Pharmaceutical contaminants in shallow groundwater and their implication to poor sanitation facilities in low-income countries.

Rudimentary onsite sanitation systems (OSSs) are extensively used in low-income countries despite the risk of groundwater contamination. The present study investigated the potential impact of community soak pits on sandy shallow aquifers in a rural area in Sri Lanka. Thirty-two groundwater samples were collected and measured for traditional indicators, i.e., fecal bacteria Escherichia coli (E.coli), total coliforms (TCs), nitrate and chloride; seven pharmaceuticals were added as wastewater indicators. Analysis showed that the local groundwater is infected by fecal bacteria, but it was unable to determine whether the source of fecal bacteria is from OSSs. Similarly, nitrate and chloride provided unclear evidence. Conversely, detection of three pharmaceuticals at trace levels in groundwater evidenced wastewater impact from OSSs. Caffeine (CAF) was detected in 89% of the sample at maximum concentration 7.9 ng/L, indicating fecal pollution. Carbamazepine (CBZ) was detected in 42% of the samples with a concentration of up to 6.9 ng/L, while sulfamethoxazole (SFM) was detected in only two samples. The presence of CBZ and SFM were also consistent with recorded drug use of the residents. E. coli showed a moderate positive correlation with CAF concentration (Kendall's tau τ = 0.38, p = 0.017), indicating concurring short-lifetime fecal bacteria and labile wastewater organic compounds. Nitrate showed a significant correlation with CBZ concentration (τ = 0.39, p = 0.016). Fecal bacteria and nitrate can be used in screening for micro-pollutants in domestic wells impacted by OSSs. This case study emphasized the potential impact of poor sanitation on groundwater resource and the necessity of sanitation improvement in achieving Sustainable Development Goals in developing countries. This article is protected by copyright. All rights reserved.