Assessment and Monitoring of Groundwater Contamination Status in Non-Sewered Sanitation Systems – A Case Study of Peri-Urban Areas of Islamabad, Pakistan

This study investigates the impact of non-sewered sanitation systems (NSS) on groundwater quality in peri-urban areas of Islamabad, Pakistan. Groundwater samples were collected from five locations served with septic tanks and pit latrines during dry and wet seasons. The study revealed significant contamination, particularly during the wet season, with high levels of ammonium-nitrogen (NH4+–N) (43 mg/L in wet season vs. 19 mg/L in dry season), Chemical Oxygen Demand (COD) (52 mg/L in wet season vs. 29 mg/L in dry season), and E. coli (> 23 CFU/100 ml) in both wet and dry season. The Water Quality Index (WQI) indicated that most groundwater samples were “unfit for drinking” with a notable deterioration during the wet season. During the dry season, 47% of samples were classified as “marginal” (WQI ≤ 100), while 53% were “poor” (WQI 100 − 200). In the wet season, nearly all samples fell into the “poor” (WQI 100 − 200) and “very poor” quality (WQI >200). The Principal Component Analysis and Multi Linear Regression (PCA-MLR) determined that high NH4+–N and COD in groundwater takes its genesis from anthropogenic sources and increasing distance between NSS and groundwater well improves water quality. Thus, groundwater in the area is unsuitable for drinking, domestic, and agricultural needs. The study highlights the critical importance of proper construction, operation, and maintenance of NSS to prevent groundwater contamination and protect community health.