Abstract：
Dissolved organic matter (DOM) plays an important role in regulating the fate of mercury (Hg), e.g., mobility, bioavailability, and toxicity. Clarifying the role of DOM in binding Hg in the treatment processes of sewage sludge is important for relieving Hg contamination risks in land applications. However, the impacts of DOM on Hg binding in sewage sludge are still unclear. In this study, we investigated the evolution of Hg and its speciation in full-scale sludge anaerobic digestion (AD) with thermal hydrolysis. The role of DOM in binding Hg(II) was further analyzed. The results showed that AD with thermal hydrolysis led to an increase in the Hg content in the sludge (from 3.72 ± 0.47 mg/kg to 10.75 ± 0.16 mg/kg) but a decrease in Hg mobility (the mercury sulfide fraction increased from 60.56 % to 79.78 %). Further adsorption experiments revealed that at equivalent DOM concentrations, DOM with a low molecular weight (MW<1 kDa) in activated sludge, DOM with a medium molecular weight (1 kDa 5 kDa) in both anaerobically digested sludge and conditioned sludge showed high binding amounts of Hg(II), with 1372.54, 535.28, 942.09 and 801.51 mg Hg/g DOM, respectively. Parallel factor analysis (PARAFAC) and fluorescence quotient (FQ) results showed that tryptophan-like and tyrosine-like substances had high binding affinities for Hg(II). Furthermore, X-ray photoelectron spectroscopy (XPS) indicated that the reduced organic sulfur contained in the DOM was potentially bound to Hg through the interactions of Hg-S and Hg-O. These results indicated that DOM may play special roles in regulating Hg speciation. The association between DOM and Hg(II), such as the significant positive correlation (p < 0.05) between the dissolution rate of Hg(II) and release of tryptophan-like substances during thermal hydrolysis, suggested the potential way for removing Hg from sludge.
摘要：
溶解性有机物(DOM)在调节汞(Hg)的归宿中起着重要作用。例如，移动性,生物利用度，和毒性。明确DOM在污水污泥处理过程中结合汞的作用对于减轻土地应用中的汞污染风险非常重要。然而,DOM对污泥中汞结合的影响尚不清楚。在这项研究中,我们研究了汞在热水解全尺度污泥厌氧消化（AD）中的演变及其形态。进一步分析了DOM在结合Hg(II)中的作用。结果表明，热水解AD导致污泥中Hg含量增加（从3.72±0.47mg/kg增加到10.75±0.16mg/kg），但Hg迁移率降低（硫化汞含量从60.56％增加到79.78％）。进一步的吸附实验表明，在相同的DOM浓度下，活性污泥中分子量低（MW<1kDa）的DOM，热水解污泥中具有中等分子量（1kDa5kDa）的DOM显示出高结合量的Hg（II），1372.54、535.28、942.09和801.51mgHg/gDOM，分别。平行因素分析（PARAFAC）和荧光商（FQ）结果表明，色氨酸样和酪氨酸样物质对Hg（II）具有较高的结合亲和力。此外，X射线光电子能谱（XPS）表明，DOM中所含的还原有机硫可能通过Hg-S和Hg-O的相互作用与Hg结合。这些结果表明，DOM可能在调节汞形态中起特殊作用。DOM和Hg(II)之间的联系，如热水解过程中Hg（II）的溶解速率与色氨酸样物质的释放之间的显着正相关（p<0.05），提出了从污泥中去除汞的潜在方法。
