TUBEWELL PLATFORM COLOR - A TOOL FOR SCREENING ARSENIC, IRON AND MANGANESE IN TUBEWELL WATER

Supply of drinking water from groundwater sources with safe level of arsenic (As), iron (Fe) and manganese (Mn) is challenging from the public health point of view. Thus it is urgent need for the governmental and international aid agencies worldwide to screen and regularly monitor tubewells (TWs) to assess the underlying health risk and prioritizing sustainable drinking water management. However, screening of TWs involves testing of groundwater from millions of sources, which is extremely difficult to achieve within suitable timeframe, particularly for developing countries like India and Bangladesh, by standard laboratory practice of using atomic absorption spectrophotometer (AAS). In this context an attempt has been made to assess and validate the concept of TW platform color as a TW screening tool for As, Fe and Mn. Statistical comparison between As, Fe and Mn concentration obtained from platform color perception and laboratory measurement by AAS shows, if Bureau of Indian Standard (BIS) drinking water guideline value (50 µg/L) is considered as cut-off value for As, with 93% certainty black colored platform determines TW would produce As free water and with 38% certainty red colored platform determines TW would produce As contaminated water with efficiency, sensitivity and specificity of 65, 85 and 59% respectively. Instead, if World Health Organization (WHO) guideline value (10 µg/L) is considered these certainty values become 73% and 84% respectively for black colored platform and red colored platform with efficiency, sensitivity and specificity of 79, 77 and 81% respectively. For Fe and Mn, validation is made only with respect to BIS value of 1 mg/L and 300 µg/L respectively. At this cut-off level, black colored platform with 69% certainty identifies TWs free from Fe and 78% certainty determines TWs contaminated with Mn and red colored platform with 92% certainty identifies TWs contaminated with Fe and with 64% certainty determines TWs free from Mn. The respective efficiency, sensitivity and specificity of the tool for Fe and Mn at this standard are 80, 75, 89% and 71, 67 and 76% respectively. Thus this study confirms that TW platform color can be regionally used as a potential screening tool of TWs for As, Fe and Mn to make subsequent well testing more focused and to prioritized mitigation program.