < viruses)
  • Treated water recycle potential for non-potable use
  • Compact, flexible system
  • Expensive, requires maintenance by trained operators and a supply chain for replacement membranes and other parts
anaerobic treatment with biogas production
Anaerobic Treatment with Biogas Production

small scale biogas plants:

decentralised treatment of household wastewater with or without agricultural waste





  • Wastewater treatment by aquatic plants and fish with nutrient recyling by human consumption
  • Offers high quality protein at low cost
  • Predominantly in Asian countries
  • Fish production of 1-6 tons/ha·year) achieved
urine storage
Urine Storage

Various containers for urine storage:

Gebers, Schweden

Lambertsmühle, Deutschland

agricultural use
Agricultural Use

direct injection of liquid fertiliser


urban agriculture

urban agriculture

dried faeces - „soil amelioration“)

composting with organic waste

urban ecosan concepts





drinking water

Urban Ecosan Concepts


urban ecosan concepts2
Urban Ecosan Concepts

Residential Area





treated greywater

drinking water

urban ecosan concepts4
Urban Ecosan Concepts





treated greywater

drinking water

Downtown Area


of urban green






urban ecosan concepts

Titel des Vortrags, einzeilig

oder zweizeilig


WfB, Rom – 12.Jan.2005

human excreta sanitation and pathogens some references
Human Excreta, Sanitation and Pathogens – Some References
  • http://www.ecosanres.org/pdf_files/Ecological_Sanitation_2004.pdf
  • http://www.tu-harburg.de/susan/downloads/TheFlushToilet_en.pdf
  • http://web.mit.edu/urbanupgrading/waterandsanitation/levels/provide-san-serv.html