IRON REMOVAL FROM GROUND WATER BY GRANULAR MEDIA FILTRATION

Abstract

Among the various methods of iron removal adsorption has received great attention in the recent years as an efficient process for heavy metals removal. Activated carbon is one of the commonly used adsorbent but it is very costly. In the recent past many low cost adsorbents were tried and found successful. Adsorption of iron was studied into different grain sizes of sand in batch system using synthetic waste water. The effect of contact time, dose, and pH was studied in batch experiments. It was found that when initial iron concentration is 4ing/1, 20 gins/1 dose of 0.5mm sand can remove 97% iron at contact time of 2 hrs, 20 gms/1 dose of 1 mm sand can remove 96.25% iron at contact time of 2 hrs. and 20 gins/I dose of 2mm sand can remove 90.5% iron at contact time of 2 hrs, at natural pH i.e. 7.5. The equilibrium behaviour corresponds to the Langmuir isotherm for different grain size of adsorbents and for the initial iron concentration 4mg/l. On comparing different grain size of sand it was observed that 0.5mm sand is much better adsorbent than other grain size of sand for iron removal. A laboratory investigation was made, using biological sand filter, to evaluate the potential of filter in removing iron from ground water and to compare the performance of biological and simple sand filter at different filtration rates under identical filtration conditions. An attempt was also made to study the nature of the iron removal process by the biological sand filter and the difference, if any, between the biological and simple sand filters in the removal process. Performance of the biological sand filter at varying filtration rates (94 Ipm/m2, 188 1pm/m2, 282 Ipm/m2 and 376 1pm/m2). iii It was observed that the biological sand filter was effective in the removal of iron from ground water by oxidation and filtration taking place in the same unit. The performance of the biological sand filter operating at 376 Ipm/m2 was better to that of the simple sand filter at 94 1pm/m2 in terms of effluent iron quality. The biological sand filter was more effective than the simple sand filter in removing the soluble ferrous form of iron while effectiveness of both were comparable in removal the ferric and insoluble ferrous forms.