Impact of pretreatment on defluoridation of drinking water by bone char adsorption

Abstract

Fluoride concentrations in drinking water in excess of 1.5 mg L-1 are unsafe for human consumption. To reduce excess fluoride intake, developing countries must use low-cost, point-of-use defluoridation techniques. Although previous work has extensively assessed defluoridation using bone char (BC), most of the advanced studies have been based on the use of fluoridated distilled water as a feed solution. In the present study, BC columns were challenged with a range of model solutions, mimicking various pretreatment options. As a result, the relative impact of dissolved organic carbon (DOC) and suspended solids (SS) on the performance of BC filters was assessed. In addition, the performance of a gravity-driven, hollow fibre ultrafiltration (UF) module was examined with regards to the potential for use as a pretreatment option. SS were observed to severely clog the columns and cause the complete cessation of flow. The subsequent removal of SS by UF improved the general filter performance as well as increasing the BC lifetime by 50 %. The UF module achieved a reduction in DOC of 34 ± 6 %, resulting in an additional 30 % increase in the lifetime of the BC column.