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Your question 1. Water from wells has a salty taste so villagers will drink contaminated river water. We need a method of removing salty taste from well water.
Answer: The most simple, low-cost method to desalinate brackish or salty water is distillation. In WELL Technical Brief 40 on Desalination - I found the following description:
“A simple, low-cost method to desalinate sea water by distillation is used in some countries where fuel is available. It requires basic kitchen utensils: two pots, one four times the size of the other, and a plastic sheet. The smaller pot is placed inside the larger one and weighed down with a stone.
Sea water is poured into the outer container up to the brim of the inner one. The larger pot is sealed using a plastic sheet and a piece of string so that the plastic sheet sags in the middle (Figure 6). This home-made still is then placed on any heat source such as a stove or wood fire, at low temperature. In a few minutes the sea water in the outer container starts to evaporate. As the plastic sheet prevents the steam from escaping, the droplets condense into the smaller vessel. Residual salt remains in the outer pot.
To conserve fuel, a still can be placed on top of a cooking- pot which is used every day, such as a rice pot. As it boils or simmers, the 'waste' heat is usefully harnessed.
Care should be taken to ensure that all pots are stable and out of reach of young children.”
Larger solar energy system
In the same document a drawing can be found of a larger solar energy system. It can be used to evaporate water from salt water for household or community water supplies by constructing sealed units covered with glass (Figure 5). There are problems with these units: growth of algae on the under- side of the glass sheet must be controlled, and the unit must be effectively sealed.
My colleague Jo Smet who is an experienced engineer told me that for a family of five people at 4 litres of potable water a unit of 5 m2 is needed.
Your question 2. The school complex depends upon latrines which are pit toilets. We need design criteria to construct new latrines which minimize the contamination of well water and the nearby river.
Answer: Below is a practical example from a photo story from a school in Kenya. Further down are school toilets design criteria.
Photo story: Water and sanitation improvements at Atono school in Kenya
Mr Daniel Odhiambo is head-master of the Atono school in Nyanza, one of only four schools in Kenya with urinals for girls. Netwas Kenya and IRC visited his school recently as part of a UNICEF Kenya study of 43 schools in four districts: Coast (Mombasa); Nyanza (Rachuonyo & Kisumu); Rift Valley (Kajiado); and North Eastern (Garissa). The aim of the study was to find out if the national Kenyan Ministry of Health’s standard ratio of 1 latrine to 25 girls and 1 toilet to 30 boys can be downgraded if the pupils also have access to urinals, and if so, what would be the new ratio.
This was a follow-up of 2004-2005 research on the enhancement of sanitation and hygiene for Kenya’s school children, carried out by IRC together with seven partner organisations in Kenya. The study showed that school toilet standards were not being met. See the online picture story with captions at www.irc.nl/page/54200.
Additional factors to consider
Below are other factors to consider from a good booklet on school toilets:
Mooijman, A. and Zomerplaag, J. (2004). Child-friendly hygiene and sanitation facilities in schools : indispensible to effective hygiene education. Delft, The Netherlands, IRC International Water and Sanitation Centre. Available at: www.irc.nl/content/view/full/9587
In this book you will find the following about ratio of school children to toilets:
“In some references, a rough standard used is a ratio of one facility for 20 students although in some countries the standard might be as high as one facility for 50 students. In addition, there are some other important factors when defining the exact number of facilities necessary:
How many girls and how many boys are there? It is recommended that at least half of the facilities are urinals. They are much cheaper than toilets and have a shorter waiting time. Where pits are used, providing urinals will extend the lifespan of the pits considerably and will cause less overall odour if they are well designed. Are children allowed to use the toilets during classes or only during breaks? When facilities are only used during breaks, there will be peaks in usage and therefore the capacity needs to be higher.
How many breaks are there? When there are few breaks the capacity needs to be higher than when there are more breaks, because children have fewer opportunities to use the facilities.
Do all classes begin and end at the same time? When timetables are different, fewer facilities are required. The ‘highest peak’ for usage has to be determined.
Will the number of students expand considerably in the future? What is the expected proportion between girls and boys?
Are there users with disabilities? Do they need specific design adaptations for sanitation facilities, hand washing or water access?
Do female/male teachers prefer to have their own facilities with sufficient privacy?”
School toilets design criteria
The best sanitation facilities that schools and parents of students can afford includes topics such as:
technology and environmental issues,
design and number of latrines needed, and
installation and maintenance considerations.
More details and technical drawings of various options can be found from a chapter from a Resource Book and that we published from School Sanitation and Hygiene Education India, which we ran together with UNICEF.
Both books contain a number of activity sheets to assist managers and trainers in their work. Although the books were developed in the context of the School Water and Sanitation Towards Health and Hygiene (SWASTHH) programme in India, they provide many useful guidelines and activities that apply to similar programmes elsewhere.
The designs start from Chapter 9 starting p 155 in the PDF file that you can download for free from our site at: www.irc.nl/page/1918.
The Handbook for Teachers may also be useful for your Malawi school programme.
Answer by Dick de Jong (IRC, retired) posted on 19 January 2011