Effect of dechlorination and defluoridation of treated sewage water on soil fertility and french bean (Phaseolus vulgaris L.) productivity

An experiment was conducted to evaluate low-cost, locally available amendments for dechlorination and defluoridation of treated sewage water and to assess their effect on soil properties, growth and yield of French bean (Phaseolus vulgaris L.). Treated sewage water from Chintamani taluk was amended with different amendments like activated alumina and alum (known for ligand exchange and surface complexation of chloride and fluoride), charcoal and biochar (possessing high surface area, porosity and negatively charged functional groups favouring halide adsorption) and calcium-based compounds such as calcium silicate, calcium carbonate and calcium sulphate (which promote fluoride removal through precipitation and ion exchange mechanisms) at a 1:1 (w/v) ratio and the supernatant was analysed after 24 hr. Pot culture trials of French bean compared irrigation with groundwater, untreated treated sewage water and dechlorinated and defluoridated (DC and DF) waters. Activated alumina, alum, charcoal and biochar reduced chloride and fluoride content markedly, with charcoal and biochar offering an economically attractive option. Plants irrigated with DC and DF water showed improved growth, yield components and higher nutrient status compared to untreated sewage and groundwater irrigations. Soil properties, including organic carbon, available N, P, K, Ca, Mg, S and DTPA-extractable micronutrients, were enhanced under certain DC and DF treatments. The study demonstrates that the effectiveness of low-cost amendments is governed by their adsorption capacity, surface chemistry and precipitation mechanisms, highlighting their potential to reduce halide toxicity in reclaimed irrigation water and to improve crop performance, yield and soil fertility in water-scarce regions.