A Subsurface Horizontal Constructed Wetland Design Approach for Wastewater Treatment: Application in Ar Riyadh, Saudi Arabia

Mohamed Elsayed Gabr, Mustafa El-Rawy (), Nassir Al-Arifi (), Wouter Zijl and Fathy Abdalla
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Mohamed Elsayed Gabr: Civil Engineering Department, Higher Institute for Engineering and Technology, Ministry of High Education, New Damietta 34517, Egypt
Mustafa El-Rawy: Civil Engineering Department, Faculty of Engineering, Minia University, Minia 61111, Egypt
Nassir Al-Arifi: Chair of Natural Hazards and Mineral Resources, Geology and Geophysics Department, King Saud University, Riyadh 11451, Saudi Arabia
Wouter Zijl: Department of Hydrology and Hydraulic Engineering, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
Fathy Abdalla: Deanship of Scientific Research, King Saud University, Riyadh 11451, Saudi Arabia

Sustainability, 2023, vol. 15, issue 22, 1-16

Abstract: In this study, a decentralized new sewage water treatment system is suggested and designed in Ar Riyadh, Saudi Arabia, to safeguard the environment and reuse treated water for irrigation purposes. The system consists of a primary treatment (septic tank), a subsurface horizontal flow constructed wetland (HSSF-CW), and a storage ground tank. The research methodology employed in this study is (i) to define the wastewater characteristics, where air temperature in winter is 18.6 °C, the wastewater flow per person (q) is 150 L/d, demonstrating an inlet design discharge of 300 m 3 /d, the influent pollutant concentrations for biological oxygen demand (BOD), total suspended solids (TSS), chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP), and fecal coliforms (FC) are 350, 1000, 700, 50, 12 mg/L, and 10 6 CFU/100 mL, respectively; (ii) to design the septic tank based on a retention time of two days and a surfacing load rate of 1.5 m/d; (iii) the P-k-C* model was used to determine the HSSF-CW surface area based on reed beds of Phragmites australis (common reed) and papyrus plants, where the removal rate was constant at 20 °C for BOD, TP, and FC in the effluent concentrations not exceeding 20 mg/L, 3.0 mg/L, and 2000 CFU/100 mL in order to satisfy Saudi Arabia’s wastewater reuse requirements; and (iv) to design the clean water tank for a hydraulic retention time of 10 h. The results demonstrate that the removing pollutants design area is 1872 m 2 divided into nine cells, each of width 8 m and length 26 m, with a hydraulic loading rate (LR) of 0.16 m/d and a hydraulic resident time (RT) of 1.1 d. The effluent pollutant concentrations for the BOD, FC, TN, and TP were 245 mg/L, 10 3 CFU/100 mL, 35, and 8.5 mg/L, respectively. The wastewater treatment system total removal efficiencies for BOD, TN, TP, and FC were estimated to be 91.8, 70, 57, and 98.5%, respectively. Design curves were developed to ease the design steps. The HSSF-CW is a green wastewater treatment technology that offers greatly decreased investment costs, and service particularly for small-scale applications up to 6000 persons.

Keywords: constructed wetlands; pollutant’s removal; hydraulic loading rate; reed beds; irrigation water (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2023
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