Zhu Nanwen

Natural attenuation and characterization of contaminants composition in landfill leachate under different disposing ages.

Chemical Oxygen Demand (COD) composition in landfill leachate would vary as the disposal time extended. Leachates with different ages were collected from Laogang Refuse Landfill of Shanghai, the largest landfill in China with a placement scale of 7600 t refuse per day. To characterize COD composition in leachate, samples were size-fractioned into suspended fractions (>0.45 microm), colloid fraction (0.45 microm<fraction<1 K Da MW) and dissolved fractions (<1 KDa MW) based on the molecular weight distribution. The fractions <0.45 microm (including colloid fraction and dissolved fractions) in leachate were further divided into 6 fractions, i.e. hydrophobic bases (Ho-base), hydrophobic acids (Ho-acid), hydrophobic neutral (Ho-neutral), hydrophilic bases (Hi-base), hydrophilic acids (Hi-acid) and hydrophilic neutral (Hi-neutral). It was found that the ratio of TOC/TC in leachate decreased over time, indicating that the percentage of organic matters in leachate decreased as the disposal time extended. It was also observed that the hydrophobic fraction accounted to about 50% of the total matters presented in the fraction <0.45 microm of all leachate samples. The main components in <0.45 microm fraction were the Ho-acid, Hi-acid and Hi-base fractions. The percentage of Ho-acid in leachate decreased from 60.8% (2 a) to 43.2% (12 a). In addition, leachate with different ages was categorized into 3 phases according to the results of Principle component analysis (PCA). TOC/COD ranges of leachate in periods I, II and III were 40-54.6%, 16.9-41.3% and 10-38.9%, respectively, indicating that the COD contribution of non-carbon reduction substances increased over time in leachate. Hence, the corresponding landfill leachate treatment process should be modified according to the leachate characterization. The results obtained in this study might provide the important information for modeling, design, and operation of landfill leachate treatment systems.

Martial recycling from renewable landfill and associated risks: A review.

Landfill is the dominant disposal choice for the non-classified waste, which results in the stockpile of materials after a long term stabilization process. A novel landfill, namely renewable landfill (RL), is developed and applied as a strategy to recycle the residual materials and reuse the land occupation, aim to reduce the inherent problems of large land occupied, materials wasted and long-term pollutants released in the conventional landfill. The principle means of RL is to accelerate the waste biodegradation process in the initial period, recover the various material resources disposal and extend the landfill volume for waste re-landfilling after waste stabilized. The residual material available and risk assessment, the methodology of landfill excavation, the potential utilization routes for different materials, and the reclamation options for the unsanitary landfill are proposed, and the integrated beneficial impacts are identified finally from the economic, social and environmental perspectives. RL could be draw as the future reservoirs for resource extraction.

Source reduction of the landfill leachate strength in a functional layer embedded landfill (FLEL).

In order to reduce the leachate strength from landfill at source, a novel landfill, functional layer embedded landfill, was developed through the introduction of the functional layers, and a comparative study was conducted between the functional layer embedded landfill (FLEL, R1) and the conventional landfill (CL, R2). It was found that the pollutant in leachate effluent from R1 was 20-50%, 14-43% and 33-75% of that from R2, in terms of COD, TN and NH(3)-N. The cumulative movement of waste settlement was about 16.4 and 13.1cm in R1 and R2 under the test period of 1 years, resulting in 13.7% and 10.9% of the original landfill height. Therefore, FLEL could save the land area and the cost of the leachate treatment process due to the reduction of leachate strength, and more waste could be disposed in landfill through the acceleration of the MSW degradation process, comparing to the CL.

Application of hydration reaction on the removal of recalcitrant contaminants in leachate after biological treatment

Leachate contains amounts of non-biodegradable matters with COD range of 400-1500mg/L after the biological treatment, and should be removed further to attain the Chinese discharge standards. Hydration reaction has the potential to combine and solidify some recalcitrant substances, and thus could be applied as the advanced leachate treatment process. It was found that COD and NH3N decreased from 485 to<250mg/L and 91 to 10mg/L, with the removal rate over 50% and 90% in the first 6d, respectively, and COD and NH3N removal capacity were around 23.7 and 9.2mg/g under the test conditions. The percentage of the substances with low Mn range of<1000 decreased from 32.9% to 3.2% in leachate after hydration reaction. Tricalcium aluminate, tricalcium silicate and dicalcium silicate were the most activity compounds successively for the pollutant removal in leachate, and hydration reaction could be the option for the advanced wastewater treatment process thereafter.

Typical MSW odor abatement using sludge derived carbon prepared by activation with Fenton’s reagent and NaClO

Sludge derived carbon (SBC) is a potential resource from sewage sludge disposal, and chemical pre-treatment is a necessary activation method for the improvement of the SBC quality. Two novel activators, i.e. Fenton and NaClO, were introduced to produce SBC precursors through the destruction of cell wall barriers and heterogeneous structures in sludge. High quality SBC-Fenton and SBC-NaClO were produced, with the BET having increased from 38 m2 g−1 in the control group to 253 m2 g−1 and 423 m2 g−1, respectively. The micro-porosity volume increased from 6% to 42% and 46% in the SBC-Fenton and SBC-NaClO, respectively, with the corresponding saturation adsorption capacity increasing from 33.1 mg g−1 to 71.5 mg g−1 and 67.8 mg g−1 based on Langmuir isotherms using methylene blue. The adsorption processes of the typical odorants H2S and NH3 were also tested using the SBC-Fenton and SBC-NaClO, which could reduce the landfill volume and odor emissions simultaneously, and around 2.1 mg g−1 and 0.68–2.24 mg g−1 of NH3 and H2S were adsorbed under different dosages. SBC could be a promising adsorption carrier and supporting substance for soil cover in landfills.