Comparison of Horizontal and Vertical Constructed Wetlands with Coagulation-Flocculation-Filtration Unit Efficiencies in the Polishing of Industrial Wastewater Effluent: A Case Study of Mourchekhort Industrial Estate Wastewater Treatment Plant, Iran

Abstract

Background: Industrial wastewater treatment has always been difficult and costly due to the presence of different pollutants with high concentration. The use of constructed wetlands is economical due to not needing any external energy sources and materials and equipment to reduce pollutants. The aim of this study was to determine the efficiency of horizontal and vertical subsurface wetlands in the removal of pollutants from the wastewater of the Mourchekhort Industrial Estate, Iran, and compare it with performance of the conventional coagulation-flocculation-filtration unit of reuse process. Methods: Two horizontal and vertical wetlands in pilot scale and two control (no plant) reactors were operated for eight months. Removal efficiency of total suspended solids (TSS), chemical oxygen demand (COD), turbidity, phosphorous and nitrogen compounds, and index bacteria were evaluated. Horizontal wetland was considered with dimensions of 0.8 × 0.65 × 2 m and floor slope of 1. Hydraulic retention time (HRT) and incoming sewage flow rate were set to to 6 days and 0.2 m3/d, respectively. Vertical subsurface reed had dimensions of 4 × 0.60 × 2 m and floor slope was equal to 1. The control pilot (no plant) was designed exactly the same as the horizontal and vertical samples. The results were compared with coagulation-flocculation-filtration process efficiency. Findings: The efficiency of vertical wetland in removal of TSS, COD, turbidity, phosphorus and nitrogen compounds, and index bacteria was 58.1, 62.4, 73.4, 20.4, 21.3, and 40.5, respectively. For horizontal wetlands, the efficiency was obtained as 57.0, 52.6, 70.3, 22.4, 18.2, 39.1, respectively, and for conventional coagulation-flocculation-filtration treatment process, it was 85.3, 69.7, 81.5, 69.2, 73.9, and 78.2, respectively. Conclusion: Although vertical wetland was more efficient than horizontal one for most of the operation parameters, both of these wetlands were less efficient than conventional coagulation-flocculation-filtration unit of reuse process. Although operating costs of wetlands are low, these systems alone cannot be considered as a substitute for the conventional pre-treatment process of coagulation-flocculation-filtration because of their low performance for the purpose of polishing. © 2022, Isfahan University of Medical Sciences(IUMS). All rights reserved.