Process-based modelling of phosphorus removal in a novel constructed wetland system using dewatered alum-sludge as substrate

摘要

A process-based model that can evaluate the transport and the fate of phosphorus (P) innagricultural wastewater was developed for a novel 4-stage dewatered alum sludge cakes (DASC)nbased constructed wetlands (CWs) system using STELLA software (version 9.1.4). The modelnconsidered adsorption, plant and microbial uptakes as the major forms of P involved in thentransformation chains. The results were obtained by experimental procedure through laboratorynmeasurement, from literature and/or calibration. The observed effluent P concentration in thenCWs ranged from 3.62 to 8.50 mg/L (stage 1), 2.00 to 4.45 mg/L (stage 2), 1.39 to 3.76 mg/L (stage 3)nand 0.52 to 2.36 mg/L (stage 4), whereas the simulated values ranged from 2.12 to 10.99 mg/Ln(stage 1), 1.32 to 5.65 mg/L (stage 2), 0.84 to 3.64 mg/L (stage 3) and 0.53 to 2.25 mg/L (stage 4),nrespectively. The simulated and observed values of P removal in the CWs system were in goodnagreement. A mass balance analysis was performed for all the major processes which resulted in anmajor pathway of P removal through adsorption (64–75%, 58–66%, 57–63% and 49–58%) followednby plant uptake (7–11%, 8–14%, 14–17% and 9–19%) and microbial uptake (3–7%, 3–5%, 9–12% andn7–12%) for stage 1, stage 2, stage 3 and stage 4, respectively. Thus the mathematical modelndeveloped in this study could be used to explain the removal processes and simulate the fate of Pnin the DASC-based CWs system.