Abstract
The safe and efficient disposal and utilization of sludge are major issues to be solved in solid waste treatment and environmental protection due to the complex characteristics of sludge and the low rate of innocuous treatments. Composting is a process of decomposing organic matter and transformed low-molecular organic acids into high-molecular humus substances under the action of microorganisms. Although land-use after composting has become an important direction for sludge treatment, heavy metal pollution is still the bottleneck problem restricting land use of sludge compost. Adding zeolite, hydroxyapatite, and other conditioning agents to the composting process affects the concentration or form of some heavy metals and effectively reduces the environmental risk. Lime and phosphorus modifiers change heavy metal speciation in samples, playing a role in decreasing biological availability and mobility. In this study, the effects of sludge composting treatment and conditioning agents on the concentrations and forms of heavy metals are reviewed. This review will provide a theoretical basis to treat heavy metals in sludge composting and lay the foundation for the land utilization and waste recycling of sludge.
Highlights
A number of environmental problems are occurring with the increase in the urban population [1,2].Among these problems, sewage sludge has increased significantly, and sewage treatment technology has been developed rapidly [3]
Wang et al [45] used phosphate modifiers during sludge composting, and the results showed that the mobility of Cu decreases by 18.8% after adding calcium magnesium phosphate
Compared with single sludge compost, the increase in exchangeable Cd decreased by 38.3% and the reduction rate of residual Cd increased by 37.7% after adding 1.5% HAP, indicating that HAP has an effect on Cd
Summary
A number of environmental problems are occurring with the increase in the urban population [1,2]. Among these problems, sewage sludge has increased significantly, and sewage treatment technology has been developed rapidly [3]. The output of urban sludge in China increased from 54.27 million tons to 74.36 million tons from 2010 to 2017, with an average annual growth rate of 4.6%. Sludge is a by-product of sewage treatment and an extremely complex heterogeneous body composed of organic debris, bacteria, inorganic particles, and colloids. Sludge has high water content, it decomposes, and it contains heavy metals, pathogens, and parasites
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
