Groundwater has become the primary source of potable water in the Northern province of Sri Lanka and extensive development projects, comprising resettlements after the civil war resulted in more extraction of groundwater. This study focused to assess water quality from the perspective of drinking by developing a Water Quality Index (WQI), applying Hierarchical Cluster Analysis (HCA) and Principal Component Analysis (PCA), and developing spatial distribution maps. Findings revealed more than 50% of samples reported higher total dissolved solid (TDS), hardness, and alkalinity values above the Sri Lankan drinking water quality standards (SLS 614:2013). 7 and 13% of sampling sites were in the ‘Excellent’ and ‘Poor’ subclasses, respectively. PCA results explained >77% of variability by the first four principal components (PCs). PC1 and PC2 reflect geogenic processes while PC3 reflects natural processes like high rainfall and PC4 indicates anthropogenic pollution sources. HCA rendered 122 sampling sites into three clusters. An integrated map of the WQI and three clusters discovers a predominant analysis of potable water quality highlighting the deterioration of groundwater quality mainly in the 18 Grama Niladhari Divisions (GNDs) of the study area. Artificial recharging at a household level and introducing proper sanitation facilities and regulations in agricultural practices shall be implemented to improve the WQI further.

The average groundwater extraction from Murunkan well field, Mannar, is around 3.4 MCM/year, and it was triggered by extensive development projects and resettlements that took place in the last decade. Manganese and Iron variations in Murunkan groundwater reported during some periods created various operational and aesthetic issues in the potable water supply. This study is focused on treating iron and manganese in groundwater using chlorination and Rapid Sand Filtration (RSF) techniques. Pebble layers, height of 205 mm with the particle sizes ranging from 2-25 mm, were filled at the bottom of RSF model filter. Filter media, height of 700 mm with 0.45 mm effective size (D10) and a uniformity coefficient (Cu) of 1.33, was placed above the pebble layers. The filter was operated continuously for 15 days, and influent and effluent water samples were collected from 15 trials. Filter backwashing was performed after every two trials to maintain a consistent filtration rate. Raw water pH values ranged from 6.74 – 7.48. Chlorine solution (1.08-1.26 ppm) was added at the inlet point, and a 2.88 m water column was maintained, allowing adequate mixing and oxidation time. The results revealed that average removals of iron and manganese as 60% and 73%, respectively, while maximum removals of 93% and 91% were observed for iron and manganese, respectively.