Rudimentary on-site 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 the traditional indicators fecal bacteria Escherichia coli, total coliforms, nitrate, and chloride; 7 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 the OSSs. Similarly, nitrate and chloride provided unclear evidence. Conversely, detection of 3 pharmaceuticals at trace levels in groundwater evidenced wastewater impact from OSSs. Caffeine was detected in 89% of the sample at a maximum concentration 7.9 ng/L, indicating fecal pollution. Carbamazepine was detected in 42% of the samples with a concentration of up to 6.9 ng/L, whereas sulfamethoxazole was detected in only 2 samples. The presence of carbamazepine and sulfamethoxazole was also consistent with recorded drug use of the residents. Escherichia coli showed a moderate positive correlation with caffeine concentration (Kendall's τ = 0.38, p = 0.017), indicating concurring short-lifetime fecal bacteria and labile wastewater organic compounds. Nitrate showed a significant correlation with carbamazepine concentration (τ = 0.39, p = 0.016). Fecal bacteria and nitrate can be used in screening for micropollutants in domestic wells impacted by OSSs. The present case study emphasizes the potential impact of poor sanitation on groundwater resources and the necessity of sanitation improvement in achieving Sustainable Development Goals in developing countries. Environ Toxicol Chem 2022;41:266-274. © 2021 SETAC.
Keywords: Groundwater; On-site sanitation systems; Pharmaceutical contaminants; Wastewater indicators.
© 2021 SETAC.