Abstract
To understand the effects of co-processing sewage sludge in the cement kiln on non-criterion pollutants emissions and its surrounding environment, the flue gas from a cement kiln stack, ambient air and soil from the background/downwind sites were collected in the cement plant. Polycyclic aromatic hydrocarbons (PAHs) and heavy metals of the samples were analyzed. The results show that PAHs in flue gas mainly exist in the gas phase and the low molecular weight PAHs are the predominant congener. The co-processing sewage sludge results in the increase in PAHs and heavy metals emissions, especially high molecular weight PAHs and low-volatile heavy metals such as Cd and Pb in the particle phase, while it does not change their compositions and distribution patterns significantly. The concentrations and their distributions of the PAHs and heavy metals between the emissions and ambient air have a positive correlation and the co-processing sewage sludge results in the increase of PAHs and heavy metals concentrations in the ambient air. The PAHs concentration level and their distribution in soil are proportional to those in the particle phase of flue gas, and the co-processing sewage sludge can accelerate the accumulation of the PAHs and heavy metals in the surrounding soil, especially high/middle molecular weight PAHs and low-volatile heavy metals.
Highlights
Rapid urbanization has increased the formation of municipal sewage sludge in China in recent years [1,2]
In order to investigate the effects of co-processing sewage sludge on non-criterial pollutant emissions, the flue gas samples from the cement kiln stack were collected and analyzed in 0 and
It can be seen that the co-processing sewage sludge results in an increase in Polycyclic aromatic hydrocarbons (PAHs) and heavy metals emissions, especially
Summary
Rapid urbanization has increased the formation of municipal sewage sludge in China in recent years [1,2]. Given the sewage sludge contains nitrogen-containing compounds, organic matters and heavy metals [3], proper disposal should be employed to avoid environmental problems. Both a high temperature and alkaline environment are provided in the cement kiln so that most of the pollutants in the sewage sludge can be effectively destroyed or solidified to reduce the harm to the environment [4,5,6]. The PAHs increment is caused by the PAHs emissions from the cement kiln because it is positively correlated with the increase of PAHs emissions from the cement production and co-processing sewage sludge
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