Influência de barreiras sanitárias na qualidade da água de chuva armazenada em cisternas no semiárido paraibano.

Abstract

The rain water captation in tanks is used of some centuries in arid and semiarid regions. Rain waters caught and stored with the appropriate sanitary security are of good quality and can be used for human consumption. Sanitary barriers can be installed along the system of captation and storage to get better the quality of the water that will be consumed. Deviation of the first ones waters of each rain event if constitutes in an important sanitary barrier of discarding of automatic form waters that carry pollutants from the atmosphere, the area of captation and the ducts. The present work had as objective to evaluate in real scale the quality of the water stored in eight agricultural tanks and pilot models, in located agricultural communities in the cities of São João do Cariri and Campina Grande in the Paraíba, under different conditions of maintenance and management, like the efficiency of physical sanitary barriers. Two models of pilot systems of Deviation had been constructed to one followed the beginning of water latch and the other with the communicating vases. The deviation had 1 mm of volume to store rain water. Parameters of quality had been measured in the rain water, in the tanks and the models pilots. The water of rain presented excellent physical and chemical quality and with small concentrations of E.coli. The waters stored in the tanks had presented sufficiently worst quality than rain water. All the tanks that had received water from water trucks had presented quality of what worse the ones that had only received water from rain. Of the tanks monitored with deviation incorporation of the first waters, they had had improvement of the quality, with prominence for the reduction of alkalinity, hardness, turbidity, SDT, electric conductivity ,salinity and chlorides. The system with principle of the water seal presented greater efficiency.In In general , the deviation of the first rain waters had been efficient and the pilots tanks had presented mean worst average values than to found in the control tanks. It stands out deviations as an important physical sanitary barrier in the removal of E.coli, with a reduction of the average concentration of the deviations for the pilot tank in the order of 80% for the model pilot with the deviation of water latch and 50% to the pilot model with the deviation with principle of the communicating vases Under controlled conditions of study with the pilot models, it was verified accented improvement in the quality of the water after 45 seconds of flow of the water in the tubing, time this equivalent approximately 0,5 mm of rain after the elimination, in deviation, of 1,0 mm of water per square meter of roof. One concludes that the water of rain in the agricultural areas of the Brazilian semiarid is of excellent quality to the adoption of multiple sanitary barriers throughout the system are basic to offer safe water the human consumption.