Occurrence of manganese in groundwater of Bangladesh and its implications on safe water supply

Analysis of data obtained from the national hydrochemical survey show that about 42% of tubewells have manganese concentrations exceeding the WHO health-based guideline value of 0.4 mg/l. High manganese concentrations in groundwater have been found in the central, northern, and western regions of Bangladesh; groundwater in the north-eastern region of Bangladesh contain relatively less manganese. Deeper wells (> 150 m) have been found to contain relatively lower concentrations of manganese. Distributions of arsenic and manganese concentrations are not similar in groundwater of Bangladesh. Areas with low arsenic in groundwater have been found to contain high manganese concentrations, and vice versa. Nationwide about 32% of wells, which contain safe level of arsenic (i.e., < 0.05 mg/l) have been found to contain unsafe level of manganese (i.e., > 0.4 mg/l). This would significantly increase the population exposed to unsafe water, beyond that estimated for arsenic alone. Detection of high concentrations of manganese in groundwater has added a new dimension to the already difficult safe water supply scenario in Bangladesh. However, manganese issue has attracted relatively less attention so far in the water supply sector. Currently iron and arsenic-iron removal plants are being used in many regions of the country. In view of the widespread presence of manganese in groundwater in addition to arsenic and iron, it is important to raise awareness among the stakeholders about the manganese issue. It is also very important to identify areas unacceptable levels of arsenic and/or manganese and to develop water treatment technologies accordingly. © 2010 Institution of Engineers, Bangladesh. All rights reserved.