Persulfate activated with calcium peroxide to remediate RAFT soil contaminated with diesel in Arctic northern villages: on-site pilot scale study.

A pilot field study was conducted in a Canadian northern village (NV) to assess the remediation efficiency of sodium persulphate (SPS) alkali activated with calcium peroxide (CP) to degrade diesel from Arctic raft soil. A minimum temperature increase in the subsurface due to overall process reactions was required. The projected context of application was imperative to preserve the integrity of the remaining permafrost. The test was performed with two soil columns of 370 L buried in the ground. The columns were contaminated with 7500 mg diesel/kg representative raft soil that was matured for a period of 11 months. The continuous delivery by gravity and the static presence of the oxidizing solution was made over 33 days. During that period, SPS concentration, pH and temperatures, were monitored. SPS was activated prior to its distribution and activation by-products were confined in a surficial tank and under a sludge form. The maturation period resulted in the important natural attenuation of diesel (47%) that occurred in the shallower horizons of the soil profile. About 35% of the diesel remaining after the maturation period was removed by chemical oxidation during the operation period on site. The temperature increase measured during the SPS activation process was not significant while the temperature increase due to diesel degradation by oxidation in the subsurface was evaluated to be below 3°C. The soil columns were not clogged by the by-products as indicated by hydraulic testing before and after oxidizing treatment.

Physical process to sort construction and demolition waste (C&DW) fines components using process water.

Modern societies are generating considerable volume of Construction and Demolition Wastes (C&DW) annually. Most recycling facilities offers viable sorting and recycling options for the coarser particles of the different materials found in those wastes. However, usual dry mechanical sorting and human sorting are not efficient on C&DW fines particles (C&DF, <10 mm) representing the third of the C&DW produced and being composed of similar materials. Recent environmental issues related to the landfilling of C&DF have pointed out the need to develop innovative alternative and adapted recycling paths for the C&DF. This study presents an efficient sorting process train based on physical separation steps used in the mining and the soil treatment industries. The use and recirculation of process water allowed to segregate and concentrate the gypsum from the 2-12 mm C&DF into a specific fraction (55-65% gypsum content) representing 40% of the total mass. Other constituents were sorted based on their relative density, size and shapes; thanks to hydraulic classification and physical sorting forming four more fractions with high recycling potential: coarse aggregates (15%), fine aggregates (9.4%), organic and inorganic fibers (10.8%) and light organic compounds (24.8%). The process has been designed to be integrated in existing sorting facilities and the process costs were evaluated to 38 CAN$/t.