2018 أبريل 27

الحُفرة الواحدة

Applicable to

Application level

City

Household

Neighborhood

Management level

Household

Public

Shared

المُدخلات

Faeces Excreta Blackwater
+ Dry Cleansing Materials + Anal Cleansing Water

المُخرَجات

Sludge
المؤلف*
Eawag المعهد الفيدرالي السويسري لعلوم وتقنيات المياه
ترجمة وتعريب مؤسسة بناء

المُلخص التنفيذي

تقنية الحُفرة الواحدة Single Pit هي واحدة من أكثر تقنيات الصرف الصحي استخدامًا، حيث يتم التخلص من فضلات الجسم مع مواد تنظيف الشرج (المياه أو المواد الصلبة) في حُفرة واحدة، كما أن تبطين الحُفرة يمنعها من الانهيار ويوفر الدعم لبنيتها الأساسية.

هناك عمليتان لتجنُّب امتلاء الحُفرة عن آخرها، والحد من معدل التراكم، وهما الرشح والتحلّل؛ حيث تتسرب المياه والبول إلى التربة عبر قاع الحُفرة وحوائطها، بينما يُحلل النشاط الميكروبي جزءًا من المكونات العضوية.

المزايا
يمكن بناؤها وإصلاحها بالمواد المتوفرة محليًا.
التكاليف الإنشائية مُنخفضة (لكنها متعددة) وذلك يعتمد على المواد المستخدمة وعُمق الحُفرة.
تتطلب مساحة صغيرة من الأرض.
العيوب
وجود ملحوظ للذباب والروائح.
تخفيض محدود في نسبة الاحتياج الحيوي للأكسجين (BOD) ومُسببات الأمراض مع احتمال تلويث المياه الجوفية.
تكاليف التفريغ قد تكون كبيرة مقارنة بالتكاليف الرئيسية.
تتطلب الحمأة معالجة ثانوية و/أو تفريغ مناسب.
المُدخلات المُخرَجات

فضلات الجسم , المياه السوداء , البراز ,مياه تنظيف الشرج ,مواد التنظيف الجافة

الحمأة

المُلاءَمَة

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تكون عمليات المُعالجة في الحُفرة الواحدة (الهوائية، واللاهوائية، والتجفيف، والتسميد، أو غيره) محدودة، ولذلك فإن معدل تخفيض مُسببات الأمراض والتحلّل العضوي ليس كبير، ولكن بما أن فضلات الجسم يتم احتواؤها، فذلك يحد من انتقال مُسببات الأمراض للمستخدمين.

وتكون تقنيات الحُفرة الواحدة مناسبة للمناطق الريفية وشبه الحضرية، على عكس المناطق المُكتظة بالسكان، حيث يكون من الصعب تفريغها و/أو لا توجد مساحة كافية للرشح. كما أنها مناسبة في حالة نُدرَة المياه، وحيث يكون منسوب المياه الجوفية مُنخفضًا، وهي غير مناسبة في حالة التربة الصخرية أو المدكوكة (التي يصعب حَفرها)، أو للأماكن التي تتكرر بها الفيضانات.

 

اعتبارات التصميم

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في المتوسط تتراكم المواد الصُّلبة بمعدل من 40 إلى 60 لترًا لكل شخص في السنة، ويصل إلى 90 لترًا لكل شخص في السنة في حال استخدام مواد تطهير جافة؛ مثل أوراق الشجر، أو المناديل الورقية، حجم الحُفرة يجب أن يُصمَّم لاستيعاب 1000 لتر على الأقل. يكون عمق الحُفرة - عادةً - 3 أمتار على الأقل وقطرها 1 متر، وإذا زاد قطر الحُفرة عن 1.5 متر فهناك احتمال كبير لانهيارها، واعتمادًا على مدى عُمق الحُفرة، فإن بعض الحُفر تبقى 20 سنة أو أكثر دون تفريغ، ولمنع تلوث المياه الجوفية فإن قاع الحُفرة يجب أن يكون أعلى من مستوى المياه الجوفية بحوالي 2 متر على الأقل (بحُكم التجربة)، وإذا كان سيُعاد استخدام الحُفرة مرة أخرى بعد تفريغها؛ فيجب عمل بطانة لها.

يُمكن أن تشمل مواد تبطين الحُفرة: الطوب، أو الخشب المضاد للعفن، أو الخرسانة، أو الحجارة، أو إلصاق مونة الجص على التربة. وإذا كانت التربة مستقرة (بمعني لا يوجد رمل أو حصى أو مواد عضوية رخوة) فلا يوجد حاجة لتبطين الحُفرة كلها، ويجب عدم تبطين قاع الحُفرة للسماح برشح السوائل منها.

بينما تتسرب السوائل من الحُفرة وتنتقل عبر التربة المسامية غير المُشبَّعة، فإن الجراثيم المُسببة للأمراض تُمتَص على سطح حبيبات التربة، وبهذه الطريقة يمكن إزالة مُسببات الأمراض قبل أن تصل إلى المياه الجوفية. وتختلف درجة الإزالة حسب نوع التربة، المسافة المقطوعة، الرطوبة وعوامل بيئية أخرى، ولذلك فإنه من الصعب تقدير المسافة الضرورية بين الحُفرة ومصدر المياه، ولكن يُنصح أن تكون المسافة الأفقية بينهما حوالي 30 مترًا على الأقل للحد من التعرض للتلوث الميكروبي.

وعندما لا يكون من الممكن حَفر حُفرةٍ عميقة، أو عندما يكون مستوى المياه الجوفية عاليًا جدًا، فإن بناء حُفرة مرتفعة يمكن أن يكون بديلًا مُجديًا، حيث يمكن تمديد الحُفرة غير العميقة عن طريق بناء حلقات أو كُتل خرسانية بشكل رأسي فوقها، ويمكن بناء الحُفرة المُرتفعة في مكان تَحدث فيه فيضانات أو سيول مُتكررة للحفاظ على المياه من التدفُّق إلى الحُفرة أثناء الأمطار الغزيرة. ومن الممكن أيضًا أن تكون الحُفرة غير العميقة وغير المُبطنة مُناسبة للمناطق التي يصعب فيها الحَفر. وعندما تمتلئ الحُفرة غير العميقة فإنه يمكن تغطيتها بأوراق الشجر والتربة وزراعة شجرة صغير فيها (انظر  الملء والتغطية/ أربولو).

تكون الحُفرة الواحدة المُطورة المُهواة  أكثر كُلفة من الحُفرة الواحدة التقليدية، لكنها تُقلل البعوض والروائح بشكلٍ كبير، وتزيد من راحة المستخدم.

وإذا تم استخدام واجهة المستخدم الفاصلة للبول، فسيتم تجميع البُراز فقط في الحُفرة وبذلك يقل الرشح.

 

التشغيل والصيانة

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لا تتطلب الحُفرة الواحدة صيانة يومية إلا إنه يجب المحافظة على نظافة الوحدة المُنشَأة.

ولكن عندما تمتلئ الحُفرة يمكن أن: 1) يتم تفريغها وإعادة استخدامها 2) تُنقل البنية الفوقية (الحمَّام) والمِرحاض لحُفرة جديدة وتُغطّى الحُفرة القديمة وتخرج من الخدمة، ويُستحسن ذلك فقط إذا كانت هناك مساحة أرضية كبيرة متاحة.

المراجع

المياه ،الصرف الصحي النظافة الصحية وظروف الإقامة في السجون

بييـر جيورجيو نمبرينـي (2009): المياه ،الصرف الصحي النظافة الصحية وظروف الإقامة في السجون . (= الطبعة العربية الاولى ). جنيف .سويسرا: اللجنة الدولية للصليب الاحمر

Language: Arabic

بناء الحمامات وطرق تحسينها وصيانتها

عبدالرقيب على حمادي (2001): بناء الحمامات وطرق تحسينها وصيانتها. المنصورية والمخأ / اليمن: ﺗﻤﻮﻳﻞ ﺍﻟﺘﻌﺎﻭﻥ ﺍﻟﻔﻨﻲ ﺍﻷﻟﻤﺎﻧﻲ ﺍﻟﻴﻤﻨﻲ ﺍﻟﺨﺪﻣﺎﺕ ﺍﻻﺳﺘﺸﺎﺭﻳﺔ ﻓﻲ ﻗﻄﺎﻉ ﺍﻟﻤﻴﺎﻩ ﻭﺍﻟﺼﺮﻑ ﺍﻟﺼﺤﻲ

Language: Arabic

الصرف الصحي الموقعي والمركزي - للمدن والتجمعات السكانية الصغيرة

برنامج التوعية السكانية .الخدمات الاستشارية في قطاع المياه والصرف الصحي (2001): الصرف الصحي الموقعي والمركزي - للمدن والتجمعات السكانية الصغيرة . اليمن: GTZ التعاون الفني الألماني اليمني

Language: Arabic

Guidelines for Assessing the Risk to Groundwater from On-Site Sanitation

Many people in developing countries rely upon untreated groundwater supplies for their drinking water (e.g. from drilled boreholes, tube wells, dug wells or springs). The introduction of on-site sanitation systems might lead to groundwater contamination. The purpose of this manual is to provide guidance on how to assess and reduce the risk of contamination of groundwater supplies from on-site sanitation systems and is aimed at those responsible for planning low cost water supply and sanitation schemes.

ARGOSS (2001): Guidelines for Assessing the Risk to Groundwater from On-Site Sanitation. (= Commissioned Report , 142 ). Keyworth: British Geological Survey URL [Accessed: 11.05.2019]

Latrine Building

This document describes how to build a squatting slab and the moulds for the frame, footrests, spacers, etc.

BRANDBERG, B. (1997): Latrine Building. A Handbook for Implementation of the Sanplat System. London: Intermediate Technology Publications

Pit Latrines and Their Impacts on Groundwater Quality: a systematic Review

This study reviews empirical studies on the impact of pit latrines on groundwater quality and identifies knowledge gaps regarding the potential and consequences of groundwater contamination by latrines.

Graham, J. ; Polizotto, M.L. (2013): Pit Latrines and Their Impacts on Groundwater Quality: a systematic Review. Advance Publication. المُدخلات: Environmental Health Perspectives: URL [Accessed: 09.04.2013]

Emergency Sanitation: Assessment and Programme Design

This book has been written to help all those involved in planning and implementing emergency sanitation programmes. The main focus is a systematic and structured approach to assessment and programme design. There is a strong emphasis on socio-cultural issues and community participation throughout.Includes an extensive “guidelines” section with rapid assessment instructions and details on programme design, planning and implementation.

HARVEY, P. BAGHRI, S. REED, B. (2002): Emergency Sanitation: Assessment and Programme Design. Loughborough: Water, Engineering and Development Centre (WEDC) URL [Accessed: 31.05.2019]

On-Site Sanitation in Areas with a High Groundwater Table

In areas that experience a seasonally high groundwater table or that are prone to flooding, constructing affordable on-site sanitation facilities can be very problematic. It is a challenge that affects many countries worldwide. This technical brief provides practical guidance on some sanitation options in such conditions.

PARRY-JONES, S. (1999): On-Site Sanitation in Areas with a High Groundwater Table. Leicestershire: , Engineering and Development Centre (WEDC) Loughborough University URL [Accessed: 31.05.2019]

Low Cost Sanitation

This survey provides information on how to calculate pit size and technology life.

PICKFORD, J. (1995): Low Cost Sanitation. A Survey of Practical Experience. London: Intermediate Technology Publications

Compendium of Sanitation Systems and Technologies. 2nd Revised Edition

This compendium gives a systematic overview on different sanitation systems and technologies and describes a wide range of available low-cost sanitation technologies.

TILLEY, E. ULRICH, L. LUETHI, C. REYMOND, P. ZURBRUEGG, C. (2014): Compendium of Sanitation Systems and Technologies. 2nd Revised Edition. Duebendorf, Switzerland: Swiss Federal Institute of Aquatic Science and Technology (Eawag) URL [Accessed: 28.07.2014] PDF
قراءات أخرى

Guidelines for Assessing the Risk to Groundwater from On-Site Sanitation

Many people in developing countries rely upon untreated groundwater supplies for their drinking water (e.g. from drilled boreholes, tube wells, dug wells or springs). The introduction of on-site sanitation systems might lead to groundwater contamination. The purpose of this manual is to provide guidance on how to assess and reduce the risk of contamination of groundwater supplies from on-site sanitation systems and is aimed at those responsible for planning low cost water supply and sanitation schemes.

ARGOSS (2001): Guidelines for Assessing the Risk to Groundwater from On-Site Sanitation. (= Commissioned Report , 142 ). Keyworth: British Geological Survey URL [Accessed: 11.05.2019]

Faecal Sludge Management.

This issue presents studies from different regions (Bangladesh, Cameroon, Burkina Faso) that mainly show the non-existence of faecal sludge management. Additionally, the last paper describes a new technological solution (LaDePa) for producing hygienically safe organic fertiliser from sludge from ventilated improved pit toilets (VIPs).

ECOSAN CLUB (2012): Faecal Sludge Management.. (= Sustainable Sanitation Practice , 13 ). Vienna: Ecosan Club URL [Accessed: 16.10.2012]

Closing the loop – Ecological Sanitation for food security

This document was compiled during an international, interdisciplinary workshop in Mexico. This manuscript increases the understanding of how to develop more sustainable sanitation systems, particularly in urban/peri-urban contexts, while contributing to food production and improved nutrition.

ESREY, S.A. ANDERSSON, I. HILLERS, A. SAWYER, R. (2001): Closing the loop – Ecological Sanitation for food security. Stockholm: Swedish International Development Cooperation Agency URL [Accessed: 24.11.2010]

Pit Latrines and Their Impacts on Groundwater Quality: a systematic Review

This study reviews empirical studies on the impact of pit latrines on groundwater quality and identifies knowledge gaps regarding the potential and consequences of groundwater contamination by latrines.

Graham, J. ; Polizotto, M.L. (2013): Pit Latrines and Their Impacts on Groundwater Quality: a systematic Review. Advance Publication. المُدخلات: Environmental Health Perspectives: URL [Accessed: 09.04.2013]

Emergency Sanitation: Assessment and Programme Design

This book has been written to help all those involved in planning and implementing emergency sanitation programmes. The main focus is a systematic and structured approach to assessment and programme design. There is a strong emphasis on socio-cultural issues and community participation throughout.Includes an extensive “guidelines” section with rapid assessment instructions and details on programme design, planning and implementation.

HARVEY, P. BAGHRI, S. REED, B. (2002): Emergency Sanitation: Assessment and Programme Design. Loughborough: Water, Engineering and Development Centre (WEDC) URL [Accessed: 31.05.2019]

Applying the Life-Cycle Costs Approach to Sanitation

This briefing note presents an application of the life-cycle costs approach (LCCA) to sanitation in rural and peri-urban areas in four different countries— Andhra Pradesh (India), Burkina Faso, Ghana, and Mozambique. The document compares the differences between the financial costs of traditional and improved latrines, and the quality of service delivered to users.

IRC (2011): Applying the Life-Cycle Costs Approach to Sanitation. (= Briefing Note , 3 ). The Hague: International Water and Sanitation Center (IRC) URL [Accessed: 18.06.2019]

How to Select Appropriate Technical Solutions for Sanitation

The purpose of this guide is to assist local contracting authorities and their partners in identifying those sanitation technologies best suited to the different contexts that exist within their town. The first part of the guide contains a planning process and a set of criteria to be completed; these assist you in characterizing each area of intervention so that you are then in a position to identify the most appropriate technical solutions. The second part of the guide consists of technical factsheets which give a practical overview of the technical and economic characteristics, the operating principle and the pros and cons of the 29 sanitation technology options most commonly used in sub-Saharan Africa.

MONVOIS, J. GABERT, J. FRENOUX, C. GUILLAUME, M. (2010): How to Select Appropriate Technical Solutions for Sanitation. (= Six Methodological Guides for a Water and Sanitation Services' Development Strategy , 4 ). Cotonou and Paris: Partenariat pour le Développement Municipal (PDM) and Programme Solidarité Eau (pS-Eau) URL [Accessed: 19.10.2011]

How fast do pit toilets fill up? A scientific understanding of sludge build up and accumulation in pit latrines

A number of possibilities exist for using fecal sludge beneficially. Data provided by Water Services Authorities indicate that most pits are filling in five to nine years. This suggests that of the more than a million ventilated improved pit latrines that have been built in the past decade many will soon reach capacity. Studies of pit filling rates across a number of communities indicate that pits generally fill at a rate of 40 liters per capita annum, with 60 liters per capita annum providing a safe margin for planning pit design and emptying programs (Link-download is free but registration required).

STILL, D. FOXON, K. (2012): How fast do pit toilets fill up? A scientific understanding of sludge build up and accumulation in pit latrines. (= Tackling the Challenges of Full Pit Latrines , 2 ). Gezina, South Africa: Water Research Commission URL [Accessed: 15.01.2013]

Adventures in search of the ideal portable pit-emptying machine

This article explores the ideal portable pit-emptying machine for South Africa owing to site access constraints. The Water Research Commission of South Africa funded experimental development of a number of technologies designed to fill the gap between large vacuum tankers and manual emptying. This paper describes these attempts.

STILL, D. O RIORDAN, M. MC BRIDE, A. LOUTON, B. (2013): Adventures in search of the ideal portable pit-emptying machine. Rugby: Practical Action Publishing URL [Accessed: 07.08.2013]

How to Manage Public Toilets and Showers

The purpose of this decision-making aid is to provide practical advice and recommendations for managing toilet blocks situated in public places. It is primarily aimed at local decision-makers in developing countries and at their partners (project planners and managers).

TOUBKISS, J. (2010): How to Manage Public Toilets and Showers. (= Six Methodological Guides for a Water and Sanitation Services' Development Strategy , 5 ). Cotonou and Paris: Partenariat pour le Développement Municipal (PDM) and Programme Solidarité Eau (pS-Eau) URL [Accessed: 19.10.2011]

Latrine and Sanitation Options Manual

This Manual aims to serve as a practical guide for the selection of sanitation technology options to satisfy local desires and meet national needs in Afghanistan. It is useful for the professionals and organisations working to address fecal contamination across Afghanistan.

USAID Afghanistan (2010): Latrine and Sanitation Options Manual. Sustainable Water Supply and Sanitation (SWSS) Project. Kabul: USAID Afghanistan URL [Accessed: 15.01.2013]

Technology Notes

These technology notes have been prepared following many general enquiries for technical information having been received by WaterAid over the years. Their purpose is to give an outline of the technologies used by WaterAid on long-term development projects in Africa and Asia, and to show alternatives, which might be appropriate in different circumstances. It may be possible to determine from the notes the technology, which would be appropriate in a particular location.

WATERAID (2008): Technology Notes. London: WaterAid URL [Accessed: 04.01.2011] PDF

A Guide to the Development of On-site Sanitation

The publication presents appropriate technologies for sanitation and highlights socio-economic aspects of planning and implementing. Emphasis is given to household-level sanitation improvements for urban areas, as well as rural areas and small communities. Background information on sanitation, in-depth technical information on the design, construction, operation and maintenance and project planning and development processes involved in projects and programmes complement the book.

WHO (1992): A Guide to the Development of On-site Sanitation. Geneva: World Health Organisation (WHO) URL [Accessed: 14.04.2010]

Guidelines for the safe use of wastewater excreta and greywater. Volume IV. Excreta and Greywater Use in Agriculture

Volume IV of the Guidelines for the Safe Use of Wastewater, Excreta and Greywater recognizes the reuse potential of wastewater and excreta (including urine) in agriculture and describes the present state of knowledge as regards potential health risks associated with the reuse as well as measures to manage these health risks following a multi-barrier approach.

WHO (2006): Guidelines for the safe use of wastewater excreta and greywater. Volume IV. Excreta and Greywater Use in Agriculture. Geneva: World Health Organisation (WHO) URL [Accessed: 09.05.2019] PDF
حالات دراسية

Pit Latrines & their Impact on Groundwater in Small Towns in Uganda. A Case of Bugiri Town Council

This paper investigates the groundwater contamination due to poorly designed pit latrines and inadequate protected water sources.

KABONGO, I. KABISWA, C. (2008): Pit Latrines & their Impact on Groundwater in Small Towns in Uganda. A Case of Bugiri Town Council. Kampala: Ecological Christian Organisation URL [Accessed: 06.12.2010]

From Pit Latrine to Ecological Toilet

This case study shows the problems of pit latrines in Garla Mare, Romania. After situation was analysed, several options were considered to improve the sanitation in the village.

SAMWEL, M. GABIZON, S. WOLTERS, A. WOLTERS, M. (2006): From Pit Latrine to Ecological Toilet. Utrecht/Munich: Women in Europe for a Common Future (WECF) URL [Accessed: 06.11.2010]

Groundwater Contamination due to Pit Latrines Located in a Sandy Aquifer. A Case Study from Maputaland

This paper describes research of groundwater contamination due to pit latrines in the coastal plain of northern Kwa Zulu-Natal, South Africa.

STILL, D.A. NASH, S.R. (2002): Groundwater Contamination due to Pit Latrines Located in a Sandy Aquifer. A Case Study from Maputaland. Dorpspruit: Partners in Development URL [Accessed: 06.11.2010]

A Directory of Environmentally Sound Technologies for the Integrated Management of Solid, Liquid and Hazardous Waste for Small Island Developing States (SIDS) in the Pacific Region

This directory is part of UNEP collaboration with SIDS on the implementation of the Waste Management chapter of the Barbados Programme of Action. It focuses primarily on proven sound environmental technologies for solid, liquid and hazardous waste management plus those currently successfully being used in SIDS within the Pacific Region.

UNEP (2002): A Directory of Environmentally Sound Technologies for the Integrated Management of Solid, Liquid and Hazardous Waste for Small Island Developing States (SIDS) in the Pacific Region. The Hague: United Nations Environment Programme (UNEP) URL [Accessed: 28.03.2012]

The search for appropriate latrine solutions for flood-prone areas of Bangladesh

The appropriateness of latrine technology depends on groundwater table, geographical context and acceptance by the community. The current study discusses defferent technologies and solutions for excreta management in flood- and cyclone-prone areas of Bangladesh.

MORSCHED, G. ; SOBHAN, A. (2010): The search for appropriate latrine solutions for flood-prone areas of Bangladesh. المُدخلات: Waterlines: Volume 29 URL [Accessed: 25.11.2015]
مواد تدريبية

A Practical Guide for Building a Simple Pit Latrine

This technical do-it-yourself guide provides step-by-step instruction on building simple pit latrines. It was designed for use at the individual household level to assist families in West Africa who have already decided to build their own latrines.The dialogue in the guide should be enacted by a facilitation team in the form of a skit followed by a debate. Each key step (placing the latrine, digging the pit, making the slab, building the superstructure) should be represented and followed by a discussion with the public, with responses and comments being provided for each step.

CAVANNA, S. DEBUS, J.-P. NIKIEMA, L.Z.P. (2011): A Practical Guide for Building a Simple Pit Latrine. West Africa Cluster: Global Water Initiative (GWI) URL [Accessed: 12.12.2011]

Latrine Slabs

This poster is part of the series of Water, Sanitation and Hygiene posters designed by the Water, Engineering and Development Center of Loughborough University.

REED, B. SHAW, R. (2013): Latrine Slabs. (= WEDC Posters , 1 ). London: Water, Engineering and Development Center (WEDC) URL [Accessed: 07.08.2013]

Simple Pit Latrines

This poster is part of the series of Water, Sanitation and Hygiene posters designed by the Water, Engineering and Development Center of Loughborough University.

REED, B. SHAW, R. (2013): Simple Pit Latrines. Poster. (= WEDC Posters , 10 ). London: Water, Engineering and Development Center (WEDC) URL [Accessed: 28.08.2013]

Emptying Pit Latrines

This technical brief describes several possibilities of emptying pit latrines and helps to find the most suitable method.

PICKFORD, J. SHAW, R. (1997): Emptying Pit Latrines. (= Technical Briefs, No. 54 ). Loughborough: Water and Environmental health at London and Loughborough (WELL) URL [Accessed: 28.05.2019]

Latrine Slabs and Seats

This technical brief describes pit latrines and possible slabs and seats to cover them.

WELL (n.y): Latrine Slabs and Seats. (= WELL Technical Briefs , 45 ). Loughborough: Water and Environmental health at London and Loughborough (WELL) URL [Accessed: 26.04.2010]

Exercise. Pits for Latrines

This is an exercise on the design of pits for a latrine of a familiy of six members.

WHO (2002): Exercise. Pits for Latrines. المُدخلات: WHO (1992): A Guide to the Development of On-site Sanitation. Geneva: 129-134.
مواد لنشر الوعي

The Microbial Contamination of Water Supplies from Pit Latrines

This factsheet describes the microbiological contamination of water supplies. It gives an overview on pathogens and its characteristics as well as methods to reduce the risk of contamination.

WELL (2006): The Microbial Contamination of Water Supplies from Pit Latrines. (= WELL Fact-sheets ). Loughborough: Water and Environmental health at London and Loughborough (WELL) URL [Accessed: 07.12.2010]

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