Chengran Fang

Investigation on characteristics of leachate and concentrated leachate in three landfill leachate treatment plants

Concentrated leachate from membrane treatment processes is a potential pollution source for the surroundings. In this study, with comparison of the landfill leachate, chemical and microbial characteristics of concentrated leachate including biodegradability, amount of nitrogenous compounds and heavy metals, dissolved organic matter composition, and microbial community were investigated in three landfill leachate treatment plants. The results showed that hydrophilic (HyI) fraction was the major dissolved organic carbon in the landfill leachates, accounting for 54.6-60.7%, while humic substances including humic acid (HA) and fulvic acid (FA) were relatively higher in the concentrated leachates, ranging from 61.7% to 69.2%. Conjugated nitrogen existed mainly in FA and HyI in the concentrated leachates. The analysis of excitation emission matrix fluorescence spectroscopy, specific ultraviolet absorbance at 254nm (SUVA254) and GC/MS showed that aromatic compounds, long-chain hydrocarbons and halohydrocarbons were abundant in the concentrated leachates. During landfill leachate treatment processes, Cl(-), SO4(2-) and heavy metals were commonly accumulated in the concentrated leachates. NO3(-)N and/or NH4(+)N were the major nitrogenous compounds in the concentrated leachates. All the leachates from three landfill sites contained toluene in the range of 44.5-728.4μgL(-1). Ethylbenzene, chlorobenzene, and the phthalic acid esters including dibutyl phthalate, dimethyl phthalate and di-n-octyl phthalate were also detected in the concentrated leachates. Higher microbial diversity was observed in the concentrated leachate in comparison with landfill leachate.

Methane oxidation in landfill waste biocover soil: Kinetics and sensitivity to ambient conditions

Waste biocover soil was investigated as an alternative in regions with a shortage of landfill cover soil. In the work, effects of the composition, ambient conditions and nitrogen stress on CH(4) oxidation in waste biocover soil were studied. The results showed that the optimal composition of waste biocover soil as a landfill cover material for CH(4) oxidation was original pH value, 45% moisture and a particle size of ≤ 4mm. CH(4) oxidation rate increased rapidly over a CH(4) concentration range of 0.01-10% (v/v), and kept stable at CH(4) concentrations of 10-30% (v/v). The Michaelis-Menten model showed a good fit for the kinetic of CH(4) oxidation in landfill waste biocover soil with a maximum of 9.03 μmol/gd.w./h. The average Q(10) was 10.6 in the batch experiments. A level of 5% of oxygen concentration was enough to sustain the activity of methanotrophs community structure in waste biocover soil. Waste biocover soil had low baseline concentrations of NH(4)(+)-N and NO(3)(-)-N. Ammonia volatilization from landfills and nitrification in landfill waste biocover soils might stimulate CH(4) consumption at concentrations below 600 mg/kg. However, the contents of NH(4)(+)-N and NO(3)(-)-N above 1200 mg/kg would inhibit CH(4) oxidation in landfill waste biocover soil. Compared with NO(3)(-)-N, NH(4)(+)-N had a greater stimulating action as nutrient at lower concentrations and inhibitory effect at higher concentrations on CH(4) oxidation in landfill waste biocover soil.

Characterization of adsorption removal of hydrogen sulfide by waste biocover soil, an alternative landfill cover

Landfill is an important anthropogenic source of odorous gases. In this work, the adsorption characteristics of H(2)S on waste biocover soil, an alternative landfill cover, were investigated. The results showed that the adsorption capacity of H(2)S increased with the reduction of particle size, the increase of pH value and water content of waste biocover soil. The optimal composition of waste biocover soil, in regard to operation cost and H(2)S removal performance, was original pH value, water content of 40% (w/w) and particle size of ≤4 mm. A net increase was observed in the adsorption capacity of H(2)S with temperatures in the range of 4-35°C. The adsorption capacity of H(2)S on waste biocover soil with optimal composition reached the maximum value of 60±1 mg/kg at oxygen concentration of 10% (v/v). When H(2)S concentration was about 5% (v/v), the adsorption capacity was near saturation, maintaining at 383±40 mg/kg. Among the four experimental soils, the highest adsorption capacity of H(2)S was observed on waste biocover soil, followed by landfill cover soil, mulberry soil, and sand soil, which was only 9.8% of that of waste biocover soil.

In situ nitrogen removal in phase-separate bioreactor landfill

The feasibility of in situ nitrogen removal in phase-separate bioreactor landfill was investigated. In the experiment, two sets of bioreactor landfill systems, namely conventional two-phase and in situ nitrogen removal bioreactor landfills, were operated. The in situ nitrogen removal bioreactor landfill (NBL) was comprised of a fresh-refuse filled reactor (NBLF), a methanogenic reactor (NBLM) and a nitrifying reactor (NBLN), while the two-phase bioreactor landfill (BL) used as control was comprised of a fresh-refuse filled reactor (BLF) and a methanogenic reactor (BLM). Furthermore, the methanogenic and nitrifying reactors used aged refuse as bulk agents. The results showed that in situ nitrogen removal was viable by phase-separation in the bioreactor landfill. In total 75.8 and 47.5 g of nitrogen were, respectively, removed from the NBL and the BL throughout the experiment. The methanogenic reactor used the aged refuse as medium was highly effective in removing organic matter from the fresh leachate. Furthermore, the aged refuse was also suitable to use as in situ nitrification medium. The degradation of fresh refuse was accelerated by denitrification in the initial stage (namely the initial hydrolyzing stage) despite being delayed by denitrification in a long-term operation.

An innovative combined on-site process for the remote rural solid waste treatment--a pilot scale case study in China.

The aim of this study was to find a feasible method for the treatment of solid waste generated in the remote rural, where the transportation costs are prohibitive and the resources to construct and maintain conventional treatment plants are not available. This process, consisted of two types of simulated bioreactor landfill (one was recirculated bioreactor landfill, and the other was comprised of fresh and aged refuse reactor) and a soil infiltration system, was operated in ambient temperature for 180 days all together. After treated by the system of fresh and aged refuse reactor, the refuse and leachate reached a strongly degraded and stable state. The remaining leachate can be treated by the soil infiltration system, and 87.5 ± 2.1%, 98.6 ± 1.0% and 95.7 ± 1.7% were achieved by 60 cm soil depths for organic matter, ammonium nitrogen and total nitrogen removal, respectively.

Effect of weathering treatment on the fractionation and leaching behavior of copper in municipal solid waste incinerator bottom ash

This work describes the effect of weathering of fresh quenched municipal solid waste incinerator (MSWI) bottom ash on the fractionation and leaching behavior of Cu. A sequential extraction procedure was used to characterize the fractionation of Cu in the fresh and weathered MSWI bottom ash samples. It showed that the organic matter bound fraction of Cu decreased drastically from 69% to 37% during the weathering treatment, while the residual fraction, Fe-Mn oxides bound fraction, carbonate bound fraction and exchangeable fraction increased from 24% to 54%, 3% to 4%, 2% to 3% and 2% to 3%, respectively. Furthermore, two standard leaching procedures, synthetic precipitation leaching procedure (SPLP) and toxicity characteristic leaching procedure (TCLP), were carried out on the fresh and weathered samples. The leaching of Cu was attenuated with the process of weathering treatment in the SPLP procedure, but was enhanced in the TCLP procedure. The results suggested that the weathering treatment could change the fractionation and leaching behavior of Cu in MSWI bottom ash. Further research is required to correlate weathering of ash and mobility of Cu.

Vertical profiles of community and activity of methanotrophs in landfill cover soils of different age

Aerobic CH4 oxidation is an important process controlling CH4 release from landfills to the atmosphere. The aim of this study was to investigate the link between CH4 oxidation activity and methanotrophs abundance and diversity in landfill cover soils of different age.

A comparative study on two extraction procedures in speciation of iron in municipal solid waste

Two extraction reagents, hydrochloric acid (HCl) and acid ammonium oxalate solution (Tamms reagent), were used to evaluate the redox state of iron in municipal solid waste (MSW) with different deposit ages. Orthogonal experiments were conducted to optimize the extraction conditions for extractable iron speciation (ferric and ferrous) in MSW. The optimal extraction conditions for HCl were determined as follows: the liquid-to-solid ratio was set at 100, and then the samples were extracted at the shaking speed of 200 rpm at 35 degrees C for 60 min by 1.00 M HCl. For Tamms reagent, the optimal extraction conditions were extracted at the shaking speed of 175 rpm at 30 degrees C for 12 h with the same liquid-to-solid ratio. However, Tamms reagent extraction is much more laborious and time-consuming. Thus the HC1 extraction might be a better choice for the evaluation of the redox state of iron in MSW. The results also showed that the yield of extractable iron increased with deposited age. About 60-83% of extractable iron was presented as ferrous in the MSW deposited for 1-8 years. This study supplied a tool for investigating the role of iron on the fate of pollutants in the landfill.

Degradation of sulfonamides during anaerobic composting of swine manure

ABSTRACT Residual antibiotics in manure pose a potential threat to public and ecological health as a result of the application of manure from animals treated with antibiotics to land. The environmental fate of sulfonamides (SAs) in swine manure after composting and field application remains largely unknown. We studied the degradation of the antibiotics sulfadiazine (SD), sulfathiazole (ST), and sulfamethazine (SM2) during anaerobic composting. We tested the effects of temperature and antibiotic concentration on degradation rates. We also evaluated the changes in pH, moisture, and biological degradation material in manure spiked with SAs and in a control. Results showed that the 3 SAs decreased by between 52.31% and 90.30% in all 9 treatments following 14 days of anaerobic composting, and the highest removal efficiencies were observed at a temperature of 35°C and initial concentrations of 6.03, 6.48, and 6.32 µg/g of SD, ST, and SM2, respectively, which were degraded by 90.30%, 85.78%, and 75.18%. Removal efficiencies for all SAs correlated well with moisture and biological degradation material of the manure. These results indicate that composting may be a practical and effective way to reduce concentrations of these three SAs in swine manure prior to its land application.

Degradation of dibutyl phthalate in refuse from different phases of landfill by its dominant bacterial strain, Enterobacter sp. T1

A facultative bacterial strain isolated from municipal solid waste (MSW) obtained from a simulated landfill bioreactor was found to have the ability to use dibutyl phthalate (DBP) as its sole source of carbon and energy. Based on its morphology, physiochemical characteristics, and 16S rDNA sequence, the strain was identified as Enterobacter sp. T1. Evaluation of the degradation of DBP in refuse collected during the initial, acidic, and methanogenic phases of landfill before and after inoculation with Enterobacter sp. T1 revealed that the degradation fits first-order kinetic models for refuse from all phases. The removal rate of DBP in the refuse of the methanogenic phase increased from 59.3% to 74.5% when Enterobacter T1 was added. The half-life of DBP in refuse from the methanogenic phase that was inoculated with Enterobacter T1 decreased by 36.7% relative to uninoculated samples, and the intermediate products monobutyl phthalate (MBP) and phthalic acid were detected in all samples. These results provide new evidence for the potential of applying Enterobacter sp. for phthalic acid ester-polluted area remediation.