Using Modified Natural Zeolite Clinoptilolite to Remove Nitrate, Phosphate and Salt from Agricultural Drainage Water in a Drainage System Model

This study examined the feasibility of using zeolite clinoptilolite to filter nitrate, phosphate pollutants and salt from the agricultural drainage water. To that end, significant pollutant absorption parameters, such as adsorbent particle size, pollutant concentration, salinity, temperature, retention time, pH, and adsorbent concentration were optimized in the batch condition. Having optimized the parameters, the researchers conducted adsorption experiments on an experimental model, similar to the subsurface drainage systems applied in farms. Adsorption experiments were carried out at the optimized parameter levels on four models, namely a reference model (D0), a model with adsorbents around the drains (D1), a model with adsorbents around the plant roots (D2), and a model with adsorbents on the soil surface (D3). These models were fed with untreated drainage water from the farms in the south of Khuzestan during the fertilization season. The results showed 63 percent nitrate removal efficiency, 39 percent phosphate removal efficiency and 79 percent salt removal efficiency by using 30 g.L-1 of 1000 µm adsorbent particles for a pH of 5, initial pollutant concentration of 80 mg.L-1 nitrate and 10 mg.L-1 phosphate in 12 dS/m salinity during a 90-minute retention time period at 50 °C ambient temperature. These parameter levels led to nitrate, phosphate, and salt removal efficiencies of 59.72 percent, 29.28 percent, and 77.47 percent respectively, in the model with clinoptilolite adsorbents around the drains (D1).