Rational use of potable water and potential use of rainwater and reclaimed water in residential buildings

Abstract

This paper presents the results of a survey on domestic water consumption inside buildings covering some countries in European and American continents, namely Portugal, United States of America – USA and Brazil.. Some studies were identified and in which one was found the percentage of waterconsumed in the various activities carried out within the buildings, either by simple activities performed by residents, as well by appliances that add up the heaviest services automatically (dish and clothes washers). Considering the residential water profiles it was identified which part could be supplied by rainwater and the essential part exclusively supplied with drinking water. From this perspective was performed some calculations to find out the water savings by using rainwater for domestic purposes and which appliances inside buildings are eligible to be supplied. As complementary and considering that waste water generated by some appliances (showers) it was performed the calculations including the wastewater reclaimed inside buildings. The study finds out an average of drinkable water savings of 28 to 100 % for WC cisterns using rainwater and reclaimed water. Some other savings are presented according to sanitary appliance and inside or outside house activities when rain and reclaimed water were used. In conclusion it is noted that for the first part of residential water consumption there is a range of possibilities to promote the rational use of water by adopting measures involving design, saving water equipment and educational campaigns. For the second part it was highlighted the use of rainwater as an alternative.