| Summary: | The research was conducted in the District Tanggulangin, Sidoarjo, to
determine the unconfined groundwater pollution due to the Lapindo mudflow
which appeared in 2006. The environmental indicator including BOD, COD,
phenol and H2S were used to assess the pollution severity. This study aimed to
determine the condition of unconfined groundwater at Tanggulangin District in
terms of physical (conductivity, color, taste, smell) and chemical properties (pH,
BOD, COD, Phenol, and H2S) and to assess the properness of unconfined
groundwater quality at Tanggulangin District to be used as a source of drinking
water.
Stratified Sampling method based on water conductivity level which was
measured after the groundwater depth was defined and Systematic grid Method to
determine the location of wells used for mapping the direction of groundwater
flow were used. Furthermore, data obtained including laboratory test result were
subjected to descriptive, graphical and spatial analysis.
The result showed that the groundwater around the studied area have
largely been polluted, indicated by the high values of BOD, COD, phenols and
H2S, which have exceeded the limit set for Water Quality Standards, issued
through Indonesia Government Regulation No. 82/2001. Samples which were
collected from the closer location to Lapindo mud ponds tended to have higher
COD value compared to the further area. BOD values and phenol level were
higher in samples collected from the further area to the ponds, especially in dense
residential areas. However, the levels of H2S in Kedensari Village groundwater
whose location is very close to the mud ponds was found to be higher than the
other samples. In addition, the groundwater also smelled which indicated the
contamination by the water of Lapindo mud ponds. The villages around the
Lapindo ponds have lower elevation than the ponds, thus the pollutants flowed to
the areas with lower groundwater surface. The BOD, COD, phenols and H2S
levels in some of the samples which exceeded the limit of drinking water quality
standard indicated that the groundwater in those areas cannot be used as drinking
water.
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