Efficiency of Slow Sand Filter in Purifying Well Water

Slow sand filter can be effective for water purification. The formation of “schmutzdecke†on the surface of the sand bed can vary the efficiency of slow sand filter. This study aimed to investigate the efficiency of slow sand filter in purifying well water using Labo River sand as the filter medium. Bacteriological analysis and turbidity tests were done on water samples from deep and shallow well before and after filtration at 0.30 m, 0.60 m and 0.90 m filter depths and at 200 L/hr.m2 , 300 L/hr.m2 and 400 L/hr.m2 flow-through rates. Percent removal of E. coli varied and efficiency was generally high at different depths and flow-through rates. However, E. coli removal in different filter depths and flow-through rates was not significant (p<0.05). Percent efficiency in reducing turbidity varied. Efficiency was increasing at increasing depths and flow-through rates. There was a significant difference on the efficiency to reduce turbidity among different sand filter depths (p<0.05). However, there was no significant difference on the efficiency to reduce turbidity among the three flow-through rates. A significant interaction between filter depth and the flow-through rate in the removal of E. coli (p<0.05) was observed which means that increasing the depth of the sand filter while slowing the filtration rate improved efficiency in E. coli removal of the raw water. Most of the bacteria and particle removal is ascribed to schmutzdecke development. This study can help address the water problem particularly in local communities that depend greatly on well water for drinking.

 

Keywords: E. coli, filtration, Labo River, schmutzdecke, turbidity.