Quantification of Total Organic Carbon in Ashes from Smoldering Combustion of Sewage Sludge via a Thermal Treatment—TGA Method

Abstract

Self-sustaining smoldering combustion is a promising technology for treating sewage sludge from wastewater treatment plants because of its low energy inputs. Proper use or disposal of the resulting ashes requires thorough characterization of their properties, including the content of total organic carbon (TOC). Here, we develop a two-step method for quantifying TOC in the raw ashes from sewage sludge smoldering combustion. The first step is to thermally treat the raw ashes at 500 °C in N2 for 1 h, followed by ultimate analysis of both the raw ashes and the thermally treated ashes. This enables the quantification of carbon released during thermal treatment. The second step is nonisothermal thermogravimetric analysis (TGA) of the thermally treated ashes, in which the samples are heated to 900 °C at 10 °C/min in air. The weight losses at 310–500 °C are confirmed to be caused by organic carbon oxidation, allowing us to determine the contents of carbon retained in the thermally treated ashes. The sums of these two portions of carbon represent the contents of TOC in the raw ashes, which are ∼0.85–6.52 wt % (dry basis), depending on their locations and particle sizes. The two-step (thermal treatment–TGA) method is validated via a method that includes acid washing of the thermally treated ashes, ultimate analysis of the acid-washed ashes, and TOC analysis of the leachates. The two-step method is simple and accurate and, importantly, provides thorough information on the thermal behavior of the raw and thermally treated ashes.

Chemical Speciation and Characterization of Coal Fly Ash and Soil Samples Sourced from Hendrina Power Station

“…The percentage organic carbon values calculated from TOC values of all CFA samples ranged from 0.22 to 8.50 wt%. According to the above EU Council decision taken in 2003 about the coal usage and utilization, the samples collected from Dams 3C, 4B, 5A and 5C as well as the control soil were only above 8 which are above the permissible limit of 5 wt% recommended by EU Council decision [20]. This can indicate that the CFA disposal in this area has contaminated even the surrounding areas in Mpumalanga Province.…”

“…However, high pH environmental matrix has more reducing agents (negative ORPs) while low pH environmental matrix has more oxidizing agents (positive ORPs) [18,19]. TOC is another important property of CFA that consists of both unburned carbon (UC) and volatile carbonaceous matter, which reflects the combustion efficiency of the power plant and leads to different effects on ecosystem due to ash improper disposal or utilization [20]. The TOC of all samples ranged between 2.22 ± 0.98 and 85.26 ± 0.93 mg/kg and for control soil was 85.82 ± 0.60 mg/kg, and values below 10000 mg/kg suggest the unrestricted mobility of metals [21].…”

Applied smouldering for co-waste management: Benefits and trade-offs

“…3a-c, respectively). Furthermore, practically all fuel was consumed, i.e., > 99% of the smoulderable mass was removed in LAB PSF3 and LAB IPM2, as some mass often remains in the crust around the perimeter [11,53]. However, the median specific mass loss rates were roughly two-fold higher in LAB PSF3 (95 kg hr − 1 m − 2 , Fig.…”

“…Smouldering combustion is emerging as a valuable application for many environmentally beneficial purposes such as: (i) land remediation [1], (ii) hazardous liquid management [2,3], (iii) decentralized sanitation [4,5], (iv) pyrolysis/torrefaction [6][7][8][9][10], (v) wastewater sludge treatment [11][12][13], (vi) organic waste treatment [14][15][16], and (vii) resource recovery/generation [17][18][19][20]. In all these cases, smouldering can be harnessed to generate energy from traditionally problematic wastes, such as those with high moisture contents (e.g., biomass sludges [15,21,22]) and low volatility (e.g., coal tars and heavy oils [2,3,[23][24][25]).…”

Prediction of Total Organic Carbon in Organic-Rich Shale Rocks Using Thermal Neutron Parameters

“…Such interest is attributed to the depletion of conventional resources and the advancements in directional drilling and hydraulic fracturing. − The total organic carbon (TOC) content is one of the very important petrophysical properties that indicate the quality of source rocks. TOC represents the amount of organic matter deposited in the rock and is one of the most critical parameters to investigate prior to drilling for its significance in hydrocarbon quantification and quality measurement of the resource. ,− Organic matter depositions are controlled by the primary production, destruction, and dilution of organic matter where it maximizes when the first is fairly greater than the latter two factors . Many researchers proved the strong relation of TOC with many source rock parameters, such as gas adsorption capacity and porosity which emphasizes the importance of TOC as a rock petrophysical feature. , …”