The accumulation of phosphorus in activated sludge in wastewater treatment plants (WWTPs) provides potential for phosphorus recovery from sewage. This study delves into the potential for releasing phosphorus from waste activated sludge through two distinct treatment methods—thermal hydrolysis and pH adjustment. The investigation was conducted with activated sludge sourced from four WWTPs, each employing distinct phosphorus removal strategies. The findings underscore the notably superior efficacy of pH adjustment in solubilizing sludge phosphorus compared to the prevailing practice of thermal hydrolysis, widely adopted to enhance sludge digestion. The reversibility of phosphorus release within pH fluctuations spanning 2 to 12 implies that the release of sludge phosphorus can be attributed to the dissolution of phosphate precipitates. Alkaline sludge treatment induced the concurrent liberation of COD, nitrogen, and phosphorus through alkaline hydrolysis of sludge biomass and the dissolution of iron or aluminium phosphates, offering potential gains in resource recovery and energy efficiency.@en

Working as natural filter, well-designed vegetation schemes have been widely applied to improve the quality of water (Aiona, 2013; Stefanakis, 2015). Proper design, however, requires appropriate physics-based modelling of their filtering capacity. Several theoretical models predicting sediment transport in vegetated flow have been proposed: Baptist (2005); Yang and Nepf (2018); Wu et. al. (2021); Tseng and Tinoco (2021); Yagci and Strom (2022); Wang et. al. (2023). Some of them have been implemented in numerical tools (e.g. Caponi et al., 2022; Li et al., 2022) and in particular in Delft 3D (Deltares, 2014). However, they have been mostly designed and verified based on bedload processes, and their performance for suspended load should be further investigated. This work compares different approaches on their ability to reproduce the effects of vegetation on suspended solids concentration in two-dimensional models built in Delft3D. The work focuses on emerging vegetation, represented as rigid cylinders, and sediment deposition. Comparisons are based on the ability to reproduce flume experiments available in the literature by analysing both flow field and sediment deposition results.@en