Suchergebnisse

AbstractConstructed wetland sediments are frequently contaminated with nitrogen and phosphorus. There is a risk that accumulated pollutants can either be remobilised or reach the groundwater. Five identical mesocosms, which were filled with subsoil collected from full‐scale integrated constructed wetland (the first cell receives the most contaminated influent), were set up to examine nutrient removal within sediment layers. The results indicated that accumulated nutrients leached out into inflow water and that the sediment capacity of nutrient retention decreased as the wetlands aged. Furthermore, the mesocosm planted withPhragmites australisachieved better treatment results compared with the one planted withAgrostis stolonifera. The risk of contamination to groundwater does not exist because none of the treated water reached the bottom outlet during the study period. Both the bentonite (clay) and biogeochemical processes taking place within sediments proved to be efficient in preventing polluted water from infiltrating into lower lying soils.

AbstractMunicipal digested sludge (MDS) has considerable phosphorus content that is between 1% and 15% in dry matter and it is a potential source for phosphorus recovery. A high amount of MDS is generated from sewage treatment plants in large cities and has many environmental concerns with its organic and inorganic constituents. In this study, phosphorus was recovered by precipitation with Ca(OH)2 and NaOH. Acid pretreatment was applied to MDS with H2SO4 and 58.7% of phosphorus was extracted from the solid phase to the liquid phase at pH 2. Up to 99% of dissolved phosphorus in the liquid phase was recovered with Ca(OH)2 and NaOH. Almost similar phosphorus precipitation rates were achieved with both bases but higher phosphorus contents (17% as P2O5) in precipitates were obtained by NaOH. The product obtained in this study can serve as a high‐quality raw material substitute for the low‐grade phosphate rocks (<15% P2O5) commonly utilized in the phosphate industry. Furthermore, this research presents a practical, environmentally friendly and cost‐effective approach for sustainable sludge management and phosphorus production.