深度脱水污泥好氧堆肥中多环芳烃的含量与风险削减研究
Content and Risk Reduction of Polycyclic Aromatic Hydrocarbons during Aerobic Composting for Deeply Dehydrated Sludge
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摘要: 污泥中存在的多环芳烃(Polycyclic aromatic hydrocarbons, PAHs)是限制污泥无害化和资源化的重要因素。本研究使用气相色谱-质谱仪和比值法分析污泥中美国环境保护署优先控制的16种PAHs的含量和来源,重点考察了深度脱水后的污泥在好氧堆肥过程中PAHs的含量和风险变化,以期为提升好氧堆肥风险削减效果提供基础数据和技术支撑。研究结果显示,16种PAHs在6组用于好氧堆肥的污泥中均有检出,其总浓度检出范围为823.07~1870.30 ng/g,组成以中高环芳烃为主,主要来源为石油污染和燃烧的混合源。好氧堆肥28天后,污泥中PAHs的总浓度下降至541.19~1456.19 ng/g,对应的降解率为13.89~56.78%,添加颗粒大的返混料能提升通气性从而更有利于PAHs的降解。采用风险熵对好氧堆肥前后污泥PAHs的风险进行评估,发现污泥中的PAHs整体处于中低风险,好氧堆肥后除堆肥组1的苯并[a]芘和堆肥组2的芴由低风险上升为中风险外,其余堆肥组PAHs的风险均保持不变或者下降。本研究结果表明,污泥中的PAHs应作为一项重要指标进行长期监测,从而避免因长期暴露引发累积性生态风险。Abstract: The presence of polycyclic aromatic hydrocarbons (PAHs) in sludge limits the soundness and recycling of sludge. This study used gas chromatography-mass spectrometry and ratio method to analyze the content and source of 16 PAHs prioritized by the U.S. Environmental Protection Agency, and specially investigated the content and risk changes of PAHs during aerobic composting of deeply dehydrated sludge, and is expected to provide basic data and technical support for improving the risk reduction of pollutants by aerobic composting. The results showed that 16 PAHs were all detected in 6 groups of sludge used for aerobic composting, and their total concentration ranged from 823.07 to 1870.30 ng/g. They were mainly composed of medium and high cyclic PAHs, and mainly from mixed sources of petroleum pollution and combustion. After 28 days of aerobic composting, the total concentration of PAHs in the sludge decreased to 541.19-1456.19 ng/g, corresponding to 13.89~54.29% degradation. The addition of back mixing of the compost products with large particle size could improve the sludge aeration, which was conducive to the degradation of PAHs. Risk entropy was used to evaluate the risk changes of PAHs in sludge before and after aerobic composting, and the overall risk of PAHs before composting was in the medium to low level. Except for the risk of BaP in composting group 1 and Flu in composting group 2 increased from the low to medium level, the risk of PAHs in all composting groups remained unchanged or decreased after aerobic composting. Our finding indicates that PAHs in sludge should be routinely monitored as an important indicator to avoid cumulative ecological risks caused by long-term exposure.
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Key words:
- sludge /
- aerobic composting /
- PAHs /
- attenuation /
- ecological risk
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