Dioxin-like compounds in Australian sewage sludge – Review and national survey

Abstract

An Australian survey of dioxin-like compounds in sewage sludge was conducted in two parts (a) a national survey, and (b) a time-study. All sewage sludge samples analysed as part of these studies had low overall concentrations of dioxin-like compounds. Out of 37 samples, all except one, were within the reported concentration range of soil within the Australian environment. The mean concentration of dioxin-like compounds in the Australian sewage sludge survey of 2006 was found to be 5.6 (s.d. 4.5) ng WHO(05) TEQkg(-1) (n=14) and were within the range of 1.2-15.3 ng WHO(05) TEQ kg(-1). All the Australian sewage sludge samples cited in these studies were below the Victorian EPA "investigation limit" of 50 ng WHO(98) TEQ kg(-1), and well below the European proposed guidelines of 100 ng I-TEQ kg(-1). The burden of dioxin-like compounds in Australian sewage sludge is low and its land application as biosolids is not likely to pose a problem. A general positive relationship was found between population of the town producing the waste and both dioxin-like PCDD/Fs and dioxin-like PCBs. The one exception to this trend was sludge from a town that had a history of smelting and had a relatively high burden of dioxin-like compounds. Sludge from one rural WWTP also had a higher burden of dioxin-like compounds. The treatment plant services a geographically isolated town with a low population and no known emitters of dioxin-like compounds. However, this sample also had a relatively high burden of dioxin-like PCBs, which could be the source of the dioxin-like PCDD/Fs found in this sludge. The time study analyzing sludges from three WWTP from the same city between the years 2002 and 2006 found no apparent difference between WWTPs, but a statistically significant decline of 1.49 ng WHO(05) TEQ kg(-1) per year. Also, a comprehensive review of the scientific literature, presents typical levels and sources of dioxin-like compounds in international sewage sludges.

Review of the current state and main sources of dioxins around the world

“…On the other hand, when using sludge in agriculture, if the concentration of dioxins is high, given the persistence property of these compounds, an agricultural use would end in the accumulation of dioxins in the soils. Nevertheless, different studies estimate that in most cases, the PCDD/F input to soils through agricultural use is lower than the input that already takes place through atmospheric deposition (McLachlan et al, 1996;Clarke et al, 2008).…”

“…Wastewater from industrial or urban sewage requires the application of certain treatments before their disposal. One of the consequences of this wastewater treatment is the formation of sludge that will also need to be treated before discarding and that shows fingerprint profiles similar to those of the wastewater (with OCDD, Hp-CDD/F, and TeCDF being the most relevant congeners), and typical concentrations between 3.47 and 88.24 ng I-TEQ/kg dry weight (Dai et al, 2007;Clarke et al, 2008;Wcgiel et al, 2014).…”

Evaluation of endocrine disruption and dioxin-like effects of organic extracts from sewage sludge in autumn in Beijing, China

“…However, the detected results had no significant correlation (P > 0.05) with the sewage treatment processes. In comparison with the Ah-R activities reported in sludge, or sediments and soils around Beijing city (Table 4), the TEQ levels (1390-6740 pg TCDD$g -1 , dw) of sewage sludge in Beijing were close to those of sewage sludge in Australia (1200-15300 pg TCDD$g -1 , dw) and Daguhe River sediments in Tianjin (1200-13900 pg TCDD$g -1 , dw), respectively [28,29,[38][39][40][41]. As the Ah-R activities of Wenyuhe River sediments (10-340 pg TCDD$g -1 , dw) [29], one of the urban drainages in Beijing, were much lower than those of the urban sewage sludge in Beijing, it could be supposed that dioxin-like pollutants were inclined to be accumulated in the sewage sludge and diluted by the drainage water.…”

“…It was also found that the TEQ level of sewage sludge composted (S9) was much lower than that of the original sewage sludge (S8). Table 4 Comparison of Ah-R agonistic activities in sludge, or sediments (soils) around Beijing city [28,29,[38][39][40][41] sampling sites Ah-R agonistic activity (TEQ, pg TCDD$g sewage sludge (UK) [38] 20-220 sewage sludge (Australia) [39] 1200-15300 sewage sludge in Catalonia (Spain) [40] 10-30 soils from reclaimed water irrigated plots (Tunisia) [28] 26600-67900 sediments of Wenyuhe River in Beijing (China) [29] 10-340 sediments of Daguhe River (China) [41] 1200-13900 sewage sludge in Beijing (current study) 1390-6740…”

Supercritical water oxidation of dioxins and furans in waste incinerator fly ash, sewage sludge and industrial soil

“…It is estimated that more than 1 million tonnes of hazardous flyash and air pollution control residues are generated in Europe each year from the incineration of municipal solid waste, much of which is landfilled [7,8]. In addition, PCDD/PCDF have been detected in sewage sludge and reported in several studies [6,[9][10][11][12][13][14]. Certain types of contaminated industrial soils are also reported to contain significant concentrations of PCDD/PCDF [15][16][17].…”