Sustainable Water Management with Design and Economic Evaluation of Recycling Greywater at Abu Dhabi University—A Case Study on Decentralization

Abstract

Wastewater can be segregated as greywater and blackwater separately. The greywater generated in malls, restaurants, and university buildings is generally dilute, while it will later become concentrated when it is merged into the main sewage collection line. It would be more economical and environmentally friendly if the greywater is treated locally using a modular wastewater treatment facility that produces treated water amenable for other uses such as irrigation or horticulture. The objective of this article is to study the economic feasibility and design a decentralized plant that produces fresh water from greywater generated at the Abu Dhabi university campus located in the United Arab Emirates. The proposed unit will consist of a compact design of filtration, chemical treatment and disinfection processes that would generate treated wastewater that can be used for horticulture in and around the local campus or can be stored and supplied for irrigation purposes. Several parameters such as total suspended solids, biological oxygen demand, and chemical oxygen demand are measured and monitored throughout the entire process and are regulated by appropriate operations performed for each unit. This study shows that decentralization of greywater treatment is not only economical but also essential for the management of fresh water, which in turn assures environmental sustainability. By using coagulation, flocculation and chlorination with a 30 mg/L alum dosage, 0.6 mg/L of polyacrylamide and 0.12 mg/L of sodium hypochlorite, respectively, greywater is treated to meet the water specification for reusing it for horticulture. Further, a modular plant with an investment of USD 8 M is proved to process 90,000 tons of greywater with a 34% discounted rate of return.