Composite radial filter for recharging aquifer with runoff from paddy field

摘要

Abstract A composite radial filter was developed and evaluated for filtration of NO3-N, P, and K2O from paddy field runoff for recharging aquifers. For zeolite (Z), granular activated charcoal (C), coarse sand (CS), and gravel (G) filter medias were placed in the annular concentric rings of the developed filter in various combinations of different thickness, viz. 1:2:4:4, 1:3:4:4, 1:2:2:4, 1:3:2:4 and 0:2:1:2 individually for five treatments, viz. T1, T2, T3, T4, and T5, respectively. At the radial filter output, a chlorination unit was used to inject sodium hypochlorite solution, commonly known in a dilute solution as bleach solution at a rate of 0.1 ml per unit discharge (lps) in order to purge bacterial contamination from the filtered water. Analysing water samples for four different inflow/outflow rates−0.42, 0.82, 1.24, and 1.66 lps before and after filtration allowed investigators to assess the efficacy of the composite radial filter. At all flow rates, the filtered water's NO3-N, P, and K2O values were determined to be within allowable limits. Based on removal efficiency of NO3-N, P, and K2O and reduced cost, the T5 treatment, which consists of filter materials C, CS, and G with thicknesses of 20, 10, and 20 cm (2:1:2), respectively, was found to be superior to the other four treatments (T1, T2, T3, and T4). After five hours of filter operation, the filter materials were cleaned and reused. Reused filter media were found to have NO3-N, P, and K2O values of 5.3, 5.8, and 10.9 ppm, respectively. These values were found to be slightly higher than those obtained from initially original filter materials for the same duration of operation.