Excreta and Household Wastewaters - Introduction Global Water, Sanitation and Hygiene ENVR 890 Section 003 ENVR 296 Section 003 Mark D.
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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 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 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 “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 - 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 - 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 • 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 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 1.0 0.8 Nutrient content 500 l 50 l Volume Liter / (Person·year) greywater urine faeces source: Otterpohl kg N,P,K / (Person·year) 0 Ca. 65-90% of excreta nutrients are in urine as chemical compounds readily accessible to plants 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 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 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 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 Pathogen Reductions Vary from: low (<90%) to Very High (>99.99+%) Typical Dry Excreta Management Conventional „drop and store“ sanitation Retention of solids Infiltration of liquids Pathogens Nitrates Polluted groundwater Viruses When filled, abandon and build and new one. Poses health risks and is ecologically unsound. Overview of Ecosan Technologies solid biowaste faeces urine greywater rainwater collection Vacuum Sewerage Gravity Sewerage (conventional or small-bore, centralised or decentralised) Solid-Liquid Separation Urine diversion Dehydration Toilet treatment Composting Toilet Storage Biogas Digestors Composting Urine Processing utilisation Wastewater treatment (centralised or decentr.) Soil conditionning with treated Excreta and Solid Biowaste Greywater Separation Treatment Reuse Fertilizing with Urine Reuse of wastewater in agriculture, aquaculture, epuvalisation, etc. Rainwater Harvesting Catchment, Treatment, Use Examples of Urine Diverting Toilets China Wost-Man, Sweden GTZ, Mali waterless: faeces and urine without flush Roediger, Germany Dubletten, Sweden dry/wet: faeces without, urine with flush dry/wet: faeces with, urine without flush wet: faeces & urine with flush Examples of urine diversion toilet slabs Urine diverting concrete slab Composting toilet with urine separation (China) Waterless Urinals vacuum urinal KfW-building, Germany Ethiopia Mon Museum, Sweden South Africa Tepoztlan, Mexico Examples of Composting Toilets composting toilet, Germany (Berger Biotechnik) Promotes microbial activity at elevated temperature with air, heat, moisture, and some large particles Schweden Examples of Composting Toilets ‘Skyloo’, with above-ground vault, Zimbabwe Examples of Dehydrating/Dessiccating Toilets various dehydration systems (with and without urine separation) “SolaSan”-prefabricated “Enviroloo”-prefabricated system, South Africa 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 • 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 elements: vacuum toilets, vacuum urinals, vacuum conductions, pumping station advantages: water saving, concentrated black water collection, decentralised treatment possible (anaerobic) manufacturer: i.e. Roediger GmbH 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 small scale biogas plants: decentralised treatment of household wastewater with or without agricultural waste Aquaculture • 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 tilapia duckweed carp Urine Storage Various containers for urine storage: Gebers, Schweden Lambertsmühle, Deutschland Agricultural Use direct injection of liquid fertiliser irrigation urban agriculture dried faeces - „soil amelioration“) composting with organic waste urban agriculture Conventional Wastewater System Urban Ecosan Concepts food faeces urine greywater drinking water Periphery Urban Ecosan Concepts Urban Ecosan Concepts Residential Area food faeces urine greywater treated greywater drinking water Urban Ecosan Concepts Urban Ecosan Concepts Downtown Area food faeces urine greywater treated greywater drinking water irrigation of urban green vacuum sewerage biogas plant Titel des Vortrags, einzeilig oder zweizeilig urban ecosan concepts WfB, Rom – 12.Jan.2005 42 Human Excreta, Sanitation and Pathogens – Some References • http://www.ecosanres.org/pdf_files/Ecologi cal_Sanitation_2004.pdf • http://www.tuharburg.de/susan/downloads/TheFlushToil et_en.pdf • http://web.mit.edu/urbanupgrading/watera ndsanitation/levels/provide-san-serv.html