Eficiência de terras úmidas construídas cultivadas com arroz (Oryza sativa) e Typha spp em substratos de areia e brita no tratamento de águas contaminadas com esgotos domésticos, Paraíba, Brasil.

Abstract

The processing of wastewater, mainly for irrigation, promotes the saving of good quality water that can be useful for more noble purposes, besides preventing sewage from being released in the receiving bodies. The nutrients restrained in these waters can be employed as fertilizers for the cultures, resulting into great economic advantage. The irrigated agriculture, through the use of wastewaters, is an asserted need, because it is a safe and a sanitary option, economically feasible and environmentally sustained, particularly in the northeastern semiarid, where the irregular distribution of rains restricts the country-man's agricultural activities for domestic consumption. The wetlands are artificial systems designed by man, which apply the basic criteria of the natural wetlands system. Among these ecosystems' essential elements, the substrate is found, the biofilm formed by bacteria, fungi and metazoans, responsible for important mechanisms of pollutant removal, the aquatic macrophytes and the roots' zone or rhizosphere, and also the hydraulical flow. This work aims at studying the effectiveness of the treatment by means of wetlands of subsurface flow, with a hydraulical detention time of 10 days, from domestic sewage's contaminated water and its application in the production of useful cultures for man. Eighteen beds (asbestos cement tanks) with sand and crushed stone substrates have been settled. The applied emergent macrophytes species have been rice (Oryza sativa) and Typha spp. The planted wetlands themselves have been compared as well as with witness tanks, bearing only sand and crushed stone. In all treatments, the nitrogen removal has been observed (varying from 50 to 90%), also the removal of organic matter (varying from 77 to 89%) and of fecal bacteria (varying from 98.78 to 99.92%). There was an excellent growth of rice and Typha spp. The results have disclosed that the wetlands are an efficient choice for the treatment of domestic sewage's contaminated water and for the reuse of its final effluent.