| Summary: | Gunung Kidul was indicated as an area with highest vulnerability index of
drought disaster. Actually, this problem can be solved by pumping out the water
from underground rivers exist there but there was a problem regarding to water
quality which does not meet the requirements of any regulatory standard of
drinking water. It needs to be treated before used for drinking water purposes.
According to IWRM research project, a suitable water treatment for Gunung
Kidul was slow sand filtration but that research did not consider the local media
(condition of local availability), temperature, raw water quality, and suitable
operation mode. Those limitations of previous research became the consideration
to conduct this research which focused on finding suitable local media and
suitable operation mode.
A laboratory experiment divided into two phases, first to find out the
suitable local media and second to find out suitable operation mode was
conducted. The assessment of the experiment was based solely on the turbidity
removal. Test of both phases used PVC columns and artificial turbidity water. The
artificial turbidity water was created from the mud of Gua Seropan and tap water
and it would be analyzed its comparison with Heilerde (surrogate material) used
by previous research whether it was representative or not. Analyses of media
characteristics (d10, d30, d60, d90, Cu, and Cc) by doing sieving analyses before they
were constructed in the columns were performed. Other parameters measured
were specific gravity, permeability, and porosity. On the phase I, five types of
local sand (lava sand, beach sand, zeolite sand, activated sand, and silica sand)
were tested by doing filtration process. Then two best media were selected to be
tested in the phase II to find out the suitable operation mode whether it was
continuous mode or intermittent mode.
According to the experiments, there were six conclusions which could be
concluded. First, slow sand filtration was a suitable water treatment method for
Gunung Kidul. Second, Heilerde was not representative as it would create higher
value of turbidity compared to the mud of Gua Seropan. Third, suitable local
media for slow sand filtration were lava sand and beach sand. Fourth, the
effectiveness of lava sand and beach sand was assessed as both were able to
reduce inlet turbidity from hundreds to below 1 NTU. Fifth, lava sand would be
more effective under low flow rate (0.1 m/h) and for beach sand under high flow
rate (0.3 m/h). Sixth, continuous mode (keeping constant water level) indicated
better effluent compared to intermittent mode.
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