| Abstract | In this study two pilot-scale rock bed filters were conducted to determine the effects of
design parameters and operating conditions namely; type and arrangement of filter media, location
of aerator and HRT on RBF's petformance. Influent used was a mixture of AIT domestic
wastewater and tap water in a ratio of 1:1. The long term behavior of sediment and biofilm was
also studied.
For filter media effect, two types of filter media, broken bricks (diameter of 10 cm) and
rocks (diameter of 20-15-10-5 cm), were installed in the reactors under the same HRT of 4 hours
(OLR of 30 gBOD/m2
.d) and aerator location. The arrangement of rocks, which was from big
ones to small ones in the reactor direction, may be recommended for better filter media
installation. Since the rock media showed higher removal efficiencies of SS and VSS than the
brick media.
In case of different aerator location, three patterns (pattern 1-3) of aerator location on
RBF's petformance were studied at 4 hour HRT (OLRs of 20-30 gBOD/m2
.d) by keeping the
similar type of filter media. Aerator were installed at 0.5-1.5 m for pattern 1, 0.5-2.0 m for pattern
2 and 1.5-2.0 m for pattern 3. In pattern 2, the highest removal efficiencies of 78.4%, 74.0%,
60.9% and 60.9% for SS, VSS, BOD and COD, respectively were obtained. This was followed
by pattern 3 and 1. However, there was only a small difference between pattern 2 and 3.
The effect of HRT was examined in three cases; namely 2, 4 and 8 hours HR.Ts. These
OLRs were 68, 20 and 17 gBOD/m2
.d respectively. The highest RBF's performance was obtained
at the longest HRT of 8 hours or the lowest OLR of 17 gBOD/m2
.d.The removal efficiencies of
pollutants seem to be directly proportional to the hydraulic retention time. The overall removal
efficiencies of SS, VSS, COD, BOD and NH4-N were 84.7, 86.5, 77.1, 76.4 and 50.3%,
respectively.
To study long term behavior of sediment at the bottom and biofilm on the media, the
accumulation of these were considered at the first-half portion of the reactors during four months
operation.
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