Abstract
Quantities of sewage sludge that are thermally treated (mostly incinerated) are increasing, resulting in growing quantities of sewage sludge ash (SSA) which also requires further management. Despite its potential as a resource, it is still largely landfilled. Considering the presence of potentially toxic and hazardous heavy metals in SSA, this paper analyzes how the change in the leaching concentrations of the selected heavy metals from landfilled SSA impacts the environment (air, water, and soil) by the means of LCA. When considering human toxicity potential as impact category, dominant impacts were due to emissions into the air, primarily caused by leaching of selenium and somewhat less cadmium, mercury and nickel. Mercury had a dominant impact when considering the terrestrial ecotoxicity potential impact. In the SSAs obtained from Croatian sludge, molybdenum leaching, along with selenium and mercury, showed a dominant impact. Therefore, due to the high variability of trace elements, detailed analysis of different SSAs is needed.
Highlights
IntroductionA significant amount of waste in the form of sewage sludge from wastewater treatment plants (WWTP) is generated
At the global level, a significant amount of waste in the form of sewage sludge from wastewater treatment plants (WWTP) is generated
As part of this study, only heavy metals content and the concentration of their leaching from ash were examined, so the following analysis will primarily consider the environmental impact of 10 selected heavy metals caused by their leaching from Sewage sludge ash (SSA) landfilled on non-hazardous waste landfill
Summary
A significant amount of waste in the form of sewage sludge from wastewater treatment plants (WWTP) is generated. Sewage sludge treatment aims to reduce its total mass and volume to facilitate its further management, for which thermal treatment technologies are successfully applied. Sewage sludge ash (SSA) is the main by-product formed in the combustion processes associated with thermal processing. Disposal of sewage sludge within the global practice is carried out in different ways. Even at EU level, there are significant differences in sewage sludge management between countries (Figure 1). Analyzing the data for 2013–2017 period, some changes in the disposal routes of sewage sludge can be observed for individual countries, with an increase in the share of thermal treatment (incineration and co-incineration) and the resulting decrease in use on agricultural and non-agricultural land.
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