Experimenting with dry toilets in El Salvador - Ron Sawyer1 and George Anna Clark2
1 SARAR TransformaciC,
2 Espacio de Salud, AC, Mexico.
A successful solution to an environmental challenge
Environmental factors, including a chronic water shortage, and
high groundwater in parts of the country have made it necessary to adopt drastic
measures in El Salvador. Increasing priority is being given to constructing dry
toilets, which require no water for the disposal of human waste and, when
properly maintained, represent a safe, sustainable alternative for family
sanitation. Committed NGOs, the Ministry of Health and the Social Investment
Fund, with the financial and technical support of UNICEF, USAID, and Sida have
constituted a strategic alliance to bring this appropriate technology to E
Salvador. This technology is being replicated, adapted, and sustained on a large
scale. A comprehensive educational strategy that integrates the construction,
use, and management of dry toilets with personal hygiene and ecological
sanitation is a key component of the programme.
Environmental factors in El Salvador have made it necessary for
the country to adopt extreme measures for improving its sanitation coverage. A
chronic water shortage in much of the country has made conventional water-borne
sewerage unrealistic, while the high water table characteristic of much of the
coastal area of El Salvador makes traditional pit latrines virtually
unthinkable. One significant change has been the increased priority given to the
construction of dry toilets, which require no water for the disposal of human
waste, while the use of impermeable above-ground chambers prevent the
contamination of sub-surface water.
A growing awareness of environmental problems and the commitment
of NGOs, the Ministry of Health and the Social Investment Fund, together with
financial and technical support from UNICEF and USAID, have helped to bring the
modified Vietnamese double-vault toilet to El Salvador. As a result of
experiments and evolving government policies, this appropriate technology is
being replicated and sustained on a large scale. With approximately 100 000 of
these dry toilets and an ongoing research and development programme funded by
UNICEF and Sida, this Central American country is rapidly becoming a world
leader in sanitation without water.
The dry toilet
The dry toilet relies on a special toilet bowl that diverts the
urine to an absorption pit or to a container where it is collected for use as
fertilizer. The faeces fall into the chamber below the toilet and are dehydrated
to destroy pathogenic organisms, so that the substance can be reused as a
fertilizer and soil conditioner.
The maintenance of the system involves a set of simple
activities. After defecating, the user sprinkles dry materials such as ashes or
lime (or a mixture of dry soil or sawdust with ash or lime) over the faeces.
Every week the contents of the chamber should be stirred with a stick and more
dry material added.
The separation of urine from faeces and the addition of dry
material, reduce unpleasant odours and flies, which are serious problems of
traditional latrines. The toilet's double chamber allows the contents on one
side to lie idle, while the family continues to use the other side. Under normal
circumstances the chamber in use fills up in not less than six months, which is
enough time to assure that the material in the other chamber has dried
adequately. By drying the faecal material for at least six months, even the most
long-lived pathogens will be destroyed, leaving an innocuous material that can
be removed and disposed of or reused as a soil conditioner.
To properly use and maintain a dry toilet, it is useful to
understand how and why the system works. Whereas the term dry
sanitation can refer to either dehydration or decomposition, it is helpful
to appreciate the basic differences between the two processes.
Dehydration means that the humidity of the contents of the vault
is brought down to below 20 per cent. For effective composting, humidity must be
kept above 60 per cent. In a dehydrating system, pathogens are destroyed by
depriving them of water and by increasing the pH above tolerable levels. Users
help the process by adding dry materials and lime (or ash) as part of routine
The humidity interval of 20-60 per cent should be avoided,
because it results in incomplete dehydration, malodorous decomposition and fly
Dry toilet cycle.
Source: Redrawn from Letrinas secas: una polca
nacional en El Salvador and Saneamiento sin agua, El Manantial. Boletde la
Red Regional de Agua y Saneamiento para Centroamca (RRAS-CA), A, # 1,
You must empty the urine
When the first chamber gets full,
you move the toilet bowl to the second chamber
While the second chamber is
filling, the first one is decomposing
Once the second chamber is full,
you empty the first one, and you move the toilet bowl again
The cycle begins again
Figure 2. The double-vault
Source: Cr Ae, Helechos No. 5, Col.
Jacarandas, CP 62420, CuernavacMorelos, Mexico.
Had these critical facts been better understood by many
sanitation pilot projects worldwide, many unfortunate failures could have been
avoided and the unjustifiable mistrust of dry sanitation technology much more
Education and mobilization
UNICEF has played a vital role in developing an educational
approach that integrates the social and technical aspects of dry sanitation.
Initially, the focus was at the family level, involving household visits by
trained community promoters (visitadoras), who follow a programmed sequence of
learning modules. This has been complemented by regular monitoring of key
aspects of individual and family hygiene, as well as toilet use and maintenance.
In 1996, to get communities more involved in the water and
sanitation programmes, SARAR TransformaciC provided training in
participatory methods (including PHAST) to technical and field staff of key
NGOs, the Ministry of Health, and UNICEF. The comprehensive educational
strategy, which integrates the construction, use, and management of dry toilets
with personal hygiene and ecological sanitation is proving to be critical for
promoting the acceptance and sustainability of alternative sanitation
approaches. An important result of this participatory learning process has been
the consolidation of an inter-institutional team of trainers sponsored by
UNICEF. These trainers, promoting participatory methods, train staff from other
institutions and other sectors, and adapt and produce non-directive learning
Three very different experiences are discussed below to
illustrate the significant learning that is taking place in El Salvador.
Hermosa Provincia. After one child fell into a pit
latrine, the Hermosa Provincia peri-urban neighbourhood in the capital city of
San Salvador was motivated to build a dry sanitation system. As a result of
intensive education in using and maintaining the dry toilets provided by the
Ministry of Health, plus effective community organization and follow-up support
from a local church, the 130 units in this community have been functioning
successfully over the past six years. Although most of the toilets are actually
built into the houses, there are no unpleasant odours, nor any flies. After a
year, the dehydrated material is removed from the chamber and is used in a
communal nursery, occasionally sold (at US$ 4.65 per 100 kg), or used as
landfill on a nearby site belonging to the church.
Figure 3. Constructing a
double-vault, desiccating toilet with urine separation
Source: Uno Winblad, Pataholm 5503, 38492 em,
Tan. The Ministry of Health, with technical support
from UNICEF and SANRES (see Box 1) is developing and testing experimental
solar-heated toilets, with urine diversion in the semi-rural village of Tan.
Unlike most other dry toilets, this type of solar toilet has just one chamber
and uses solar energy to accelerate the desiccation process. Built entirely
above ground, the 36 experimental units include urine diversion, and produce a
dry product from the human faeces that can be safely used after storage of at
least six months.
Box 1. SANRES Project3
SANRES (Sanitation Research) is a Sida-funded project that has
been supporting dry sanitation research and development activities in El
Salvador since 1994. The SANRES project is currently active in seven countries
(Bolivia, China, El Salvador, Guatemala, Mexico, South Africa, and Vietnam) and
has created an informal network in 20 countries. SANRES holds that any
intervention in sanitation must take into account that sanitation is a system
including the natural environment; society (with its beliefs, values, practices,
technologies); a device (the physical structure that receives the human excreta;
and processes (the physical, chemical, and biological processes, such as
dehydration or decomposition, that take place inside the device). Unless each of
the system's elements is considered with equal rigour, effective and sustainable
intervention will be difficult to achieve.
3 For more information, contact Uno
Winblad, SANRES, fax: +46 499 24253 or email: email@example.com.
The Tan toilets produce no flies or odours, but do require
that the user shifts the pile under the toilet seat to the back of the chamber
every one or two weeks. On some units, a mechanical pusher is used
to shift the pile without opening the chamber. Because of the chamber's limited
size, the material at the rear of the chamber must then be emptied every second
or third month, to be stored until disposed of or used in the garden as a soil
conditioner or fertilizer, composted or used as the drying agent in the toilet.
This project is demonstrating that the size of the dry toilet
can be significantly reduced (the volume of the chamber has varied from 0.35 to
0.6 m3), thus lowering the cost of construction materials. The direct
cost (materials and labour only) of a solar toilet is US$ 225, compared to US$
271 for a standard dry toilet. Space requirements have also been reduced
significantly, which is a very important consideration in highly dense urban
Studies are being conducted to reduce maintenance needs to a
minimum while still assuring an acceptable level of pathogen destruction, before
promoting and constructing solar toilets on a large scale. In addition, the
project is continuing to experiment with optimal design and location. The 36
units now in use are being expanded to 500 units to test the applicability of
the system on a larger scale. This next research phase will concentrate on the
sociocultural issues (user education and training, extension support) associated
with safe, sustainable use.
Chicuma. ProVida, an innovative national NGO, supported
by UNICEF, has introduced a change to the traditional pit toilets in the rural
community of Chicuma, inhabited by former guerrillas. In an otherwise
traditional 1.5-2 m deep pit toilet, faeces and urine are kept apart by using
the urine-diverting seat.
Over two years ago, about 70 families installed the seats for
urine diversion, while a few households built traditional toilets. The latter
continue to have odour, fly, and mosquito problems, while the former generally
do not. Only during the rainy season, and only for a short period of time, when
there is an increase of humidity in the otherwise dry pit, do flies and odour
become a nuisance in the modified toilets. It has been observed that the depth
of the pit in the modified toilet can be reduced. Overall the community is very
satisfied with this innovative pit toilet, which is seen as a positive first
step towards gradually introducing the standard dry toilet.
Although evaluations and additional technical studies (for
example, on the die-off rate for pathogens and parasites) are necessary, El
Salvador's experiences with dry toilets corroborate several basic sanitation
principles. As with any sanitation system, to be safe and environmentally sound,
dry toilet programmes require a clear understanding of the technology to be used
and the prevailing natural conditions. Community organization and education are
important components to assure the system's sustainability. Since the family
must undertake more maintenance than required for traditional toilets. But
wherever these conditions are met, dry toilets have proved to be a sustainable
solution for family sanitation.
Key institutions and responsible persons
WATSAN Project Officer
San Salvador, El Salvador
Tel: +503 263 3380
Fax: +503 263
Tel: +46 499 24255
Fax: +46 499 24253
Brand T. Letrinas secas: una polca nacional en El Salvador
and Saneamiento sin agua, El Manantial - Boletde la Red Regional de Agua y
Saneamiento para Centroamca (RRASCA), A, # 1, August 1996.
Winblad U, Dudley E. Dry toilets for urban areas: the
findings of the second SANRES workshop. Mexico City, November 23-26, 1994.
Report for consideration at the El Salvador Meeting.
Meeting of the Water Supply and Sanitation Collaborative Council, 25-29 March