the necessity and health aspects of the reuse of water

shortage of water has been a great consideration since ancient times in iran. the yearly average atmospheric precipitation in iran is around 250 mm considering the total area of the country, it can be estimated that our share of water is 420 x 109 per year. due to evaporation and run off to the sea through rivers and infliction it has been estimated the available water can not be more than 120 × 109 m 3 per year. assuming, hopefully, that out national family planning program becomes a success, still there will be approximately 50 × 106 people in this country with due regard to our trend of industrialization, urbanization and agricultural activities, we would assume much higher water demand in the year 2000. water demand for the morning of the first day of 21st. century of the united states is forecasted to be 7500 m 3 per capita per year, based on this figure if we foresee 3,000 m 3 per capita per year, it could be seen that there will be a shortage of 50xl09 m 3 per year, which will affect our national development. our hope would be planning to reuse the available water where there is no other choice such as salt water conversion. centrally speaking, application of sewage for any purpose needs some degree of treatment. best method of including chlorination can reduce coliforms by a factor of 99.99 per cent and pathogen, probably, by 90 per cent.