Hybrid RO & Softening Birjand Water Treatment Plant

In this research, results from a pilot plant are investigated in order to construct a multipurpose water treatment plant in the city of Birjand, east of Iran. The main target parameters for treatment are softening and chromium VI (cr+6) remediation due to its high concentration in water sources.The plant capacity is 0.64 m3/s in which 0.42 m3/s is forwarded to the pellet reactor for softening and the rest of the stream is fed to a nanofiltration / reverse osmosis (NF/RO) () unit for desalination. The pellet reactor is a cylindrical vessel with a conical lower section. The reactor is partially filled with a proper seed material such as silver sand or garnet. The effluent of the pellet reactor is mixed with the outflow of NF/RO unit to reach a desirable quality. Calcium and some chromium are removed by the pellet reactor. Calcium carbonate and chromium deposits are washed out from the pellet reactor. Then the remaining chromium and partial magnesium can be removed in the continuous sand filters.Present research reveals that it is essential to feed very low turbidity water in order for the pellet reactor to work properly. In addition, sedimentation pretreatment without media filtration will led to an improper feed stream of the pellet reactor. Effluent water quality results show that pellet reactor treatment decreases calcium concentration nearly 43%. In addition, 74% reduction in chromium concentration is obtained by using this treatment technique based on influent water quality