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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: Systems

    an Alternative to Surface Water Discharge

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

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

    Typical dry excreta management
    Typical Dry Excreta Management Systems

    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 Systems


    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 Systems

    Urine diverting concrete slab

    Composting toilet with urine separation (China)

    Waterless urinals
    Waterless Urinals Systems

    vacuum urinal

    KfW-building, Germany


    Mon Museum, Sweden

    South Africa

    Tepoztlan, Mexico

    Examples of composting toilets
    Examples of Composting Toilets Systems

    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 Systems

    ‘Skyloo’, with above-ground vault, Zimbabwe

    Examples of dehydrating dessiccating toilets
    Examples of Dehydrating/Dessiccating Toilets Systems

    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 Systems

    • 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 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 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 Systems

    • 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 Systems

    small scale biogas plants:

    decentralised treatment of household wastewater with or without agricultural waste


    tilapia Systems




    • 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 Systems

    Various containers for urine storage:

    Gebers, Schweden

    Lambertsmühle, Deutschland

    Agricultural use
    Agricultural Use Systems

    direct injection of liquid fertiliser


    urban agriculture

    urban agriculture

    dried faeces - „soil amelioration“)

    composting with organic waste

    Urban ecosan concepts

    food Systems




    drinking water

    Urban Ecosan Concepts


    Urban ecosan concepts2
    Urban Ecosan Concepts Systems

    Residential Area





    treated greywater

    drinking water

    Urban ecosan concepts4
    Urban Ecosan Concepts Systems





    treated greywater

    drinking water

    Downtown Area


    of urban green





    urban ecosan concepts Systems

    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 Systems

    • 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