Narrow Results

Sludge-derived activated carbon (SDAC) is prepared from sewage sludge and can be used to treat pollutants. SDAC can also be used to dope catalytic materials to improve their pollutant degradation ability. However, there needs to be more research on doping TiO₂ with SDAC. In this study, TiO₂ was doped with SDAC by Ultraviolet light irradiation method under room temperature. The doping process saved a large amount of energy. The TiO₂ doped with SDAC had the ability to degrade dyes under visible light. The results showed that the removal rates of SDAC-doped TiO₂ for methyl orange (MO) and methylene blue (MB) were over 90% and 94% under visible light conditions. After five cycles, the removal rate of MO was 75%, while the removal rate of MB decreased to 45%. Molecular dynamics simulation results showed that the valence band and conduction band of SDAC-doped TiO₂ shifted downward, and three apparent impurity levels appeared near the Fermi level after SDAC doping.

An experimental PGNAA set-up using a 1 Ci Am–Be source has been developed and used for analysis of bulk sewage sludge samples issued from a wastewater treatment plant situated in an industrial area of Algiers. The sample dimensions were optimized using thermal neutron flux calculations carried out with the MCNP5 Monte Carlo Code. A methodology is then proposed to perform quantitative analysis using the absolute method. For this, average thermal neutron flux inside the sludge samples is deduced using average thermal neutron flux in reference water samples and thermal flux measurements with the aid of a ³He neutron detector. The average absolute gamma detection efficiency is determined using the prompt gammas emitted by chlorine dissolved in a water sample. The gamma detection efficiency is normalized for sludge samples using gamma attenuation factors calculated with the MCNP5 code for water and sludge. Wet and dehydrated sludge samples were analyzed. Nutritive elements (Ca, N, P, K) and heavy metals elements like Cr and Mn were determined. For some elements, the PGNAA values were compared to those obtained using Atomic Absorption Spectroscopy (AAS) and Inductively Coupled Plasma (ICP) methods. Good agreement is observed between the different values. Heavy element concentrations are very high compared to normal values; this is related to the fact that the wastewater treatment plant is treating not only domestic but also industrial wastewater that is probably rejected by industries without removal of pollutant elements. The detection limits for almost all elements of interest are sufficiently low for the method to be well suited for such analysis.