Stopgap coagulation technology for arsenic removal from rural household drinking water

This study is intended to develop a stopgap coagulation protocol for immediate health protection of residents exposed to high arsenic from drinking water. The results of a simulated manual jar-test showed that ferric sulfate can maintain a satisfactory arsenic removal efficiency (>95%), and be relatively independent of water conditions. Combining with effective sand filtration, 20, 30, 60 mg/L of ferric sulfate were suitable for removing <0.5, 0.5–1.0, 1.0–2.0 mg/L of As(V), respectively. With decanting (after settling for 8∼10 h), however, ferric sulfate of 60 or 70 mg/L was needed to remove <0.5 or 0.5–1.0 mg/L of As(V), respectively. The removal rates of As(III) could achieve similar levels to that of As(V) once the water samples were pre-oxidized. The javelle water was selected as site applicable oxidant for As(III), although ozone sparging, hydrogen dioxide solution and bleaching powder also showed good performances. It was noted that the stopgap coagulation protocol was readily and acceptable to be applied by the local residents. The makeshift strategy will immediately protect the health of local residents before some kinds of long term and effective ways could be applied. Experiences obtained in this study provide valuable information for other places encountering the arsenic problem in rural drinking water.