Abstract:
Although ground water is available in almost all of the
rural areas of Bangladesh, due to traditional habit, vast
majority of rural people still use surface water sources for
various domestic purposes. Water from these sources is
physically and bacteriologically contaminated due to
unhygienic practices and need proper treatment to make it
potable.
Treatment methods $uch as slow sand and rapid sand filtration
are not directly applicable in many cases due to high
concentration of turbidity and also economically not feasible
under rural economic condition in Bangladesh. This research
investigates the effectiveness of horizontal flow coarse
media roughing filter for a simple pretreatment of the highly
turbid and bacteriologically contaminated surface water.
A model horizontal flow roughing filter consists of three
chambers was filled with aggregates of different sizes.
Artificially contaminated turbid water of 130 NTU turbidity
was allowed to pass through the filter medias with constant
rate of filtration. The model plant effectively reduced the
raw water turbidity to the level of average 3.27 NTU.
Provision of an intermediate buffer zone in first chamber
increased the effective length of filter run by about 80
percent. A sedimentation basin, designed on the basis of settling
column test has been observed advantageous over second
chamber of roughing filter.
The third chamber of the model plant which consists of only
gravel and coarse sand significantly reduced the bacterial
concentration, but traditional method of filtration/
disinfaction is further necessary to reduce the coliform
counts to the level of acceptance.
