Qualidade da água de chuva para consumo humano armazenada em cisternas de placa estudo de caso: estudo de caso: Araçuaí, MG

Abstract

The present work had as its main objective the evaluation of the rain water quality destined to the human consumption stored in plates cisterns. The study was developed in the municipal district of Araçuaí, Médio Jequitinhonha, semi-arid area of Minas Gerais State, where thereare water shortage problems in long droughts periods. Sixteen cisterns were chosen in two rural communities. Of those, eight were new, that is to say, they were storing the first rain cycle in 2005, and the eight remaining had more than two years of use. Some microbiological,physical and chemical parameters were analyzed to check the water quality variation during the storage, comparing them with the patterns established by the drinking water pertinent legislations. During the visits to the communities for collections, an inspection of the system was carried out, trying to identify the problems existence in the rainwater catchment system. At the same moment, the owners were questioned about the cares they had during the catchment and with the water storage /treatment. A register of the cisterns built at Araçuaí-MG was done as complementary work, to obtain a general view of the catchment systems already built in the municipal district. Even so, for the great number of communities and for the distance among them, just 17 of the 66 existent communities were assisted. Observing the monitoring results, differences in some parameters analyzed in the rainwater stored in thecisterns were verified. There was no statistically significant difference between the results of pH, iron, zinc, total coliforms and fecal streptococcos among the two cistern groups. The new ones presented elevated values of aluminum and sodium, maybe because these cisterns are more susceptible to the water corrosive action, because they are storing the first rain cycle. The old cisterns had problems related with microbiological contamination and with organic matter, presenting elevated values of E.coli, heterotrofic count, C.perfringens and nitrate,probably because of the structure bad state of conservation and the non-accomplishment of the periodic cleaning. It was verified that the disinfection process was accomplished for just 38% of the families. For the registered systems analysis, the structure depreciation with theelapsing of the time was noticed. The zinc covers showed not to be appropriated, because they got damaged under the heat action, turning the cisterns more susceptible to the dusts and small animals entrance, contaminating the water. The cracks presence was detected in 52%of the cisterns in Araçuaí, which demonstrates the structure fragility. The present research conclusion is that some modifications are necessary in the system constructive aspect, as well as implanting a constant educational action for the population that has rain as their source ofmore reliable water.