The potential of downscaled dynamic column extraction for fast and reliable assessment of natural weathering effects of municipal solid waste incineration bottom ashes

Fluidized-bed column method for automatic dynamic extraction and determination of trace element bioaccessibility in highly heterogeneous solid wastes

“…The validated macrocolumn setup operating under fluidizedbed extraction conditions was compared with a recently reported dynamic leaching test, so-called flow injection/sequential injection microcolumn extraction [10,12,14,16,19,21,22,39], in terms of accuracy in the determination of TCLP available fractions of trace elements and repeatability of the assays. To this end, the microcolumn described elsewhere [10] and oriented in the upright position was packed with 300 mg of bottom ash as recommended in a recent article [19] and a cumulative volume of 400 mL of extractant was collected.…”

“…The idea behind is to ascertain worse case environmental risk scenarios as it has been proven that trace elements accumulate primarily in the finest fraction of bottom ashes [32][33][34]. Once weathered for >1 year to prevent changer on leachable metal fractions as a consequence of sample carbonation [19], a 2 kg subsample was obtained by sampling randomly at ten different pile locations. The bottom ashes were dried at 105 • C until two consecutive measurements provided identical masses, sieved to 2 mm to withdraw silica particles, and stored in a polyethylene bottle.…”

“…The minute quantities of solid samples loaded into the flow assemblies have limited the applicability of flow-based dynamic extraction methods to merely homogeneous solids or materials with a certain degree of heterogeneity but with preliminary sample milling or crushing to assure particle size homogenization, which would inevitably lead to the overestimation of the extractable content of target species because inaccessible phases would become exposed to the extractant [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]. Evaluation of the actual environmental availability of trace elements in highly heterogeneous raw solid wastes, e.g., municipal solid waste incineration (MSWI) bottom ashes exploiting the aforementioned flow setups would thus be inconceivable as the test portion assayed is to be most likely not representative of the bulk medium.…”

“…Intensive research in the field of dynamic extraction has been over the past few years devoted to the design of low to moderate pressure flow setups capitalized on the different generations of flow analysis, that is, continuous-flow analysis, flow injection analysis and sequential injection analysis, wherein the amount of solid sample usually loaded into the flow-through container ranged from 5 to 300 mg [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] to prevent excessive backpressure in the flow network. In continuous-flow rotating column-based fractionation assays, larger sample masses have been partitioned, yet the particle size distribution should be carefully controlled (samples are frequently sieved down to 250 m) because of the narrow tubing of the column, usually 1.5 mm i.d.…”

Heavy Metals Leaching of MSWI Bottom Ash: Effect of Short-term Natural Weathering

“…MSWI produces two mains type of by-products: bottom (BA) and fly (FA) ashes (in amount of about 33% of the incinerated waste (Qiao et al 2008;Ferraris et al 2009;Gori et al 2011). BA accounts for 85-95% of all the residues produced during MSWI (Rednek et al 2006;Rosende et al 2008). These ashes consist of inorganic matter (stone, ceramic, glass), ferrous and non-ferrous metals and unburned organic matter (plastic, fibre, wood etc.)…”