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Zhen G.,Tongji University | Yan X.,Shanghai Sewage Company | Zhou H.,Shanghai Laogang Waste Treatment Company | Chen H.,Shanghai Sewage Company | And 2 more authors.
Journal of Environmental Sciences | Year: 2011

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 CaCl 2, Na 2S0 4 and CaS0 4 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% CaS0 4 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 CaS0 4 obviously improved the S/S performance, causing higher strength level. X-ray diffraction, scanning electron microscopy and thermogravimetry-diiferential scanning calorimetry investigations revealed that a large amount of hydrates (viz., gismondine and CaC0 3) 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. © 2011 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Source


Zhen G.,Tongji University | Zhou H.,Shanghai Laogang Waste Treatment Company | Zhao T.,Tongji University | Zhao Y.,Tongji University
Chinese Journal of Chemical Engineering | Year: 2012

This research evaluated the use of sewage sludge and refuse incineration bottom ash to replace calcium sulfoaluminate cement (C A) in making controlled low-strength material (CLSM). Various properties of CLSM mixtures were characterized in terms of unconfined compressive strength, microstructure and leachability. It was found that the strength of tested CLSM mixtures ranged from 3.6 to 9.0 MPa, over the upper excavatable limit of 2.1 MPa. The micro-structural analysis revealed that sewage sludge and bottom ash were crystallochemically incorporated within CLSM systems by forming the needle-like ettringite (C 3A·3C·H 32) with exiguous tubers via the typical Pozzolanic Reaction, leading to a dense and low-porosity microstructure. Furthermore, the toxicity characteristic leaching procedure evidenced that the cumulative leachable metals in the leachate were much below the regulatory thresholds. The potential for using sewage sludge and bottom ash in CLSM making was thus confirmed. © 2012 Chemical Industry and Engineering Society of China (CIESC) and Chemical Industry Press (CIP). Source


Niu J.,Tongji University | Zhang T.,Shanghai Guanglian Construction Development Co. | He Y.,Shanghai Guanglian Construction Development Co. | Zhou H.,Shanghai Laogang Waste Treatment Company | And 2 more authors.
Journal of Hazardous Materials | Year: 2013

A pilot-scale deep shaft aeration bioreactor (DSAB) with 110m in depth and 0.5m in diameter for the pretreatment of landfill leachate in winter was operated at a daily treatment scale of around 10-20tons. It was found that the performance of the DSAB mainly depended on the inflow loads and concentrations of pollutants. NH3-N, TN, COD, TOC removals of 66-94%, 41-64%, 67-87%, 55-92% at organic load rate of 1.7-9.4g CODL-1day-1 and hydraulic retention time of 1-2d were obtained using DSAB, respectively, with the lowest ambient temperature of -3°C. The effluent COD can be reduced to below 1000mg/L, an acceptable level for advanced treatment using reverse osmosis system, when the influent COD was below 7000mg/L at 10t/d. The EEM and GPC analysis implied that the non-biodegradable contaminants such as humic- and fulvic-like DOM dominated in the organic fractions of the effluent, which rendered the biological treatment ineffective. Compared with 20-40% removals obtained using traditional biological processes below 15°C, DSAB showed a higher treatment efficiency for COD and NH3-N, even though at adverse conditions of poor carbon source, lower C/N ratio and high nitrite concentrations in the leachate of test. © 2013 Elsevier B.V. Source

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