Off-flavours in drinking water : Analytical procedures and treatment effects in biologically active sand filters

Abstract: Taste and odour problems in drinking water are primarily caused by naturally produced, volatile, organic compounds. So far, research in this field has focused on a relatively small number of known compounds. However, several results indicate that the origin of objectionable tastes and odours in water can be attributed to a much larger group of compounds, many of them so far unidentified.The complex composition of off· flavours in drinking water calls for a systematic method of establishing cause-effect relationships. In the present study such a method was developed. After enrichment of odorous organic compounds by stripping, solvent extraction and adsorption on XAD-2, the extracts obtained were fractionated by preparative gas chromatography with subsequent sensory evaluation of the fractionsredissolved in water. It is suggested that this technique, in combination with chromatographic sniffing, may play a crucial role in isolation and identification of the compounds causing the off· flavour of a water sample.Abatement of off-flavours in water is mainly accomplished by means of different filtration techniques. In the present study, the removal of off-flavour compounds during filtration through biologically active sand filters was investigated. This was done during both full-scale operation of the artificial ground water recharge technique and laboratory-scale column experiments with or without pretreatment with ozone. The efficient removal of off-flavours obtained in the sand filters studied, demonstrated the potential of treatment methods based on biological activity. Artificial groundwater recharge and related sand filtration techniques deserve an increased attention in drinking water treatment.