Spatio-temporal variation and hazard assessment of potentially toxic metal element contamination in sediments and water before and after a water-level fluctuation cycle in the Three Gorges Reservoir, Wanzhou, China.

Previous investigations on heavy metals in the water-sediment compartment focused on their spatial distribution, and the influence of sediment pH and organic matter (OM) on metal environmental occurrences. However, there are limited studies on the effects of physicochemical properties on the migration and transformation of heavy metals in the water-sediment compartments. This study investigated the relationship between the physicochemical properties of sediments and the distribution and chemical speciation of heavy metals, and the potential environmental risk of heavy metals in water and sediment using Risk Assessment Code (RAC) values and the Tessier five-step extraction method.

Effect of dewatering conditioners on phosphorus removal efficiency of sludge biochar.

Based on the best dehydration effect, this study compared the adsorption phosphorus effect of sludge biochar after sludge conditioning with FeCl, KMnO, and cationic polyacrylamide (CPAM). This provided insights into the effects of chemical conditioning during the sludge dewatering stage on the overall phosphate adsorption of the dewatered sludge biochar. The phosphorus adsorption mechanism of the dewatering sludge biochar was analysed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier-transform infrared spectroscopy.

Comparative study of the effect of rice husk-based powders used as physical conditioners on sludge dewatering.

The effects of rice husk flour (RHF), rice husk biochar (RHB), and rice husk-sludge cake biochar (RH-SCB, expresses sludge cake biochar deriving from a sludge that has been previously conditioned with rice husk) used as physical conditioners on sludge dewaterability were compared. The effects of characteristics of physical conditioners on sludge compressibility and zeta potential were analyzed. The optimal rice husk-based powder was RH-SCB, which presented the highest net sludge solid yield (Y, expresses the dry mass flow by filtration) at 20.