| Summary: | Purification and recycling of greywater, to make unconventional source, is considered as an appropriate solution for increasing fresh water demand and dealing with water crisis. In this study, physico-chemical treatment system (coagulation, flocculation and sedimentation) was used for treating and recycling of washing machine greywater. At the beginning, to determine appropriate type and concentration of coagulants, jar test was performed using four coagulants including, aluminum sulfate, Iron(II) sulfate, Iron(III) sulfate and Iron(III) chloride in concentration range of 5-135 milligram per liter (according to aluminum or iron concentration) . Jar test results shows that aluminum sulfate with lowest dose in comparison with other coagulants (348/7 milligram per liter according to aluminum sulfate concentration) has best efficiency in turbidity removal (98/5 percent). To evaluate the efficiency of treatment system, parameters such as pH, total dissolved solids, total suspended solids, electrical conductivity, turbidity, nitrate, nitrite, ammonia, phosphate, anionic surfactant and chemical oxygen demand (COD) were measured for both untreated and treated water. Removal of turbidity, suspended solids, nitrite, nitrate, phosphate, anionic surfactant and chemical oxygen demand (COD), respectively, reach to an acceptable level of 98/4, 95, 83/5, 75, 91/3, 67 and 69 percent. Also coagulation reduces pH only 21 percent. It should be noted that the removal of ammonia, electrical conductivity and TDS in this study was negligible.
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