Modeling of Barium and Silica Removal from Wastewater of Reverse Osmosis in ZLD Process

The concentration of elements such as calcium, magnesium, barium and silica would gradually increase in the wastewater treatment using RO systems. Reusing this wastewater in a second RO would cause precipitation of such elements on the surface of membrane and would decrease its permeability. Zero liquid discharge (ZLD) is the most advanced management technique for saline wastewater of RO systems. The aim of this study was to determine a mathematical model to estimate barium and silica removal from RO wastewater in ZLD multistep process. This research was conducted on samples from the effluent of the RO system in Tang-e Alhad in Hajiabad, Zarin Dasht in Fars Province, Iran. The experiments consisted of chemical precipitation, fluidized bed crystallization (FBC) and fluidized bed crystallization with chemical precipitation. During different ZLD processes, a correlation was observed between critical elements removal. The correlations between Ca with Ba and also SiO2 with alkalinity were observed in all experiments. According to the results the mathematical models for removal of barium and silica were determined according to the initial and final concentrations of barium, calcium, and silica and alkalinity. The results showed a very suitable correlation (R2=0.99) between these concentrations and removal of silica and barium.