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Pit toilet sanitation design and improving salty water – Malawi

The Kasimu Education Fund, a US based 501c3 non-profit organization has been operating in Malawi for over five years to improve the education, economy and health of 5,000 villagers served by the Kasimu Elementary School. (see website kefmalawi.com)

We need assistance in two areas:

  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.

  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.

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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 ... (more)

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2013-01-18 07:48:14 -0500
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Last updated:
Jan 18 '13