Recycled cellular concrete to improve phosphorous removal by floating treatment wetlands: A pilot experiment for meat-processing factory's wastewater

Abstract

Floating Treatment Wetlands (FTW) are a promising solution for improving the quality of wastewater discharges, yet they exhibit a wide range of Total Phosphorous (TP) removal performances, raising uncertainty about their reliability. This study investigates the potential of enhanced FTW equipped with recycled cellular concrete (CC) to improve the phosphorous (P) treatment of agri-food wastewater. A side-by-side evaluation of different size FTWs (representing 24 %, 48 %, and 72 % of pilot lagoons' surface with 5, 10 and 15 kg CC, respectively) and a control (pilot lagoon without FTW) was performed. The pilot lagoon with a 72 % coverage ratio exhibited the highest TP mass removal, averaging 29 ± 9 % and resulting in a 16 % median increase compared to the control lagoon. The 24 % and 48 % coverage FTW promoted more consistent and less variable TP treatment efficiency than the control lagoon, which achieved P removal only during algal blooms. Phosphorous was mostly sorbed onto CC within FTW (min-max: 79–94 % of TP removed). Plants had little contribution to overall phosphorous removal and were responsible for 4–6 % of TP removed depending on plant density. Sedimentation and algal assimilation and were responsible for 14 % of TP removed in the densest FTW, and were the main TP removal driving force in the control lagoon. From a circular economy perspective, up to 31 g P/kg CC were sorbed on CC, of which 89 % (weakly and calcium-bound P) could be available to plant assimilation. Further investigation over CC could provide insight into the best valorization route.