Islam M Sirajul, Mahmud Zahid Hayat, Islam M Shafiqul, Saha Ganesh Chandra, Zahid Anwar, Ali Ahm Zulfiquar, Hassan M Qumrul, Islam Khairul, Jahan Hasin, Hossain Yakub, Hasan M Masud, Cairncross Sandy, Carter Richard, Luby Stephen P, Cravioto Alejandro, Endtz Hubert Ph, Faruque Shah M, Clemens John D
International Centre for Diarrhoeal Disease Research, Bangladesh, Mohakhali, Dhaka, 1212, Bangladesh.
Environmental Microbiology Laboratory, Laboratory Sciences and Services Division, icddr,b, GPO Box-128, Dhaka, 1000, Bangladesh.
J Health Popul Nutr. 2016 Aug 19;35(1):26. doi: 10.1186/s41043-016-0063-z.
Groundwater drawn from shallow tubewells in Bangladesh is often polluted by nearby pit latrines, which are commonly used toilets in rural and sub-urban areas of the country.
To determine the minimum safe distance of a tubewell from a pit latrine in different hydrogeological conditions of Bangladesh, 20 monitoring wells were installed at three study sites (Manda, Mohanpur and Bagmara) with the vertical and horizontal distances ranging from 18-47 to 2-15 m, respectively. Water samples were collected three times in three seasons and tested for faecal coliforms (FC) and faecal streptococci (FS) as indicators of contamination. Soil samples were analysed for texture, bulk density and hydraulic conductivity following standard procedures. Sediment samples were collected to prepare lithological logs.
When the shallow aquifers at one of the three sites (Mohanpur) were overlained by 18-23-m-thick aquitards, the groundwater of the monitoring wells was found contaminated with a lateral and vertical distances of 2 and 31 m, respectively. However, where the aquitard was only 9 m thick, contamination was found up to lateral and vertical distances of 4.5 and 40.5 m, respectively. The soil textures of all the sites were mainly composed of loam and sandy loam. The hydraulic conductivities in the first aquifer at Manda, Mohanpur and Bagmara were 5.2-7.3, 8.2 and 1.4-15.7 m/h, respectively.
The results showed that the safe distance from the tubewell to the pit latrine varied from site to site depending on the horizontal and vertical distances of the tubewell as well as hydrogeological conditions of a particular area.
在孟加拉国,从浅管井抽取的地下水常常受到附近坑式厕所的污染,坑式厕所在该国农村和城郊地区是常用的厕所。
为了确定在孟加拉国不同水文地质条件下管井与坑式厕所之间的最小安全距离,在三个研究地点(曼达、莫汉布尔和巴格马拉)安装了20口监测井,垂直距离和水平距离分别为18 - 47米和2 - 15米。在三个季节中采集三次水样,并检测粪便大肠菌群(FC)和粪链球菌(FS)作为污染指标。按照标准程序对土壤样本进行质地、容重和水力传导率分析。采集沉积物样本以编制岩性日志。
当三个地点之一(莫汉布尔)的浅层含水层被18 - 23米厚的隔水层覆盖时,监测井的地下水在水平距离2米和垂直距离31米处被发现受到污染。然而,当隔水层仅9米厚时,分别在水平距离4.5米和垂直距离40.5米处发现了污染。所有地点的土壤质地主要由壤土和砂壤土组成。曼达、莫汉布尔和巴格马拉第一个含水层的水力传导率分别为5.2 - 7.3、8.2和1.4 - 15.7米/小时。
结果表明,管井到坑式厕所的安全距离因地点而异,这取决于管井的水平和垂直距离以及特定区域的水文地质条件。