DECONTAMINATION OF DRINKING-WATER BY DIRECT HEATING IN SOLAR PANELS

A device was developed for direct heating of water by solar radiation in a flow-through system of copper pipes. An adjustable thermostat val iie prevents water below the chosen temperature from being withdrawn. The results show that it is possible to eliminate coliform and thermo tolerant coliform bacteria from naturally contaminated river water by heating to temperatures of 65 degrees C or above. Artificial additions of Salmonella typhimurium, Streptococcus faecalis and Escherichia col i to contaminated river water were also inactivated after heating to 6 5 degrees C and above, The total viable count could be reduced by a fa ctor of 1000. The heat-resistant bacteria isolated from the Mlalakuva River (Tanzania) were spore-forming bacteria which exhibited greater h eat resistance than commonly used test bacteria originating from count ries with colder climates. To provide a good safety margin it is recom mended that an outlet water temperature of 75 degrees C be used, At th at temperature the daily production was about 501 of decontaminated wa ter per m(2) of solar panel, an amount that could be doubled by using a heat exchanger to recycle the heat.