Understanding the groundwater sanitation nexus in small towns: a case study from India

The separation of greywater and blackwater at the household scale has successfully addressed the issue of open defecation in rural villages and small towns across India. Eighty per cent of the population in India depends on groundwater sources to meet their domestic and livestock water demand. The impact of the high density of pit latrines on groundwater quality is well documented in the literature. Several solutions, such as the deployment of modified septic tanks and constructed wetlands, have been proposed to address the groundwater contamination issues. However, few studies have assessed and compared the impact of greywater and blackwater on groundwater quality. Our study on understanding the groundwater sanitation nexus in one of the small towns in India aims to assess the relative impact of greywater and blackwater disposal on groundwater quality. We categorised borewells into three subsets: a) located in the densely populated region, b) located near the open stormwater drains, and c) within the village. The water quality data showed the presence of nitrates (above drinking water standards) in borewells located within a densely populated area and near stormwater drains. The contaminant load varied across seasons, with maximum levels observed during the pre-monsoon period. Compared to borewells in the village, high COD levels were also observed in the borewells located near the open stormwater drain, indicating the contribution of greywater to organic contaminant load in groundwater. 

Groundwater quality data was obtained from samples that were collected from agricultural fields where the density of soak pits or Onsite Sanitation Systems (OSS) was low and semi-urban areas where the density of OSS was high.