As an alternative to conventional treatment techniques of waste waters, a series of systems based on purifying mechanisms existing in nature have been developed. These systems are called “Natural Treatment Systems” .Design parameters which appear in the literature on this topic are linked to the studies carried out in countries with cold and mild climate.

The work presented deals with the study of wetlands with horizontal subsuperficial flow for the specific conditions of tropical climates, taking into account the biological and hydraulic parameters. The studies carried out from the biological and hydraulical point of views provide design parameters as a useful tool for designers and researchers, design methodologies as well as specific methodologies for the evaluation of its hydraulic behaviour using tracer techniques. In the study of the biological parameters the efficiency of contaminants removal is evaluated, applying mathematical models reported in international literature and the trends equations obtained in the removal of such parameters. Besides, area indexes by equivalent population and values of the constant of biological reaction of the different systems under study are given for the first time. The use of the butterfly jasmin as emerging plant can be considered a contribution to international level, because studies of this kind have not been reported in international literature. The use of two different types of emerging plants allowed to compare their purifying capacity in the specific conditions of Cuba.

Data obtained on the growth of biomass in the systems of subsuperficial flow are of great utility because they do not appear in the consulted international literature. Tracers are used for the first time in the country for the hydraulic evaluation of this kind of device and allows the observation of flow behaviour creating a base for the research and debate about this important and troublesome topic at national and world level. Mathematical models representing a contribution to international level are also presented .

The work makes evident the need to change the development model in relation to environment, by applying low cost and low energy consuming sustainable technologies. The work has been applied to the project of a wet land for the treatment of waste waters which spring into the Almendares river, located at the Havana Metropolitan Park and in two Guantanamo areas. Savings obtained with the use of this kind of facility are estimated in 14 788 pesos every year. It has the corresponding recommendations for its introduction and also about the results obtained. The developed technology was awarded with an international prize at the contest “Doctoral theses for sustainable development” convened by Aguas de Barcelona group. Main results have been presented in seven international events and have been published in five scientific articles, two of them abroad .