Sand Barriers around Latrine Pits Reduce Fecal Bacterial Leaching into Shallow Groundwater: A Randomized Controlled Trial in Coastal Bangladesh

We evaluated the effectiveness of
a sand barrier around latrine
pits in reducing fecal indicator bacteria (FIB) leaching into shallow
groundwater. We constructed 68 new offset single pit pour flush latrines
in the Galachipa subdistrict of coastal Bangladesh. We randomly assigned
34 latrines to include a 50 cm thick sand barrier under and around
the pit and 34 received no sand barrier. Four monitoring wells were
constructed around each pit to collect water samples at baseline and
subsequent nine follow-up visits over 24 months. Samples were tested
using the IDEXX Colilert method to enumerate E. coli and thermotolerant coliforms most probable number (MPN). We determined
the difference in mean log10MPN FIB counts/100 mL in monitoring
well samples between latrines with and without a sand barrier using
multilevel linear models and reported cluster robust standard error.
The sand barrier latrine monitoring well samples had 0.38 mean log10MPN fewer E. coli (95% CI: 0.16, 0.59; p = 0.001) and 0.38 mean log10MPN fewer thermotolerant
coliforms (95% CI: 0.14, 0.62; p = 0.002), compared
to latrines without sand barriers, a reduction of 27% E. coli and 24% thermotolerant coliforms mean counts. A sand barrier can
modestly reduce the risk presented by pit leaching.