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

Abstract

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

Influence of intermittent aeration and organic loading rate on lab-scale constructed wetland systems treating synthetic wastewater

“…However, the phosphorus in bacteria only accounts for less than 2% of the nutrients removed. Only when OLRs are very high, can the TP removed by micro-organisms reach a significant percentage [46].…”

Pollutant Removal from Sewage in Tropical Climate by Constructed Wetland System: An Asset for Irrigation

“…The microbes in wastewater and soil contributes to 7% and 6% and adsorption in soil contributes to 71%. According toKumar et al (2011) a maximum of 64-75% of TP is removed by adsorption process in the system, 9-19% by plant uptake and 7-12% by microbial metabolism. Cyperus papyrus has the ability to uptake 28.5% of nitrogen and 11.2% of phosphate from the system(Kyambadde et al 2005).The efficiency of wetland in nutrient removal is higher in summer than other seasons (RamakrishnaRao et al 2013, Mesquita et al 2017.…”