WATER QUALITY OF DRINKING WATER WELL SAMPLES, MATLAB, BANGLADESH

Arsenic (As) contamination in groundwater has become one of the prime research issues in the Bangladesh water sector. The sustainability of a targeted low-As, shallow brownish oxidized aquifer, as an arsenic mitigation option is currently being investigated in Matlab, one of the worst arsenic affected areas in Bangladesh. The present study focuses on overall evaluation of groundwater quality in relation to safe water supply. Groundwater samples were collected from 82 tubewells, among which 59 wells tap water within a depth of 300 ft, while the remaining 23 wells range between 525 and 950 ft. The water samples were collected before monsoon of this year (2009). Arsenic, iron, manganese and other drinking water quality parameters such as fluoride, boron along with the major ions have been analyzed by high-precision ICP-OES and ion chromatography.

75 percent of the shallow wells exceeded WHO drinking water limit of 10 µg/L for As. The deeper wells have been essentially found below this limit. Most water samples are dominated by bicarbonate and chloride with a very low concentration of sulphate, nitrate and phosphate. About half of the samples exceeded chloride concentration of 250 mg/L. The shallow wells have a wide range of Fe concentrations with 78% samples above the USEPA and WHO recommended limit of 0.3 mg/L, while the concentrations are consistently low in the deeper wells. However, higher concentration of manganese has been observed in shallow wells compared to the deeper ones. In all deeper samples, manganese was found below 0.5 mg/L. On the contrary, 60% of shallow wells exceeded 1 mg/L of manganese, with a maximum value of 4.3 mg/L. Most of the wells had fluoride concentrations below the WHO drinking water guideline of 1.5 mg/L, while about 5% of wells indicated higher flluoride content reaching upto 3.9 mg/L. Boron concentrations were consistently low (< 0.1 mg/L). It is thus important that the assessment of the groundwater quality is needed for a comprehensive risk management of the drinking water wells from the perspectives of water safety plan in Bangladesh.