Quality assessment of harvested rainwater and seasonal variations in the southwest coastal area, Bangladesh

Abstract

Secure potable water is indispensable to life. The presence of salinity in potable water has become a serious problem worldwide and it is essential to ensure secure potable water, particularly in the coastal areas of Bangladesh. In this work, 48 (forty-eight) harvested rainwater samples were assessed from Upazila (sub-district) of Mongla and Sarankhola, Bagerhat district, Bangladesh during the monsoon (May) and post-monsoon (October) periods. The objective was to examine the effect of seasonal variations on the quality of harvested rainwater. The harvested rainwater was analyzed for fecal coliform, total coliform, lead (Pb), zinc (Zn), pH, and turbidity. The mean pH in monsoon and post-monsoon periods was 6.93 and 7.24, respectively, which was within both the WHO guideline and Bangladesh Drinking Standard. In the monsoon season, turbidity levels in samples met the Bangladesh water quality standard but 10% of the harvested rainfall samples had Pb levels that exceeded the WHO drinking water limit. The turbidity of harvested rainwater in post-monsoon exceeded the WHO and Bangladesh Drinking Standard by 21% (10 out of 48) and 6% (3 out of 48), respectively. The fecal coliform of harvested rainwater exceeded both WHO and Bangladesh Drinking Standard by 56% (27 out of 48) and 67% (32 out of 48) in the monsoon and post-monsoon, correspondingly. Conversely, total coliform of harvested rainwater exceeded both the WHO and Bangladesh Drinking Standard by 67% (32 out of 48) and 79% (38 out of 48), accordingly in the monsoon and post-monsoon seasons. The Zn was below the WHO and Bangladesh Drinking Standard but Pb exceeded the WHO guideline in the monsoon and post-monsoon by 15% (7 out of 48) and 17% (8 out of 48), respectively. Pb is toxic to humans and children are especially vulnerable. The harvested rainwater should be treated effectively to reduce the toxicity and danger posed by Pb, fecal coliform, and total coliform before it is fit for drinking purposes.