Design concept and performance of a constructed wetland system engineered for the circular economy

The design concept and performance of a novel constructed wetland system engineered for the circular economy is presented. The constructed wetland system provided a means for resource (phosphorus, P) recovery, thereby further promoting the concept of the circular economy. The process design of the constructed wetland system entailed two unique features: (i) P removal via ligand exchange by the dewatered waterworks sludge cakes (alum sludge)—this was used as the main substrate in the system; and (ii) use of the “tidal flow” aeration strategy for air input. With mean influent values (± SD) of 392.67 ± 95.62 (mg BOD 5 /L) and 579.76 ± 141.96 (mg COD/L), average (± SD) percentage removal efficiencies of 90.59 ± 7.52 and 71.81 ± 10.23, respectively, for BOD 5 and COD were achieved in the system. The system also proved very effective for P removal, particularly in removing soluble reactive phosphorus (SRP). Average (± SD) overall removal efficiency of 93.29 ± 2.7% and 97.62 ± 1.86% was obtained, respectively, for RP (reactive phosphorus) and SRP. The novel system provides an excellent example of the circular economy, whereby a by-product has been reused as a major component for enhancing pollutants removal in a wastewater treatment system.