Synchronous fluorescence spectroscopy and 3-dimensional excitation emission matrices spectra (3DEEM) were used to study the composition variation of dissolved organic matter (DOM) in landfill leachate in the adsorption process with 717 resin. The synchronous fluorescence spectra showed fluorescence intensities of longer wavelength went down greatly while those of shorter wavelength went up in the first 10 min, then there were little changes. 3DEEM results indicated that there were two fulvic-like fluorescence peaks, whose intensities decreased dramatically, the peak intensities ratio (I(UV)/I(Vis)) also decreased, and the blue shifts of emission wavelengths took place obviously with the time rising. It was indicated that the adsorption rate of DOM by 717 resin was fast, and the main adsorbed DOM had higher molecular weight and higher degree of complexity, which was potential to facilitate subsequent bio-treatment.
Landfilling is a dominant municipal solid waste (MSW) disposal method in most developing countries. In China, approximately 85% of the generated MSW is being disposed of in the landfills. The amount of MSW is growing rapidly with the rate of approximately 8-10% annually, which contains a high quantity of moisture and organic matters. The problems of leachate treatment and landfill gas (LFG) emissions are increasing gradually. Reducing the hazard before emplacement, pretreatment of MSW before landfilling has become very important for the conventional landfill. In this study, aerobic pretreatment of mixed MSW was used, and much attention has been given to the natural convection of air in the mixed and unshredded MSW for bioconversion of organic matter (OM). This study is an attempt to investigate aerobic pretreatment suitability for the mixed and unshredded MSW at Beijing. A pilot-scale aerobic pretreatment simulator (APS) was developed at Beishen Shu Landfill in Beijing. To work out the biodegradation of the OM in the APS, fresh and pretreated MSW samples were collected and analyzed for OM, moisture content, temperature, chemical oxygen demand, total organic carbon, carbon, nitrogen, hydrogen, lignocelluloses, and biochemical methane potential at various stages of the pretreatment. Furthermore, results of the fresh and pretreated MSW are compared. Significant reduction in the observed parameters of the pretreated waste samples is observed. This work demonstrates that pretreatment is significantly effective in reducing the landfill emissions that is leachate and LFG.
Using time domain reflectometry (TDR) technology, waste moisture content variation in aerobic and anaerobic landfill of MSW was monitored, in order to study its disciplinarian. The results showed that volume moisture content of waste increased with landfill time and water holding capacity of waste improved continuously. The correlation of water quantity and moisture content was positive in early aerobic landfill, but it became negative later. In anaerobic landfill, moisture content variation was caused by settlement and compression of MSW. TDR readings and waste material-based volume moisture content had a good correlation. The maximum error between them is about +/- 5% in aerobic landfill and +/- 2% in anaerobic landfill. TDR technology is applicable to measure moisture content in practical landfill engineering.
Thermal oxidation is efficient for enhancing the photocatalysis performance of graphitic carbon nitride (g-C3N4), while its effect on adsorption performance has not been fully studied, which is crucial to the application of g-C3N4 as adsorbents and photocatalysts. In this study, thermal oxidation was used to prepare sheet-like g-C3N4 (TCN), and its application for adsorption of humic acids (HA) and fulvic acids (FA) was evaluated. The results showed that thermal oxidation clearly affected the properties of TCN. After thermal oxidation, the adsorption performance of TCN was enhanced significantly, and the adsorption amount of HA increased from 63.23 (the bulk g-C3N4) to 145.35 mg/g [TCN prepared at 600 °C (TCN-600)]. Based on fitting results using the Sips model, the maximum adsorption amounts of TCN-600 for HA and FA were 327.88 and 213.58 mg/g, respectively. The adsorption for HA and FA was markedly affected by pH, alkaline, and alkaline earth metals due to electrostatic interactions. The major adsorption mechanisms included electrostatic interactions, π-π interactions, hydrogen bonding, along with a special pH-dependent conformation (for HA). These findings implied that TCN prepared from environmental-friendly thermal oxidation showed promising prospects for humic substances (HSs) adsorption in natural water and wastewater.
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