A Mathematical Model for Organic Matter Removal in Constructed Wetlands Case Study: Wastewater Treatment Plant of Qasr-E Shirin, Iran



Davoodi R¹ ; Almasi A² ; Hoseiniahagh MM³ ; Dargahi A^{2, 4} ; Karami A⁴ Show Affiliations
Source: International Journal of Pharmacy and Technology Published:2016

Abstract

The ability of large aquatic plants (macrophytes) to assist the breakdown of human and animal derived wastewater, remove disease-causing microorganisms and pollutants has only recently been scientifically investigated. Since the mid- 1980s, reed bed systems, with the advantage of low energy consumption and operating cost, have been increasingly used in the treatment of wastewater. Although a large number of reed beds have been built and operated, pollutant dynamics in these systems are still scarcely comprehended. The lack of understanding on pollutant dynamics can lead to inaccurate design, giving poor pollutant removal efficiency and operation problem. As most reed beds are applied in sewage treatment, organic matter (BOD) removal is the primary target of system design, which requires the kinetics of BOD removal and the flow pattern of wastewater to be pre-determined. This paper reports a comparative study of four kinetic models that can be applied in the design of subsurface horizontal flow reed beds for wastewater treatment, in The Ghasre Shirin Subsurface Constructed wetlands Constructed wastewater treatment plant. The models were developed from different combinations of Monod kinetics, first-order kinetics, and continuous stirred-tank reactor and plug flow patterns. Using statistical parameters, were analysis of these models. For predicting organic matter removal, the combination of Monod kinetics with plug flow pattern gave the closest match between theoretical predictions and actual performances of 80 horizontal flow reed beds. In all models, except for the combination of Monod kinetics with plugflow pattern, the coefficients of BOD removal were found to decrease slightly with BOD loading. The ratios of BOD/COD had no correlation with the coefficients, indicating that in the Subsurface flow reed beds the degradation of organic matter is insensitive to the nature of organics in the wastewater. © 2016, International Journal of Pharmacy and Technology. All rights reserved.