Leaching characteristics of calcium-based compounds in MSWI Residues: From the viewpoint of clogging risk.
Leachate collection system (LCS) clogging caused by calcium precipitation would be disadvantageous to landfill stability and operation. Meanwhile, calcium-based compounds are the main constituents in both municipal solid waste incineration bottom ash (MSWIBA) and stabilized air pollution control residues (SAPCR), which would increase the risk of LCS clogging once these calcium-rich residues were disposed in landfills. The leaching behaviors of calcium from the four compounds and municipal solid waste incineration (MSWI) residues were studied, and the influencing factors on leaching were discussed. The results showed that pH was the crucial factor in the calcium leaching process. CaCO3 and CaSiO3 began leaching when the leachate pH decreased to less than 7 and 10, respectively, while Ca3(PO4)2 leached at pH<12. CaSO4 could hardly dissolve in the experimental conditions. Moreover, the sequence of the leaching rate for the different calcium-based compounds is as follows: CaSiO3>Ca3(PO4)2>CaCO3. The calcium leaching from the MSWIBA and SAPCR separately started from pH<7 and pH<12, resulting from CaCO3 and Ca3(PO4)2 leaching respectively, which was proven by the X-ray diffraction results. Based on the leaching characteristics of the different calcium compounds and the mineral phase of calcium in the incineration residues, simulated computation of their clogging potential was conducted, providing the theoretical basis for the risk assessment pertaining to LCS clogging in landfills.
State Key Laboratory of Pollution Control & Resource Reuse, Tongji University, Shanghai 200092, PR China; Institute of Waste Treatment and Reclamation, Tongji University, Shanghai 200092, PR China.
Yi
Y
Xia
State Key Laboratory of Pollution Control & Resource Reuse, Tongji University, Shanghai 200092, PR China. Electronic address: zhanghua_tj@tongji.edu.cn.
Hua
H
Zhang
State Key Laboratory of Pollution Control & Resource Reuse, Tongji University, Shanghai 200092, PR China; Institute of Waste Treatment and Reclamation, Tongji University, Shanghai 200092, PR China.
Khamphe
K
Phoungthong
Changzhou Domestic Waste Treatment Center, Changzhou 213000, PR China.
Dong-Xiao
DX
Shi
Changzhou Domestic Waste Treatment Center, Changzhou 213000, PR China.
Wen-Hui
WH
Shen
Institute of Waste Treatment and Reclamation, Tongji University, Shanghai 200092, PR China; Center for the Technology Research and Training on Household Waste in Small Towns & Rural Area, Ministry of Housing and Urban-Rural Development of PR China (MOHURD), Shanghai 200092, PR China.
Li-Ming
LM
Shao
Institute of Waste Treatment and Reclamation, Tongji University, Shanghai 200092, PR China; Center for the Technology Research and Training on Household Waste in Small Towns & Rural Area, Ministry of Housing and Urban-Rural Development of PR China (MOHURD), Shanghai 200092, PR China. Electronic address: solidwaste@tongji.edu.cn.
Pin-Jing
PJ
He
D017610:Calcium Compounds / Q000032:analysis*; D060729:Coal Ash / Q000032:analysis*; D017745:Incineration; D012037:Refuse Disposal; D012989:Soil Pollutants / Q000032:analysis*; D062611:Solid Waste / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014961:X-Ray Diffraction
D017610:Calcium Compounds; D060729:Coal Ash; D012989:Soil Pollutants; D062611:Solid Waste; D014874:Water Pollutants, Chemical
Calcium-based compounds; Clogging potential computation; Leachate collection system clogging; Leaching kinetics; pH-dependent leaching characteristic