Water treatment efficiency of aerator and roughing filter in treating groundwater; A case study in Mullaitivu

Abstract

The paper describes an investigation into the efficiency of the water treatment process used in the Mullaitivu well field in Sri Lanka. The well field experiences significant groundwater extraction, approximately 1,440,000 liters per day, due to developments and resettlements in the area over the past decade. However, the groundwater quality does not meet the standards set in SLS 614;2013. The treatment process employed in the well field includes a fountain type aerator and vertical-flow roughing filters. The fountain type aerator has four drops with varying heights. The water then passes through four medial filter layers in the roughing filters, each with different particle sizes and layer thicknesses. To assess the effectiveness of the treatment process, water samples were collected at regular intervals of 6 hours during 72 hours continuous operatio. The samples were taken before and after aeration and after passing through the roughing filters. The selected water quality parameters tested in the study were turbidity, color, total iron, and manganese. The results showed that the treatment process using the aerator and roughing filters significantly removed color and total iron from the raw water. The removal efficiencies were found to be 84% for color and 88% for total iron. Additionally, the treated water's turbidity was well below the threshold limit of 2 NTU, the treated manganese level was below the limit of 0.1 mg/l, and the treated total iron level was below the limit of 0.3 mg/l specified in SLS 614;2013 for drinking water. Based on the findings, the paper recommends including pre-chlorination in the treatment process to enhance oxidation and increase the total iron and manganese removal efficiency. By doing so, the removal efficiency for turbidity and color will also be improved. Overall, the investigation suggests that the combination of the fountain type aerator and vertical-flow roughing filters can effectively improve the water quality in the Mullaitivu well field. The findings could be valuable for addressing the water quality challenges in the area and ensuring a safe drinking water supply for the local population.