Eco-Friendly Innovation for Electrical Conductivity Reduction of Persian Gulf Seawater Using Highly Efficient Recyclable Sorbent

The use of seawater containing Reverse Osmosis effluent is very serious for the daily living of the coastal residents, especially for farmers. In this study, a one-year field test was carried out for electrical conductivity reduction of Persian Gulf seawater in Iran, during 2017 and 2018. The test was conducted in two filters each with a diameter 2.5 cm (or 0.025 m) and 18.5 cm (or 0.185 m). In the filters, crumb mineral mussel was used as one of the main components of filter materials. The minor components of filter materials were comprised of coarse-grained gravel, fine-grained activated carbon, and fine-grained sand. The well water as low-saline water for the background of seawater treatment and seawater as super-saline water were treated. The test was performed as the pilot, batch, and column design with three replicates. The volume of daily treated seawater and the efficiency of reduction of electrical conductivity and salinity were determined. The volume of treated seawater by each of the filters was at least 10 times the diameter of each of those. The maximum reduction efficiency of electrical conductivity and salinity in a filter with 2.5 cm (or 0.025 m) diameter was 97.09% (from 85.2 to 2.48 mS/cm or from 8.52 to 0.248 S/m) and it was 98.2% (from 61 to 1.1), respectively. Maximum reduction efficiency of the parameters in filter with 18.5 cm (or 0.185 m) diameter was 97.5% (from 84.8 to 2.12 mS/cm or from 8.48 to 0.212 S/m) and it was 97.69% (from 60.7 to 1.4), respectively. Electrical conductivity in outlet water from filters was less than 3 mS/cm (or 0.3 S/m), below the permissible limit recommended by World Health Organization and also the Iranian Department of Environment for agriculture and irrigation usage. Based on these results a non-continuous method seems promising in the biological growing phase in filters.