In view of this, it should be noted how much the regulatory
Brazilian standard (ABNT, 1997) is conservative with respect to the
threshold of anaerobic effluents in the hydraulic loading rate for
building such combined
filtration system. This standard establishes
the maximum rate of 100 L m2 day1 for anaerobic
effluents. Furthermore, it should be underlined that the threshold
set out by USEPA (200 L m2 day1) for building sand
filters cannot
be adopted for countries with warmer weather, as Brazil. In this
study, the adoption of the rate of 800 L m2 day1 ensured the
production of an effluent in accordance with the applicable legal
standards.