Brackish water RO concentrate treatment and water recovery using cost lowering integrated technology

Abstract

Membrane concentrate has to be taken into consideration when the membrane technologies are presented as a robust solution for the water reuse and reclamation. In this study, brackish water reverse osmosis concentrate stream was recovered as source water with cost lowering integrated technology and over 70 % water recovery rate. Integrated technology consists of softening, ceramic MF/UF membrane and NF/RO membrane processes. By using this process scheme, it is aimed to benefit from the advantage of not easily fouling of ceramic membranes and to reduce the fouling load that may arise from the softening process on polymeric membranes, thus completing the water cycle by making water recovery. With this method, the reverse osmosis concentrate stream with the value of 2675 ± 323 µS/cm electrical conductivity, 1299 ± 40 mg CaCO3/L total hardness and 51 ± 1.5 ppm SiO2 was recovered in quality close to the well water character that reverse osmosis feed stream. Compared with other concentrate management technologies, proposed technology seems cost competitive with 1.349 US$/m3 total cost of integrated system and final cost is 0.519 US$/m3 after excluding water cost (0.830 US$/m3). Total 72 % of concentrate flow rate may be recovered to reverse osmosis feed stream and remaining 28 % of concentrate flow rate may be turned back to softening process. Thus, it is thought that it will make an important contribution to the near zero discharge liquid concept, which is of great importance for the protection of water resources today.