Iran has an arid to semi-arid climate. There is a shortage of fresh and clean water supplies.With rising of population and development of small-sized cities and villages, the demand forwater has been increasing day by day. At the same time, the volume of domestic wastewaterhas also been increasing. This water is discharged into the nature, mostly untreated andso, has been polluting the natural resources including the limited fresh water. Treatment ofwastewater and its reuse is considered an appropriate solution for this problem. The “Bio-Sand Filter” treatment system is one of the natural techniques, is cost-effective, eco-friendlyand is capable of separating organic and mineral components from the wastewater. In “Bio-Sand Filter” treatment system, the output wastewater from the building is discharged into theseptic tank and the fi rst phase of treatment process is done there including settlement of solidmaterials and their synthesis by anaerobic bacteria. Discharged wastewater from septic tankenters into a pond with appropriate dimensions; which are fi lled by crushed stones. In theseponds, several aquatic plants are cultivated, which in addition to treating wastewater, makesthe site aesthetic. These plants take in the existing nutrients from sewage while the microbesadjacent to their roots, consume organic chemicals as source of nutrition and energy. If thissystem is designed properly, the output wastewater will get adequately treated before enteringinto environment.
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