Real and Synthetic Greywater Treatment by a Combined Process of Ozonation, Granular Activated Carbon, and Ultrafiltration

Abstract

Background: The water crisis in different parts of the world forces people to manage water resources. Greywater can be used to reduce water stress. The annual rainfall average in Iran is hardly one-third of the world. In this study, the treatment of synthetic greywater at low, medium, and high organic load and real greywater (RGW) by a combined process of ozonation/granular activated carbon (GAC)/ultrafiltration (UF) have been investigated. Objectives: This study aimed to find a greywater treatment method that is effective, new, environment-friendly, and cost-effective. Methods: Chemicals and commercial compounds were used to prepare synthetic greywater, and the research pilot was developed. After several preparation steps, the GAC was transferred to a GAC reactor. A continuous flow of synthetic greywater entered the treatment system with low: 6.1, medium: 12.2, and high: 18.3 gCOD/L.d organic loading rates for 6 months. Next, the RGW samples from a residential complex in Shiraz, Iran, entered the treatment system for two weeks. After chemical analysis, an analysis of variance was carried out to compare the removal efficiency of parameters: [chemical oxygen demand (COD), five-day biochemical oxygen demand (BOD5), turbidity, and linear alkylbenzene sulfonates (LAS)] at various organic loads (low, medium, and high) of synthetic greywater and RGW. Results: We found the average COD removal in low, medium, and high organic loads of synthetic greywater and RGW as approximately 79.3%, 86.1%, 77.3%, and 97.3%, respectively. Moreover, the average BOD5 removal in the mentioned groups was about 69.6%, 48.9%, 42.7%, and 86.8%, respectively. The average of turbidity removal was 95.6%, 98.3%, 97.4%, and 97.9%, and average LAS removal was 90.1%, 88.9%, 88.3%, and 91.9%, respectively. Conclusions: This treatment method is remarkable for real and synthetic greywater treatment. It can effectively remove COD, BOD5, turbidity, and LAS. In addition, it is a relatively low-cost and environment-friendly system. Therefore, it can be recommended as a greywater treatment method, especially in countries with inadequate water supplies, such as Iran.