Abstract
Arsenic (As) removal plants were installed in As-endemic areas of Bangladesh to remove As from well water. In many cases, these removal plants did not perform satisfactorily. This study evaluated the efficiency of 20 As and iron (Fe) removal plants (AIRPs) during pre- and post-monsoon conditions in rural Bangladesh. Results revealed that As removal efficiencies ranged from 67% to 98% and 74 to 93% during the pre- and post-monsoons periods, respectively. In the post-monsoon season As removal at individual AIRP sites was on average (4.01%) greater than in the pre-monsoon season. However, two removal plants were unable to remove As below 50 µg L−1 (Bangladesh drinking water standard) during pre-monsoon, while 11 samples out of 20 were unable to remove As below the WHO provisional guideline value of 10 µg L−1. During post-monsoon, none of the samples exceeded 50 µg L−1, but eight of them exceeded 10 µg L−1. The Fe removal efficiencies of AIRPs were evident in more than 80% samples. Although As removal efficiency was found to be substantial, a cancer risk assessment indicates that hazard quotient (HQ) and carcinogenic risk (CR) of As in treated water for adults and children are above the threshold limits. Thus, additional reductions of As concentrations in treated water are needed to further reduce the excess cancer risk due to As in drinking water. Since 55% and 40% of the AIRPs were unable to remove As < 10 µg L−1 during pre-monsoon and post-monsoon, further improvement including changes in AIRP design, regular cleaning of sludge, and periodic monitoring of water quality are suggested. Future research is needed to determine whether these modifications improve the performance of AIRPs.
Highlights
Arsenic (As) is a known human carcinogen and elevated concentrations of As have been detected in the groundwater in many parts of the world [1,2,3]
The extent of risks both for adults and children were calculated in terms of hazard quotient (HQ) and carcinogenic risk (CR) for As in raw water and treated water during premonsoon and post-monsoon periods
As and risks associated with its consumption through drinking water
Summary
Since the seasonal variation has major implications for mitigation efforts, we investigated whether interseason variation wields any influence on AIRPs’ efficiency in removing As and Fe. Based on a 2-year efficiency study on 18 AIRPs from As-affected areas of West Bengal [40], it was reported that, firstly, none of the AIRPs could maintain As in treated water below the WHO provisional guideline value (10 μg L−1 ); and secondly, only two could meet the previous Indian standard value (50 μg L−1 ). Brennan and McBean [10] evaluated the performance of 21 installed AIRPs in the Manikgong district in Bangladesh They observed that all of the AIRPs achieved the Bangladesh drinking water standard for As (50 μg L−1 ), but four of them failed to reach the WHO provisional guideline value of As (10 μg L−1 ); on average the removal efficiency was 87% [10]. (ii) the role of Fe/As ratio in removal efficiencies; (iii) the impacts of AIRP treatment on health risk assessment in Jashore district’s rural areas in southwest Bangladesh
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