title: Effects of calcined aluminum salts on the advanced dewatering and solidification/stabilization of sewage sludge.
abstract: The high moisture content (80%) in the sewage dewatered sludge is the main obstacle to disposal and recycling. A chemical dewatering and stabilization/solidification (S/S) alternative for the sludge was developed, using calcined aluminum salts (AS) as solidifier, and CaCl2, Na2SO4 and CaSO4 as accelerators, to enhance the mechanical compressibility making the landfill operation possible. The properties of the resultant matrixes were determined in terms of moisture contents, unconfined compressive strength, products of hydration, and toxicity characteristics. The results showed that AS exhibited a moderate pozzolanic activity, and the mortar AS(0) obtained with 5% AS and 10% CaSO4 of AS by weight presented a moisture contents below 50%-60% and a compressive strength of (51.32 +/- 2.9) kPa after 5-7 days of curing time, meeting the minimum requirement for sanitary landfill. The use of CaSO4 obviously improved the S/S performance, causing higher strength level. X-ray diffraction, scanning electron microscopy and thermogravimetry-differential scanning calorimetry investigations revealed that a large amount of hydrates (viz., gismondine and CaCO3) were present in solidified sludge, leading to the depletion of evaporable water and the enhancement of the strength. In addition, the toxicity characteristic leaching procedure (TCLP) and horizontal vibration (HJ 557-2009) leaching test were conducted to evaluate their environmental compatibility. It was found that the solidified products conformed to the toxicity characteristic criteria in China and could be safely disposed of in a sanitary landfill.
authors: The State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai 200092, China. zhengguangyin@163.com
authors: Guangyin
authors: G
authors: Zhen
authors: Xiaofei
authors: X
authors: Yan
authors: Haiyan
authors: H
authors: Zhou
authors: Hua
authors: H
authors: Chen
authors: Tiantao
authors: T
authors: Zhao
authors: Youcai
authors: Y
authors: Zhao
mesh_terms: D000535:Aluminum; D012037:Refuse Disposal / Q000379:methods*; D012722:Sewage / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D012722:Sewage; D000535:Aluminum