Youcai Zhao

Recycling of aged refuse from a closed landfill

In this study, refuse excavated from a typical refuse landfill in Shanghai after 8-10 years of placement was characterized in terms of particle size, total nitrogen, total phosphorus, and biodegradable matter. The refuse contained a large and diverse population of micro-organisms with a high capacity for decomposing refractory organic matter present in some waste-waters, including leachate. It was found that the aged refuse was quite stable after about a decade of decomposition in the warm, humid climate of southern China. The fine fractions resembled and had the properties of black soil, a medium that is suitable for green construction, organic fertilizer, or as bio-reactor media for biological treatment of organic wastewaters. Excavation of the aged refuse would make about 50% of the space available for fresh refuse. The plastics, glass, textiles, and cans can be readily mechanically separated and recycled after cleaning. It is estimated that at least 200 millions tonnes of such aged refuse are available in China alone, and at least 10 times that much is buried worldwide. Hence, the evaluation of mined landfill waste and consideration of its potential uses is of great significance.

Characterization of microalgae-bacteria consortium cultured in landfill leachate for carbon fixation and lipid production.

The characteristics of cultivating high-density microalgae-bacteria consortium with landfill leachate was tested in this study. Landfill leachate was collected from Laogang landfill operated for over 10 years in Shanghai, China. The maximum biomass concentration of 1.58g L(-1) and chlorophyll a level of 22mg L(-1) were obtained in 10% leachate spike ratio. Meanwhile, up to 90% of the total nitrogen in landfill leachate was removed in culture with 10% leachate spike ratio with a total nitrogen concentration of 221.6mg L(-1). The fluorescence peak of humic-like organic matters red shifted to longer wavelengths by the end of culture, indicating that microalgae-bacteria consortium was effective for treating landfill leachate contaminants. Furthermore, with the leachate spike ratio of 10%, the maximum lipid productivity and carbon fixation were 24.1 and 65.8mg L(-1)d(-1), respectively. Results of this research provide valuable information for optimizing microalgae culture in landfill leachate.

Complexion between mercury and humic substances from different landfill stabilization processes and its implication for the environment

Three-dimensional excitation emission matrix (EEM) fluorescence spectroscopy was employed to investigate the structural properties and Hg(II)-binding behavior of humic substances (HS) extracted from different landfill stabilization processes. The EEM fluorescence properties of humic acid (HA) are characterized by intense fluorescence at Ex/Em=440/500 nm and Ex/Em=380/460 nm. Two relatively strong fluorescence peaks appeared in the region of Ex/Em=260-290/350-370 nm with the landfill time extended, which represented a protein-like or soluble microbial byproduct structure. The fluorescence EEM spectrum of fulvic acid (FA) featured a prominent peak of strong relative fluorescence intensity (FI=1598) at Ex/Em=330/440 nm (peak C) accompanied by a weak fluorophore (FI=594) located at Ex/Em=275/445 nm (peak D). There were strong interactions between HA and Hg, and the overall stability constant of Hg(II)-HA was mainly determined by the abundant O-ligands existing in HA. FA had a much higher Hg(II)-complexing capacity compared to HA samples, which may be ascribed to its relatively high content of carboxylic groups. The Hg(II)-complexing capacity of HA tended to decrease with stabilization process extension. The much higher Hg(II)-complexing capacity of FA than that of HA implied that FA played an important role in binding Hg(II) in early landfill stabilization process.

Sulfamethoxazole, tetracycline and oxytetracycline and related antibiotic resistance genes in a large-scale landfill, China.

Landfills are likely to be important reservoirs of antibiotics and antibiotic resistant genes (ARGs) as they receive unused and unwanted antibiotics and ARGs in municipal solid waste (MSW). The distribution, transportation and dynamics of antibiotics and ARGs in landfills remain largely unknown. In the present study, 3 antibiotics - sulfamethoxazole (SMX), tetracycline (TC), and oxytetracycline (OTC) - and their related ARGs (sulI and tetO) were quantified in 51 refuse samples from different depths at 8 locations within a large-scale landfill in central China. The average concentration of OTC was the highest, up to 100.9±141.81μg/kg (dw, n=48), followed by TC (63.8±37.7μg/kg, n=40), and SMX (47.9±8.1μg/kg, n=30). Both sulI and tetO were detected in all samples. Of the ARGs, sul1 (-3.06±1.18, n=51, log10 ARGs/16SrDNA) was more abundant than tetO (-4.37±0.97) in all refuse samples (p<0.05). Both sulI and tetO negatively correlated to refuse age, suggesting they are attenuated during landfill stabilization. OTC and TC positively correlated to tetO (r=0.41, p<0.01) and sulI (r=0.29, p=0.04), respectively. Chemical conditions (e.g. moisture content and nitrate concentrations) within the refuse correlated to antibiotics and ARGs suggesting environmental factors impact the distribution of antibiotics and ARGs in landfill matrix. This study is the first comprehensive in situ landfill study to connect the concentrations of antibiotic residues to ARGs.

A comprehensive overview of rural solid waste management in China

This paper aims to conduct a comprehensive review of rural solid waste (RSW) in terms of characteristics, management and legislation. Survey results show that RSW generation rates range from 0.25 to 2.1 kg ∙(capita∙d)−1 in different rural villages across regions of China. Total RSW generation has been increasing, which is far higher than official data in 2014. RSW are dominated by food residue and coal ash/cinder/dust (at approximately 70%). Most of RSW are still discarded randomly without any treatment in China. Scattered RSW generation sources, imperfect legislation system, poor infrastructure on treatment and disposal are identified as the biggest challenge for RSW management currently in China. To improve RSW management, increasing financial resources, establishing sorting collection and transportation network, promoting sorting collection and recycling, improving treatment technology are proposed as the possible solution.

Separation of Fenoxaprop-p-ethyl Biodegradation Products by HPTLC

Fenoxaprop-p-ethyl (Figure 1) is widely used in China as an active broad-spectrum herbicide for control of most grassy weeds. Several methods for determination of fenoxaprop-pethyl have been reported, including GC–ECD [1] and HPLC [2]. Ingelse et al. [3] separated fenoxaprop-p-ethyl and its enantiomers from ergot alkaloids by use of a capillary electrophoretic method. Although substantial research has been performed on the behavior of fenoxaprop-p-ethyl, there are no reports on the biodegradation or biodegradation products of fenoxaprop-p-ethyl.

Pretreatment of landfill leachate using deep shaft aeration bioreactor (DSAB) in cold winter season

A pilot-scale deep shaft aeration bioreactor (DSAB) with 110 m in depth and 0.5m in diameter for the pretreatment of landfill leachate in winter was operated at a daily treatment scale of around 10-20 tons. 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 1.7-9.4 g CODL(-1)day(-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 1000 mg/L, an acceptable level for advanced treatment using reverse osmosis system, when the influent COD was below 7000 mg/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.

Pollution of hazardous substances in industrial construction and demolition wastes and their multi-path risk within an abandoned pesticide manufacturing plant

AbstractExploration of heavy metals and organic pollutants, their leaching capacity along with health and environmental risks in contaminated industrial construction and demolition waste (ICDW) within a pesticide manufacturing plant were investigated. A maximum content of 90.8 mg•kg–1 Cd was found present in the wastes, which might originate from phosphorus rocks and industrial sulfuric acid used in pesticide production processes. An average concentration of 979.8 mg•kg–1 dichlorovos and other 11 organophosphorus pesticide were also detected. Relatively high leaching rates of around 4.14‰were obtained from laboratory simulated ICDW using both glacial acetic acid-sodium hydroxide and deionized water. Pesticide pollutants had the strongest tendency to retaining on dry bricks (leaching rate 1.68‰) compared to mortar-coatings, etc. due to their different physical characteristics and octanol-water partioning coefficient. Mobility of pesticide from on-site ICDW by water was spatially correlated to waste types, process sections and human activities, with a flux of leaching rate between 5.9‰ to 27.4%. Risk-based corrective action (RBCA) model was used to simulate the risk of contaminated ICDW debris randomly scattered. Oral and dermal ingestion amount by local workers was 9.8 × 10–3 and 1.9 × 10–2 mg•(kg•d)–1, respectively. Potential leaching risk to aquatic systems exceeded the limit for nearly 75% waste. Environmental and health risk exceedance was found in most ICDW, while the risk value of the most severely contaminated brick waste was 660 times beyond critical level. Implications for waste management involving construction and deconstruction work, waste transferring and regulation supplying were also provided.

Environmental impacts of a large-scale incinerator with mixed MSW of high water content from a LCA perspective

Large-scale incinerators are applied widely as a result of the heavy burden of municipal solid waste (MSW) generated, while strong opposition is arising from the public living nearby. A large-scale working incineration plant of 1500 ton/day was chosen for evaluation using life cycle assessment. It was found that the corresponding human toxicity impacts via soil (HTs), human toxicity impacts via water (HTw) and human toxicity impacts via air (HTa) categories are 0.213, 2.171, and 0.012 personal equivalents (PE), and global warming (GW100) and nutrient enrichment (NE) impacts are 0.002 and 0.001 PE per ton of waste burned for this plant. Heavy metals in flue gas, such as Hg and Pb, are the two dominant contributors to the toxicity impact categories, and energy recovery could reduce the GW100 and NE greatly. The corresponding HTs, HTw and HTa decrease to 0.087, 0.911 and 0.008 PE, and GW100 turns into savings of -0.007 PE due to the increase of the heating value from 3935 to 5811 kJ/kg, if a trommel screener of 40 mm mesh size is used to pre-separate MSW. MSW sorting and the reduction of water content by physical pressure might be two promising pre-treatment methods to improve the combustion performance, and the application of stricter standards for leachate discharge and the flue gas purification process are two critical factors for improvement of the environmental profile identified in this work.

Synthesis composite hydrogels from inorganic-organic hybrids based on leftover rice for environment-friendly controlled-release urea fertilizers

Nearly 1.3 billion tons of food are discarded annually in the production process. In this study, a novel slow-release nitrogen fertilizer with water absorbency was developed using leftover rice and crosslinking methods. Urea was incorporated as the nitrogen source in a leftover rice-g-poly(acrylic acid)/montmorillonite (LR-g-PAA/MMT) network, and then the leftover rice-g-poly(acrylic acid)/montmorillonite/Urea (LR-g-PAA/MMT/Urea) retained in the soil, and used as the loss control agent for water and nutrients. Variables including concentrations of acrylic acid, montmorillonite, N,N´-methylenebis acrylamide (MBA), and potassium persulfate (KPS) were investigated. Samples were with a water absorbency of 102.6g/g in distilled water and 25.1g/g in 1.0wt% NaCl solution under optimized conditions. Swelling measurements and water-retention indicated that higher-covalent cations would aggregate the hydrogels and decrease swelling. Investigating leaching behavior showed that these samples have the potential to carry the necessary nitrogen (N). The results demonstrated that the LR-g-PAA/MMT/Urea had a low leaching losses of N (19.7%) compared with pure urea (52.3%). Therefore, the developed fertilizer may be widely applicable in agriculture and horticulture, and could provide a new platform for reusing leftover rice.