A study on arsenic removal from household drinking water.

Arsenic removal from household drinking water has been receiving considerable attention in the field of water supply engineering. To develop the optimal coagulation protocol, the effectiveness of several operation options such as coagulants, coagulant aids and additives, as well as flocs separation systems were investigated in this study through the use of orthogonal array experiment based on Taguchi method. Arsenic removal mechanism during household coagulation (via manual mixing) was also discussed. The results showed that the addition of kaoline and powder activated carbon (PAC) did not enhance arsenic removal efficiency of ferric sulfate or aluminum sulfate. Similarly, mixture of ferric sulfate and aluminum sulfate (MFA) as well as polymeric ferric silicate sulfate (PFSiS) was also unable to improve the overall arsenic removal efficiency. The mechanism of arsenic removal during coagulation was somewhat different from those experienced in conventional processes. Coprecipitation appeared to be the crucial mechanism for arsenic removal. It is noted from this study that arsenic adsorption isotherm under household operation condition could be described by Langmuir equation. An efficient flocs separation system subsequent to coagulation was essential to achieve the effectiveness of overall arsenic removal. The results obtained from field experiment demonstrated that the method of ferric sulfate coagulation/sand filtration for arsenic removal from household drinking water was acceptable and affordable.