The public health significance of latrines discharging to groundwater used for drinking

Abstract

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Faecal contamination of groundwater from pit latrines is widely perceived as a major threat to the 22 safety of drinking water for several billion people in rural and peri-urban areas worldwide. On the 23 floodplains of the Ganges-Brahmaputra-Meghna delta in Bangladesh, we constructed latrines and 24 monitored piezometer nests monthly for two years. We detected faecal coliforms (FC) in 3.3 -25 23.3% of samples at four sites. We differentiate a near-field, characterised by high concentrations 26 and frequent, persistent and contiguous contamination in all directions, and a far-field characterised 27 by rare, impersistent, discontinuous low-level detections in variable directions. Far-field FC 28 concentrations at four sites exceeded 0 and 10 cfu/100ml in 2.4 -9.6% and 0.2 -2.3% of sampling 29 events respectively. The lesser contamination of in-situ groundwater compared to water at the point-30 M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPTof-collection from domestic wells, which itself is less contaminated than at the point-of-31 consumption, demonstrates the importance of recontamination in the well-pump system. We present 32 a conceptual model comprising four sub-pathways: the latrine-aquifer interface (near-field); 33 groundwater flowing from latrine to well (far-field); the well-pump system; and post-collection 34 handling and storage. Applying a hypothetical dose-response model suggests that 1 -2% of the 35 diarrhoeal disease burden from drinking water is derived from the aquifer, 29% from the well-pump 36 system, and 70% from post-collection handling. The important implications are (i) that leakage 37 from pit latrines is a minor contributor to faecal contamination of drinking water in alluvial-deltaic 38 terrains; (ii) fears of increased groundwater pollution should not constrain expanding latrine 39 coverage, and (iii) that more attention should be given to reducing contamination around the well-40 head. 41 42

Do Sanitation Improvements Reduce Fecal Contamination of Water, Hands, Food, Soil, and Flies? Evidence from a Cluster-Randomized Controlled Trial in Rural Bangladesh

“…Additionally, subsurface infiltration from new pit latrines is higher during the initial few months and diminishes afterward, potentially due to the formation of a layer (like the schmutzdecke on biosand filters) that attenuates contamination. 47 Finally, while E. coli typically survives <20 days in soil, 49 it can persist for extended durations in tropical soils. 50 It is therefore possible that a longer follow-up period would capture more pronounced impact from sanitation improvements on environmental contamination.…”

Initial observations of water quality indicators in the Dili City unconfined, shallow aquifer, Timor-Leste, and suggestions for management of this common-pool groundwater resource

“…Microbiological contamination of groundwater provides the clearest indicator of pollution by animal and/or human organic waste, and even small amounts of contamination pose a significant public health risk (Howard, et al, 2003, Ravenscroft, Mahmud, Islam, Hossain, Zahid, Saha, Zulfiquar Ali, Islam, Cairncross, Clemens andIslam, 2017). This enhanced risk is reflected in the zero MPN/100ml limit for bacteria in drinking water (WHO, 2011).…”

“…Ravenscroft et al (2017) used a carefully controlled study to document sources and contributions of fecal contaminants through a latrine-aquifer-well-user system, and proposed a four-component conceptual model. Of the four contaminant pathways (leakage of bacteria through the latrineaquifer interface; leachate migration to the borehole; transport through and contamination of the well equipment; contamination of the drawn water), they concluded that leakage from pit latrines contributes little to the disease burden beyond a latrine-well spacing of c.10 m; rather, they emphasized the importance of recontamination at the well, and between the well and the user, from non-latrine sources.…”

Assessing willingness to pay for upgrading toilets in rural areas of Shaanxi and Inner Mongolia, China

“…Unsanitary toilets are a threat to the environment [1][2][3][4][5][6] and public health [5,[7][8][9][10][11][12]. Recognizing this fact, the Chinese government inaugurated the toilet revolution to improve unsanitary toilets in rural areas in October 2014.…”