Quantitative characterization of organic diffusion using an analytical diffusion-reaction model and its application to assessing BOD removal when treating municipal wastewater in a plug flow reactor
Journal
Water Research
Journal Volume
121
Pages
329-337
Date Issued
2017
Author(s)
Abstract
The present study aimed to derive an analytical formula to quantify the diffusion of organic contaminant in a biofilm. The experiments were conducted to investigate the BOD degradation under the conditions of influent COD concentration from 50 to 300 mg/L, COD:N:P ratios of 100:5:1 and 100:15:3, with and without auxiliary aeration. The BOD removal rate was around 73% for non-aerated influent COD of 50 mg/L with 1-h hydraulic retention time. The BOD removal rate increased as the influent loading and hydraulic retention time increased while the influent COD was no more than 150 mg/L. Without aeration, the removal rate dropped significantly when influent COD increased to the range no less than 200 mg/L, due to the fact that the BOD diffusive flux driven by the biomass uptake was not further enhanced by higher ambient organic loading. The diffusion coefficient was calculated to be 1.12 × 10−6 m2/d with influent COD of 50 mg/L at COD:N:P ratio of 100:5:1 and 1 h hydraulic retention time and aeration, and the coefficient increased to 3.35 × 10−6 m2/d as the influent COD concentration increased to 300 mg/L. The diffusion coefficient decreased to 4.09 × 10−7 m2/d as the retention time increased to 3 h. The overall diffusion coefficients showed an increasing trend as the influent organic loading increased. The difference in diffusion coefficients between 1 and 2 h was apparently greater than that between 2 and 3 h, indicating a smaller overall diffusive flux due to a longer retention time. Further analysis revealed that BOD diffusion activity exhibited a declining trend as the wastewater travelled through the system. An analytical diffusion-reaction model was developed to characterize the diffusion behaviour, and applied to estimating the treatment efficiency for real domestic sewage. The result showed that the estimated effluent BOD concentrations were quite comparable to those from experimental measurements. © 2017 Elsevier Ltd
Subjects
Biochemical oxygen demand; Biofilm; Diffusion coefficient; Domestic sewage; Wastewater treatment
Other Subjects
Biochemical oxygen demand; Biofilms; Diffusion; Effluents; Sewage; Wastewater treatment; Analytical formulas; Diffusion-reaction model; Domestic sewage; Hydraulic retention time; Municipal wastewaters; Organic contaminant; Quantitative characterization; Treatment efficiency; Loading; aeration; biochemical oxygen demand; biofilm; chemical oxygen demand; chemical reaction; diffusion; domestic waste; organic pollutant; pollutant removal; quantitative analysis; sewage treatment; wastewater treatment; aeration; Article; biochemical oxygen demand; biomass; chemical oxygen demand; diffusion; measurement; plug flow reactor; priority journal; retention time; waste water; waste water management; bioreactor; diffusion; sewage; waste water; sewage; waste water; Biomass; Bioreactors; Diffusion; Sewage; Waste Disposal, Fluid; Waste Water
Type
journal article