Influence of dry deposition and modification in automatic device on rainwater quality

ABSTRACT

The use of cisterns for rainwater storage is a common practice in Brazilian semi-arid region, which has been historically used for human consumption. Atmospheric air quality, dry deposition and management are important factors that affect the quality of rainwater. Sanitary barriers contribute to minimize pollutants entering in cisterns and are essential for maintaining the quality of rainwater, allowing uses for more restrictive purposes. In this research, in the first stage, the performance of the first flush device was evaluated in the retention of pollutants after a dry deposition interval of up to 15 days. In the second stage, a change was made to the original configuration in order to improve the retention of floating materials. In the first stage, it was observed that the rainwater contamination increased over the days of dry deposition. An increase in true color was obtained after the sixth day without precipitation and the highest color removal efficiency was 66.6%. For turbidity, only one day of dry deposition was enough to disqualify the quality of rainwater for human consumption, despite the good efficiency of removing turbidity (above 90%). Thus, the results of first stage indicate that the initial first flush device must be emptied after each day of dry deposition. The results of the second stage indicated that the change in the device configuration resulted in the efficiency of pollutants removal, represented by true color (22.8%), turbidity (13.0%), and total coliforms (99.4%).

Keywords:
rainwater collection; dry deposition; sanitary barrier